Anyone who reads this blog regularly will know that I don’t call that luminary in the sky “the Moon”, but Cynthia. This is because I think it’s important to acknowledge its existence as a body in the Solar System in its own right rather than simply an adjunct to Earth, and because calling it “the Moon” is like calling Earth “the Planet” without having any other name for it. Also, Cynthia is arguably not actually a moon at all. Looked at from the Sun’s (yes I know) perspective, Earth and Cynthia weave in and out of each other’s paths as they orbit and if Pluto is excluded, Cynthia’s mass is a far greater fraction of Earth’s at 1/81 than the moon of any other major planet. The pull of solar gravity on Cynthia is greater than Earth’s.
This leads us into the “nut” situation, where the thing which we think of as the quintessential example of a category turns out not to be, such as peanuts, almonds and so forth, because maybe “the Moon” is not a moon at all. Further, we get to the predicament of claiming that Earth has no moon at all, and that “the Moon” is something else. This sounds absurd. However, the question arises of whether Earth has any moons now, or had any in the past, or perhaps had more moons which collided and became Cynthia, and again whether these “moons” counted as moons.
One thing which comes to my mind is the Chicxulub Impactor, which wiped out the non-avian dinosaurs sixty-six million years ago. Is it conceivable that that orbited Earth for a while before it crashed down onto it? There isn’t any scientific reason to suppose either that it did or didn’t, assuming it to be an asteroid rather than a comet. If it was a comet, it’s unlikely to have done so as most of its substance would’ve vaporised if it had orbited us for long. It may be worth considering the Chicxulub Impactor separately than just in this post, because the situation is complex and research has suggested different things. Also, in a sense there’s nothing special about it, as this planet has been repeatedly hit by massive bodies in the current Phanerozoic Eon (the time since hard-shelled animals evolved). It’s unlikely that the scientific method can be applied to the paths of any of these objects to determine whether or not they were previously in a long-term orbit about our planet. A side issue here, which I’ve mentioned previously, is the possibility that Earth has had rings at some point due to asteroids approaching this planet but not hitting, and breaking up close to the surface but still beyond the atmosphere. Again, all that can be said about this is that it’s plausible. Evidence might involve finding a higher incidence of meteorites around the equator or climatic differences, but those would both depend on the position of the continents at the time.
In fact it looks like rocky inner planets tend not to have moons if our system is anything to go by. Neither Mercury nor Venus have any, though in the past both were thought to have one at different times. Mariner 10 was briefly thought to have discovered a moon of Mercury in March 1974 but it was actually the star 31 Crateris. Venus was also once thought to have one, named Neith, repeatedly observed by astronomers from 1650 onwards but never detected during a transit. It is odd that it was supposèdly seen so many times even though it doesn’t exist. It was considered to be proportionately the same size as Cynthia and to orbit perpendicular to the ecliptic, which is in itself quite peculiar. It’s now thought that most of the apparent observations were merely stars near the line of sight. Inner planets in general have a bit of a problem keeping moons due to the fact that the Sun’s gravity is relatively greater and the radius in which a moon can exist is small. In fact Cynthia is a good example of this because it orbits separately from Earth.
Mars, of course, has two small moons, but its case is a little different. It orbits closest to the asteroid belt, enabling it to capture asteroids, and being further from the Sun gives it more opportunity to do so. However, its moons orbit unusually close to it and one is unstable and will be broken up by tidal forces in a few tens of millions of years, becoming a ring. I suspect Mars has had a series of moons due to its proximity to a large number of asteroids. If Earth were closer to the belt, it seems likely that it too could acquire at least temporary moons. As it stands, asteroids are mercifully sparser at our orbit and the “price” we pay for this is that we have no captured moons.
Another aspect of this, already noted in the case of Cynthia, is that orbits look different depending on where you see them from. As far as we’re concerned, Cynthia orbits us once a month and it’s very simple, but from a solar perspective the orbits of the two bodies are braided, somewhat like the coörbitals of Saturn. The same applies to some of the possible moons of Earth. The classic example right now is Cruithne (“kroo-ee-nyer”). This asteroid takes a year, actually 364 days, to orbit the Sun in a roughly similar looking orbit interlocking with Earth’s, but from Earth’s perspective it describes a centuries-long path consisting of various alembic and horseshoe shapes as it moves around us. It’s been described as our second moon, but this isn’t really true, and there are a number of other bodies with similar relationships to both Earth and the Sun. It has a diameter of around five kilometres and its orbit is not entirely stable.
In 1846 an astronomer called Frederic Petit, of Toulouse, reported the discovery of a moon which orbited this planet once every two and three-quarter hours with an apogee of 3 570 kilometres and a perigee of only 11.4! At the time, it wasn’t known how to account for air resistance but even back then scientists were sceptical of a moon which dipped thoroughly into what we’d now call the troposphere. As was fashionable at the time, Petit claimed this accounted for irregularities in Cynthia’s orbit around Earth. His results were never reproduced, but he did end up having his idea mentioned in Jules Verne’s 1865 novel «De la Terre à la Lune». This spurred a lot of people into looking for it, and notably William Henry Pickering, who predicted the position of Pluto and claimed to have detected plants growing on Cynthia, actually looked for a secondary moon of Cynthia itself, which he presumed would have to be a maximum of three metres in diameter.
