highlands – A Box Of Chocolates

I’m revisiting this. A few mirs ago (I’ll tell you about that in a bit) I made a Martian calendar for the mir 214. I used the Darian calendar with the Rotterdam month naming system. This brings up the first issue: Mars cannot have real months because its moons take around eight and thirty hours to orbit, and its day lasts less than twenty-five. Therefore the subdivision of the mir – the Martian year – is fairly arbitrary although it can be more freely divided than if it had meaningful moons.

The compilation of the Martian calendar proved to be a bit nightmarish. I bought a new printer to produce the colour illustrations of the pages, and used the trusty old monochrome laser printer to do the rest. The latter did absolutely fine. The former was an inkjet, and reports of its capacity turned out to be a big overestimate. Since I’d worked out the price point based in that capacity being true, I ended up making a loss on every copy. Because of this, I ended up flinging the printer forcefully into the pantry in a fit of rage. Something has really got to be done about the scam that is the inkjet printer, but that’s another topic.

Due to the research I’d had to do to prepare the calendar, the point came when I felt probably more familiar with Mars than I am currently with Antarctica. I began to get a real feel for the planet which I don’t even have for Cynthia, and certainly more than any other planet or moon apart from Earth. It’s kind of like a cross between Cynthia and Earth. Alternatively, it could be looked at as an extreme version of Antarctica without the ice, or a dwarf version of Earth. Its terrain is divided into highlands and lowlands, with one largely monolithic example of each, meaning that unlike Venus with its several plateaux and similar size to Earth, it or Earth with its connected but somewhat separated oceans and six continents, it can be thought of as having a single continent and a single ocean, having in toto a surface area almost exactly the same as the total land surface of our own planet. However, it has a thicker crust and no plate tectonics. This is demonstrated by the area known as Tharsis, named after Tarshish, an old name for the Iberian peninsula.

As a child, I used to think Tharsis looked like someone had stuck a fork in Mars. It’s dominated and was formed by a series of volcanoes in a line with the largest volcano in the Solar System to the northwest, the famous twenty kilometre high Olympus Mons, previously known as Nix Olympica. These have contributed an enormous shield of solidified lava to the surface which on Earth would’ve become a chain of mountains or islands, as with Hawaiʻi, but because the Martian crust is stationary the rock has simply built up, and the lower gravity has allowed it to rise higher than it could’ve done here, and weigh down the crust to the extent that it’s caused a crack to form, known as Valles Marineris, a giant canyon stretching across something like a quarter of the planet. All of these structures dwarf their counterparts on Earth, and since Mars only has about half Earth’s diameter, they dominate the surface. When it’s midday at one end of Valles Marineris, the other end is in darkness and consequently winds blow along its length.

Here’s a relief map of the planet:

The lower elevations are blue, the higher ones red. Tharsis is the red blob on the right. One feature I haven’t mentioned yet is the great basin known as Hellas, which is the deepest dent on the planet and is almost deep enough to have liquid water at its bottom because of the density of the atmosphere there, although it doesn’t quite get there. This is the purple oval in the bottom right quadrant. It can be seen that if the planet was flooded there would be an ocean in the northern hemisphere plus a large lake in the southern. Maps of planets are quite confusing as the convention seems to have changed. Whereas previously south was at the top because astronomical telescopes don’t bother to turn the image the right way up (extra lens means loss of light), it seems to have changed to putting north at the top.

The regions of Mars have names like Chryse (Gold), Argyre (Silver) and Margaritifer (Mother Of Pearl). There was also a complete revolution in nomenclature due to the discovery in the mid-1960s CE that the canals were optical illusions. Before that, Mars was considered to have canals, previously considered to be “channels” but due to translation the word “canali” became “canals” in English, and its features were named according to brightness. When Mariner 4 flew by Mars in 1965, it was a huge shock to astronomers and other space scientists because of how different, and more hostile, it turned out to be compared to Earth and the presuppositions projected onto Mars and Venus more or less demonstrate that the expected panic and other impact conjectured from First Contact are perhaps overestimated. After all, for something like a century it was popularly assumed that there was complex life on both Venus and Mars and intelligent life on Mars and it didn’t cause societal breakdown. The question arises of whether society has changed in such a way that it now would.

