Where to settle on Mars?

A few weeks ago I wrote an introductory post on Martian settlement issues (https://wordpress.com/post/ianmillerblog.wordpress.com/716 ). I am now going to ask, where should such a settlement be? Obviously, this is a matter of opinion, but there are some facts to consider. The first is seasons. The northern hemisphere spring and summer is about 75 Martian days longer than the autumn and winter (and opposite for the southern hemisphere. This is a consequence of the elliptical orbit, but it also means that the longer seasons mean the planet is further from the sun (which is why it is going slower) and because of the axial tilt that generates the seasons as well as the elliptical orbit, most likely places can get up to 40% less sunlight in winter than in summer. Add to that that by being so much further from the sun, Mars never gets more than about half the Earth’s solar energy. So the southern hemisphere has a shorter but warmer pair of seasons, and a longer colder other pair. Temperatures in summer can get up to 20 degrees C in the day and in winter, fall to minus 120 degrees C during the night. No plant can survive that, so besides providing air, heat is also required.

There is a reasonably easy way to get around the heat problem. Assuming you have a nearby power plant, and as I shall show in other posts, if a settlement is to be viable, it will have a heavy demand for high quality energy, then there will inevitably be waste heat. Space mirrors can also supplement the heat and light. Heating the planet is not on (you would need mirrors of area greater than the Martian cross-sectional area) but heating a settlement is plausible.

The location could be decided on the basis of nearness to raw materials, but that leaves open the question of which ones? The obvious one is metal ores, but here we do not know where they are, of even if they are. Again this can be left for another post.

The next question is air. Air pressure depends on altitude, and much of the exploration so far has been around the zero of altitude, where we get pressures of around 6 -8 millibar, depending on the season. In the southern hemisphere summer, the pole shrinks and vaporizes a lot of carbon dioxide, thus increasing atmospheric pressure. In my novel Red Gold I put the initial settlement at the bottom of Hellas Planitia. That is in the southern hemisphere, and is a giant impact crater, the bottom of which is about nine kilometres deep. That gives more atmospheric pressure, but at the cost of a cold winter. The important point of Hellas Planitia is that at the bottom of the impact crater the pressure, is high enough to be the only place on Mars for liquid water to exist, particularly in summer. The reason this was important, at least in my novel, is that unless you find water, you will probably have to pump it from the atmosphere and condense it. Also, while you are pumping up domes, you will want to get the dust out of the air. The dust is extremely fine. That means very fine filters, which easily clog; electrostatic dust precipitators, which may be too slow for many uses; or a form of water filtration. In Red Gold, I opted for a water-ring type pump. Of course here you need a certain amount of water to get started, and that will not be a small amount. The water will still evaporate fairly quickly, hence the need to have plenty of water, but the evaporite will go into the dome, so it is recoverable or usable. It could also be frozen out before going in; whatever else is in short supply on Mars, cold is not one of them, although with the low atmospheric pressure, the heat capacity of air is fairly low.

So strictly speaking, based on heat and air, both have to be heavily supplemented, it does not matter where you go. However, I think there is another good reason for selecting Hellas Planitia as the site. It is generally considered that water, or at least a fluid, flowed on Mars. The lower parts of Hellas have signs that there was water there once, and to the east two great channels, the Dao and the Harmarkis, seemingly emptied themselves into the Hellas basin. Water will flow downhill, so a lot of it would have resided in depressions, and either evaporated, or solidified, or both. So, there is a good chance that there is water there, or anything that got dissolved in the water. The higher air pressure will also help reduce sublimation by a little bit, so perhaps there will be more there than most places.

The next issue is, you wish to grow food and have plants make oxygen. Obviously you will need some fairly sophisticated equipment to get the oxygen from the plants to wherever you are going to live, assuming you don’t live with the plants, but the plants have to grow first. For that you need soil, water and fertilizer. The soil is the first problem. It is highly oxidised, and chlorides have been oxidised to perchlorates. That is fine for making a little oxygen, but it has to be treated or it will kill plants. Apparently it is something as good as bleaching powder. Again, you will have to take the treatment chemicals with you; forget something critical or do not bring enough, and you will be dead. Mars is not a forgiving place.