In 1898, the Hamburger Dr Georg Waltemath claimed not just one moon but a whole string of them. One of them, he claimed, was approximately a million kilometres away, took almost six months to orbit and had a diameter of around seven hundred kilometres. He claimed it had been seen in Greenland during the night period of winter in 1881, and further that it would transit the Sun. He and some companions reported that an object about six arc minutes in diameter did indeed do so, but it so happened that some other astronomers were observing the Sun at the same time and only saw sunspots, so that was the end of that. It may be an illustration of how easily one can be drawn into perceiving something by another’s enthusiasm, conviction or charisma, or maybe just of the power of suggestion. The largest of these moons was named Lilith by an astrologer and an ephemeris was prepared.
Now there are thousands of artificial objects in orbit, to the extent that they threaten future space missions. These are in a sense moons in their own right, though artificial ones. These could also provide evidence for the presence of other moons because of their gravitational influence on their orbits. It has been claimed that this happens, but the data used, at the end of the 1960s CE, were insufficiently accurate to judge. Hence although it seemed that something was detected, it was within the margin of error in the measurements, and it can’t be concluded that there’s anything there.
One thing which definitely does happen is that small asteroids occasionally get temporarily captured by our gravity. Kamoʻoalewa is the name of an object which appears to be a small chunk of Cynthia which is temporarily orbiting Earth. Like many other small planetoids in the system, it’s quite red, but the particular shade of red is dissimilar to those of various asteroids so it’s likely to have come from our main satellite. It appears to be about forty metres across, although it may be very irregular, and actually does describe the kind of orbit attributed to Neith, perpendicular to Earth’s orbital plane. However, although it circles us, it’s also beyond the distance where Earth is the main gravitational influence on it. Like Cruithne, Kamoʻoalewa is what’s known as a quasi-satellite, taking almost exactly the same time to orbit the Sun as Earth does and therefore staying close to this planet, but from Earth’s perspective appearing to travel around us in the opposite direction to our orbit in a kind of bent closed curve. The phenomenon is a little like retrograde Mercury. Mercury occasionally appears to be moving backwards in a loop from our perspective, but it’s because of the relative speed and positions of the two orbits around the Sun, except that it’s exaggerated by the asteroid’s extreme proximity.
There are something like five other asteroids with this kind of relationship with Earth, and incidentally Earth is not unique in this respect. As mentioned previously, there are also the Lagrange points of both the Earth-Sun and terrestrial-lunar systems. Analogous positions associated with other bodies are common, particularly Neptune, as I’ve already been into. There are both clouds of dust occupying the terrestrial-lunar Lagrange points and Earth trojans 60° ahead of or behind Earth in its orbit. No trailing trojans have been detected so far but there are at least two leading ones, one of which has a diameter of three hundred metres. I covered much of this in Antichthon (apparently I called it “Counter-Earth”).
Many, perhaps most, NEOs are analogous to extra moons. A group I haven’t mentioned yet is the Amor asteroids, named after the asteroid Amor and also including Eros. These come within 0.3 AU of Earth, or 45 million kilometres, and approach the Sun closest outside our orbit with a period greater than a year. This means they always orbit outside our own path round the Sun and are therefore not Earth-crossers. Four dozen Amor asteroids come within seven and a half million kilometres of Earth’s average distance from the Sun. Of them, Eros has actually been visited by a spacecraft. Most of them cross Mars’s orbit, putting them in the asteroid belt proper at their greatest distance from the Sun.
To finish then, Earth currently has no permanent (other) moons, as might be expected given the status of the other inner planets, and in fact we arguably have no moons at all because of Cynthia’s peculiar nature. If we were closer to the asteroid belt we might acquire some. This raises the question of how many otherwise Earth-like planets have any moons and whether this is significant for the evolution of Homo sapiens, but as I’ve said before, this series is not going to focus on life because everything does that. Interestingly though, although it hasn’t been demonstrated scientifically, it’s quite plausible to suggest that we have had other moons in the past and just as a closing comment, some people believe Cynthia was originally two bodies which collided, partly explaining the difference between the near and far sides.
Right now, the chances are that everyone reading this is a basic human like me, living on Earth, or at an outside chance, in low Earth orbit (who am I kidding‽). Consider that condition. What are the chances that that’s what you are if human life goes on and our descendants fan out into the Galaxy? I’ve gone into this many times of course, and the Doomsday Argument, as this is called, is flawed, but it’s worth going into it again for the purposes of applying it to the situation in which the human race finds itself today.
I’ll just recap briefly. There was a guy who visited the Berlin Wall in the 1960s and predicted that it would come down at approximately the time it did through estimating the probability of where he was in the total number of visitors to the Wall, using only probability, statistics and the time since it had been put up. His name was Brandon Carter, and he later applied a similar argument to estimating how long the human race has left based on the assumption that one is about half way through the total number of human births. When I did this calculation based on my own date of birth, the 1977 CE estimate that 75 thousand million people had been born before me, which covered the past six hundred millennia and a doubling period somewhere around three decades, as it was at the time, it gave me the result that the last human birth would take place around 2130. There are various silly aspects to this argument. For instance, if Adam existed and had made this calculation just before Eve appeared, he would conclude that the human race would be most likely to end with Eve’s death. By the way, I am not fundamentalist and therefore do not believe Eve and Adam ever existed. I just want to make that clear.
