Did David Bowie Ask The Wrong Question?

I often do bait and switch on here and I should honour the title to some extent, so here it is. There’s much to admire about David Bowie and the world lost a genius a few years ago. I’ve blogged about him before and whereas I can’t be bothered to fish those bits out I do remember tracing his reference to superhumans in ‘Oh You Pretty Things’ back via Arthur C Clarke’s ‘Childhood’s End’ to Olaf Stapledon’s writing, particularly ‘Odd John’. But that isn’t what I’m thinking of right now. I’ll never forget the first time I heard ‘Space Oddity’. It was an oddity to hear that accent on the radio. I don’t know why exactly, because there were lots of southern English rock stars at the time, but somehow it seemed really, I don’t know, ground breaking. Of course he was groundbreaking in other ways. My ex is a big Bowie fan, and has found him a gateway into sci-fi, a genre she previously despised, but as I said to her, and for some reason I think this applies to him in particular, you can’t take things too far from his lyrics without ruining them. For instance, in the album ‘Ziggy Stardust’ and his Mott The Hoople single ‘All The Young Dudes’, we seem to be expected to believe that there will be a mains supply for electric guitars, organs and amplifiers during the apocalypse. In fact, maybe there will be and that’s a mark of his visionary nature, but it bothers me. They should’ve been acoustic.

What I have in mind today though is ‘Life On Mars’. This has now famously been used as the basis for the excellent time travel police procedural series, which to me felt like Sam Tyler travelling back to a time when things were “normal”. Unsettlingly, that series itself is now almost twenty years old and the same gap separates us from Windows 3.1 as Sam Tyler from Gene Hunt. Well, sort of – no spoilers! My take on the track itself, though, is that it’s about someone despairing of how life is here on Earth and hoping there’s life on Mars instead because at least then there’d be something better out there. I’ve said before that my greatest fear is that there is no life elsewhere in the Universe, mysterious encounters in Sussex chalkpits notwithstanding. This is also why I’m so peed off with the scarcity of phosphorus. Anyway, this is in fact a major reason why I’m so focussed on the possibility of alien life. I may have just written a nine thousand word long rambling blog post about silicon-based life, but the subtext is the same as Bowie’s song’s. As Monty Python put it, “pray to God there’s intelligent life somewhere up in space, ‘cos there’s bugger all down here on Earth”. I don’t entirely agree with that by the way. I think many of us choose not to think complexly, which is one reason we’re in this mess.

Okay, have I done enough of that now? Enough relatable stuff? Seriously though, I’ll try not to go off on one.

Because as you must know by now, it really looks like there might at some point have been life on Mars, according to recent discoveries there. I have to admit that at this point in the proceedings I have little idea what they’ve found, but I seem to remember it’s an iron compound which is found as a product of terrestrial life, possibly a sulphur one, which needs to have quite a lot of energy input to form but is then stable and has no known non-biochemical routes to its formation, that is, including the biochemical route involving the evolution of a technological species which can do sums like many of us, which I’m sure nobody sensible is suggesting. This is the latest stage in a long history of claims about Martians, and at some point it was considered so certain that there was intelligent life there that a competition for ways to communicate with aliens specifically excluded Mars because it was thought too easy. There have been claims of canals, lichens, and later on a scaled-down set of claims regarding something like bacteria. In particular there was the Labeled Release (American spelling) Experiment on the Viking lander which appeared to show positive results, i.e. the results which NASA had pre-decided would be best explained by life, but the problem was that the other two experiments were negative. It’s frustrated me until recently that they did this but right now it seems more like the way the scientific method works: come up with an idea, test it and then do everything you can possibly think of to prove a positive result wrong. On the other hand, looking at it non-scientifically at the time, it felt like they were in denial about the existence of life, possibly because it’s an audacious and potentially career-ending claim if it ends up being refuted, but also because it’s such an Earth-shattering claim. But this puzzles me a bit because in fact for a long time, since at least 1877 up until 1965, it was basically considered a dead cert that there was life there, and often also on Venus at the same time, and it didn’t seem to make much difference to the human race that we thought it was out there. Maybe this is to do with most people not being very focussed on space, but at least in the ’50s and ’60s this was definitely not so and in fact this was probably one source of inspiration for Bowie’s track. Getting back to Viking, it’s now thought that the results of the experiment were caused by perchlorate in the soil, a bleach-like substance which it’s also been claimed originated from the sterilisation process in the reaction chamber before the lander left Earth, although I think it’s now established that perchlorate is high in Martian soil. In fact I seem to remember (look at me failing to check my sources – sorry) that it makes Andy Weir’s ‘The Martian’ unfeasible, though maybe ingenuity would’ve got him out of his predicament some other way. Weir has since said that Watney could’ve washed it thoroughly first, so maybe, although wouldn’t he then have ended up with most of his water full of bleach? Maybe not. I’m not a chemist. There’s also been a view that the dendritic appearance of some terrain close to the poles is due to the action of microbes, something I went into in depth when I put the Martian calendar for 214 TE (telescopic era) together if anyone remembers that – it involved me throwing an inkjet printer into the larder with considerable force at one point.

What’s happened is that the Perseverence Rover in Jezero Crater has found what they call “leopard spots” on rock samples. Organic carbon-containing mudstones have been found to contain nodules and reaction fronts rich in ferrous iron phosphate and sulphide minerals. Vivianite is one possible candidate, which probably coincidentally is found in bivalve shells, and another is greigite, which is a ferrimagnetic mineral regarded as a biosignature, in other words a sign of life. Other processes which could have produced these minerals involve heating which doesn’t seem to have happened to the rocks in question as they would show other signs, for instance in their crystal structure. It seems that redox reactions have occurred there, that is, reactions involving the transfer of electrons between substances, one example of which is burning and another internal respiration. These rocks are around three thousand million years old, and at that time the same chemical reactions were occurring on Earth, mediated by microorganisms. So there are these two neighbouring planets on both of which chemical reactions usually associated with life are taking place. On Earth, it’s known that this is due to life, but what about Mars? The paper in question has eliminated other possibilities as likely explanations. Further investigation by NASA is of course not likely to occur due to funding cuts, but China might end up doing a sample return mission, that is, bringing samples back to Earth, in the next decade.

For me there are a couple of takeaways from this. One is that space exploration moves agonisingly slowly. This is probably an artifact of being born in the 1960s CE., but I was under the impression that there would be a human mission to the Red Planet from 1979 to 1981. This then got repeatedly postponed. The other is that science tends to do the same thing, although it’s also punctuated by revolutionary bursts of activity, according to the philosopher Thomas Kuhn anyway. It’s very cautious and tries hard to be boring. We seem to be edging very gradually into a position of accepting that there has been life elsewhere in the Universe, and that it was also found elsewhere in this solar system in a similar condition to its state on Earth at the time. Whether it exists on Mars now is another question, although of course “life finds a way”. Whereas that’s a bit of pop-culture tat, there is an element of truth in it and to be fair it’s quite a good line. You only have to look at a seedling growing between two paving stones to see that, but living on a practically airless, arid rock bathed in ultraviolet and dropping daily below the temperature of Antarctica is a considerably taller order than that. Maybe.

There are several possible worlds in this solar system other than Earth which may be hospitable to life as we know it. These include Venus, Mars, Ceres, Ganymede, Callisto, Europa, possibly Jupiter, Enceladus, Titan and maybe even Triton, Pluto and Charon. Several of these are quite a bit friendlier to it than Mars, although the question of it arising in those places in the first place also arises. Maybe it didn’t arise on those worlds though, and simply seeded them having arisen in space. If that’s so, maybe it’s the cloud that formed this solar system which gave rise to life, which then arrived on various planets, moons, asteroids, comets, wherever, and either died or, metaphorically, took root there. If that’s so, with reference to the previous post on here, it would probably show up as having the same chirality of molecules as we, i.e. left-handed proteins and right-handed carbs. It’s been suggested that life here must have pre-dated the Earth for two reasons: it seemed to arrive almost before it was possible for it to form, and looking at mutation rates in DNA takes it back to a point before the formation of this planet. To clarify, there’s a set mutation rate in DNA and RNA which enables scientists to date roughly when diverse organisms had a common ancestor, and incidentally this is usually before the first definite members of two groups turn up separately as fossils, which could mean a couple of things. The complexity of many genomes has increased over time as well, and this too can be measured from the genes which organisms still share. If you extrapolate these rates back to the point where the minimum information for an organism to function is present in the genome, you get a period of about nine or ten thousand million years ago, or roughly twice the age of the Earth. This isn’t generally regarded as solid evidence though. What it does suggest, interestingly, is that not only does life here descend from organisms present in the solar nebula, but actually it’s from a source which existed before this solar system had even begun to form.

I’m not going to base anything firmly on that possibility, but others have been suggested, one of which is that life arrived here from Mars aeons ago, which is supported by the likelihood that Mars was probably actually friendlier to life back then than Earth was. These redox reactions may be from the exact same taxon of organisms on both planets. And this is where it gets difficult.

David Bowie asked “is there life on Mars?”, but was this the right question? Many people have said that if life can be found there, or in or on any other world in this solar system, it guarantees that there’s life elsewhere in the Universe. Well, it really, really does not. Suppose we do find incontrovertible evidence that there is, just now, life on Mars, and also on several other worlds in this solar system, and moreover that it’s remarkably similar in some ways to life on Earth, for instance possibly sharing some genes with us, and has the same chiralities in proteins and carbs as us. That means that all of that life has a common ancestor. That common ancestor might have arisen in this solar system, or at least locally before this solar system formed. In terms of chirality, maybe there’s something about the processes of the Universe which lead right- and left-handed molecules of the respective types to form and persist while their mirror images don’t, or maybe there’s something about mirror life which means it won’t function, in which case all life of the kind we know in the Universe would have those chiralities for some very fundamental reason, but we’re still drawing conclusions from a very small sample. Maybe there’s either just something about this solar system which makes it more likely that life would emerge here, such as the relative abundance of phosphorus, or maybe it just did emerge here against all odds because we live in a very large Universe, many of whose planets are covered in a reddish-brown tarry goo instead of life.

For all we know, planets and moons here could be rich in life forms, and that would be a cheering thought, but that doesn’t of itself guarantee that the rest of the Cosmos is not utterly barren. For all we know, there could be endless lifeless worlds filling the Universe, which nothing whatsoever wrong with them but simply because the chances of it arising are vanishingly small. I’m sometimes haunted by the thought of some very, very Earth-like planet orbiting, I dunno, Delta Pavonis or whatever, with a perfectly comfortable surface temperature, oceans, continents, rain, thunderstorms, rainbows, mud, puddles children would love to splash in, sunsets over idyllic beaches lovers could walk along, or other phenomena alien beings could appreciate in their own way if they existed, but which will never, ever even see a single bacterium before their stars overheat and destroy them. Trillions of them, all without life. And this solar system being full of life would be of no significance, no consequence to that situation, because life just arose this one time. And this is why I say that if it could be proven that life existed nowhere in the Universe, I would stop worshipping God. It’s like a deal-breaker in a relationship for me. I would be terminally angry with such a Creator for sustaining in existence such a vast and uninhabited Cosmos. It would be really bad.

This, then, is why I say David Bowie is asking the wrong question. It’s the right one if understood in terms broader than just Mars, that is, if Mars is just a stand-in for another planet or other location where life could persist. Mars is just our next door neighbour, and we already know our bushes might end up growing over the fence or our aphids might end up infesting next door’s roses. Big deal. The Universe is so big that the size of this solar system is nothing to it.

The Beehive

My eyesight is terrible. When I go to the opticians for a new prescription as opposed to handing over the new one, they use a special chart with a single letter filling all of it and ask me if I can see it at all, and the answer is always no. Because of this, as a child I expected to go blind and trained myself to find my way around without looking, which annoys Sarada as it seems to mean I notice details more than I do large objects, although that’s probably partly an aspect of my neurodivergence.

Therefore, in general when I look up at the night sky without binoculars or a telescope, I see very little because the starlight is too blurry if I don’t wear glasses and if I do the lenses cut out most of the light. Most of the time, it’s hardly mattered because, for example, in Loughborough the sky was overcast at night or ruined by street lamps. However, here in southwest Scotland, the situation is different, rather like that in and around Herstmonceux, where I trained as a herbalist and where the Greenwich Observatory was moved when the skies got too bright. This region is one of the dark sky sanctuaries, although apparently it gets darker even than this a little to the west:

Compare this to South to Mid-Wales, the South of England and the English Midlands:

Much of Devon and mid-Wales are fine there, but I’ve never lived anywhere near them, and the area around Herstmonceux is now pretty much the same as the rest of the South nowadays.

Surprisingly, on looking at the sky here, as I did the night before last, through binoculars and with my eyes plus spectacles, I was able to perceive another, well, spectacle in the form of a clear sky and a vista out into the local arm of the Galaxy, as well as of our closer neighbours Mars and Jupiter. The lunar absence helped but the magnification of the binoculars decidedly didn’t, as it was impossible for me to hold them steadily enough to see either planet clearly. For some reason the binoculars I use are 16 x, which I understand are usually mounted on a tripod for this reason but they don’t have anywhere to screw them in. I’m guessing you can get a frame of some kind to address this issue but I don’t think I have one. Frustratingly, I finally found the telescope yesterday, too late to aim it at the sky on that particular occasion but tomorrow is another night.

It was helpful that Mars was so clearly visible. I understand it’s currently near opposition, i.e. about as near as it gets, because it’s quite distinctive and enabled me to find Castor and Pollux, as it’s currently in Gemini, which in turn helped me find something I’ve never managed to see before: Praesepe, also known as the Beehive Cluster. Before I dilate on this, I want to point out that turning one’s attention to the stars is a fantastic escape from the troubles of this microscopic blue dot, and perhaps also a unifying factor, but there is unfortunately nowadays a fly in the ointment because of Elon Musk’s satellites interfering with a clear view of everything. However, I don’t want to dwell on that.