Interestingly, the person who “discovered” the “canals” was a draughtsperson rather than an artist, and later cartographers with an artistic background didn’t produce so many of them because they were trained to draw what they saw. Giovanni Schiaparelli was in fact related to the fashion designer, in case you’re wondering, and appropriately enough canals were all the rage for decades. For old time’s sake I’ll reproduce one of those maps:

I could’ve found a better map but preferred to furnish you with the yellowing and disintegrating ’60s paperback I learnt much of my initial astronomy from, for old time’s sake. Note south is at the top, and compare with a modern map:

This is from here. This is not a very clear image but it’s hard to find a cylindrical projection of Mars. The PDF linked is much more legible. The most prominent feature of all, Syrtis Major, the “great bog”, is visible in both. Acidalia Planitia is also named in the older map as Mare Acidalium. Conspicuous by their absence are of course almost all of the canals. The closest one gets is Valle Marineris. It’s hard to imagine how utterly different things have become since the early ’60s in this respect.

The Martian atmosphere is to ours as ours is to the Venusian one, in that it’s below a hundredth of the sea level density of ours and ours is a ninetieth of the solid surface density of that of Venus. In another way, Venus and Mars have similar atmospheres as both are mainly carbon dioxide. This makes them unlike Earth’s primordial atmosphere, which was mainly nitrogen, but before the outgassing, Venus would’ve had a mainly nitrogen atmosphere and most of Mars’s atmosphere has been lost to space. The pressure at the surface of Mars is about the same as Earth’s thirty kilometres above sea level, but because it’s much thinner and the Martian surface more variable than Earth’s, the gravity being lower, the variation in pressure is much greater, but it never reaches the point where ordinary water can be liquid at all there.

Mars is the only surface as far as I know in the Solar System which has both extensive cratering and signs of water erosion. Usually the two would tend to rule the other out. It has teardrop shaped “islands” and branching river patterns leading down from the highlands to the lowlands, but some of those islands are formed by craters:

Many of the craters on Mars are quite eroded, probably by wind:

Such images were first sent back from the 1965 mission, and have no analogues on Mercury or Cynthia. The rims can be seen to be eroded or partly erased by the movement of sand or actually rubbed out by the process of sand-blasting by the wind. Winds on Mars can reach up to half the speed of sound.

I’ve described the process as sand-blasting. Like describing the Martian regolith as “soil”, this can mislead. It looks like wet sand, but is about as fine as talcum powder, is also high in iron, hence the rusty colour, and like moondust also contains substances which on Earth would have reacted with oxygen or water, which makes the scenario in ‘The Martian’ less plausible. It effectively contains bleach. A substance called perchlorate consists of a chloride ion attached to four oxygen atoms in a tetrahedron, and is negatively charged. It’s toxic to humans, causing lung damage, aplastic anæmia (where the body permanently shuts down red blood corpuscle production) and causes underactive thyroid, for which it’s used as a drug to treat overactive thyroid. However, it can also be burnt to release oxygen and finds use as an oxidant in rocket fuel. Its presence in Martian sand makes it harder to imagine what kind of life could survive there. However, this series is not about life on Mars.