Although this is not a particularly marvellous argument, I do think a similar one works fairly well in one particular area, as I’ve mentioned before. It does in fact seem fair to assume the principle of mediocrity about one’s own existence. In that respect, it’s fair to assume I’m a typical example of a human and have been born at a time when prevailing conditions are “normal”, i.e. that the fact that I find myself living at a time when we have only ever lived on one planet and are not cyborgs to a greater extent than Donna Haraway claims. Transhumanism is not the usual human condition and there are neither orbiting space colonies nor settlements on other worlds. If we even settled ten other worlds they would only need a population over the whole period humans dwelt on them about equivalent to the current population of this planet for us to be outnumbered, and that’s a very modest estimate of how human history would unfold if we began to live elsewhere than on this planet. It would be more likely for there to be numerous settlements, either in the form of space stations or people living on other habitable planets. Say there were a million planets settled, which is still a conservative estimate for the number of suitable planets in the Milky Way, and they were settled for only a thousand years each. That’s an æon of human life on other planets. For it to be more probable for us to be here now than there then, it would need the population on each of those planets to average out at less than seven dozen. That is clearly absurd, so we have to conclude that as a species we will never settle on any other planets or build any permanent space habitats, or that our existence here and now just happens to be fantastically impossible.
For this to be the case, we have to conclude that our efforts to go into space are also only ever going to be very minor to non-existent, something which is confirmed right now by the fact that only twelve people have ever visited another celestial body. Even that was difficult because one crew didn’t make it. Now we’re supposed to try again with the Artemis Project, the current plan to go back to where Apollo went. Incidentally, I’ve long thought that one of the issues with the conspiracy theory is that getting there is only equivalent to going round the world ten times. Patrick Moore had a car which had gone further than twice that distance, and the average flight crew probably notch that up in a couple of weeks. Not that it wasn’t an amazing achievement. But humanity didn’t go on to do anything else afterwards, is the issue.
We’re confronted with a problem in the current moment then. It’s looking like there will be more people walking about up there in a couple of years, but if that happens it looks suspiciously like this version of the Doomsday Argument will have been refuted. But before I go there, I want to talk about Brooke Bond.
In 1971, Brooke Bond brought out a series of collector’s cards on the Space Race which started with Sputnik 1 (let’s Russ that up a little: Спутник-1) and proceeded through the various early satellites, planetary missions and the like up to Apollo and then past into the future. I collected the cards and got the book to stick them in. It must’ve been 1971 because it had the pound marked in both shillings and “p”, and they only did that in that year if I recall correctly. Anyway, it was from this publication that I learnt of the plan to send a human mission to Mars via Venus launching in the late ’70s. I remember looking at the years and thinking “1979” and “1980” looked really strange and futuristic, like the numbers on the public library date stamp which had yet to be used. But yes, there was a tentative plan at that point to send astronauts to Venus and Mars which everyone seems to have forgotten. There have in fact been a very large number of such proposals, but I didn’t know that at the time:
Actually, looking at this I realise I got it the wrong way round. They were going to visit Mars first and then do a Venus flyby. My confusion arises from the fact that there were so many different plans to do this. The Russians even considered a Venus mission to be launched in the early 1960s. I remember eagerly awaiting this, in full expectation that it would happen, and the dates passing with nothing to show for them, and how disillusioning it all was. This was a feature of my life at the time. When they found CFCs were destroying the ozone layer and that carbon dioxide emissions were causing climate change, I was convinced that they’d just go, “right, lets take the fluorocarbons out of aerosols and stop using fossil fuels”, and it’s the same kind of disappointment, from which you can see that I wasn’t your typical space nerd or environmental activist, because I suspect rather few people were equally enthusiastic about Green politics and astronautics, but that’s who I am. There is a seamless disappointment there. It’s all part of my same imaginary world, and it was very hard to cope with at the time. I can’t believe how slowly everything except IT progresses, and it’s also weird that IT did advance that quickly compared to everything else. I have certain theories about that, not conspiracy theories but something else, which I’ll leave for another time.
The space-based Doomsday Argument, which I’m going to call “Space Doomsday”, can easily explain why this didn’t happen, although maybe “why” is the wrong word here. The immediate reason the Mars mission didn’t happen was budgetary cuts to NASA in 1970. However, considering our lives as a relatively random sample of human history, we are aware that it’s improbable that human space exploration will ever make much progress, or we probably wouldn’t be here sitting on this single planet where we originated. It’s possible but improbable. The idea that we will in fact end up doing this isn’t ruled out by the fact. It’s similar to the idea that if you have lung cancer, you have probably been a long-term tobacco smoker. That’s something you can reasonably conclude about someone’s previous life given their current condition, although it may also be that they got it from passive smoking or asbestos exposure, for example. It isn’t a dead cert, but it’s probable. Hence it’s probable that something would happen to prevent people from landing on Mars, assuming of course that the expansion into space follows such activities, and in that sense Space Doomsday has predictive power, or perhaps forecasting power. We know we’re here on Earth, so we can reasonably believe the human race does not have a spacefaring future. A slightly less reasonable conclusion is that there will be no human missions to other celestial bodies in our future.