I’m sure you’re familiar with the bundle of eggs a spider lays – a ball made up of the mother’s embryonic young yet to hatch. When they do emerge, they scatter themselves having eaten the mother’s body, at least according to ‘Blade Runner’ if that’s not a false memory. This brings to mind how stars form in globular clusters like this:

Sid Leach/Adam Block/Mount Lemmon SkyCenter

After a while, they fly apart and the result is an open cluster like the aforementioned Beehive. Other nearby examples are the Pleiades and Hyades, quite nearby in our sky. Cancer, the constellation where the Beehive is, is generally quite dim and I had the impression that the cluster was too but apparently its total brightness is something like 3.7. I should explain what this means. The faintest stars visible to the naked eye of someone with good eyesight are of magnitude six, and the brightest, one hundred times brighter, are around magnitude zero, an example being Vega. This makes it a logarithmic scale with each step around two and a half times that of the one above. It also illustrates that we perceive things such as brightness on a logarithmic rather than linear scale, and a similar scale for sound volume, decibels (which are not actually a unit of loudness but it’s too involved to explain here), doubles every three, so 86 decibels is twice as loud as 83. I’m just going to say one more thing about decibels which indicates their oddness: how far from the sound source are you when you judge it? A seventy decibel sound ten metres away becomes a seventy-six decibel sound five metres away because it’s four times as loud. But does it?

Praesepe, the Beehive, is a fuzzy patch in Cancer around six hundred light years away larger than the Sun looks in our sky, with a magnitude of 3.7. That means that all the stars together are that bright, and it’s the area which is that bright rather than the mean magnitude of all the stars in the cluster. There are supposed to be about two hundred stars in it altogether, although being an open cluster its edges are vague, although it’s about twenty light years in diameter. “Praesepe” means “manger” or “crib” (I’m from Kent so I say “manger” for both, which I suspect is dialect and I’ve never used it outside Kent, but I don’t honestly know), and it is in fact a nursery for stars, so it’s peculiarly appropriate. You only get one chance to use that though, so although the other open clusters are also nurseries they can’t be called that too. The Pleiades or Seven Sisters, probably the best known open cluster, consists of stars which are mainly roughly the same size and temperature as each other, being blue giants, but the Beehive is not like that. The Seven Sisters are actually younger than the extinction of the non-avian dinosaurs, but the Beehive is about six hundred million years old, so it’s considerably older than the first trilobites. It varies a lot more, containing white dwarfs, red giants and also yellow dwarfs, which are Sun-like stars. Moreover, several of these stars are known to have planets and one of them has at least two if I remember correctly (I always write this stuff off the cuff). However, as is very common, they’re all “hot Jupiters”, that is, they are red hot, partly vapourised planets which would’ve been rocky at a greater distance. Using the current popular method, hot Jupiters are easier to detect than other exoplanets because they’re large and closer to their suns, as it involves measuring fluctuations in brightness, which is likelier to be detected if the planet is relatively large compared to its primary and orbits it quickly. The planet also needs to be orbiting edge-on to our view. There are other ways of detecting planets but they haven’t been used for decades, and when they were it turned out they produced spurious results, such as simply recording when the lenses in telescopes were cleaned and put back at a different angle! Nowadays, it seems feasible that they would work, so I don’t know why they’re not using them.

There are roughly a thousand stars in an approximate sphere with a radius of ten light years, and those are just the ones detected from Earth. There are probably more because many of the known closest stars to our solar system are red dwarfs, the lightest and smallest stars, and the smaller a star type is, the more common it tends to be. A sphere with a radius of ten light years has a volume of around 4200 cubic light years, and with two hundred stars in the cluster that means a cube with a volume of 4.2 cubic light years on a side would contain on average one star and the mean distance between stars in the cluster would be only 1.6 light years. However, if they’re anywhere near randomly distributed, that distance is likely to vary quite a lot although the centre of the cluster might be denser, as can be seen from the photograph if those alignments are not optical illusions. There are many optical double stars in general which just happen to be along the same line of sight. This means that even given the known stars, which include red giants, the sky of a planet in the cluster would be a lot fuller and brighter than Earth’s, always assuming its atmosphere isn’t too dense or cloudy to see through and that it isn’t very close to its own sun. If we were that distance from α Centauri, it would be about as bright as Venus and capable of casting shadows, and if a red giant the size of Arcturus were involved it would be getting on for lunar level brightness and light up the whole sky.

Back in the 1960s or possibly the ’70s, a nuclear-powered starship called Daedalus was designed which couldn’t be built because it would violate treaties on nuclear weapons. However, if it had been, it could’ve reached the nearest star within fifty years. In a cluster such as this, it might take only twenty years to get there, which is a much more manageable interval. There are Sun-like stars in the Beehive and there’s no reason to suppose they don’t have Earth-like planets circling them, perhaps many such planets throughout the cluster. And there’s more.

One thing which really stimulates evolution here on Earth is frequent mass extinctions. For instance, something massive hit this planet sixty-six million years ago which led to the ascendance of the mammals. Various other causes led to other mass extinctions, some possibly due to other impacts. Had none of that happened, evolution might not have led to us appearing because life would’ve been too easy on this planet. Hardship and adverse circumstances lead to creativity here too. Furthermore, Earth is unusual in having a large moon, due again to a major impact, this time from an object the size of Mars, which led to the development of a strong magnetic field protecting us from ionising radiation. All of those events are more likely in the cluster due to its crowded nature, with stars interfering with each others’ comets and asteroids, but as said before, it’s only six hundred million years old and it seems unlikely that there could’ve been enough stimuli for even the simplest multicellular life forms to have evolved in that time. However, if that did happen in such a cluster, interstellar travel would be far easier to achieve than we find it, as would observation of other star systems. For instance, planets orbiting a Sun-like star would be on average sixteen times brighter when observed from adjacent star systems than they would be from α Centauri.

As I’ve said before, I try not to focus too much on life, intelligent life, life as we know it or humanoid life on this blog because that’s a bias which I think makes the Universe less interesting, and the emphasis on life is a bit anthropocentric and perhaps also rather science fictional.

Half the mass of the cluster is contained within 12.7 light years of the centre and its gravity is capable of pulling stars towards it from thirty-nine light years away. There are also stars moving through it which have no real association with it. It shares motion with the Hyades, the closest star cluster of any kind to us, and its composition is similar, so they were probably once part of the same structure. They are only 150 light years away from us.

Pre-Emptive Moon Landing Denial

First of all, an apology. I’m generally committed to not referring to our natural satellite as “the Moon” because perspective is important, so I often call it Cynthia. I regret choosing this name, although it’s a valid label since it is one of the Greek lunar goddesses. Some others are Selene, which I like, Diana and Artemis. There’s an association with hunting because a bright nocturnal celestial luminary renders prey more visible. All of these names have a Western bias, so maybe that could be addressed for once as it would be good if one of the best-known and oft-mentioned celestial bodies had a non-European name. Because it also seems weird and distracting to keep calling it (her?) Cynthia, and indeed “her”, much of the time I refer to our companion in circumlocutory terms, so for example I talk about astronauts reaching “the lunar surface” or do what I just did. This is actually already why it’s been called “Luna” rather than “Mensis”, the older Latin name, since “menses” refers to menstruation and the Romans seem to have felt like they were referring to a “period” in the sky, which could’ve been quite positive but they were the Romans so it wasn’t seen that way.

Now for lunar landing denial, and there’s the circumlocution again. Humans did land on the lunar surface. Twelve of them in fact, between 1969 CE and 1972. Many people only remember Neil Armstrong and Edwin “Buzz” Aldrin, so I’m going to list all of them here: Neil Armstrong, Buzz Aldrin, Charles “Pete” Conrad, Alan Bean, Alan Shepard, Edgar Mitchell, David Scott, James Irwin, John Young, Charles Duke, Eugene Cernan and Harrison Schmitt. There were also six command module pilots and three people who attempted to land but failed due to an explosion. Although I’m tempted to mention their names, along with the three Apollo astronauts killed on the launchpad, I think I’ve made my point: that twelve people have walked on the lunar surface. The reason this needs stating is twofold: most people have no recollection of the other ten and apparently lunar landing deniers are under the impression that there’s only one lunar landing to deny.

How can we be confident that they happened? Well, for example, there are laser reflectors on the surface placed there by Apollo astronauts used by astronomers all over the world, although also one on the Lunokhod automatic lunar rover put there by the Russians, footage of dust kicked up by the Apollo lunar rovers describes a trajectory only possible in a near-vacuum under about one sixth of Earth gravity, returnees develop cataracts significantly earlier than people who have never been there. Add to that that if it really was a conspiracy, all the people involved who knew about it would’ve had to have taken the secret to their graves or haven’t spoken up about it yet. I really can’t be bothered to go into too much detail about this, and other people have done it better than I could, but I’ll mention a couple of things. Stanley Kubrick’s ‘2001’ came out around the same time as the Apollo missions, so he is often named as a co-conspirator, but his lunar landscapes look like others did before they were refuted by images from low orbiters or the astronauts themselves: they’re craggy and covered in cracks because the surface was thought to be more or less uneroded, but actual pictures show soft, undulating hills and fairly thick dusty soil, which however, wasn’t as deep as some astronomers expected and didn’t engulf the Lunar Module or the astronauts. The absolute minimum that happened was that the astronauts orbited and dropped probes, and that there was a sample return mission, and if they did all that they may as well have genuinely gone there. So believe me: humans have walked on the lunar surface.

HOWEVER

There is another issue.

Suppose it’s 1968. Apollo has yet to take anyone to another heavenly body. Moreover, it probably never will. This is because if it did, and that was the start of humanity spreading out into space and settling on other planets across the Galaxy, and at the time many people thought it was, that would probably mean that the total population of the human race would dwarf the number of humans who have lived up until now, since at a very conservative estimate there could be a million Earth-like planets suitable for us to live on in the Galaxy. Each of those would only have to have a total population throughout their human history of less than a hundred thousand for the chances of being born before or after Neil Armstrong to be fifty-fifty, and that’s a tiny number of people. Therefore the chances of him setting foot on the Sea of Tranquility are practically zero unless it doesn’t lead to any further missions to settle, there or elsewhere, or for that matter build any space habitats. Therefore, from the perspective of the late 1960s it makes perfect sense to assert that the Apollo missions will either fail or be fake. They’re a hoax.

Only they weren’t, were they? As I’ve just said, the lunar landings happened. Returning to the present though, 2024 right now, the same argument applies, although it is in fact rather stronger because now, more humans have been born than in 1968. We live in a young world. The median age of the world population is now thirty, meaning that most people alive today have been born since 1994. We also lived in a young world back then, with the baby boom for example, though that was just in the West. More people have lived now, and all of them have still lived on this planet. The chances of this happening have fallen for everyone who was born since 1972.

This is of course similar to the Doomsday Argument, which I’ve mentioned on this blog before. The Doomsday Argument is an attempt to estimate whenabouts we are in human history by considering one’s birth as a random event in time. Given a thirty-year doubling time in human population growth and a birth in the late 1960s, such as mine, and assuming my birth was about halfway through the total number of human births ever, this would mean that the last human birth would take place around 2130. Right now, this seems to be an overestimate and for environmental reasons to do with climate change the human race can be expected to go extinct in about 2060. That said, human population growth is also slowing, and it’s a highly egocentric argument because if someone else, born say in 2006, were to make the same calculation, even given the same doubling rate of population the last human birth would take place quite a bit later.

We now have the Artemis program, aiming to return humans to the lunar surface in the near future, and to facilitate human missions to Mars. If this happens as described, it sounds like it would be the start of this species spreading into space and we are once again probably confronted with trillions of future humans whose existence entails that living before that happens is very improbable. This is the second time this has happened, in almost exactly the same way. The first time, it actually did happen. This time, just as I would’ve said in 1968, it won’t. Whatever has happened in the past has a 100% probability of having happened because it did happen. This is true in one sense. In another, it isn’t. For instance, if you chose a random nation state in 2000, it would probably be a republic, but if you chose one in 1700 it would probably be a kingdom, and the past can’t be perfectly known. It can, though, probably be known more accurately than many future trends and events. Anyway, this means that because humans did reach the lunar surface, they have a 100% chance of having done so. Paradoxically though, if the same prediction had been made in 1968, it would also probably be true. This does raise issues about the nature of probability.

There’s this thing called “immanentising the Eschaton”, which is forbidden by the Roman Catholic Church. It means trying to make the world end by bringing about the kind of things that seem to be prophesied in the Book of Revelation. In the 1980s, Ronald Reagan was accused of doing this because of the Cold War. Well, this is what’s worrying me right now: the Artemis program was looking ever more likely but we “know” that it can’t happen, because if it did it would make our current existence improbable. Therefore, events can be expected to intervene to prevent it and any other such events from happening, because we’re alive now and living on Earth rather than in space or on another planet. The more likely it becomes, the more drastic the event preventing it would have to be. We can be confident that no chain of events which leads to a high-population future off Earth can happen, but we don’t know why it won’t. Any extinction event is incompatible with future human beings being born and carries a high degree of certainty, so to speak, of preventing a “space future”. Nuclear holocaust, catastrophic climate change, pandemic, the Artificial General Intelligence apocalypse – any would be fine. We have what feels like an ever-lengthening list of apocalyptic scenarios.

There are ways in which both Apollo and Artemis could be predicted to happen. If they don’t lead to a likely expansion into space, they’re absolutely fine. Apollo was substantially a Cold War publicity stunt by the West, mainly the US, and could be expected not to lead to anything else. In fact, its scaling down and cancellation is possibly “predictable” simply because we’re still here. The same could apply to Artemis. If it’s just a pipe dream, it won’t happen. Also, if it’s hyped and does not in fact lead either to a permanent base or people going to Mars, we might also be safe. On the other hand, anything which looks like it’s going to lead to an open future of humanity living permanently off this planet immediately becomes improbable because of that, and the probability of that happening kind of retroactively “causes” events which prevent it.

This is not necessarily a pessimistic scenario. It simply means that if we have a long future, which right now seems very unlikely, it will be on Earth, and at no point will there be permanent settlements of fertile people in space or on other planets. It also suggests a rather weird solution to the Fermi Paradox – where are all the aliens? Maybe the solution is that everybody realises this and has a failure of nerve, so nobody takes the risk. On the other hand, it also suggests there is a Great Filter approaching. The immediate solution to the Fermi Paradox in this case is the very vague idea that something stops aliens travelling through space, assuming they exist. The obvious alternative is that there are no aliens. It would also mean that the Great Filter hasn’t already happened.

