The Maretian

by Kris Overstreet

Chapter 17: Sol 24

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Well, the cave farm project just ran into a problem. Actually, problem is the wrong word, because NASA uses the word “problem” to describe an issue that can be overcome. This is more of a “contingency”, which is what NASA calls it when the only thing you can do is sweep up the debris and begin the investigation.

The dirt doubling went well. The ponies have been watering the dirt regularly, twice a day, using their spacesuits. I’ve committed two-thirds of the stockpiled water to the soil- two hundred liters total- but levels in the water reclaimer’s tanks are rising from humidity taken out of the air. If this keeps up we’ll eventually have damp, fertile soil and full water tanks as well.

I’ve been doing a lot of EVAs recently, what with the cave and salvaging the pony ship and all, so I decided to stay indoors today. I had those soil samples from the cave to analyze, and I need to think about how we were going to turn the cave into a farm anyway.

My biggest concern about the cave was air. That cave is a giant geode, and geodes are porous- otherwise the water couldn’t get inside and, duh, you wouldn’t get a geode. The good news is, it’s not Swiss-cheese porous, and most of the cave is buried under several feet of compacted sand and permafrost. But a billion microscopic holes will leak air just as efficiently as one really big hole, and I hadn’t come up with a solution for that. Still haven’t.

But the soil samples changed my priorities. Air is no longer my biggest problem. My biggest problem, to put it in numbers, is 2.3% perchlorates. Or, to be more accurate, 1.5% potassium perchlorate and 0.8% magnesium perchlorate in the two deepest samples, with the more shallow samples tapering off to a low of 1.2% combined perchlorates.

Still: shit.

The perchlorate-eating bacteria in my Earth soil are reducing the perchlorates in the Martian soil we’ve brought in here because the soil is shallow (which allows for oxygen to penetrate through the whole layer) and because the perchlorates are comparatively low. By the time the bacteria manage to get down deep enough to eliminate all those perchlorates thirty centimeters down in the dirt, the ponies will be out of their food packs and possibly out of all the vegetarian options in my food packs. We can’t wait that long.

“But Mark,” you say, “don’t you only need the topsoil?” With potatoes that would be true; their root system is shallow. But alfalfa is just the opposite. A mature alfalfa plant sends down roots an average of five meters in depth, and can go twice that far in search of groundwater if necessary. Here in the Hab I can maybe counter for that by providing tons of water at the surface, but in the cave there’s no Hab floor to stop the roots. They’re going to go down as far as we can heat the soil, and they’re going to bring back up whatever they find- including those toxic perchlorates.

So, right this minute, the cave farm idea isn’t looking so hot. I’m sitting down now considering my non-cave farming options.

The Hab floor is already covered with dirt. I don’t want to fill the airlocks, because in case of emergency I might want to use those as secure storage areas. They all have automatic cutoff valves on their air lines in case the Hab ruptures so that whatever air is inside them will stay there. I could repurpose the bunks and worktables for more surface area at two square meters each, give or take, but that would put the ponies out, and anyway I want a clean bed and a clean worktable for myself.

I need at least one rover operating to get me to the Ares IV MAV four years from now, and for safety’s sake I need to keep both intact. Something in one or the other might break, and the only spares I have are two spare wheels with motors. Farming in them is no go, especially since the interiors are about the same as a large van- not more than three square meters each of space.

But each rover has a pop-tent in case of emergencies. The pop-tent is built to automatically deploy from the rover’s airlock in under a second, using the rover’s air to inflate. And once inflated the pop-tent’s interior is a lot roomier than the rover’s interior- with a floor that almost precisely ten square meters in size. So that’s twenty square meters more farmland.

Problem: thanks to Not Invented Here, the rover and pop-tent airlocks aren’t compatible with the Hab airlocks. I should be grateful, though- pop-tents are for emergency use only and are intended to be used only once. I don’t know if it was NASA paranoia or the contractor’s mix of genius and idiocy that made them give the pop-tents their own independent airlocks, but whatever it was, I’m grateful. They’re crappy airlocks- nothing more than two doors and a couple of hand-valves, and they’re inefficient as hell- but they’ll make it possible for me to convert them into food production.

Better yet, they come with separate air valves that are compatible with the Hab’s exterior air links, because NASA absolutely insisted that all hoses, valves and cables be standardized. That means the pop-tents can run on the Hab’s heat- no supplemental heating required. The interior lighting isn’t as good, but I think it’s good enough. Better than nothing, anyway.

The only other thing I have is the MDV. The storm, and the debris from the antenna farm, absolutely wrecked it. One of the landing legs is collapsed, and there’s four separate holes in the hull. And the space inside is tiny anyway. It was made as light as humanly possible and just barely large enough to get six human beings from Mars orbit to the ground safely, with seventy-two hours of life support in case of major problems setting up the HAB or launching the MAV. I could waste half my spare Hab canvas (6 sq. m, for emergency repairs only) re-sealing the MDV, but considering the small interior and the lack of convenient air and heat, it’s not worth it.