This could potentially lead to a weird version of “Moonlanding” denial conspiracy theory. Obviously I accept humans landed on Cynthia six times owing to not being delusional in that respect, but suppose Artemis happens. I am wedded to the idea that humans will never go there again because of Space Doomsday, so if they do go there I’m tempted to deny that due to it not fitting in with my world view, and the same applies to any planned Mars mission. Am I perhaps a tinfoil hat conspiracy theorist in the making? If someone believed in Space Doomsday in the 1960s, would they have ended up denying the Apollo missions were real? If the news that Artemis does succeed appears in the media and we see pictures from the lunar surface and the rest, it’s fair to conclude that we probably have gone there in a second batch of missions, but one’s belief in Space Doomsday could be so strong that it would lead to K-skepticism. For me, that would be motivated by depressive thinking, but others might have more positive reasons for doubt, such as the idea that it isn’t appropriate for so much money and resources to be spent on space missions when there are enough problems on this planet to be addressed.
Speaking of this planet, there could be a link between these two major sources of disappointment emanating from my childhood. Alternative futures are possible from these. In one, we simply don’t go into space much. Perhaps robotic probes become ever more sophisticated, take over from us, and colonise the Galaxy themselves, or maybe there’s just no impetus to do so and we all become more focussed on whatever’s going on down here. This is a relatively positive future compared to the other one, which is that this apparent lack of concern for environmental disaster simply wipes out the human race in a few years, before anyone gets the chance to go to Mars. This chimes with the apparent, though egocentric, forecast that the last human birth will occur around 2130.
The interesting thing about Space Doomsday is that it seems to have predictive power. For instance, it predicts that there will be a reason why nobody will go to Mars or the Artemis project won’t come to fruition. In fact, Artemis has indeed met with problems. The plan is for at least eight missions, the first two of which won’t involve a lunar landing. Artemis I is an unoccupied test of the spacecraft which will orbit Cynthia and return, splashing down on Earth, next year (2022). Artemis II happens the year after and involves a crew orbiting Cynthia, which would be the first time anyone has left cis lunar space since 1972. 2024 is expected to see humans back on the surface for the first time since Apollo, and a series of missions after that will involve building a lunar base for permanent habitation. This looks like the point of no return for human settlement in space, although it might just not happen or not go any further. But in order to be “scientific” about this, I need to define exactly what I mean by the statement that humans will never settle on other worlds or establish a permanent presence in space. That initial statement looks wrong for a start because of the International Space Station, which is a permanent presence. Otherwise, I’m moving the goalposts, and I might say after Artemis I, “well I never said the hardware wouldn’t work” or after Artemis II, “well I never said nobody would ever leave cis lunar space again” and so on. I need to be more precise, and base it on evidence.
My claim is based on the idea that the total number of human births is likely to be at most 150 thousand million. More than this and the chances of living now rather than later in history fall below fifty percent. In fact, therefore, it’s possible to forecast from this position that the total population of space will always be less than seventy five thousand million minus the population still on this planet. In fact if it were ever close to being that high, that would seem to herald the extinction of the human species for probability-related reasons, which suggests further that there will never be self-sufficient space colonies or that some perhaps solar-related disaster will befall life in this Solar System.
Artemis is supposed to lay the foundations for the eventual exploration of Mars. This in itself means it’s unlikely to succeed, not because that’s over-ambitious but because it means it does in fact appear to be a stepping stone to people living permanently off Earth, which either can’t happen or is likely to end in disaster, or at best peter out. Hence it can be expected that there will be major snags in the program. Now it’s difficult to tell whether I’m seeing patterns where there are none, as any major long-term complicated undertaking is likely to meet with the occasional problem. Thinking again of our hypothetical Space Doomsday person living in the ’60s, they might focus on the Apollo I fire and the Apollo XIII disaster as signs that it wasn’t going to work, that there would turn out, for example, to be insurmountable safety obstacles to strapping three guys into a seat on top of a hundred metre column of high explosive. I mean, who’d’ve thought it? But there were six successful missions as well as more successful translunar incursions (excursions?). It is probably true, speaking from my deeply uninformed position, that the risks taken on those missions were much higher than they would be today, and presumably are on the Artemis program, but maybe not. I confess to not paying much attention to Artemis because I don’t want to be disappointed again, so I don’t know much about it.
There are sound economic reasons for returning, including the presence of metals such as titanium more easily accessible than here and, if fusion ever happens, and that’s another thing which seems infinitely deferred, helium-3 in the soil, and water is now known to be available, in the form of ice in the parts of polar craters in permanent shadow, freeing a base from the necessity of a water supply from Earth. It was detected by the Clementine mission in March 1996, in Shackleton Crater.
The spacesuits for Artemis have been delayed, it was announced this August. This will prevent a 2024 landing, since they won’t be ready until April 2025 at the earliest. That puts it later than the next presidential election, and if for example Trump is re-elected, which unfortunately is still possible it seems, he could cancel the program before then. The current space suits are not intended to be used for extensive periods on the lunar surface, hence the need for new ones. One reason for the delay is budget cuts and another is the pandemic. But you could look at it, rather unscientifically, as a curse or fate. There is reason to deduce that something will always stop it happening because it’s possible that we can be confident nobody will ever go there again or to Mars at all. The details of the cause are apparently not available, but right now they seem to include Trump, the pandemic and budget cuts.