The Great Filter is the idea that sometime between the appearance of the simplest life to the existence of advanced interstellar civilisations, a significant barrier prevents them from reaching this stage. There are two major possibilities: it’s already happened and we’ve gotten through it, and it hasn’t happened yet but it will. It could be pretty benign. For instance, maybe everyone decides not to bother going into space because they want to solve social problems at home, become spiritually enlightened and lose interest in doing so. I’ve mentioned various attempted solutions on here, including the combined importance and scarcity of phosphorus, the possibility that we might just be swamped in a Galaxy teeming with civilisations, that everyone else might be really bad at maths or that we’ve committed some kind of faux pas that puts us beyond the pale. Another intriguing idea, and calling it a possibility may be going too far, is that civilisations get to the point where they discover backwards time travel and destroy themselves to the extent that they never existed in the first place or are automatically pruned by that very discovery. In a way, this might be the same as being that everyone else might actually be too good at maths: so good that they discover time travel using it and that causes them never to have existed.

The Great Filter could be divided into past and future, but there could of course be a third possibility: maybe it’s happening to us right now. Perhaps all our problems are combining together to wipe us out, or a specific event is occurring which is incompatible with us having a future of any kind.

But maybe Artemis won’t lead to an open space future. The plans after the lunar landing are vague and might not lead to anything much in the long term, so it could be a similar stunt to Apollo. The Chinese have a plan to build a base at the South Pole there too though, so the possibility of them making further plans could be considered. Another possibility is private enterprise taking over, but this might not be good. This is where I get into the whole “Up Wing” business, and maybe I shouldn’t go there. It could just be that due to the probabilistic argument, every attempt at a major space development project is destined to fail and Artemis is just one of those. The Chinese program is too, and all of this can be concluded by the simple fact that we’re around now, not having settled elsewhere in the Universe. It isn’t because of any particular reason so much as that our existence ends up selecting a future without space travel. It is, I’ve long thought, very odd that the predicted developments such as rotary space colonies and going to Mars did not come to pass, but maybe it’s just that if they had, the average human being would be someone living thousands of years in the future. If this is so, space exploration might simply look jinxed for no apparent reason. This does actually seem to happen in at least one particular case, referred to as the “Mars Curse”. Only 53% of missions to Mars succeed completely. This may not even be specifically because of something Mars does, as the flights have been known to fail before even leaving the atmosphere. Rather than adopting a superstitious approach, maybe it’s just because of probability: it scuppers the chances of humans getting there if we don’t find out enough about it, so that’s what happens.

If it really is true that the probability argument works, there seem to be at least two applications to prediction here. One is the Doomsday Argument in general, which appears to have fairly major flaws (for instance it might just predict the end of mortality or pessimism rather than the human race because it focusses on the births, but could be about the thought of extinction itself becoming extinct). Another is the possibility of eliminating an apparently plausible future, which may also connect to the Fermi Paradox. But might there not be other things which this kind of argument could predict? The Mars Curse could be a real thing which does not, however, have any causal or for that matter acausal explanation, but is just how things happen to be. It seems to me that this has potential, but it’s all rather imponderable.

Meanwhile in the real world, Artemis faces delays and constantly recedes from the near future, like the invention of efficient fusion power. What a surprise.

Racism And Astronomy

I am of course incredibly White, so the immediate question here is why a White non-astronomer is qualified to talk about racism in astronomy. Well, strictly speaking of course I can’t really, or rather, I am unlikely to be able to wade into it in enough depth to swim knowledgeably. Nonetheless I can give a kind of overview of it and comment on some of the active racism involved.

Photo by Faik Akmd on Pexels.com

This is a time lapse picture of the night sky. The main reason we can know it was taken here on Earth, apart from the fact that astronomical pictures taken from other celestial bodies are rare and poor quality (in fact I only know of one body they have been taken from, and that’s Mars) is the colour of the sky and the presence of liquid and solid on the surface at the bottom of the picture. It also seems to have been taken from the northern hemisphere because of the relatively stable and bright streak at the centre, which is presumably Polaris. Had it been taken from the south, the much dimmer Sigma Octantis would be at the centre of the swirl.

The sky seems non-specific and impassive to us, and also very little influenced by conflict or politics going on here on Earth among humans, and that is one reason I’m so keen on astronomy. Contemplating the Universe makes the problems we have here seem less important and seems to put them in perspective. I would personally say the stars are something to aspire to. I so want there to be humans out there among them one day. Of course, we are already among the stars but apparently only one of them hosts us. Nevertheless, there are cultural dominances and biasses in how we view the Universe and also very clear and overt racism exists among the astronomical community.

This sounds like an accusation, as the words “racism”, “sexism”, “ableism” and others often do, but that would imply that people are consciously and deliberately reserving much of the academic world to White people. That may happen as well, but it’s more important to look at the issue as a structural thing. As a White person, I have the privilege of firstly being unaware of racial bias among astronomers and secondly of being able to contemplate astronomy in a meaningful way. There are other ways in which I am trivially disadvantaged to do with my situation. For instance, I can’t see objects in the night sky very easily because of my poor eyesight, so the best I can usually manage to do is to view maybe first magnitude stars such as Antares, and basically nothing else. This is more on the disability side than ethnicity of course, but there is another set of issues which is fairly obvious to me regarding gender, namely that a man may feel much more confident to go out at night to a park or remote area to look at the sky in a place without light pollution than a woman might, and beyond that the kind of systemic biasses which prefer able-bodied middle-aged WASP men work against women, the disabled and ethnic minorities. Hence in the richer parts of the world, Black people are likely to live in places with more light pollution and less likely to be able to afford a good telescope. Ironically, much of Afrika, for example, would be very suitable indeed for telescopic astronomy. Here’s a map of the continent showing lighting at night:

(would’ve been better without the labels). And here’s Europe:

This means that treating every location as equally likely, which is not so because of lack of population, one stands a much better chance of seeing the night sky well in Afrika than in Europe. Also, along the Equator one can see both celestial hemispheres, so one can see more of it in Afrika than Europe.

There will inevitably be systemic racism in who becomes an astronomer in Europe and North America, although I’m guessing this isn’t any worse than who becomes a palaeontologist. The latter presents a rather different problem as there are issues regarding the plunder of resources by colonialists and the treatment of indigenous peoples and ethnic minorities in the field, which may not be so big a problem with astronomy. However, there can be problems with the siting of observatories in a similar sense, the most well-known one at the moment being the positioning of the Thirty Metre Array in Hawai’i, which was to be situated on Mauna Kea, a sacred site to the people of that archipelago. The issue here is that the planned observatory is one of several near that site, and in the past the excavation of the site has desecrated the graves of ancient high chiefs. In the past, promises regarding the building of telescopes have been broken, with insistence that this would be the last development, followed by more of the same. The northern hemisphere is low in such observatories, and a possible alternate site in La Palma in the Canary Islands is less suitable for infrared astronomy due to the warmer climate and lower elevation. Mauna Kea is the highest mountain on Earth measured from its base, so there’s less atmosphere to look through. There is a peaceful protest ongoing there. Some of the indigenous people view the idea of looking for other habitable planets as encouraging an attitude that Earth is disposable. Despite losing their case in the courts, the actions taken to build the observatory seem to meet the legal definition of desecration. Elders in their seventies and eighties have been arrested for peaceful protests, and because the site is sacred all protestors are committed to non-violence. This has also divided the community as the police officers are sometimes related to the protestors. Beyond that is the issue of how the United States government acquired the islands in the first place, on the grounds that the White businessmen were more fit to run the island than the recently independent natives. The federal government also had no legal jurisdiction over the country.

This story makes me wonder about whether there are other observatories with similar histories. There is also a separate issue regarding the Arecibo Telescope, which is an enormous radio telescope built in a basin in Puerto Rico. This was used to send the first message into interstellar space for detection by aliens, although it was only a semi-serious attempt for publicity purposes. In 2020 CE, the telescope collapsed, primarily due to lack of funding making maintenance unaffordable. Like Hawai’i, part of the rhetoric for siting the telescope there is that it brings money into the local economy, but that money is no longer forthcoming. Elsewhere on the planet, the Karoo Square Kilometre Array in South Africa requires a 13 000 hectare “quiet zone” which minimises electromagnetic transmissions to enable the telescopes to detect signals from the sky more easily. The San used to live in this region and were forced to move north by the colonial government in the century before last, and there’s the issue of purchase of the land from White farmers to prevent radio interference. Employment is low and deprivation high in the area, and it’s possible that building the extra telescopes may lead to jobs. The San were, however, displaced when the government brought Black farmers to the area some time ago. The SKA is situated where it is thanks to a government bidding process which brought it into the area.

Then there’s the Atacama Large Millimeter/submillimeter Array. This was afflicted in 2013 by a workers’ contract dispute between the Washington CD-based organisation which runs the facility and the four-fifths of employees at the site who are Chilean. All of these things taken together look like a process where scientific institutions in the wealthy and light-polluted (and also electromagnetic radiation more generally) North of the planet uses places with colonial histories to site its astronomical facilities, without much respect being paid to the people who actually live there. As I say, I don’t know much about these things but it seems to be a clear example of racism in astronomy. The Polynesian people and the San do of course also have their own astronomical traditions. Western astronomers were not the first.

In 2017, only nine percent of US STEM academics were POC. The Black population of the US is 13.6%. As for Black women, only sixty-six of them got doctorates in physics compared to 27 000 White men. This is not about problematising STEM departments or the scientific community in particular, but in a racist society this kind of disparity can be expected if nothing is done to address it. In general, diversity is an asset because new perspectives can be brought to bear on research, so this is not simply about justice for ethnic minorities but about having a well-functioning scientific discipline. Problems encountered in physics and astronomy for POC include microaggressions from White students, not feeling welcomed or included, imposter syndrome, a lack of role models, financial struggles and an absence of academic support. There is a second problem with examining racism specifically in astronomy caused by the tendency for physics and astronomy to be lumped together, perhaps because physics is perceived as a more “useful” subject, and it may also be that astronomers are less aware of the need to combat racism in their discipline than physicists. Researchers into the issue have not managed to visit astronomy departments as easily as physics ones, meaning that no firm conclusions can be drawn about the relative differences.

The White Florida emeritus astronomy professor Haywood Smith has state

d that he does not believe systemic racism exists at a time when only two percent of American astronomers are Black. His own department had had one Black employee, in admin, hired in the early 1990s. On the positive side, Black students report that the environment in the department is generally very positive and supportive. However, I can’t help but be reminded of Patrick Moore, who was chair of the right wing United Country Party, which opposed immigration. He was also an admirer of Enoch Powell, condemned the Race Relations Act and regarded the absolute monarchy of Liechtenstein as the “best political system in the world”. This last point is more complex, mainly because Liechtenstein is a microstate, but it still means that, like Britain, Liechtenstein’s head of state is very likely always to be White.

It would be unfair to use both of these astronomers as typical of their profession. Even so, it does remind me of the interesting phenomenon of right wing animal liberationists. There are people whom I might describe as “animal lovers” who look at the world very differently than I do, and whose veganism, if that’s an accurate description, is also very different to mine. For instance, there are some animal liberationists who are anti-abortion and see that as consistent, and there’s also an attitude that whereas humans are terrible, and behave terribly towards each other, other species do not perpetrate deliberate cruelty but simply try to survive and thrive, and take care of their offspring. For such people, other species seem to constitute a similar escape from the woeful interaction of human beings with each other as astronomy does for me. Maybe actively racist White astronomers are similar. I don’t feel I’ve exactly captured the issue, but I can see the sense in this apparently incongruous juxtaposition.

The way it might work for White astronomers is that they want to rise above this morass of apparent nonsense that infests the world, but their nonsense is not the same as my nonsense. Mine is the endless grind of global capitalism, greed and hatred between groups to ensure divided opposition to oppression. Theirs is a reflection of the privilege which enabled them to become astronomers in the first place. It could also be a kind of innocence. They may be so focussed on the stars that they’re oblivious of what’s happening on the ground. But it’s been said that not taking a position in a dispute about oppression is taking the side of the oppressor. Some might also say that there’s an issue with even having astronomy departments “when the world’s in such a mess”. I completely disagree with this though, because awareness of the existence of the rest of the cosmos has a function similar to spirituality and art in allowing one to continue and cope in order to continue fighting for a better world. Being a science, astronomy also has the usual function of science in training people in critical thinking. This is how astronomy graduates will be coming out the other end of the degree machine, whether or not they use their qualification vocationally. Astronomy is also just plain useful, for instance in detecting asteroids hurtling towards the planet and wiping out all life as we know it.

Another aspect of astronomy and racism is the question of sky cultures and names for objects. I’ve already mentioned the Square Kilometre Array and the observatories on Mauna Kea. Both of these are unsurprisingly both associated with indigenous communities, namely the San and Polynesians respectively. A sky culture is how a particular culture sees the sky. There are several Polynesian sky cultures just as there are many Polyesian languages. It could be expected that a set of people who have settled in various places across the Pacific and Indian Oceans would have a highly disparate set of cultures. The Austronesian language family had the largest geographical range of any language family before colonialism: Hawai’i and Madagascar both speak Austronesian languages and are 17 000 kilometres apart. Their broad distribution is a factor in their astronomy, as it was important to have some understanding of constellations in order to navigate. In order to record the positions of the stars, some Polynesians used “stick charts”, made from palm fronds, cowries and plant cordage:

By Sterilgutassistentin – This file has been extracted from another file, GPL, https://commons.wikimedia.org/w/index.php?curid=51775534

Curved links indicate ocean currents and winds and the charts are effectively maps of the ocean. Pacific Islands tend to be around one to three hundred kilometres apart with the exception of such outliers as Hawai’i. The information was memorised and navigators were also spiritual and political leaders, navigation being a spiritual and religious act. Astronomy was part of this. Guiding stars were used when low in the sky, with imaginary vertical lines projected onto the horizon to indicate direction, but these move as the night goes on due to the rotation of the planet. The direction indicated by the star is maintained until another star rises. The paths between these stars are referred to as “kavenga” – “star paths” – named after the brightest star and all stars are referred to by the name of the brightest. However, these are not applicable all year round, so the year is divided into four unequal seasons with different kavenga. These are Ke Ka O Makali’i (the northern winter – Hawai’i has no seasons of course), Ka Iwikuamo’o (northern spring), Manaiakalani (northern summer) and the overlapping Ka Lupu O Kawelo (northern autumn into winter, including some of Ke Ka O Makali’i). Kavenga could also be kept on one side or other of the boat, or the boat could be aimed between two kavenga. There is also the star compass, which uses the presence of Polaris and Crux Australis, as we in the West call them, and the stars around them as they rise and set, to locate the north and south celestial poles. They also picked out a number of other asterisms (star patterns), including what we call Orion’s Belt, Scorpio, and the Pleiades, and used their rising and setting to mark another six points on the horizon and construct the directions in which other stars were since their positions would then be known. This enables the navigator to find out where the boat is when the sky is partly cloudy. There are also, unsurprisingly, stories associated with the star paths and asterisms. Apart from being meaningful in other ways, these serve as mnemonics for the location of the star paths.

