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.


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