The Artemis program involves the building and transport of infrastructure and equipment separately from the crewed missions. This is a factor in its demise. If it was just about astronauts visiting without setting up a permanent base, it could well go ahead as that’s a less significant step in establishing a foothold elsewhere in the Solar System. Hence the crewed lunar orbital mission is more likely to happen, although this is also a step on the way. It would also be more likely to happen if it wasn’t supposed to be a preliminary to going to Mars. There was a plan, decades ago, for the first astronaut to arrive to start putting together a permanent lunar base, which it’s possible to predict wouldn’t happen for the same reason.
I’m not going to deny that a lot of this post is motivated by depressive thinking, although I’m not actually depressed just now. To counter that, I want to point out that depressive realism helps one perceive unpleasant truths, one of which appears to be that our descendants are trapped on this planet forever. And I’m not even saying that Earth is not a wonderful and beautiful place. It’s for this exact reason that humans should move many of their activities, and for that matter bodies, into space, off this planet, to preserve it and allow it to recover. Moreover, there was always going to be positive fallout from space travel, such as the Overview Effect, the Spaceship Earth concept, the discovery of the possibility of nuclear winter, the reminder Venus gives us of how easily climate change can get out of hand, not to mention the various technological benefits. Nonetheless, some people would see being stuck here as a positive thing, and it has positie aspects. It means, for example, that there is no escape from the effects of pollution, reduced biodiversity and anthropogenic climate change, except that maybe there is for the rich and powerful but not the poor and oppressed.
So wouldn’t it be nice if we had a lunar base, went to Mars and built space colonies for the people left here on Earth?
Before I get going on this, I want to explain the noun game with this title. Humpty-Dumpty’s dictum, “When I use a word, it means just what I choose it to mean—neither more nor less”, is clearly absurd, which is one reason why non-standard personal pronouns are such a struggle. I try to avoid using the term “the Moon”, because I think it encourages small-mindedness. It isn’t “the moon”. There are hundreds of moons in this Solar System, many of which have proper names. Ours also has proper names, in the form of what it (or she?) has been called in various different cultures, not in the sense of “that big hunk of rock up there” but in terms of deities associated with her. In a sense, we don’t appreciate her enough because there are two contrary forces involved in not giving her a name. On the one hand, it gives a sense of her being special in a way which excludes other special moons, such as those of Jupiter and Saturn. On the other, it paradoxically makes her generic: she’s just “a moon”, the nearest one. When we look at that luminary in the sky, we fail to appreciate that she is both special and not special, and whatever else we do we fail to appreciate her individuality (I’ll come to gender in a minute).
Although there are many deities associated with our sleeping satellite and there’s a good case to be made for calling celestial bodies by non-Western names such as Sedna, the fact is that she’s been associated with several Greco-Roman divinities, including Diana, Selene, Artemis and of course the name I chose for her, Cynthia. Using a name which is in common use as a human given name may seem odd at first but it does happen the other way round with other names for celestial bodies in English-speaking cultures, as with Venus Williams, so it isn’t unknown. Of the names listed, Diana and Cynthia are the most prosaic, although I’m sure there are people out there called Artemis and Selene. The big issue, of course, is that every time I mention Cynthia to people who might not have heard me do so before, I have to explain by doing something like putting “(‘The Moon’)” immediately thereafter, which is quite inelegant.
The gender issue is a side thing. Six of the seven known planets besides Earth in the Solar System have masculine names, as did Pluto when he was a planet. There’s a risk of it sounding like I’m objectifying women by using “she” for Cynthia the satellite, but I do this as part of my aim to reduce the association with sexes and would therefore equally refer to the likes of Mercury and Mars as “he”. Also, in a sense we are all “it” because underlying the interpersonal and emotional elements of our relationships, we are also conscious objects. It is, however, annoying that there are so many masculine celestial bodies.
And I’ve used that word again. “Celestial” bothers me too. Earth is in space. All there is is sky. Space is as much below us as above us. Everyone knows this of course, unless they’re Flat Earthers, but it’s easily forgotten and we have a tendency to revert to the sandwich model of the Universe we probably grew up with as a species. Earth is a celestial body – a heavenly body if you like.
The main theme of this post, though, is to consider Cynthia as a heavenly body among others that we know, that is, other planets and moons in our particular star system, and decide whether she’s boring. That is, if we were observing her as a moon of Venus, say, and sending space probes there and the like, what would we think? Or as a planet in her own solar orbit (which she nearly is)? It definitely seems that some worlds are more interesting than others, and it is quite diverting to have a large world orbiting us at close quarters, whatever it might be. Sarada is very captivated by seeing her sometimes, and I wish I could see past what I think might be disappointment that people haven’t got further into space, or rather further from Earth, than they currently have, because for me that taints it. But imagining Cynthia replaced with Io for instance, with that moon staying in her current state, which arises from the tidal forces acting upon her in the Jovian system due to the proximity of other satellites and the fact that she orbits within the planet’s magnetosphere, it would seem much more interesting stuff would be going on there, such as the volcanic eruptions and the multicoloured surface. Compared to that, our own moon just seems to sit there not doing very much. One of the people who went there said that if he wanted to see something which was exactly the same colour as the surface, he’d go out and look at his concrete driveway. It’s mainly various shades of grey, which is not exciting. Colour isn’t everything of course, and Apollo XVII is known for having discovered orange soil at Taurus-Littrow. Also, one of the most remarkable things about Cynthia is her maria and their distribution – the smooth lava plains which were deposited after the Late Heavy Bombardment which scarred the whole globe with craters, as it did elsewhere in the Solar System, such as on Callisto. The oddest thing about the maria is that until the 1960s CE, nobody realised there were practically none on the far side which can’t be seen from Earth. There are small smooth areas at the bottoms of craters, but no extensive plains. Nobody knows why.