There isn’t time to cover all Polynesian sky cultures here, so I will now move on to the San. Although it must be remembered that the biological construction of ethnicity as race is distinctly dubious, politically speaking, it’s also worth noting the identity of the San, whose genetic profiles are highly unusual. The San appear to be the group genetically closest to the earliest examples of Homo sapiens. Both their Y-chromosomal and mitochondrial DNA branched off early from the rest of the species and they seem to have diverged from about two hundred millennia in the past. They’re also the most diverse group of humans genetically. Two San can be as different generically from each other as two randomly chosen people from anywhere on Earth. Besides this, albinos are unusually common among them. I mention all this to indicate that they are very much not simply Black people even though Europeans might lump all Afrikans who are not fair-skinned together. They have a very distinct identity. Afrikans generally are more genetically diverse than the rest of the human race, so as I’ve said previously, if you want a construction of race based on genetics, and I don’t really know why you would, it makes sense to see Afrika as including about ten ethnicities and the rest of the world about fourteen, but with entire continents in some cases only having a couple, so the human race basically consists of a series of genetic groups which often vary in skin tone and other features within those groups plus a large number of mainly dark-skinned groups all of whom originate recently from Afrika. The idea of skin tone as a major feature distinguishing ethnicities makes no genetic sense, and of course people don’t just “breed” within their own hermetically sealed racial units.

One tantalising possibility exists regarding San sky lore, which is that it may be directly descended from early human mythology. On the other hand, behavioural modernity seems to have appeared after the split between them and the rest of the species, so maybe not. One difficulty with recovering it is that Christian missionaries have obscured and suppressed the content, but one story is that a woman was baking a root vegetable on a fire and wouldn’t let her daughter eat it, so the daughter kicked at the fire and scattered the ashes across the night sky, forming the Milky Way, and the red embers formed the red stars in the sky. Kham (the Moon, Cynthia) is a man who has angered the Sun, gains weight each month and then is cut away by the Sun until only the backbone is left, and he pleads that this crescent he has become be left for his children, who then repeat the cycle. The Sun, in a possibly different tribal tradition, becomes a rhino at sunset, is eaten by a different tribe who then throw her scapula over to the east, where it becomes a new animal and rises again. The celestial bodies are the elder race and all personified. The Sun, and again this seems to be a different tradition, is a man with luminous armpits, armpits being considered a source of sweat which contains supernatural power, who refused to share his light to dry out the termites for eating, so the first San threw him into the sky so that his armpits could illuminate the world. The “Moon”, is the shoe of a male trickster deity, /kaggen, the name literally meaning “mantis”, who threw it into the sky, and an alternate theory is that it’s an ostrich feather also throw into the sky by /kaggen, who commanded it to become that celestial body. All of /kaggen his possessions are magically intelligent and the “Moon” alone speaks using a retroflex click. Like many other cultures, there is an association between a lagomorph, this time a hare, and this luminary. The spirits of the dead are carried by the dark side, so the full phase is considered good luck for hunting, as is a blood moon. The stars are named after various animals such as lions, antelopes and tortoises, and a stone used for digging. For them, the sky was a stone dome with holes in it through which the Sun shone. The three stars of Orion’s belt are zebras, the Pleiades the daughters of the deity of the dawn and sky, Tsui. Her unnamed husband is Aldebaran. Betelgeuse is a lion who is also stalking the zebras, so Aldebaran can’t get them without getting killed, so he’s slowly starving to death.

There’s quite a contrast, then, between the sky cultures of the Polynesians and those of the San, and of course there are plenty of others, but the dominant one, used by Western astronomers, is of course the Greco-Roman and more widely European eighty-eight classical constellations with stars named using Greek letters, numbers and often Arabic names. The presence of Arabic in this system demonstrates how the Arab world didn’t go into the Dark Ages like Christendom and for a long time their astronomy was more advanced than ours. There is a clear division in the names of the constellations between north and south because of what was visible from the Med at the time, so the zodiacal and the more prominent northern constellations were given names by the Greeks and Romans, but there are also fainter northern constellations with newer names and the southern names, also given by Westerners, tend to be very different. Some are neutral and uncontroversial, such as Crux Australis and Triangulum Australe, and the southern polar constellation is called Octans due to its obvious association with navigation. Several others have nautical or navigational names, such as Sextans, Quadrans (which is obsolete), Pyxis (the Compass), and some more are named after birds such as Tucana and Apus. The rather dim Indus was named by a Dutch astronomer and is clearly supposed to represent an individual of non-European origin, but their exact ethnicity is unclear due to the practice of referring to native Americans as “Indians”. There are also some obsolete constellations, one of which, Quandrans, has already been mentioned. Unfortunately one of these is Antinous, the homosexual lover of the Roman Emperor Hadrian. There was also a pangolin, and some others whose names seem perfectly normal and acceptable, such as the Cat, the Bee and the Sundial. Others used to be nationalistic or partisan, such as Sobieskii’s Shield, now known simply as the Shield, and Charles’s Oak. Also, in the seventeenth century, an attempt was made by one astronomer to give all the constellations Christian designations, replacing the northern constellations with New Testament names, the southern with Old Testament ones and the zodiac with the twelve apostles. This is a diffeent kind of cultural bias.

I’m sure there’s plenty more to be said about racism and astronomy, but I want to finish by mentioning the recent renaming of certain celestial objects such as NGC 2392, formerly known as “The Eskimo Nebula”. The name “Esquimau” is considered racist because it isn’t what the Inuit call themselves and it was widely believed to mean “eater of raw flesh”. In fact, it may not do but instead may be derived from “Ayeshkimu”, meaning “netters of snow shoes”. However, whatever its origin it’s considered as a colonial term with a racist origin by the Inuit, so the colloquial name has now been replaced by the New General Catalogue number. Similarly NGC 4567 and 4568, twin galaxies, were formerly referred to as the “Siamese Twin Galaxies”, which has again now been dropped. NASA also has an Office of Diversity and Equal Opportunity which addresses issues affecting marginalised groups.

As I said at the start of this post, I am not really the right person to be talking about racism in astronomy as I am White and not an astronomer, but I hope I’ve been able to provide some kind of sketchy survey of some of the issues involved. There’s bound to be a lot more.

The Safest Satellite

Calista Flockhart sticks in my mind. She used to play Ally McBeal, and most remarkably she’s the absolute double of a friend of mine who lived in Yorkshire when it was on. I used to commute to Leeds at the time and stay over at her house. But there are three other reasons Ms Flockhart has come to my attention intermittently. She was the “single female lawyer” of Futurama fame, impersonated by Turanga Leela with a stick-on googly eye. She was rather thin, and that used to worry me although I suppose I mustn’t “skinny-shame”. And finally, her name was similar to that of Jupiter’s outermost large moon, Callisto, illustrated above.

I’m sure the actor wasn’t named after the moon, but ultimately the Greek nymph. Once again, Kallisto, or more correctly Καλλιστώ, was one of Zeus’s “conquests”. I can’t help but think that some kind of “me too” moment should’ve come to pass in Olympus at some point, and I’m not really joking. Being a religious figure, Zeus was I imagine seen as a rôle model by many a Greek male, and seems to have spent most of his time raping and sexually harrassing people. Then again, maybe this was around anyway and merely served as an expression of that behaviour. However, just as Ganymede was Zeus’s homosexual lover, so was Kallisto, even though she was female. Zeus transformed himself into the likeness of Artemis to seduce her, meaning that they were lesbian lovers. So we have the two hetero moons and the two gay moons, which in a way is neat. Kallisto’s other claim to fame is that while pregnant she was thrown into the sky to escape the anger of the real Artemis, which stretched her tail and changed her into Ursa Major. ‘Αρκας, their son, became Ursa Minor.

Kallisto means “most beautiful”. When I learnt this, I suddenly realised that the Greek ending for the superlative, -ιστος, was cognate with its English and Germanic equivalent “-est”, although I don’t think you can do much with καλλος in that way. Anyway, I thought it was neat.

Callisto the moon is beautiful if you like that sort of thing. It’s somewhat similar to Ganymede but has an older surface, is a little smaller and is somewhat apart from the other Galileans, taking more than sixteen days to orbit, and therefore having a day more than two weeks long. Due to its separation, it doesn’t undergo the tidal stresses and strains of the others and therefore hasn’t had its surface remodelled at all since it formed. It’s both the most heavily cratered known body in the system and, at least when the Voyager probes visited, the least dense. It continues the trend of reducing density found among the Galileans. It’s also unique among them in orbiting outside the radiation belts, although it’s still within a fairly strong magnetic field. This is what makes it the “safest satellite”. Unlike the others, if humans ever went there landing on Callisto would be basically the same job as the Apollo astronauts did, and if anything there’d be less radiation because it’s five times as far from the Sun, although perhaps Jovian cosmic rays would still be a hazard.

It’s slightly smaller than Mercury, by about twenty kilometres, but still larger than Cynthia and Pluto. By mass, it’s the twelfth largest world in the system, being somewhat more massive than Cynthia and Io. It has the lowest gravity of the Galileans at around an eighth of Earth’s. There are so many craters that it’s hard for any more to fit on. Any new craters would probably overlap with old ones. This has happened because the surface froze before the Late Heavy Bombardment, so it retains a record of how violent the early Solar System was. Extremely, it seems. This also suggests strongly that Jupiter was almost like a second Sun at the time, although by Callisto’s distance, 1 882 700 kilometres away, it was well-frozen. However, an important influence on the inner moons is the tidal tugs on each other, which don’t affect Callisto, so that heating effect is absent. Nonetheless, Io’s density and complete absence of water does seem to indicate it was pretty hot that close.

The place nowadays all seems to be all about peace and serenity, which considering the onslaught it clearly received thousands of millions of years ago and the scars it still bears is pretty ironic. All the other moons have got something going on, Io most of all but the others show signs of activity fairly recently. Callisto doesn’t. It lacks anything like the regiones and sulci of Ganymede or the smooth surface of Europa, which implies that the latter underwent some melting after most of its meteorites hit. Of the four therefore, Callisto has the oldest surface. Nothing ever happens there, at least on the surface.

However, that doesn’t mean it’s boring! There are two gigantic impact basins, Valhalla and Asgard, the former of which is three hundred and sixty kilometres across at the centre and is surrounded, like Asgard, with rings, in this case up to eighteen hundred kilometres from the centre. It is in fact the largest impact basin in the system, comparable in appearance to Mare Orientale on Cynthia and Caloris Basin on Mercury. If the centre of Valhalla was in Glasgow, the outermost ring would cross Lithuania, southern Spain and Kalaalit Nunaat (Greenland), and this is on a moon with less than a seventh our planet’s diameter. On the moon itself it stretches across almost a quarter of the way round its world. The central crater is a palimpsest, a type of crater also common on Ganymede which has been partly eroded over time in one way or another. I personally imagine the cause in this case is that the impactor melted the surface, considering it’s mainly made of ice, but I don’t know what the experts think. The ringed area around it has outward facing slopes with steep escarpments, and although those sound like waves emanating from the impact they’re probably grabens – downward fractured areas like the equatorial rings on Vesta. Further out still, at the edge of the area, the rings are more vaguely defined and consist of troughs.

The other impact basin, Asgard, is a “mere” sixteen hundred kilometres in diameter, making it the size of Greenland/Kalaalit Nunaat. The centres of the two basins are about nine thousand kilometres apart. At its centre is the crater Doh, which has a large raised area at the centre. A third ringed structure is superimposed on it, called Utgard, which is slightly smaller than Adlinda, the third largest. There are also faculæ, which are frosty-looking spots dotted about, of which only one, Kol, seems to be named. The features on Callisto are named after mythological beings and items in Nordic and Inuit folklore.

The presence of the ringed basins on Callisto would be expected to lead to distinctive features on their antipodes, because the shape of the moon would focus the shockwaves on the other side as they travelled across the surface, but I haven’t heard that this is so, even though there are good-quality images of that side.

Considering the number of craters on Callisto, it’s unsurprising that there are also catenæ. These are chains of craters caused by objects breaking up before they reach the surface, which happens due to their size and also when they’re rubble piles, which many small objects are. There are at least eight of these. They occur elsewhere in the system, but are bound to be more common on this moon due to the extreme nature of the cratering. I first learnt the word “catena”, meaning chain, from this context, and eventually noticed the Castilian word «cadena». It may be worth answering the question at this point of why craters tend to be circular. After all, don’t they strike the surface of a body at various angles? If a hard projectile is thrown at a soft surface, it would only produce a round dent if it was perpendicular. The reason craters are circular is that it isn’t the mechanical impact of the object that causes the dent, but the heat and explosion of the energy release, so craters of this kind are more like bomb craters than the kind induced by a pebble hitting some mud. The catena above, Gomul, is actually within the rings of Valhalla.