The planet is periodically enveloped in a global dust storm. This actually happened while Mariner 4 was on its way there in ’65, when only the Tharsis volcanoes were visible above the clouds. Carl Sagan was very focussed on this, leading to them being referred to as “Carl’s marks”, but it would’ve been pretty disastrous if the storm hadn’t cleared by the time the spacecraft got there because nothing else of interest would’ve been visible. Maybe the idea of the planet being Earth-like would’ve continued for longer. Again, in ‘The Martian’, the dust storm is portrayed as much more destructive than it would in fact have been because although the wind is very fast, the low pressure means it isn’t very forceful. They happen about once every three mirs, although there are more localised ones in between. Like the possible “mists” on Cynthia, Martian dust particles become statically charged in the process of being blown about and rubbed against each other, leading to them sticking to every available surface, including the likes of solar panels, potentially to space suits and moving parts on landers and rovers. This blocks sunlight from reaching solar cells and makes it difficult to design rovers, which also get covered in the stuff. What happens is that the sunlight warms the ground, leading to a temperature inversion similar to the one causing tornadoes here on Earth and this causes dust devils and ultimately dust storms. They tend to be stronger in the southern hemisphere, which brings up another issue I’ll go into in a minute. A very important consequence of the study of dust storms on Mars, which would justify the Mars missions on its own and emphasises the vital rôle of space exploration, is that a model applied to the Martian atmosphere was applied to our own if it was filled with soot after a nuclear holocaust, and predicted the nuclear winter scenario as depicted in the BBC TV drama ‘Threads’. This seems to have contributed to the end of the Cold War. Whether the prediction is valid has become a controversial issue which I don’t want to cover here.

The Martian orbit varies between 1.666 and 1.381 AU (1 AU=average distance of Earth from the Sun), making it the second most eccentric planet after Mercury. Unlike Mercury, Mars has a fair axial tilt which causes seasons. Due to this eccentricity, the seasons are more extreme south of the equator since the surface is tilted away from sunlight which is already weaker in the winter and towards stronger sunlight in the summer there, and the reverse is the case in the north. From here the most obvious effect is a larger southern ice cap in the winter, which I think I’ve managed to see through binoculars. This eccentricity also makes the seasons different lengths in the different hemispheres.

Frost and “snow” makes Mars seem more Earth-like than other planets. Mariner took photos of frost in craters, which is a rare combination over most of the planet but is found in polar craters on Mercury and Cynthia. This frost, however, doesn’t fall but freezes out of the atmosphere and is dry ice, i.e. frozen carbon dioxide. For a long time it was unclear whether there was real snowfall on Mars, in a couple of respects. It wasn’t clear whether there was water ice in the snow or whether it actually fell or just appeared like frost from the atmosphere, which is almost completely carbon dioxide. It’s now thought probable that water ice snowfalls occur every night of the northern summer. Actual flakes, from high in the atmosphere. That said, much of the ice on the surface is dry ice, and just as dry ice sublimes (turns from solid to gas without melting) on Earth, so does it on Mars. The water ice snow situation is less straightforward because it tends to become dusty, allowing it to absorb heat from the Sun. At night, water ice clouds lose heat to space, causing them to cool, thereby becoming denser and falling towards the ground as snow. The temperature difference leads to winds, which blow the snow around and there are in fact blizzards. There’s also virga – precipitation which doesn’t reach the ground.

Although the amount of water vapour in the atmosphere is tiny compared to Earth’s quotient, the thinness of the Martian atmosphere means it’s still almost saturated and there are therefore water-based clouds there. There are no cumulus clouds – “little fluffy clouds” – but other kinds are present such as cirrus, the ice clouds found high in our own atmosphere. There are also wave clouds, fog and hurricanes. Noctis Labyrintus, the network of gorges west of Valles Marineris, fills with fog every morning. There are also orographic clouds, which are clouds caused by mountains or high ground lifting saturated air past the point where it can still hold all the moisture. Entirely separate from the water ice clouds are the dry ice ones, which form when it’s cold enough to drop below -78°C, the freezing point of CO₂. I find this quite odd as it’s the actual atmosphere freezing and snowing. This also happens on Triton, Neptune’s largest moon, where the nitrogen atmosphere freezes and precipitates onto the surface.

Mars has dunes. These have ice on them, but this isn’t always so. These particular ones are unlike Earth’s in that they have a kind of network pattern on them, thought to be due to thawing and subliming. There are also wind-blown streaks.

It’s difficult to know where to stop with this. I acquired a lot of information about Mars when I did the calendar and there’s so much I could mention but I feel this is getting somewhat delayed by me adding to it, so now I’m just going to publish it “as is”. So there you go. Lots more about Mars could be said but that’s it for now.