All that leaves is the pony ship. The engineering section has that big hole in the deck, and I can’t patch that without removing the entire outer hull in that section. Even then it could blow out at any time. That leaves the flight deck and the mid-deck. I’ll have to measure to be accurate, but call it forty meters of surface area. It has incandescent bulbs and windows for lighting. It can’t be hooked to the Hab’s air or heat, and I don’t know what heater systems it has with its main life support offline. But if it’s the difference between starving and not starving, we’ll make it work somehow.

So- if the pony ship can be made into a second greenhouse, that brings me up to a total of approximately 152 m2 of farmland. The question is: will that be enough? If not, how much time will it buy us? I’ll work on that tomorrow.

For tonight it’s more Partridge Family. Last night Starlight used her magic to ask me where the people were that were laughing now and again. I had to tell her I didn’t know. Then she asked me why they were laughing, and I had to admit I didn’t know that either.


Transcript: conversation between Mark Watney and Starlight Glimmer:

STARLIGHT: Good mor-ning, Mark! (note: spell is not active yet- Starlight actually said this in English! She’s picking up more words! And her pronunciation is pretty good!)

WATNEY (trying to say the pony equivalent of “good morning”: Bo-rIIIYYneduh!

STARLIGHT: (rubs head with hoof, then stands on hind legs to put same hoof on my mouth) Don’t. (Note: English again.)

WATNEY: That bad?

STARLIGHT: Yes. Bad-bad. What do morning?

WATNEY: There’s a big problem with turning the cave into a farm. I’m trying to figure out if we can do without it. (Note: This was too much for Starlight, and she turned on the translation magic. I repeated it.)

STARLIGHT (translation): What was problem? Help I possible?

WATNEY: Not unless you can get several tons of perchlorates out of soil.

STARLIGHT: Say word again. (turns off spell)

WATNEY: Per-chlor-ates.

STARLIGHT (reactivates spell): What be by-made-of-green? Why you want? (Note: Starlight said “perchlorates” in English, and the spell tried to translate it anyway, as “by-made-of-green”.)

WATNEY: Don’t want. I want to get rid of ‘em. They’re toxic chemicals. Poisonous.

STARLIGHT: Chemicals? (turns off spell, fetches whiteboard and marker, draws out chemical notation for sucrose- well, symbol-12, symbol-11, symbol-22, so I assume sucrose- a model of a water molecule, and organic molecule chains for butane and ethyl alcohol) Draw! (Note: Starlight’s favorite English word so far.)

WATNEY (signals for spell, waits): Do you know the periodic table?

STARLIGHT: (shuts off spell, spends a couple moments mumbling to herself, then brightens as she works it out) Yes! (draws a very quick and rough outline that mostly matches the normal periodic table, but no details)

WATNEY: (calls up reference app on computer, pulls up periodic table for Starlight’s benefit, then writes “K Cl O4” and draws a potassium perchlorate graph with the potassium ion hanging off the perchlorate molecule; then: “Mg ((Cl O4) X 2)” and a magnesium ion flanked by two perchlorate molecules)

STARLIGHT: (looks at periodic table, at my drawings, scribbles something in her own language at bottom of whiteboard) Yes fix! (Note: again, no translation spell.)

WATNEY: You mean you can fix this?

STARLIGHT: Slow. (another favorite of Starlight’s in the last couple of days)

WATNEY (spacing words out carefully): You-can-fix-this?

STARLIGHT: Can-fix-this. Yes.

WATNEY: You can remove perchlorates from tons of soil?

STARLIGHT: (turns spell back on): Idea I have. Need work time on it. Done be it can, don’t worry!

(Starlight’s looking tired at the point, so I signal to end the conversation.)

I should have asked her about the air problem. That’s almost as urgent, really. I’ll have to carry air in tanks to the cave and release it, and then I’ll have to bring Mars air into the Hab for the oxygenator and atmospheric reclaimer to make breathable.

I have a plan to do that. The MAV spends years on the surface of Mars making its own fuel by combining hydrogen brought from home with carbon from Mars's atmosphere. The fuel plant is in the landing stage, so the crew left it behind when they launched, and it survived the storm intact. That means I have a machine that will compress Martian air into liquid and store it in a tank. If I want oxygen I have to release the air in the Hab and let the oxygenator work on it, but that's doable. The problem is, it’s a slow process, and if we plug the cave and air still leaks out faster than we can bring it in, there’s no point.

But obviously Starlight has a magic solution on her mind. I’ve noticed that her first reaction to any major problem is to whip out the old Box of Sparkly Lights and Shit. I especially noticed that the other day when she accidentally turned a pebble into a bullet and came within twenty degrees of aim of putting a hole in the Hab canvas. I have no clue what kind of “science” she was trying, but I’m glad she didn’t try it twice.

It’s pretty obvious that her crewmates already know about her magic-mania. A lot of their arguments are making a bit more sense in retrospect. The gauge on those batteries barely rises overnight, and I’ve seen myself just how fast that charge can be burned off. Obviously they want her to save the magic for really important things.