Another mysterious feature is Transient Lunar Phenomena, which I know I’ve mentioned before on here, but anyway. These are temporary changes in light, colour or other appearance, and have the distinction of being something Patrick Moore was the world expert on. Explanations include outgassing, meteorite impacts and statically charged dust being repelled from the surface. Most TLPs have been observed in craters with cracked floors or around the edges of maria. A whole third of them are observed around the crater Aristarchus. They’re difficult to confirm because the same area would have to be observed at the same time by different people, which doesn’t often happen. NASA monitors meteor impacts, which are sporadic but also occur more often around the times of the famous regular meteor showers such as the Leonids or Quadrantids, because the two worlds are in practically the same place.
There’s also an “atmosphere” of dust. Sunlight ionises particles on the surface and they become statically charged, as mentioned above, then fall down to the surface and may bounce. This is happening all the time, with the result that there’s a constant fine mist of dust constisting of transient specks of dust. Additionally there’s a real atmosphere, though very, very thin. It’s estimated that the Apollo engines temporarily added more to the local atmosphere than was there before the landings. There are about a thousand million atoms and molecules per cubic decimetre just above the lunar surface, which is so sparse as to constitute a high vacuum in terrestrial terms. It’s also a ballistic gas: the particles are so far apart that they hardly ever encounter each other and undergo the same kind of bouncing trajectories as dust does there. It consists of helium, which is I imagine the result of alpha particles getting ionised, argon, which is also common in our atmosphere, potassium and sodium, which are relatively high in our upper atmosphere, ammonia and carbon dioxide. In fact, the atmosphere is similar in many characteristics to our own as it blends into cis lunar space, i.e. it’s an exosphere, the difference being that it’s at ground level.
The distance and size of Cynthia are also quite remarkable. She’s proportionately the largest natural satellite by far of an actual planet in the Solar System, as opposed to Pluto whose satellite is considerably larger but is not officially a planet. The closest rival is Neptune and Triton, with a mass ratio around 750:1 compared to Cynthia’s 81:1 ratio compared to Earth’s. In the inner system, only Mars has moons and they’re captured asteroids and very much smaller. The other thing about Cynthia’s size and distance is that she happens to be exactly the same size as the Sun in the sky, which is unknown for any other moon seen from the surface of their planet, although I understand Callisto comes fairly close on Jupiter. This makes solar eclipses possible in the sense that the Sun’s visible surface can be perfectly hidden while still allowing the corona, the solar atmosphere, to be visible. This doesn’t always happen because sometimes Cynthia is too far away, in which case the result is an annular eclipse with the Sun’s surface visible as a thin ring. Eclipses do occur elsewhere but not with such a perfect match, and this is very improbable. Nor does it seem to be directly connected to the necessity for life as we know it to exist on this planet. Although we may well need a large moon, it needn’t as far as anyone can tell be exactly the right size for that kind of eclipse, and this fact has been cited as an example of a possible Easter Egg if it turns out we’re living in a simulation. It could also be thought of as a sign of divine favour. The other thing about this is that because we’re moving apart at about a centimetre a year, it’s a temporary situation which will end in several hundred million years and didn’t happen until a few hundred million years ago, although that was before complex multicellular life existed.
Although Cynthia is very likely to be important for the existence of complex land life on Earth, I don’t want to consider this in this post as this is about her, not life. Just briefly though, tides within the planet’s iron core act as a dynamo and generate the magnetic field which keeps ionising radiation away from our surface and she also has a rôle in stabilising the axis of rotation. However, as with the above considerations, these are things to do with the relationship between the two rather than Cynthia herself. Before I leave thisses orbit entirely though, it’s worth pointing out that she’s the result of the outer layers of the planet which became Earth getting “chipped off” through a collision, and as a result she’s less dense than Earth by a considerable margin. Interestingly, and that’s what we’re looking for, the large bodies of the inner solar system fall into two neat categories regarding density. Earth, Venus and Mercury are all something over five times the density of water, and Cynthia and Mars around three. I don’t know why Mars is less dense, although it may be to do with the increasing temperature as one approaches the Sun causing lighter materials to evaporate. However, there was once an alternate explanation of the formation of Cynthia, where she was formed along with Mars from an initial body whose remnants are found as Earth. This kind of means Mars isn’t so much a smaller Earth as a larger Cynthia with a proper atmosphere, which is a little depressing.
There is magnetism, although Cynthia as a whole has no significant magnetic field, individual parts of the surface do have various magnetic fields, which are based in the crust rather than the core. The field tends to be weakest under the maria, particularly Oceanus Procellarum, and strongest at their antipodes, so the far side is more strongly magnetic than the side we can see. There may also be temporarily magnetised regions when meteorites hit the surface and cause melting. This lack of a global field also means that helium-3 is likely to have managed to accumulate, which is important if anyone can ever get nuclear fusion power to work.
