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When watching The Martian, it seems self-evident that the potato plants did not survive being frozen – but what made the soil infertile?

Soil freezes around the Arctic Circle every winter but plants still grow after the thaw. The roof was still there, so radiation doesn't seem to be the answer, either. He got the bacteria in the soil from raiding the feces collected from the other astronauts; over time, he could repeat this trick using only his own feces.

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2 Answers 2

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Explained in the source novel.

The farm is dead.

With a complete loss of pressure, most of the water boiled off. Also, the temperature is well below freezing. Not even the bacteria in the soil can survive a catastrophe like that. Some of the crops were in pop-tents off the Hab. But they’re dead, too. I had them connected directly to the Hab via hoses to maintain air supply and temperature. When the Hab blew, the pop-tents depressurized as well. Even if they hadn’t, the freezing cold would have killed the crops.

Potatoes are now extinct on Mars.

So is the soil bacteria. I’ll never grow another plant so long as I’m here

I shall leave it to others in the inevitable comments below to describe why this is wrong.

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    Even Watney realizes it's wrong later in the novel, but by that time, he's abandoned growing potatoes. for other survival options.
    – notovny
    Jan 8 at 13:23
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    Yes, Watney did say that in an experiment done by request from Earth, after comms were restored, that he found some still alive in the soil.
    – Steve
    Jan 9 at 0:57
  • so the answer isn't that the bacteria suffocates, but depressurization kills them when the water boils? Jan 9 at 10:07
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    @Adam.at.Epsilon he just decided at that moment, that bacteria is dead due to the depressurization and cold. Water just escaped the farm. Jan 9 at 10:46
  • Even with the revelation later on about some of the bacteria surviving, theres no guarantee that there was enough to sustain a viable growing environment and he had no time to re-grow the bacteria like he did before (by doubling) without starving.
    – Moo
    Jan 18 at 21:29
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Mentioning the bacteria is just a side note. The main point is that he has no viable seeds left.

Remember that, earlier in the book, he makes a point of mentioning that the potatoes he used as his initial seed were not frozen for the transfer to Mars -- which is the lucky coincidence that makes them viable in the first place.

Freezing destroys the cell structure. The potato will not sprout, just rot. After the decompression, he has nothing to plant, even if he could somehow make the soil viable again. (Which is why he doesn't really bother checking the soil until later.)

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    I don't think there's a thing called seed potato. As far as I know (backed by few years of working on a small farm back when I yay-high), if you have a fresh potato ( that is: not cooked, fried or baked), you can plant it and it will grow. You don't even have to have a whole potato for that... From my own experience, this s**t will grow when you have it in a long-term storage. It needs just to be warm and moist enough, and then your stash for winter spawns sprouts...
    – AcePL
    Jan 10 at 8:07
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    @AcePL It makes perfect sense in context. They would normally not bother keeping the potatoes alive - it was very fortunate for him that these were. He didn't keep any live potatoes in separate safe storage (it was mentioned he even did that on purpose, to make sure the bacteria from the other people's feces didn't harm him), so all of them died in the accident. He still had potatoes to eat, but no potatoes to use as seed . Dead plants don't sprout.
    – Luaan
    Jan 10 at 8:14
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    @AcePL - in the context given, "seed anything" is one or more anythings that can be used to grow new anythings - for example, seed capital is just money that is used to invest in a business that will generate more money. So any potato planted for the purpose of growing more potatoes is a seed potato. Also, but purely anecdotally, my father used to grow potatoes and rather than replant actual spuds, he would let one or two stay in the ground until they flowered and produced many actual seeds - these he referred to as his "seed potatoes" in the most literal sense.
    – Spratty
    Jan 10 at 10:41
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    I used the term "seed potato" as a 1:1 head translation of "the potatoes he used as seeds". Turned out that is the correct botanical term. Changed the wording to avoid the off-topic discussion. (Also, AcePL and myself cleared up that issue -- and others -- already, but removed the discussion afterwards due to some misconceptions that were just as off-topic.)
    – DevSolar
    Jan 10 at 13:12
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    "seed potatoes" are just potatoes set aside for the purpose of planting rather than eating. You could just as easily cook and eat your "seed" potatoes or plant your "eating" potatoes. All that matters is that they are stored in a way that does not impair them for the intended use.
    – Anthony X
    Jan 18 at 22:04

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