Ganymede may have a complex interior consisting of alternating shells of ice of various kinds separated by water, and the similarity between the two moons might lead one to expect Callisto to have the same, but this doesn’t appear to be so. Instead, it probably looks like this:

As mentioned in the post about Ganymede, hexagonal ice is the kind we’re likely to encounter on Earth’s surface. The ocean is hundred and fifty to two hundred kilometres deep and since the moon is not geologically active, it has no thermal vents supplying it with energy. In any case, the ice is so thick there’s no chance of penetration. The rock portion at the centre is also even proportionately much smaller than Ganymede’s and there seems to be no magnetic field either. The interior also differs from Ganymede’s in containing a layer of ice VII. Surprisingly, ice VII is actually present on Earth inside diamonds. It can only form with a combination of high pressure and low temperature, so it proved to be a surprise that it was present on Earth, but on Callisto it’s to be expected. It’s fifty percent denser than our own ice and has a cubic crystal habit. This doesn’t mean it has cube-shaped crystals, but that the axes of symmetry are equal and at right angles to each other. Diamonds also have cubic symmetry, so in a way ice VII is like diamond, and it’s also extremely hard, being about as tough as quartz. Its melting point is always at least 82°C and can be above 400, so in many ways this is not like the ice we’re familiar with at all. The moon also gets steadily rockier towards the centre. The lack of activity means there is no magnetic field, which would be generated by currents in metallic liquid. This also means that unlike Ganymede there is no aurora, but there probably wouldn’t be anyway because it’s too far from the radiation belt.

There is an atmosphere, although it’s unsurprisingly extremely thin. It consists of carbon dioxide, and it’s a little surprising even that’s there because left alone it would leave the moon within a hundred hours due to its low escape velocity. It’s thought that there is dry ice slowly subliming from the surface, which also contributes to the smoothing out of the features seen, for instance, in the lower and gentler crater peaks. Ther’s also atomic hydrogen, which stretches higher up from the leading hemisphere.

The question arises here of whether Callisto is actually just a moon, unlike the other Galileans. The recent rival definition of planet requires it to be geologically active, and this is certainly true of Io in particular but also Europa and Ganymede. Callisto, however, is only active in that carbon dioxide seems to be gradually evaporating from its surface and it lacks any apparent internal or surface activity. Nothing much seems to have happened on its ancient surface for over four æons apart from the occasional meteor or comet strike: most of the craters are very old. Therefore, although I doubt anyone has ever considered the question, the body isn’t really a planet, but just a moon. In fact it may even be the largest moon that isn’t also a planet.

Out of all the bodies in the system, strangely Callisto may be one of the most hospitable to humans for exploration and settlement. The level of radiation on the surface is not only relatively low compared to the other Galileans, but actually lower than most of the inner planets and bodies in the asteroid belt except for Earth. This is because it’s over five times further out. It’s also more accessible than more distant moons, and is also fairly large. It’s larger than Cynthia and almost the same size as Mercury. Consequently, it has been considered as a potential target for astronaut visitation. As just mentioned, it’s extremely geologically stable, and there’s an ample source of water on the moon. It could also serve as a base for activities on the other Galileans and Jupiter, which is a good source of fuel for interstellar travel. In fact the moon itself provides this in the form of water ice, which could also be used as a source of oxygen for breathing. The interior, having water in liquid form, is also likely to be warm enough for habitation at some level. NASA carried out an investigation into the possibility in 2003 called HOPE – the Human Outer Planets Exploration – and suggested that it would be possible to reach Callisto by 2040. Of course this won’t happen but it’s nice to dream. I remember noticing that Nigel Calder included Callisto as a major power base in a simulation of Solar System power politics in his 1978 TV series ‘Spaceships Of The Mind’, although I’m surprised enough was known about it that far back to suggest such a situation.

Callisto doesn’t seem to crop up much in science fiction, possibly because not much happens there, but an exception is Asimov’s ‘The Callistan Menace’. This is a story about the mystery of astronauts attempting to visit the moon but never returning. I’m not going to spoil it, but its depiction of the place is quite inaccurate as it’s given a substantial atmosphere even though the author knew it couldn’t have one even back then. It’s also a bit unusual in referring to it as Callisto at a time when usual practice was to number the moons – Callisto is “Jupiter IV”.

Right, that’s it for Callisto. I’m not sure what to do next because Jupiter has something like eighty more moons but the Jovian system has already been covered. I might talk about the Galileans as a group, or I might move on to Saturn.

Vesta – Curry World?

Not to be confused with PC World, Vesta is saddled with a problem a number of other celestial bodies also experience of having weird pop culture associations. There’s Pluto, after which the Disney dog was apparently named, and while I’m at it, as observed in ‘Dazed And Confused’, why does a cartoon dog have another cartoon dog as a pet? There’s also Uranus, whose name can be pronounced as either “your anus” or “urine-us”. And getting back to the original subject, there is Vesta.

I don’t know how widely the fame of Vesta curries extends, but certainly in England the name has been substantially associated with the things White people used to get in boxes from the supermarket in the 1970s CE, and one of my friends reckoned that the TV series ‘Adrian Mole’ succeeded in nailing the working class Leicester experience perfectly when they ate a Vesta. Goodness knows what South Asians would’ve thought of them. Having said that, I’ve never tried them and that’s even though I’ve been reduced to buying samosas from Sainsbury’s because of the cultural desert I seem to live in nowadays. A quick Google confirms that they do still exist. I mean, I liked Marvel dried milk and Smash instant mash back in the day, so maybe I’d’ve liked them, I dunno.

Why, though, has Vesta got the same name as Vesta, or for that matter Vesta or Vesta? There’s a car, a box of matches and a world in the asteroid belt, and that last one I will get round to in a minute, but for now it’s in order to mention the original Vesta. Vesta was the Roman goddess of hearth and home, which of course immediately makes me think of Dexy’s Midnight Runners because my brain doesn’t work properly:

This is the surrealist painter Max Ernst’s 1937 painting ‘The Angel Of Hearth And Home’, which will be removed on request. It’s one of his few overtly political paintings and represents the spirit of chaos spreading across Europe in the wake of the Spanish Civil War. The title is meant to increase the sense of unease and disorientation one feels on looking at it. It is a vaguely humanoid figure with a fierce-looking fanged mouth and a seven-fingered hand sprouting from its knee. It’s actually the opposite of what one might expect from an angel of hearth and home, and more like death. Well, this opposite figure is the Anti-Vesta. The main association people make nowadays is of course with Vestal Virgins, who undertook not to have sex for thirty years while tending the sacred fire in Rome, considered to be vital to the city’s security. Hence they were tending the hearth of the whole Empire. This is part of a theme in asteroid naming in the early nineteenth century, where the names of female figures were chosen who were also somewhat domestic in nature. I’ve already mentioned Ceres, there’s Vesta, and also her Greek counterpart Hygeia, Juno goddess of marriage and childbirth as well as rather more outward-going things like the state, Flora, Hecuba (Priam’s wife), Victoria and so on. They also often have their own sigils at this early stage, but the point appears to have come when there were so many of them that they gave up.

⚶

This is Vesta’s sigil, clearly representing the eternal flame. Maybe one day it’ll grace a flag. This is Vesta itself:

I’ve selected this rather dingy picture because it shows two features of the body (I’ll talk about its exact nature in a bit) which are particularly distinctive, namely the streaks and the “Snowman””, which is the cluster of craters on the right hand side of the picture. Once again, then, there’s a body with a number of distinctive streaks, like Phobos.

What, though, is Vesta? Is it an asteroid? Ceres kind of turned out not to be, and Vesta may be the second largest. Whereas Ceres is large enough to eclipse the whole of Great Britain and Ireland, Vesta is only big enough to cover Ireland. It’s also the brightest member of the asteroid belt, bright enough in fact to be visible to the naked eye on occasion, although it wasn’t actually discovered until 1807, which happens on occasion. Uranus is also sometimes visible but wasn’t discovered until the eighteenth century. Then again, for many millions of years there must have been animals on whose retinæ images of Vesta, Uranus and even fainter worlds must’ve registered and influenced their visual cortices, but actually recognising it as something orbiting the Sun is another matter. But in any case, Vesta is the brightest asteroid, if asteroid it be. It’s probably also the second largest body orbiting twixt Mars and Jupiter except that Pallas is very close to it in size and it may therefore not be. It has a diameter of 525 kilometres on average, but is considerably less round than Ceres. This makes it definitely larger than Ireland, and in terms of area it gets harder to work it out, but assuming it to be a sphere, which is definitely not true, it’s slightly smaller than Pakistan. Perhaps surprisingly there is no straightforward formula for working out the perimeter or an ellipse, and therefore I’m assuming that no such formula exists for working out the surface area of an ellipsoid either. It’s larger than Mimas, which I always think of as the smallest round body in the system and as a kind of limit below which I kind of have less respect for objects, which may be unfair. Hence there must be something about Vesta’s substance which enables it to retain non-sphericality at a fairly large size, and I imagine this is linked to its rockiness as Mimas is probably much icier.

Although Ceres is the largest object in the asteroid belt, Vesta is the largest one native to it. The large amount of ammonia on and in Ceres suggests that it was originally in the outer system and only arrived in the belt later. Vesta is not like that and has probably always been there. It takes up nine percent of the mass of the asteroid belt and is quite close to being spherical, but just misses out on being a dwarf planet, although it may be the largest object in the system which is decidedly non-spherical. Unlike Ceres, it actually was discovered by the celestial police force set up to find bodies between Mars and Jupiter, and was the fourth discovered by Heinrich Olbers of Olbers’ Paradox fame (why is the night sky dark rather than bright? This is actually a very important question with massive consequences for the nature of the Universe but I don’t want to talk about it here. It’s basically because space must be expanding). It was in fact the last asteroid to be discovered for a long time, and it’s a little surprising that it was only the fourth to be found because it’s so bright and large. The next one, Astræa, wouldn’t be found until 1845, after all the original discoverers had died, then there was a spate of further revelations after that. Vesta therefore probably counts best as the largest asteroid, unless Pallas is, and traditionally people would’ve said Ceres.

Vesta isn’t like Ceres at all, but it is very much like a number of other asteroids in the belt. Some of these are former bits of Vesta which have chipped off due to impacts, but some have orbits which indicate they could never have been anywhere near it and must therefore have formed separately. It’s also responsible for quite a large number of meteorites which reach Earth, and therefore we actually have samples of it. Some of them are even from quite deep inside the asteroid, so its composition can be ascertained fairly well, and it can be seen from these that the asteroid is layered rather than mixed, as a smaller one would be, meaning that it’s heated and melted internally at some point. Its surface has for some time been known to be basalt, which on Earth comprises ninety percent of igneous rocks. On most rocky worlds in the system, igneous and metamorphic rocks are almost all there is. There are some exceptions, such as the strata on Mars, but on the whole there are no sedimentary rocks and the idea of sedimentary as a category is fairly specific to Earth, although there is, for example, clay and the layers of substance on Io, which aren’t sedimentary but are stratified. However, tuff, which is layered volcanic ash, is sedimentary, so water or any other fluid medium isn’t required.

Vesta and Ceres are kind of in each others’ vicinity. The average distance is 2.36 AU from the Sun compared to Ceres’s 2.77, which is around 61 million kilometres apart, about the same as Earth and Mars. This isn’t particularly close of course and reflects the fact that the asteroid belt is actually pretty sparse, but it is roughly as close as the orbits of Earth and Mars. However, the minimum distance is only five million kilometres, although this can only occur when the orbits are precisely aligned. It wouldn’t happen every orbit or even every thousand orbits, because it would depend on the ellipses shuffling round. Vesta’s orbit is also less tilted than Ceres’s at 7°, so they may not pass as closely to each other as might initially seem. The year is three and two-thirds longer than Earth’s. Vesta actually approached the Sun most closely only a month ago, on 26th December 2021.

Earth is slightly flattened at the poles and bulges at the Equator because of its rotation pulling the substance of the planet outwards during formation, when it rotated much faster and was softer. I’m not sure how much contribution the current centrifugal effect has on it. Nonetheless the deviation from sphericality in our case is only 0.3%. In Vesta’s case, the asteroid is kind of tangerine-shaped and its oblateness is around 22%. Also, its equator is elliptical too. An object whose gravity is so low (2.5% Earth’s, which is somewhat lower than that of Ceres) is able to have higher irregularities on its surface, and therefore Vesta also has a mountain which is almost the highest in the system – Rheasilivia is the biggest crater and unlike those on Ceres has a central peak, in this case two hundred kilometres across and is twenty to twenty-five kilometres high, comparable to the Martian Olympus Mons. The crater surrounding it is relatively enormous too, at five hundred and five kilometres diameter or roughly a “πth” of the circumference. In other words, the crater is actually wider than the asteroid in one of its dimensions, and in a way the asteroid could be looked at as simply the site of the crater. As such the rings of streaks may make a lot of sense as ejecta, although I don’t know for sure that’s what they are.

The streaks, known as fossæ, are troughs in the surface encircling the asteroid at the equator. They include Divalia and Saturnalia, the former being larger than the Grand Canyon and twenty kilometres deep. This scale reflects Vestan low gravity, which allows absolutely larger features which give worlds of this size an almost cartoonish or “cute” appearance, with exaggerated features which look out of scale to humans like the big eyes or other features of an animated or cartoon character. The fossæ are grabens, that is, valleys caused by faulting between which the surface has dropped, caused by the impact of the object which formed Rheasilvia. The central belt of Scotland is an example on Earth. Divalia is around ten kilometres wide and 465 kilometres long, making it four times as long but only a quarter as wide as the Lowlands. The fossæ collectively are in the top twenty largest rift valleys in the system. Earth is actually the world with the most large rift valleys, although the very largest is on Venus. Earth’s largest is the Atlantic. Saturnalia Fossa is associated with Veneneia, a crater overlapping with Rheasilvia and only slightly smaller than it at 400 kilometres diameter. Saturnalia is thirty-nine kilometres wide and 365 kilometres long, possibly longer because its end was lost in shadow when Dawn surveyed the asteroid.

Although Vesta is near Ceres and other asteroids relative to the scale of the system, it’s still pretty remote considering its size. If you were living on Vesta, it would take a lot of resources to bring anything you didn’t already have to you. It’s like a desert island in a way, and has resources of its own. Geologically, it’s stony, unlike Ceres which has a lot of clay stuff going on, and is more like an inner system planet in its composition than Ceres is. It’s like a mini-rocky planet, although it isn’t large enough to be a dwarf planet.