When I look up, I never see a face in Cynthia. In fact, I’d consider it to be somewhat disturbing to see what would amount to a giant skull orbiting our planet, so I’d say that was a blessing. What I do see, independently of the other cultures which claim to see something like this, is a rabbit. This is of course the Far Eastern intepretation, along with a similar native American view that it’s a horned toad (not the lizard but an actual toad with horns). However, I don’t think I see the same bits as corresponding to these for the far eastern and western (who are of course linked) cultures. I see Oceanus Procellarum as the body, Mare Imbrium as the thigh, Maria Nubium & Humorum as the feet, Mare Tranquilitatis as the head and Maria Crisium & Fecunditatis as the ears. As I understand it, the Far Eastern interpretation is more upright and makes Maria Nubium & Humorum a mortar, which may be because they tend to view it from a different angle. I don’t know how the Native American projection works, or indeed if there’s more than one version although I suspect there would be. Cynthia holds the distinction of being the first body to be recognised as celestial to have her features named, and of course the selenography, as it’s known, is known in much greater detail than the “geographies” of anything in trans lunar space, although that gap narrowed somewhat from the 1960s onward.
It’s been claimed that even experts can’t tell the difference between closeup images of Mercury and Cynthia in some areas, and the two bodies bear comparison. Were it not for the maria, a casual observer wouldn’t be able to tell the difference between images of the two, particularly if Mercury was compared to our satellite’s far side. I’m not sure this is so because up until fairly recently only one quality source existed for images of Mercury, the Mariner 10 probe which flew by in September 1974 (and incidentally, briefly appeared to show that Mercury had a moon, which is not so). Compare and contrast these two pictures:
Ignoring external clues, are these interchangeable? Much of the appearance of the two bodies suggests that there is a kind of “standard” small rocky planet, possibly found throughout the Universe, which looks like Mercury, and Cynthia is one of these too. Callisto is a fairly good example:
Although Mercury does have smooth plains, they’re the same shade as the rest of the surface and don’t stand out. Mercury’s surface gravity is close to that of Mars but there’s no substantial atmosphere, partly because the planet is smaller and this makes it easier for molecules to escape the gravitational pull. This higher gravity makes a difference to the appearance of the craters, because when meteorites hit Mercury’s surface, the ejecta and hummocky rings are closer to the centre than they are on Cynthia, and are also more crowded because the material kicked up doesn’t rise as high or go as far. Mercury’s surface is also a lot more varied than Cynthia’s, but I don’t want to get too diverted onto the issue of the planet as opposed to the satellite.
There are quakes, which have several causes. One is the impact of meteorites, and it’s becoming clear that this is a very significant aspect of the place. The other can be divided into several more detailed causes, including tides, which start deep under the surface, and changes in temperature causing rocks to expand and contract. All of them are very mild compared to earthquakes, but they are associated with TLPs. The total energy involved is much less than a thousand millionth of those here, because we have tectonic plates and continental drift and Cynthia hasn’t.
There are “mascons” in the centres of the maria. These are regions of higher density detected when spacecraft orbited during the ’60s. In fact, these are unusually pronounced on Cynthia compared to other bodies in the solar system and amount to variations in gravity of over one percent. This is actually a distinctive feature not directly related to her position or relationship with us. They’re thought to be buried asteroids which have been there since soon after formation.
The dust is definitely worth mentioning. It used to be thought that it might be so deep that there was a risk of astronauts sinking into it like quicksand, but it turned out to be quite shallow, and this has been used as evidence by young Earth creationists. It also gets everywhere and is an inhalation risk like asbestos. It’s never been exposed to oxygen or moisture, so it has different characteristics than the kind of dust found on Earth. It’s technically just very fine particles of lunar soil or regolith, so there’s no definite cutoff between dust and soil. Due to the lack of exposure to water or air, it’s more reactive when it actually does come into contact with living tissue or just a wide variety of substances with which it comes into contact, which makes it a health risk in ways which silicate dust here wouldn’t be, and it hasn’t been smoothed by erosion and is therefore more jagged and has a larger relative surface area over which such chemical reactions can take place. It can jam mechanical equipment and interfere with wiring, and it also becomes statically charged quite easily. It’s nasty stuff, but probably not unusual because the same processes which generate it, meteorite impacts (again!) and radiation gradually breaking up the rocks, and I presume variations in temperature which are much more extreme than they are here due to the almost non-existent atmosphere, will also be operating on Mercury and inner system asteroids, and that implies that there will be similar processes going on once again all over the Universe.
The rock itself resembles certain rocks found on Earth but here it tends to be much rarer because we have weathering and erosion along with continental drift. Here, it tends to be of Precambrian origin and is therefore most common in places like Canada. Unsurprisingly, the maria and highlands are of different composition. In the former, pyroxene is the most common mineral, at about fifty percent of the surface there, and is made up of calcium, magnesium, iron and silicate. It forms yellow-brown crystals. The other common minerals are olivine, gabbro, breccias and anorthosites such as plagioclase. Olivine has pale green crystals and is a mixture of silicates of magnesium and iron which doesn’t survive long on Earth’s surface but is actually the most common mineral here. It releases heat as it combines with carbon dioxide or water and is therefore a potential fuel for heating which is actually carbon-negative, and is found copiously on the surface – a good reason to go back there I’d say. Plagioclase is a feldspar found in the highlands and is also the most common Martian mineral. It’s light grey or blue, so I presume that when we look at Cynthia, that’s what we see away from the maria. It consists of a framework of silicate groups in which are embedded aluminium, sodium and calcium atoms.
