The Maretian

by Kris Overstreet

Chapter 211: Sol 387

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Tomorrow’s the last hay harvest.

On the one hand I should be happy about that (and even happier that the final potato harvest comes five days later). The rover mods are all finished except for loading the weight in, so we can go straight to field tests. I should be eager to get started. But I’m not.

No matter how sick I am of eating potatoes- and have I mentioned yet that I would like to take a time machine back to the first European explorer who brought potatoes from the New World back to Europe and kill him because there isn’t a prayer of killing the first Inca or Maya or whatever who cultivated the goddamn things? I’m that sick of potatoes, and the ponies are that sick of raw hay, but we invested three hundred and fifty sols, give or take, into the farm- damn near an entire Earth year. That leaves a mark on a person.

Dragonfly says the farm wants to live. That’s fair. So do I. But I don’t know how we’re going to arrange it. We’ve fixed the water issue, and it looks like the heat issue is also covered, but the biggest problem remains: air. The plants require a lot more carbon dioxide than the soil bacteria will ever provide. Without it they’ll suffocate pretty quickly- maybe as slowly as a month, maybe as quick as a couple of days. I’m not sure. It depends on a number of factors.

I’ve thought of a lot of ideas for getting more CO2 into the cave, mostly bad ones.

1) Make hole for Mars atmosphere to enter the cave. This is primo grade-A stupid because (and follow closely here, the details are really technical) if we put a hole in the cave wall, all the air will leave. Take this, write it down on a piece of paper, and underline it: Breach hull, all die. (Well, all the plants. We’ll be long gone. I hope.)

2) Move atmospheric regulator from the Hab to the cave. It’d be nice if that would work, but it can’t. NASA never thought, “Hey, you know what problem our astronauts might have that we’ve overlooked? NOT ENOUGH CARBON DIOXIDE! We better fix that right now!” They’ve never thought it because it’s a dumbass thing. Every aspect of the Hab’s life support is dedicated to extracting CO2 and then ripping it apart in the oxygenator. It can’t be shifted into reverse. And the programming for the atmospheric regulator is on non-programmable ROM chips. So, even if we could power it at the cave, it wouldn’t help.

3) Use MAV fuel plant air compressor to pump CO2 from the outside into the cave. Okay, let’s say we could do this without losing all the air inside. With a bit of thought that’s doable. But here’s the problem: without an atmospheric reclaimer or the ponies’ direct line to their homeworld’s atmosphere, the cave doesn’t have any mechanism to regulate its internal air pressure. The MAV fuel plant would steadily pump compressed outside air into the cave, and the air would stay there, until either the fuel plant died or the overpressurized cave blew out. Breach hull, all die. Not an option.

4) Get Starlight Glimmer to make crystals that exchange molecule for molecule. This is my best idea, but I’m still troubled by it.

Here’s why. Let’s say you enchant a pair of crystals to move air in two directions between them, like the pony space suits and ship life support use. Further refine the spell so that, instead of a free flow of air, the spell detects when a molecule of carbon dioxide hits the outdoor crystal and exhanges it instantly with an oxygen molecule from inside. Simple, right?

Nuh-uh. A molecule of oxygen is two oxygen atoms, total atomic mass roughly 32 atomic units. A molecule of carbon dioxide is two oxygen atoms (dioxide, see?) plus a carbon atom, for a total atomic mass of 44. That’s a net imbalance in the exchange of twelve atomic units- or, put it another way, roughly a third more mass would be entering the cave than leaving. And that’s keeping it simple and not attempting to use the system to squeeze some scarce water vapor out of the air (atomic mass 18).

Now, almost all the carbon atoms will eventually go to making more plants, at a much higher material density than one atmosphere. But more plants take up more space, leaving less space for the existing amount of air. How long will it take before the imbalance causes a problem? And would it even provide enough CO2 fast enough to supply the needs of the plants? I have no idea.

I haven’t floated this one to NASA because they’ve got other things on their minds, namely getting me home and my friends rescued on Sol 551. To them the cave farm is unimportant. It’s only a side issue, one we can do without. When NASA returns, even the dead remains of the farm would have enough data for a generation of future botanists to write page after page about how Mark Watney screwed up or about how there were never any magical aliens, Watney had a psychotic break and made up the whole thing, including the alfalfa.

But it bugs me. It bugs me a lot. We can dump a bunch of water into the cistern before we leave and give the farm enough of a water cycle to last for years. We’ve already given them circulation for water and heating to survive on. But for the cave farm, air is the critical thing, and I wish I had a better solution.

Oh, well. I’ll talk with Starlight about it tomorrow during the harvest and see if she has any better ideas.

Author's Notes:

Today was better for sales, but not good. I'm still in the red.

And I'll have to try to find something to write tomorrow, probably about the hay harvest itself.

Next Chapter: Sol 388 Estimated time remaining: 8 Hours, 35 Minutes
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