About six percent of meteorites falling here on Earth are from Vesta. This can be determined because they are exactly the same colour, that is, their spectra are identical. This is more common than any other body, even though Cynthia is so close and there are also meteorites from Mars and Mercury, both of which are closer most of the time. The light grey colour of the asteroid can be seen in the meteorites too. Vesta’s brightness is partly due to it being large and close, but it reflects more than 42% of the sunlight falling on it, which is more than any of the large planets except Venus. This is because it hasn’t been subject to “space weathering”, which occurs on bodies with only weak magnetic fields and is caused by the attraction of solar wind particles to the surfaces, where they vaporise iron on the surface, turning it into a dark coating. This means that Vesta is either low in iron or has an appreciable magnetic field. Since samples of the asteroid are readily available, it’s possible to test this by seeing if magnetic specks within the meteorites are lined up, and they do seem to be, meaning that the asteroid must be generating the same kind of dynamo-style magnetic field as we have on our home planet.

This brings up the issue of the innards of the place. NASA’s Dawn mission was able to collect data implying that unlike Ceres, Vesta does indeed have an iron core, which is about 110 kilometres in diameter, which means it must have melted early in its history. There are so many meteorites from the asteroid that it’s possible to mount a similar kind of museum exhibition about its mineralogy as it is of Earth’s, actually better in some ways because its smaller size means relatively deeper samples are available than from Earth. As mentioned previously, the most common such asteroid is known as HED – Howardite-Eucrite-Diogenite. I’ve covered these on the linked post. Incidentally, I love the fact that some are called “diogenites”, which suggests they’re either very messy inside or don’t require much in home comforts. It’s just a shame they aren’t called damoclites, like they’re hanging over us waiting to wreak havoc, although that would be rather geocentric.

I ought to mention the Snowman. This is a short chain of relatively large craters, named from bottom to top of this image, Marcia, Calpurnia and Minucia. Together they form a shape reminiscent of a snowman. The method of relative dating of craters works well here as impacts will cause newer crater borders to impinge on older ones rather than the other way round, making it possible to reconstruct what happened, though without much of a timescale.

Like Ceres, Vesta is a protoplanet, though one not given much chance due to being close to Jupiter. Had it been able to form into a proper planet, what can be seen today would’ve been buried deep within its core, or rather, its substance would’ve been distributed throughout the planet’s interior. It has a relatively short day for an asteroid of five and a third hours and a tilt of around 29°, meaning that again unlike Ceres it has seasons.

One of Asimov’s earliest short stories was called ‘Marooned Off Vesta’. It’s actually his first published story, from March 1939, where a spaceship is hit by a meteoroid, leaving three survivors in a fragment with only enough air for three days but the entire water supply for the spaceliner. They’re near Vesta, where a few people have settled. It was followed up by a later ‘Anniversary’ story twenty years later where the survivors have a reunion and discover something surprising about what they salvaged. It dates from the time when the asteroid belt was thought to be strewn with hazardous débris, which is now known not to be so.

That’s it really. Vesta is the largest proper asteroid, the brightest asteroid and, most remarkably, the source of more meteorites which reach Earth than any other body in the Solar System. That’s it really.

Titan

Sometimes I think I should just go through all the major bodies in the Solar System on this blog because so many of them suggest themselves. This post in particular has an interesting origin. I sometimes try to generate blog ideas using an AI technique called a generative adversarial network. When I did this yesterday, I put a number of post titles in and was rewarded not with a list of titles but some body text which looked like it came from a post about Titan, Saturn’s largest moon, and it actually made quite a bit of sense. I’ve since deleted it, but it was the inspiration for this.

When the Voyager probes reached Saturn in the early ’80s CE, I was really surprised to find that Titan had a mainly nitrogen atmosphere like Earth’s which was actually denser than ours. I don’t know if it was news to astronomers or not. Titan had been thought to be potentially the largest moon in the Solar System, but I think it was the Voyagers that established that it wasn’t. Unlike the Jovian satellite system, which has four planet-sized moons and a large number of assorted objects orbiting it at various distances, Saturn has one very large one, several medium-sized moons and an even larger number than Jupiter of much smaller ones. At first glance, Titan seems to be a bit anomalous, and it is in fact quite unique in the Solar System in being the only moon with a substantial atmosphere. Other moons do have tenuous gaseous envelopes, but Titan’s is thousands or millions of times thicker than any of the others, and even thicker than ours. Among the terrestrial planets, only Venus has a more substantial atmosphere.

In fact there are ways in which Titan is the most similar world to Earth in the entire system. Not only is its atmosphere of similar composition, being mainly nitrogen like ours, but it’s also the only place other than here where bodies of liquid, including lakes and rivers, can be found on the solid surface along with islands. There’s even a similar division as we have here between fresh and salty water in the form of methane containing ethane and purer methane, and it also rains there and there are forms, including pebbles, which are shaped by liquid erosion. The last is also true of Mars but there it’s more historical. At the same time, the surface gravity there is about the same as on Cynthia (“the Moon”). This would seem to make Titan this weird floaty place where not only is the gravity weak, but also the atmosphere is thick enough to slow the fall of really quite massive objects. Dust particles float in our air. On Titan, they could be at least the size of grains of sand and do the same. The surface level pressure of Titan’s atmosphere is over 1½ times ours at sea level, but is not merely fifty percent denser than ours because the gravity is also lower. It’s actually something like nine times the density, with correspondingly higher buoyancy, further enhanced by the lower pull downwards. This would make any winds much stronger at the same velocity.

The surface temperature averages out at around -182°C, although it also varies a fair bit. Because Titan is orbiting near Saturn’s equatorial plane and Saturn is itself tilted, its seasons are determined by its planet’s orbit more than its own, as it usually the case for moons. This gives it seasons around 7½ years long. A spacecraft would need to stay in the vicinity for almost three decades to observe all the seasonal changes. There is also photochemical smog formed in a similar process to that in urban areas, and this reflects some of the heat from the Sun back into space, making the moon colder than it would be if its atmosphere were clearer, but methane is also a greenhouse gas so the overall effect is that it’s warmer than a bare moon such as Dione would be at that distance from the Sun. Like Earth, Titan has a layer which absorbs ultraviolet light high in its atmosphere. Like many other moons Titan’s spin is locked to its planet, giving it a day lasting just over a fortnight. Saturn would appear ten times the diameter of the Sun from Earth in Titan’s sky, except that this would only be visible above the haze. However, eclipses would only occur rarely because of the angle at which Titan and Saturn orbit the Sun. The rings would also be practically invisible because it’s so close to their plane. This is true of most of the moons of Saturn, sadly, and they only become visible from the outer satellites, by which time the planet looks quite small. Eclipses would occur at the same time of day and only at the equinoctes, their maximum duration being about five hours.

Although there is no direct evidence for life on the surface of Titan, it resembles the larger moons of Jupiter in having a watery mantle like the rocky mantle of Earth, which could constitute a habitat for life as we know it. However, thicker layers of water may be less suitable for life because they’re further from energy sources and may not have very concentrated salts. The fact that this is a possibility, however, raises the question of whether inorganic life forms might exist in the magma mantles of rocky worlds, which I’ve mentioned elsewhere. The surface is less promising, at least if one expects a polar solvent and organic life, because there simply are no liquid polar solvents on it. To explain, some liquids consist of molecules which are more positively charged on one side and more negatively charged on the other. A very good example is water:

This difference in electrical charge allows water to dissolve a very wide variety of substances, which are then able to react with each other. There are plenty of other polar solvents in existence, including ammonia:

and formaldehyde:

All of these molecules are quite common in the Universe, although water is the most. All of them have a certain asymmetry to them which renders them polar. However, the melting point of ammonia is -77°C and that of formaldehyde is -19°C, so neither would be liquid on Titan. The liquids which are plentiful there are ethane and methane, both of which are non-polar and not good solvents. Hence they can cycle around like water, evaporating from the lakes into the clouds which then become saturated and fall as rain, and possibly snow, forming streams and rivers, and generally behave rather like water, but that’s never going to contribute to biochemistry like ours, which is all we know.

One unusual chemical which is found on Titan is cyclopropenylidene. This consists of molecules made up of a triangle of carbon atoms, two with double bonds and linked to hydrogen atoms: C₃H₂. It has two free electrons and is therefore highly reactive. It’s unique to Titan in this solar system although it is also found in interstellar space. It’s of the kind of molecule which might form purines and pyrimidines in combination with nitrogen, which are the information-carrying parts of DNA and RNA – genes in other words. However, although such substances might form on Titan, they’re unlikely to get anywhere due to the absence of polar solvents, so the likelihood is that the chemistry of Titan is going to be constantly on the brink of producing life but never quite getting there, until that is the Sun heats up in thousands of millions of years time and melts the water ice. At that point, the whole moon will become a very deep ocean which will slowly boil into space, so life might just start briefly and then get cooked to death, but it’s not going to happen for something like fifteen hundred million years if it does. This could be taken as a salutary demonstration of the fragility of life in the Cosmos but it probably won’t be.

Other gases or aerosols in the atmosphere include propane, hydrogen cyanide, cyanogen, diacetylene, methylacetylene, carbon dioxide and carbon monoxide. All of these are at less than one part per million. Much higher is the six percent of helium present. All of the hydrocarbons are more concentrated than they are on Jupiter and Saturn. The moon orbits within a torus of rarefied hydrogen which has escaped from its gravitational pull but not from Saturn’s, extending in to the orbit of the next large moon in, Rhea. The list of gases includes a couple which contain nitrogen and are, I’m guessing, the result of reactions with cyclopropenylidine. Hydrogen cyanide in particular is a vital step on the way to amino acids and DNA. The hemispheres differ in colour, the northern hemisphere being darker and redder at the time of the Voyagers’ encounters.

NASA considered Titan so important that of the two Voyager missions, Voyager 1 was sent over Saturn’s south pole to bring it as close to Titan as possible, which sent it out of the ecliptic (the plane of the Solar System) and ended its mission to the planets. Had that failed, Voyager 2 would’ve been sent on a similar trajectory and Uranus and Neptune would still never have been visited. I’m personally glad that this didn’t happen although there’s not a lot going on with those two compared to the two larger gas giants. This means that the two spacecraft are heading in very different directions and are already very far apart. Voyager 1 is heading towards the red dwarf star Gliese 445 in Camelopardalis, which is towards the next arm in of the Milky Way, although it isn’t currently in the position where it will be encountered and it will pass 1.6 light years from it in four hundred centuries’ time. Voyager 2 will pass near Ross 248, another red dwarf in Andromeda, and that name of course indicates that it’s heading out of the Galaxy in the approximate direction of the Andromeda Galaxy. Voyager 2 is further out than Voyager 1 right now by about nine times the distance of Earth from the Sun.

The Cassini-Huygens mission made Titan the first moon to be landed on by a terrestrial space probe. Huygens sent back this image of the surface:

The geography of Titan is now quite well-known thanks to both the Cassini-Huygens mission and the Hubble space telescope. One bright area, about the size of Australia, that springs to mind is Xanadu, and one of the seas is called Ligeia Mare. Unlike the lunar “seas” or maria, these are real bodies of liquid. Another sea is called Kraken. The seas can be seen to glint in infrared sunlight from orbiting spacecraft, or rather the one orbiting spacecraft which has been there to detect that. There are wind-blown streaks of particles hundreds of kilometres in length. The rivers have carved out canyons. There are flash floods and torrential downpours interspersed with long periods of drought. Craters are practically absent due to liquid and wind erosion.

Economically speaking, Titan is a potentially useful place. It has easily available hydrocarbons on the surface in vast quantities for use in petrochemical industries and as fuel, whether or not that would be environmentally desirable. These resources, unlike the vastly greater ones on and in the gas giants, are also only weakly anchored to the moon gravitationally, although there is a thick atmosphere above them. However, the atmosphere itself is a potential resource of the same kind. Whether that’s desirable is another question entirely, and of course I believe in orbital solar power, which would be much easier to achieve than acquiring resources from this moon. Nonetheless this formed the basis of Arthur C. Clarke’s classic 1976 novel ‘Imperial Earth’, where a third-generation clone of the original governor of Titan travels to Earth to have himself cloned again and celebrate the US quincentennial. This is kind of Clarke’s equivalent of Asimov’s ‘Bicentennial Man’, written to celebrate that event. Another prominent science fictional reference to the place is found in Kurt Vonnegut’s ‘The SIrens Of Titan’, which inspired the Al Stewart track of the same name. This novel was pieced together at a party in a few hours off the top of Vonnegut’s head. It’s the first work of his, as far as I know, to feature the Tralfamadoreans who appear much more prominently in ‘Slaughterhouse Five’. Although it is a good novel, the moon is not very prominent in the story and its characteristics don’t drive the plot. As far as I can recall, the world’s richest man Niles Mumfoord has become trapped in a ‘Chrono-Synclastic Infundibulum’ on the way to Mars and is now distributed in a spiral stretching from the Sun to Betelgeuse, becoming manifest on bodies as they cross its path. On Titan, however, the spiral is in perfect sync with its orbit and therefore Mumfoord is permanently manifested there, meaning that he effectively lives on the moon full-time. He is able to see the past and the future since he’s no longer localised in space-time. However, this is not the main plot of the novel, although Mumfoord does influence events. A major theme in the novel is that of free will and determinism, which kind of links back to yesterday’s post. Here’s Al Stewart’s take on it:

For some reason I’ve never been able to understand, the novel is used on risk management courses. The book also has the catchphrase “I was the victim of a series of accidents, as are we all.”

There are two successful SF novels simply entitled ‘Titan’, one by Stephen Baxter, the other John Varley. Both are too optimistic in their timeline. I haven’t read either, but the Baxter novel forms the second volume of his NASA Trilogy, whereof ‘Voyage’ is absolutely awesome. That I have read. I seem to remember the film ‘GATTACA’ ends with a mission to Titan but on the whole I regard cinematic SF as a minor and inconsequential cul de sac compared to the main written tradition. I wish it wasn’t though.