Much of the rock and dust is composed of glass, which also acts as an adhesive binding together fragments of other minerals. This is again because of meteorite impacts heating the surface which then cools rapidly, and this makes me wonder whether the same is true on Mercury because it’s hotter during the day but just as cold at night. When I say glass, I don’t mean the sodium silicate used to make windows and bottles on this planet, although lunar glasses do sometimes contain sodium and usually, possibly even always, silicates, but they would be less pure than what we use as glass.
I don’t honestly know if this is interesting or not. It seems plausible that there would be semiprecious stones and crystals in some places, which is quite appealing. Olivine looks quite nice:
This is actually a gemstone, when it’s known as peridot, and can be cut as such:
However, these kinds of olivine are close to being pure magnesium silicate and I don’t know if that applies to lunar olivine.
The existence of crystals gives me to wonder if there are any objects whose formation resembles living things, such as dendritic patterns in rocks or something like desert rose gypsum. It seems unlikely though, since there’s no water to act as a solvent and the place is very uneventful. It’s also likely that if olivine became easily available, since it’s so common on the surface, that it would cease to be a precious stone and if it can be used as fuel it would more or less have to drop in price.
There are no carbonates or sulphates on Cynthia, and also no hydrated minerals. However, there is a little ice in polar craters, which counts as a mineral there more than it does here in a way. These are craters in permanent shadow, and the same is true on Mercury. There is a general problem with raw materials due to the importance of water in concentrating useful mineral deposits here on Earth. Although the metals are often there in some shape or form, they don’t seem to be in the usual readily-extractable ores found here, and this of course reduces the incentive for going back.
Thus far I’ve mentioned the maria, highlands and craters, but there are other selenographical features. For example, although the maria are not real seas, they are smoother than the highlands, darker and have “shores” like the real oceans and seas here have. This means in particular that they have bays and tend to flood craters, the former being craters on the border of maria. One famous example of this is the Sinus Iridum – the “Bay Of Rainbows” – at the northwest of Mare Imbrium. The maria themselves also have features, including craters which are more recent than their formation and other craters which have become submerged under lava when the maria formed, sometimes called “ghost craters”. Lunar domes are present, previously thought to be “blisters” which had not ruptured to form craters in the days before their formation was attributed to meteorite impact, but they are in fact shield volcanoes with central non-meteoritic craters. The most concentrated collection of these is the Marius Hills, which range between two and five hectometres above the surface of the mare in Oceanus Procellarum. Of course, just saying they’re in Oceanus Procellarum is a bit like saying a geographical feature on this planet is “in the Pacific Ocean”, but unsurprisingly they’re near a crater named after the astronomer Marius, who may have discovered the Galilean satellites of Jupiter although their name suggests he didn’t. Among the hills is a forty metre wide pit apparently opening into a lava tube or rille. Lava tubes are basically long, sinuous lunar caves which form when lava solidifies on the outside but continues to flow out of the hollow tube thus formed. Their roofs can later fall in, forming a channel referred to as a valley or rille. Rilles can also form when parallel faults allow the ground between them to fall, in which case they will be roughly straight.
There are also ridges on maria, formed from the contraction of cooling magma, and these are also found on Mars and other moons and planets. They’re officially known as dorsa. Catenæ are also common elsewhere and consist of chains (hence the name) of craters, formed when tidal forces cause meteors to break up before impact. My impression is that catenæ are not as common on Cynthia as on some other bodies in this solar system, but that may be my imagination.
And there are mountains of course, although here a problem arises. On Earth, the height of a mountain is easily expressed as above sea level, though this can be misleading as it makes Everest seem to be the highest, which it may not be because Earth is not perfectly spherical. On Cynthia, a fairly arbitrary decision has to be made which has been given different values at different times, involving deviation from a presumed diameter of a sphere. Height of the peaks above the surrounding surface is easy to measure because they cast shadows and since the angle of the Sun and the distance are both known, it can be straightforwardly estimated. Mountains can be isolated or parts of ranges. The tallest mountain is Huygens, at 5.5 kilometres. This is a little surprising, as one might expect a body with lower gravity to be able to form higher mountains, which would then be fairly immune to erosion due to the practically absent atmosphere. The highest possible elevation of granite on the surface would be something like eighty kilometres, so this is very much in need of an explanation in my mind, and I would guess it has something to do with there not being the same kind of mountain-forming processes on Cynthia as there are here. That said, Mars lacks them too and yet has a mountain over twenty kilometres high. Isolated peaks unlike anything found on Earth occur in the centre of craters.
So to conclude, is this interesting or not? Mere proximity enables us to observe features likely to be found everywhere, even on planets and moons gigaparsecs from here, but as a body Cynthia does have distinctive features too. The maria being confined to the visible side, the presence of mascons to a greater extent than in other known worlds and the presence of transient lunar phenomena are all interesting. The greyness and familiarity make her seem dull, but there’s more to her than might at first be supposed. If she were a continent, her surface area would be second largest, somewhat larger than Afrika, and maybe in a way that’s a profitable way to think of her. She’s like a seventh continent which happens to be in orbit around the rest, more drastically different from them than Antarctica is to the other five, or perhaps a feature of Earth like the bottom of the oceans, and she is interesting. If you could drive there, she’d only orbit the rest of us nine times, and Concorde could travel that distance in eight days, so she really isn’t that far away, and definitely worth going back to. But I can relate to the dullness.
A Box Of Chocolates 