“Aw, but all the other unicorns back in Pony-land get to have neato magic all the time!” “We’re not in Pony-land now, are we? Now eat your gruel and get back to scrubbing the dirt!” “Aw, you never let me have any fun…”

Yeah, I know that’s not up to the usual rapier wit you’ve come to expect from intrepid space explorer Mark Watney. The truth is, I’m not in the mood. I just finished crunching some numbers, and the news is even worse than I thought.

A mature stand of alfalfa, under normal proper care, will produce about three and a half short tons of fodder per acre per harvest. The four ponies, being a lot smaller than Earth horses, only require about two pounds of food per day. (I’m counting Dragonfly, even if she almost never eats. How is she not starving? She looks just as energetic and healthy as the day they arrived. Must ask Starlight.) I did the math, and if I don’t allow for any safety margin whatever, 220 square meters would be enough to feed the four of them from one harvest to the next.

Note I said them, and not them plus me. I can’t eat alfalfa. Oh, I could eat the leaves, but not the stems. My gut can’t digest the cellulose. I’m assuming theirs can, and so far none of them has done anything to discourage me on that point. No, for me it’s potatoes, potatoes, and more potatoes, once the food packs run out.

But the thing is, remember yesterday’s math? If we convert everything that will hold air and carry dirt except for our bunks, our tables, the airlocks and the rovers, that only gets us to roughly 152 square meters. That’s not enough even if Dragonfly turns out to be a magic bug that lives off of sunshine and hugs. And even then, that would leave a grand total of no square meters for me to plant potatoes in.

So, what happens if I go the other direction, abandon the alfalfa, and plant nothing but potatoes? Sure, the plants and non-tuber roots are all poisonous, but I’ve seen the ponies shove their noses into mashed potatoes with gravy from my food packs with no problems. (I haven't told them how the gravy is made.) I’m assuming the tubers are safe for them.

With potatoes the math gets worse. Sure, I can cram potato plants on top of one another until there’s more spud than dirt underfoot come harvest time- it’ll destroy the soil after a few harvests, but I can do it. But absolute best case scenario, I figure, is about 2200 potatoes every sixty to seventy days. That’s about 5500 calories per day between harvests, as long as the soil holds out. It would work fine for just me, and maybe all right for three people if we tightened our belts and spent all day in bed.

But 1100 calories per person is sub-survival levels. It’s starvation. And after a week at that level we wouldn’t be strong enough to tend the plants. So that’s no good.

And, by the way, all of these estimates are based on the most optimistic yield. It’s based on the total absence of parasites or diseases and on constant daily attention to the plants. If I can’t convince the alfalfa to grow properly despite the shallow soil, or if the potatoes refuse to grow tubers because the soil’s too crowded, or if any number of other things go wrong, all the numbers I just threw out there go down, not up.

The goal of all this has to be to grow food faster than we can eat it, so we have a reserve when the food runs out or something happens or, eventually, when the soil depletes itself. That’s the biggest long-term problem. The alfalfa will help with that by fixing nitrogen, but it sucks up loads of potassium and phosphorus. The dirt around the Hab has both of those in abundance in the form of billion-year-old volcanic ash, but it’s not an infinite supply. In deep soil, bacterial action will bring some replacement minerals up from below, but the Hab can’t hold deep soil. When this dirt goes dead, we have to have enough food to last us the rest of the way to rescue.

The Hab won’t be enough. Perchlorates or not, we need that cave.

I just noticed something: Dragonfly can do magic, too. I just saw her levitating a marker like Starlight sometimes does. Her magic is green, not light blue like Starlight’s. Weird.

They’ve taken over the privacy curtain by the shit-box and are sketching out diagrams on it. Looks like they’re working on a procedure to remove the cargo airlock from their ship. Obviously they think they can make the cave airtight. Starlight certainly doesn’t seem to think the perchlorates will be a problem.

I just hope they’re right.

Author's Notes:

The buffer is now three chapters, despite my having to cut and set aside five hundred words of today's product because it didn't fit with the circumstances of Sols 28-29. Most of it will get recycled sometime after Sol 43.

As you see here, the cave isn't an instant ready-to-go thing. It will take a lot of magic and some science and outright MacGyvering to make the farm work. And if they get it to work, there's no guarantee it will stay working- just like, in the book, Watney found out the hard way when the Hab's warranty expired.

But the math holds up- at least, based on the original book and the sources I looked up. The castaways absolutely need the crop space that cave provides. And going all one crop or all the other isn't going to work.

Those of you familiar with the book may have noticed that the square meters of soil don't line up. The difference is (a) Watney's counting Amicitas as potential planting area, and (b) in the book Watney converted five bunks and two of his three work tables to soil at two square meters each. (Big bunks and tables for a space mission!) Those are all taken up by his guests now, so they're not available for planting.

Next Chapter: Sol 26 Estimated time remaining: 28 Hours, 42 Minutes
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