Leaving fiction behind, Titan’s magnitude from here maxes out at 8.2 which is something like eight times too faint to be seen by the naked eye (and maybe a hundred or so for me because of my poor eyesight), meaning that alone among the Saturnian satellites it can be seen through binoculars with at least 60 mm aperture. Right now it’s in Capricorn and very close visually to Saturn itself, meaning that it might be easy to identify but on the other hand might be obscured by the planet’s glare. That’s the real Titan, discovered in 1655 by Christiaan Huygens, hence the name of the lander. I always think it’s important to anchor astronomy in what you can actually experience personally, but since I live in England and have terrible eyesight this is unlikely in this case. Nobody will ever go there of course, but they could and it wouldn’t be that difficult, and there’s even a crass commercial reason for doing so. Long after we’ve become the victim of a series of accidents ourselves in some easily avoidable but still inevitable way which nobody could be bothered to do anything about, life might just flicker into being briefly in the last days of the Solar System, just before being boiled to death. So that’s something at least. And after all, not taking any risks is the greatest risk of all.

Living On Pluto

(c) Ludek Pesek 1980, will be removed on request

Several of the planets, or former planets, in this Solar System have a kind of iconic symbolism to them. Saturn is the “classic” planet with the ring round it. If you want a symbol of a planet, it serves well, mainly because otherwise a symbolic planet would just be a circle with no particular significance. Mars and Venus benefit from being next to Earth, Venus being the “planet of love” and Mars the “planet of war”, which is why we get invaded from Mars a lot in old sci-fi. Saturn, Uranus, Neptune and Pluto have all also been seen as the “outer limits”: as new discoveries were made, each of them was demoted from this position. In ‘Last And First Men’, Olaf Stapledon has the human race move to Neptune to escape the Sun’s increasing radiation about an æon from today, and although he acknowledged the existence of several planets beyond Neptune, he was writing just before Pluto was discovered and hence his Neptune occupies that rôle right then. Saturn worked very well in this niche because of its prominent rings, forming a kind of pale around it which reinforce the idea of limits. But for many of us alive in the last two-thirds of the twentieth Christian century, Pluto fills that slot.

Pluto has a remarkable astrological history which makes me wonder about the nature of that approach as opposed to the science of astronomy. Astrologers have been known to call Pluto “Lowell-Pluto” to distinguish it from the other astrological Plutos, Pagan-Pluto, Wemyss-Pluto and Thierens-Pluto, each named after their respective astrological advocates. The first of these is associated with Scorpio, like the Pluto we’re most familiar with, and was designated in 1911, nineteen years before Pluto was discovered. Wemyss-Pluto is far out, with a sidereal period several times that of Pluto as we know it, of 1 566 years, and rules over Cancer rather than Scorpio, and Thierens-Pluto is a renamed Osiris, a hypothetical planet paired with I*s*i*s (not sure what search algorithms do with that sequence of characters sans stars), and is one of four trans-Neptunian planets. All of these are known as hypothetical planets in astrology, and some have been given ephemerides (tables of their movements and conjunctions etc.). I won’t cover all these in enormous depth, but just want to observe that it’s interesting that astrologers “discovered” Pluto under that name long before it officially received it. Traditionally Scorpio was ruled over by “Negative Mars”, which makes sense because of the red giant Antares – “anti-Mars” – in that constellation. Negative Mars is nocturnal, feminine and negative as opposed to the Martial attributes of diurnality, masculinity and positivity. In astrology, there is a negative planet for each positive one, also referred to as feminine planets, although as I understand it this idea is not currently used.

Astrologically, Pluto is a disrupting and disturbing influence in keeping with the original idea that there had to be a massive planet beyond Neptune which was perturbing the orbits of planets further in, and also Pluto is a bit of an oddball, considered as a planet, because it isn’t a gas giant, unlike the four planets beyond the asteroid belt. Besides that, its orbit brings it closer to the Sun than Neptune for a dozenth of its year. Being associated with the underworld, partly because of its name, it also has associations with crime and “degeneracy”, and also obsessions. The era of its discovery is also considered significant. There have been attempts to write an extra piece for Holst’s ‘The Planet Suite’, composed before its discovery, which to my uneducated ear sounds appropriately atonal and modern, perhaps like Charles Ives or Messiaen.

Pluto, then, is Ultima Thule. Ultima Thule is the most distant location for the Greco-Roman world and it isn’t clear if it’s a real place. The Orkneys, among other islands, have been suggested as its real world equivalent. The original name was Thule, but it became metaphorically associated with the most distant possible place, hence “ultima”, meaning “last” or “final”. The back of beyond, in other words. The name Ultima Thule was also applied to a very distant trans-Neptunian object, 486958 Arrokoth, visited by the New Horizons probe after Pluto. It’s also given a name to the sixty-ninth element, thulium, I’m guessing because it’s the rarest of all the stable rare-earth elements, or was considered to be so at the time of its discovery. Thule was also used in Nazi ideology as the name for a far northern original homeland of the Aryan folk, and due to that association the name is no longer used for the object encountered above, Arrokoth, which was named officially by a Pamunkhey tribal elder in a ceremony in November 2019.

The “Ultima Thule” idea clearly has great power, and for a long time Pluto was a modern version of this notion. For instance, in ‘Not The Royal Wedding’, one of the ‘Not The Nine O’Clock News’ books, Brezhnev’s share of the royal wedding cake was described as the size of “a microbe’s frisbee seen through the wrong end of a telescope well beyond Pluto”, i.e. something very small indeed, and also distant. This is of course just one of countless examples of “Pluto as metaphor” used between 1930 and 2006, in which it has the attributes of being very cold, dark and distant. In fact this doesn’t quite work as well as might be thought, but before I go into that it’s fair to observe that one reason Pluto is such a potent symbol is that very little was known about it for a very long time, allowing all sorts of thoughts to be projected onto it from a great distance, with little accountability in a way, because it seemed unlikely that anyone would ever find out much about it.

I can’t help thinking that if the International Astronomical Union had decided to demote Pluto earlier, it would’ve been less likely that New Horizons would ever have been sent there. It was launched only seven months before the decision, and plans must have been underway for many years before that, so the mere act of changing Pluto’s status right then probably wouldn’t’ve been enough to do it, but had that happened long before, or if Pluto had never been considered a planet, I don’t believe the mission would’ve taken place. It’s fine to send a spacecraft to some Kuiper Belt objects, and also interesting and useful, but I don’t think it would’ve been good publicity for NASA to do that if it had never been regarded as a planet. The sheer distance probably makes it seem like an excessive mission to the minds of many non-astronomical folk, and it might therefore be associated with the idea that it was a waste of money. Nevertheless, we got a mission and I’m very happy personally that we did.

The surface temperature of Pluto is -226 to -240°C. Although this is colder than Uranus, that rather than Pluto is now deemed the coldest planet in the Solar System. NASA gives a temperature of -233°C. There’s no denying it’s cold. Only three elements would be gaseous at that point: hydrogen, helium and neon, although on a hot “day” fluorine would be close to achieving that. However, it’s still above the ambient temperature of almost all the Universe, which is -270°C, and of course well above absolute zero. There’s a remarkable story by Larry Niven of an astronaut who has frozen on Pluto but whose nervous system becomes superconducting during the day when the temperature gets high enough and is therefore still conscious, waiting perhaps centuries to be rescued, unable to move, which sounds like a recipe for madness or Hell, rather appropriately for a planet named after the kind of the underworld. Not a fiery Hell though.

It’s often said that the Sun is just a star from that distance. That is true, because it’s forty times as far as Earth from it, meaning that it wouldn’t show a visible disc to the naked eye, but on the other hand the Sun would still be hundreds of times brighter than Cynthia at its brightest, and would illuminate the dwarf planet about as strongly as the light we experience just after sunset. The surface wouldn’t look poorly-lit to us there. There would also be the light from Charon, a relatively extremely large and close moon, which is locked into the same position in the sky at all times, and is therefore invisible from the other side, and of course the other moons.

The coldness of Pluto has sometimes been represented in paintings of its surface in the form of the likes of snow and icicles. Whereas this communicates, mildly, the conditions there, it seems unlikely that it ever actually snows there at all. On Neptune’s moon Triton, the nitrogen atmosphere snows in the eighty-two year long winter. A point needs to be made here about Pluto’s climate and the influences on it. Pluto is not strongly illuminated by the Sun, but has a very eccentric orbit and a considerable axial tilt. Because of the weak radiation at that distance, the tilt, which would normally strongly influence the weather and seasons, such as they are, is less significant than the highly elliptical orbit. The axis tilts between 102° and 126°, which can also be thought of as being 54° and 88° but rotating in the reverse direction to most of the planets, and this means it has overlapping polar and tropical zones rather than polar, temperate and tropical ones. It sounds a bit weird to talk about Pluto having a tropical climate, and this is only relative as of course the maximum temperature at the equator at midsummer during its closest approach to the Sun is still enormously colder than the midwinter temperature at our own South Pole, which is true in fact of every planet from Jupiter outward though not necessarily their moons, but on Pluto water is effectively a kind of rock anyway so it’s not like we’re talking about rain and snow. Also, water ice is not the main constituent of the surface but frozen nitrogen with some methane and carbon monoxide. It’s easy to think of the carbon monoxide as a poisonous gas, but again, since its freezing point is -205°C, once again it’s something of a technicality that it happens to be toxic to us life forms living thousands of millions of kilometres away on a world so hot that we have oceans of molten rock, comparatively speaking.

Pluto’s day lasts getting on for a week. 6.4 days is a more accurate figure. The star that is the Sun would therefore be below the horizon in some places for more than three days at a time, and because of the highly tilted axis it would be in the sky for over a century, followed by more than a century of night. And it would in fact look very different when it wasn’t there because the night would be dark like ours, though perhaps lit by an extremely large and close moon in the sky, permanently hanging in the same position.

What, then, would it be like to live there? There is actually a more pressing question here: what would be the point of living there? Why would anyone bother? It took New Horizons nine and a half years to reach it and it takes five hours to send a signal at the speed of light over that distance, so people are not really going to be having real time conversations with anyone on Earth, or for that matter Neptune. There seems to be no practical reason at all to go there. Jupiter is a rich source of hydrogen and helium, Mars is relatively nearby and might once, or maybe even still, has life on it, but living on Pluto wouldn’t be much different from living in a space habitat that far out with the added difficulty of making it hospitable rather an building a friendly environment from scratch. There’s also a serious lack of useful resources within easy reach, and the surface gravity is extremely low at only a fifteenth of hours, meaning that unless something was done to maintain muscle mass, bone density, cardiac health and the like, living there would be a life sentence. You’d never be able to return to Earth, assuming you’d come from here in the first place. I think probably the main motive would be to do something extreme, a little like walking to a pole. It’s a Ranulph Fiennes-type thing to do. I can imagine the rest of the human population of the Solar System rolling their eyes at people choosing to live on Pluto and wondering what the heck the point of it all was.

This is not to say that the place has no merits. Its orbit is sufficiently large that the Centauri system would actually just about visibly shift position in the sky through the year, although only people who lived to 120 would be able to experience that and it’s hardly noticeable. There may be at least two active volcanoes there, Piccard and Wright near the south pole. There may also be a very deep internal ocean of water, which could conceivably have life in it. The whole world is smaller than our moon at 2376 km diameter, giving it a surface area about the same as Russia and a little larger than Antarctica. The micronation of Aerica claims part of Pluto as its territory, which seems to be another “Ultima Thule” thing, and the Empire also claims a made-up planet called Verden.

In some ways, the world is quite rich in resources, if by “resources” you mean the likes of water and oxygen. You’d never go short of those. However, if you wanted metal or many other minerals essential to life, you might get a bit stuck unless you took them with you and kept them in a closed cycle. Nitrogen is fine, but there’s the usual issue with phosphorus and possibly even sulphur. If the ocean exists and there is any cycling between the mantle and crust, there might be some heavier elements in the form of salts where water ice outcrops exist. There are nitrogen glaciers fed by the thin atmosphere precipitating out in the “winter”, whatever that is, which tend to smooth out craters. Unlike elsewhere in the Solar System, this ice would be soft and gelatinous. There do appear to be winds of some kinds because there are streaks of red material. It isn’t clear what that red material is, because it isn’t tholin. You could even get something like fossil fuels from the place because there’s methane ice on the surface.

What I have in mind, then, is a kind of horizontally-oriented rotating wheel oriented somewhere either in sunlight lasting a century or so, or in a region where the day-night cycle is about six days. It would need to rotate to keep the inhabitants healthy. It could be warmed by burning methane or hydrogen, and there would be no concern regarding sources of water, oxygen or nitrogen, but other materials, including metals, would be sparse and this suggests that the base would need to be made out of some kind of synthetic material, which I would call plastic except that this makes it sound like it’s weak and flexible whereas I have something much tougher in mind. There would be relatively little risk from ionising radiation because there’s nowhere for it to come from.

But as to whether there would be any point, apart from proving it’s possible, I do not know.

Mercury and Bepicolombo

Boy Mercury shooting through every degree

The B52s, ‘Roam’, (c) 1989 CE

Most people, if they wanted to associate music with the planet Mercury, would probably either think of Freddie Mercury or Gustav Holst’s Planet Suite. Not me of course, because I can’t think of the obvious. It seems that this song has erotic innuendo which totally whooshed over my head, but that still doesn’t exempt it from being associated with Beppicolombo today. So far as I can tell, there’s nothing particularly special about today’s encounter compared to the series of other encounters which the probe will undergo over the next few years, but it’s also true that Beppicolombo is only the third spacecraft ever sent to the planet in question. The first, Mariner 10, flew past in 1974 and erroneously reported the presence of a moon, and I think that was also the one which established that Mercury didn’t simply show one face to the Sun all the time. Certainly this is what was reported in the popular science books and articles I read at the time. It also detected a strong magnetic field, which is apart from Earth the only planet in the inner solar system with one.

MESSENGER was the next probe, whose mission took place in the first half of the 2010s. The problem is that Mercury is difficult to reach because spacecraft have to be moving relatively fast and because it’s near the Sun the gravity of the star will overwhelm that of the planet at a low altitude above the surface, since it’s also the smallest and least massive major planet. This would, incidentally, make the presence of any moons hard to maintain. But Mercury is not just a clone of Cynthia even though the two seem quite similar, and even are to some extent.