That leaves fertilizer. Most rock has some potassium and phosphate in it, and if these have been washed out, their residues will be where the water ended, so that should be no problem if you go to the right place. Nitrogen is slightly different. The atmosphere has very little nitrogen. On Earth, plants get their nitrogen from nitrates washed down in rain, from decayed biomass, and from farmers applying it. None of that works there immediately. Legumes can “fix” nitrogen from the air, but there isn’t much there to fix and partial pressure is important. You can, of course, pump it up and get rid of carbon dioxide. A lot of these issues were in the background of my ebook novel Red Gold, ad there, I proposed that Mars originally had somewhat more nitrogen, but it ended up underground. The reason is for another post, but the reason I had then ended up as being the start of my theory regarding planetary formation. However, the possibility of what was leached out or condensed out being at the bottom of the crater is why I think Hellas Planitia is as good a place as any to start a settlement.

Quick Commercial: Red Gold will be discounted to 99 c for six days starting the 13th. It is basically about fraud, late 1980s style, but much of the details of settling Mars are there.

The Martian. Hollywood science!

The Martian: coming to a theatre near you! Even before release, an article turned up in our local newspaper where “experts” criticized the science in this movie. Now, I love it when people start to take science seriously, but is it fair? This story by Andy Weir started life as an ebook, and I purchased it and reviewed it on Amazon well before it took off, mainly because I too had self-published an ebook on Mars colonization and I started reviewing ebooks to help other independent authors. So, is the science OK in the book?

The biggest blooper is the storm (which I have seen in the film trailer). Martian winds can hit up to 200 k/h, but gas pressures are about 1% of Earth’s. Force is rate of change of momentum, so even after correcting for the lower gravitational acceleration and the mass of dust, the forces are comparable to a very gentle breeze here. Of course, if this were corrected there would be no story.

The next criticism of the film was that Matt Damon walks about as if he were on Earth (which he was!). Yes, the Martian gravity is slightly less than 40% of Earth’s, but who cares in a film? Worse, it would be rather difficult to get this exactly right, and if you try, the critics will soon be out finding flaws in what you do. As far as I am concerned, Hollywood is forgiven for this. It just is not worth trying to get it right, especially as the costs will add up, and I doubt getting it right would add many extra seats sold.

I shall be interested to see how close the film follows the book, because there are some more serious issues. The newspaper article mentioned radiation, and suggested that cancer was omitted from the film. I am not so sure that is important because the cancer would not appear until after the film was over, but there is another consequence of radiation, and that would relate to his living quarters, which were described as being like a tent and made of something flexible. Polymers need a good molecular weight to remain flexible, and ionizing radiation would very quickly embrittle most polymers, and if there are fibres in the tent material, make the matrix holding it together more porous, and less effective at holding gas under pressure. In my Red Gold, I got around that with two suggestions. The first was that the growing of vegetables was done in triple-layered glass houses. Glass does not degrade because it is held together with ionic forces, and should a sodium atom inadvertently be struck by a proton, well, magnesium will hold it more strongly. Eventually, it will haze, but that will also happen through other mechanical abrasion. My second defence against ionizing radiation was to have a giant superconducting magnet at the Mars-Sun L1 position, which would give a small deflecting nudge to incoming charged particles. This Lagrange point is where the planet and star’s gravitational fields equal the centripetal force required for any body to have the same orbital period as the planet. This position is only metastable, so corrections are needed, but this can be minimized by having the body orbit the position (carrying out a Lissajous orbit). Would this work? I hope so! So far nobody has criticized me for it.

However, another problem in the book, and I shall be curious about how the film does this, revolves around growing potatoes. Mark Watney (the character) needs water. Don’t try what he did, or if you must, try to be just a tad more competent. The method in the book is just plain ugly. Also, there had to be some other way because originally the crew would have needed water. In Red Gold, my method was to condense it from the atmosphere (50% humidity). Of course there is not much atmosphere, but it has to be pumped up to a useful pressure anyway. You cannot live in a space suit. The second method, once you find it, is to dig it up. Mars has plenty of ice, although finding a convenient lump depends on where you are. A more serious problem is nitrogen. You cannot grow things without certain elements in the soil. Potassium and phosphorous are probably there in small amounts in any soil, but nitrogen is different. So far, minor amounts have been found at Gale Crater, but not by other rovers, although in some cases they did not have the capability of detecting it. The Martian atmosphere has very little nitrogen, so unless there is a lot buried, settling on Mars could be difficult. Certainly, the growing of potatoes under the conditions described in the book would need somewhat more nutritious soil than analyses have so far indicated.

Is this important? I think so, because apparently there are people signing up for a one-way trip to Mars. I would hope they know what they are letting themselves in for.