Mercury and Earth are the densest planets in this Solar System. They also both have strong magnetic fields. The surface gravity is close to that of Mars, but because it’s physically smaller and a lot hotter it has much more difficulty holding onto an atmosphere, which is extremely thin and consists of what to us would seem like a bizarre array of gases such as calcium, sodium, potassium, hydrogen, atomic oxygen, helium and molecular oxygen along with water vapour. The hydrogen and helium are captured from the solar wind by the magnetic field and I presume the water vapour is from ice in polar craters. Because it has hardly any axial tilt, there are craters near the poles, such as Chao Meng-Fu, which are in permanent darkness at their bottoms, where the ice resides. The metals are forced away from the surface by the Sun and form a tail so many millions of kilometres long along the orbit that they are something like an eighth of the way round before they become undetectable. This feature is shared with Jupiter’s moon Io, which also has a sodium tail. However, it seems a bit of an exaggeration to dignify the sparse atoms and molecules of gas hanging around near the surface as an atmosphere, since they never collide with each other like they would in an ordinary gas, but do the same kind of things as they do on Cynthia, ricocheting off the surface, bouncing up and down and so forth.

So far as I know, Beppicolombo has no colour cameras. It was also going to deposit a lander, which it didn’t do in the end because it would’ve been too expensive. Both of these decisions, if the first is true, strike me as bad PR. Colour photos of Mercury and data, and hopefully images, from the surface would surely be really impressive, and it’s worth doing those just to engage the public, but apparently not.

Just a quick infodump to get all this out of the way. Mercury is intermediate between Cynthia and Mars in size, is the densest planet in the Solar System other than Earth and has a lemon-shaped orbit, which is again the most elliptical of any solar planet known. It rotates once every fifty-seven days with a negligible axial tilt and orbits once every eighty-eight. It isn’t as hot as the solid surface of Venus during the day, at around 400°C, but is the coldest planet in the Solar System at night at -200°C. It has a fairly heavily cratered surface and it can be difficult to distinguish whether a small portion of the surface is Cynthia or it. It was instrumental in corroborating the General Theory of Relativity which predicted that its orbit shifted its angle by 1.2 arcseconds each time, but before Einstein it was thought that there was an even closer planet to the Sun, named Vulcan, which explained this orbital perturbation. There are Mercury-crossing asteroids, including the relatively famous Icarus. Astrologically, Mercury often goes retrograde, meaning that it appears to reverse its direction in the sky, because it’s orbiting inside our orbit and will inevitably dip towards or fall away from the Sun from our perspective. There are even some professional astronomers who have never seen it because it stays so close to the Sun and is smaller and further away than Venus along with reflecting less light. It can, however, be observed in broad daylight with the right telescope if you know where you’re looking, though this would be risky to the eyesight. I think that’s it as far as what I assume “everybody” knows about the planet.

The reason it used to be thought that Mercury always faced the Sun was that it rotates three times for each two of its years and its synodic period (the time taken between successive closest approaches to us) is almost exactly two Mercurian days.

The above map was made by the Greek astronomer Antoniadi in the mid-twentieth century. Although like many such maps it’s pretty inaccurate, it does at least record the presence of Caloris Basin in the southeast as Solitudo Hermæ Trismegisti. Some of the features on Mercury have quite odd names. For instance, there’s a series of cliffs called Pourquoi Pas Rupes and the twentieth longitudinal parallel is called Hun Kal after the Mayan for twenty. Caloris Basin is somewhat similar to the Mare Orientale on Cynthia or Asgard and Valhalla on Callisto, being a vast impact crater, but Mercury doesn’t really have maria like Cynthia.

There should as far as possible be a link between people’s everyday experience and scientific phenomena. This is difficult with Mercury because it’s almost invisible to most people. If you believe in Western astrology, you’re probably aware of Mercury retrograde at least, and Mercury does transit the Sun more often than Venus from where we are. This is where Mercury can be seen to cross the Sun’s disc, meaning that it might be projectable using a telescope. They happen in May or November, and occur much more often than Venus at about once every seven years on average. Sometimes Mercury only passes over the edge of the Sun. The planet is both smaller and further away than Venus when it transits. Venus I have observed doing it, and it gave me a major impression of the sheer size of the Solar System that even the nearest planet, practically Earth-sized, looked that tiny when it was closest to us. Mercury is kind of more like Cynthia orbiting alone. One significant issue with Mercury’s transit compared to that of Venus is whether the black drop effect would be visible. When Venus, with her thick atmosphere, crosses the limb of the Sun, there’s a kind of fuzzy line joining the shadow to the rest of the sky, and this is often attributed to that atmosphere, but in fact Mercury, with no significant atmosphere, exhibits the same effect even when observed from space, thereby eliminating the factor of our own air. Hence it doesn’t seem to be due to a planet having an atmosphere. This is also significant for detecting planets orbiting other stars and whether they have atmospheres. Incidentally, it’s also possible to observe changes in light level caused by transits by observing moonlight, although of course it’s very subtle. There will be a simultaneous transit of the two planets in the year 69163, and before that Mercury will transit the Sun during a partial solar eclipse in 6757.

Meteorites very occasionally reach us from Mercury. One was found in the northwestern Sahara containing chromium diopside crystals, which are green, but may not be Mercurian given known facts about the composition of the surface. Although this is not the meteorite, this is what chromium diopside looks like:

By Rob Lavinsky, iRocks.com – CC-BY-SA-3.0, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=10151574

It reminds me of lunar olivine, and like it, is a semi-precious stone. This is an actual chunk of the meteorite itself:

It’s a magnesium calcium silicate, and can become asbestos. There are faults on the surface of the planet, meaning that like Earth and no other planet in the system, it’s tectonically active, which in turn means that if this mineral is indeed from Mercury, it could have been transformed to asbestos on its surface. However, this may not make it intrinsically more hazardous to potential astronauts (and there will be none) than moondust, which is also potentially quite harmful, being jagged and unoxidised until it comes in contact with a terrestrial organism and this rock may not be from Mercury anyway. I would imagine that the extremes of temperature there have considerably weathered the terrain.

The interior is largely taken up by a core rich in iron and the magnetic field may be caused by the same dynamo effect as here, since the Sun’s tidal forces are much stronger there than here, or it may be residual from formation or the result of being directly magnetised by the solar magnetic field. I don’t know if this is true, but I would expect the crust to be higher in heavy elements than here, and for them to be more exposed due to the lack of weather and oxygen, although I would also suppose that their distribution would tend not to be in the form of specific ores due to the lack of liquid water. There are no Van Allen belts because the magnetic field is too weak in comparison with the solar wind. Heat could also be expected to weaken the magnetosphere.

Hun Kal is at 20° because the prime meridian had been decided approximately as the subsolar point at the first perihelion in 1950, and when Mariner 10 got there that location was on the night side. At the time, presumably it had been thought that that point was permanently at noon with the Sun directly overhead.

Caloris Basin is so-called because it’s directly under the Sun at closest approach, and is therefore the hottest area on Mercury. It has about the same area as Mexico, which by scale is similar to the size of Antarctica compared to Earth, and is surrounded by a ring of fairly small mountains. It’s many times the size of Mare Orientale. Around the exact opposite point is an area of so-called “weird terrain”, which is hilly and thought to result from the conduction of seismic vibrations around the planet from the impact into a focal point there. Just as on Earth the type and deflection of quake waves is like an X-ray of the planet, revealing where the solid core is, so does the terrain on the opposite side from Caloris Basin reveal Mercury’s internal structure, since much of it was formed by the shock waves. Superimposed on that are the ejecta splashed up by the impact, which also travelled all round the planet.

Unique to Mercury are the “blue hollows”. Although these are somewhat mysterious they seem to be linked to the evaporation of solid material and resemble craters to a limited extent except for showing none of the usual signs other than being dents in the surface. There’s no rim, central peak or ejecta. They are of course blue, light blue in fact.

The planet seems to have shrunk by seven kilometres since its formation, which has led to ridges appearing on the surface. I wonder if this is to do with substances such as potassium and sodium with low sublimation points being lost to space during the day, which I also think might explain the hollows.

There’s something about craters, though, which I find somehow tedious and deadening. I could go on and on about the craters there at this point but it would probably bore you stiff. And the question there is why? Mountains are not boring after all, are they? This links into my post about whether Cynthia is boring. I suppose the thing about mountains is that you can imagine climbing or exploring them. But a crater such as Arizona Meteor Crater seems very interesting to me, as does the Chicxulub Impact which wiped out the non-avian dinosaurs. Maybe it’s just me. So that concludes this bit of the post.

Only three spacecraft have ever been sent to Mercury. The first of these was in 1974, Mariner 10. For over three decades this was the only source of images of the planet and only just over a third of the surface had been photographed. By a stroke of luck, Caloris Basin was at the terminator at the time, meaning that the weird terrain was also, but this also meant that the full extent of the basin was unknown. It also flew by Venus. Mariner 10 was the first spacecraft to use the gravity of another planet to aid its trajectory and also the first to send back live TV pictures of another planet, although I would expect “live” to be a fairly misleading description of something whose bandwidth was 117.6 kilobaud. This is actually pretty impressive when you consider modems of the turn of the millennium were only half that fast. Because it used the gravity of Venus, it didn’t need to carry much fuel, as that was only needed to make fine course corrections, which it did by attitude adjustment nozzles firing nitrogen along the edges of the two solar panels. It used a sunshade to protect its instruments against the intense radiation at the orbit of Mercury. Like many other space probes it was designed to orient itself using the Sun and the bright star Canopus. It carried a TV camera connected to a Cassegrain telescope, which gave it a long focal length in a short tube, able to image things in ultraviolet as well as visible light. The resolution was a total of 640 000 pixels, which is 800×800 if that’s the aspect ratio decided, each pixel being represented by a byte. There was also a radiometer able to measure temperatures to within 0.5°C, a plasma detector which discovered Mercury’s magnetic field, a magnetometer, a second telescope to detect charged particles which also detected the magnetic field and an airglow spectrometer which was able to detect the glow of sodium in the atmosphere and beyond. This is actually bright enough to be seen by the human eye, so looking into the sky on Mercury an astronaut would perceive a faint orange tinge. Another instrument was able to detect gases by absorption of light.

When I look at something like that, it always makes me think that technology even that long ago was a lot more advanced than we give it credit for. Although it obviously wasn’t using internet protocols, this probe was able to transmit wireless data over millions of kilometres at twice the rate of a dial-up modem two dozen years later, and 800×800 resolution in eight-bit colour, which is what this and many other spacecraft had in conjunction with Mission Control, wasn’t achieved in affordable PCs until the late 1990s either. On the other hand, the processing power of these machines was very limited. Although I can’t track down the details, Mariner 10 cannot possibly have been using a microprocessor to do its stuff and even the Mars rovers only used CPUs which went out of date in about 1980. This isn’t so much a criticism of them as the hardware which exists now. If you can build a spacecraft which goes to Mercury and does all that stuff without even using a microchip, and if later on very modest processors indeed can be used to achieve even more, why are we now using so much more advanced computers to do much less impressive stuff?

We had to wait until the next century for the next probe, MESSENGER. This is named after the messenger of the gods, Mercury, but it actually purports to stand for “MErcury Surface, Space ENvironment, GEochemistry, and Ranging”, clearly a backronym. MESSENGER managed to image the entire globe, as it was designed to go into orbit around it. It detected the first clear images of the blue hollows, which Mariner 10 had only managed to get rather blurry pics of. It imaged the whole of Caloris Basin, measured the concentration of calcium over the planet anddiscovered that the magnetosphere was at twenty degrees to the axis of rotation. It also imaged a “family portrait” of the whole Solar System and was eventually crashed into the planet. It described one of the more recent and to me baffling trajectories which seem to involve a large number of orbits around the Sun while the spacecraft gradually approaches its destination, therefore taking several years to reach it. If you think about it, no destination within our orbit ought to take more than half a year. I’m sure there’s an answer.

Bepicolombo is of course the current mission. It’s joint European-Japanese and I’d expect it to be a lot more sophisticated again, although I’m not sure what that would mean. Like MESSENGER, and presumably all contemporary probes, it’s doing the same kind of weird orbit which takes a very long time to get anywhere. I really want to know what that’s about. It comprises a photographic orbiter and a magnetosphere investigating satellite – two different satellites and is named after the scientist who came up with the slingshot idea for Mariner 10. Since its name is in the title, I’d better go on about it.

It’s flown by Venus twice, the second time on 10th August this year (2021) and has just flown past Mercury for the first time, only seven and a half weeks after Venus. I think this may be the fastest journey between planets ever. It will fly by the planet a further five times, then go into orbit round it on 5th December 2025. It has an ion drive, using xenon. It’s about time really – the concept behind these, which is to ionise atoms and accelerate them out of the engine using linear induction and can theoretically accelerate up to over 160 000 kph, is decades old and even though it has one I have my doubts about whether it’s really using it in earnest or it’s just there to be fancy. It isn’t being used as the main propulsion system and will only be used with a very low thrust, and there are also chemical rockets. One of the instruments was built in Leicester, which makes me happy. It isn’t the first time either.

Mercury is seen as breaking a pattern because for the other terrestrial planets there is a relationship between their density and their size, such that the smaller a planet is, the lighter the materials it’s made from are. This applies to Cynthia as well. However, Mercury is an exception. It’s also particularly close to its (and our) sun and this is a possible clue as to what happened in other solar systems, which also have very close planets. There’s a hypothesis that Mercury was previously a gas giant but has lost all its atmosphere because it fell so close to the Sun, but I think this idea is deprecated now. It also has an unusual orbit, which is also strongly influenced by the other planets in the Solar System. For all these reasons, the European Space Agency and the Japan Aerospace Exploration Agency are quite interested in it. It’s also searching for asteroids inside Earth’s orbit. The bandwidth is slower than Mariner 10’s was, I presume because data compression is better nowadays.

The Mercury Surface Element, which was cancelled, would’ve been a 44 kg disc ninety centimetres across to land 85° from the equator near the terminator, battery-powered due to 40% of the landscape there being likely to be in shadow and it would’ve had a camera. I just think it’s really sad they didn’t do this.

Right: that’s it. This is unfortunately later than I’d hoped as I missed the actual first rendezvous, but it is what it is.