My arm hurts, and the raw skin under my dressing itches like fuck, but I can’t touch it. I’m off the magic pony pills, and I’m not feeling any withdrawal symptoms, aside from the nagging reminder that aspirin doesn’t do shit.

But survival demands I get off my ass, so I put in a full day’s work today. So did Starlight, who is obviously still in bad shape but won’t stay down. Spitfire’s mad at both of us- especially Starlight, after she snuck around her to make me a magic spacesuit comm that can talk with theirs. It consists of a brick-sized magic battery from their ship, an enchanted gem from Fireball's snacks, and a few other odds and ends, all of which I have to wear inside my suit, but it works.

When she found out we intended to work, Spitfire almost hit the dome, she chicken-flapped so hard. She wanted to ground us, but we insisted: if everybody doesn't work, everybody dies. The pony food packs are counting down to starvation, and once they’re gone I only have a few days’ worth after that before they begin starving. The only way crops will be ready in time is if we get them planted now.

The boom on Sol 40 might have got NASA’s attention, so yesterday I added a couple of words to my doctoral thesis written in Morse code just north of the solar farm. True, “Burned, healing” will make NASA worry if they read it. But if they read my message before seeing smoke coming from the cave, me saying nothing would make them worry a lot more.

Of course, the odds are they haven’t noticed either one. As big as the perchlorate explosion was close up, it was less than a fly’s fart so far as the surface of Mars was concerned. They’d have to have been looking right at Site Epsilon to notice anything. An hour either side of the explosion, there wouldn’t have been anything to see. But there’s a chance, so I updated my rock blog.

Today was a dirt doubling- probably the last, but definitely the most ambitious. All the dirt in the Hab and pop-tents is now fertile, but we need starter dirt for the cave farm, assuming that’s still workable. So today Fireball carried one bin of dirt at a time out to the alien ship for storage. It has air and heat now, thanks to their life support system and Hab power running the one heater they left inside, so the soil bacteria will survive there. Meanwhile Cherry, Dragonfly and Spitfire dragged even more Martian dirt inside to replace all the dirt that got put in storage for the cave.

I should have helped with that, but I had other things to do. Also, I figured I could make Spitfire happy and get out of the way while all sorts of human germs and pony germs and dragon germs and whatever-Dragonfly-is germs get stirred up and tossed into the air. And she’s right to want me out. Burns are really susceptible to infections. I could get tetanus, or e. coli, or flesh-eating bacteria. Or some magical pony super-bug that leaves me perfectly healthy except that my hair turns green and my arm falls off for no apparent reason.

This is a serious concern. If my arm falls off, NASA will kick me out of the space program, and I’ll not only be stranded on Mars, I’ll be stranded and unemployed on Mars. I only hope I can get the unemployment office to do direct-deposit, because I don’t think my bank has a branch out here.

Okay, enough lame jokes. Yes, I spent a couple of days worrying about cross-species infections, all War of the Worlds and shit. But I didn’t mention it here for the same reason that I eventually got over it: we’re all living in the Hab now, so it’s inevitable that we’ll be exposed to each other’s bacteria. Nothing can be done about that, even if we weren’t wading in each other’s shit every week to produce fertile soil for our upcoming crops. We either risk death by disease, or we guarantee death by not working together and doing whatever we can to save our butts.

And, up to now, it’s actually worked out okay. Starlight keeps pushing herself to exhaustion, and Dragonfly appears to be running out of steam, and of course I got myself burned like a stupid action hero, but nobody has actually gotten sick. The Ares-III crew was in strict quarantine for two weeks prior to launch specifically to rule out most contagious diseases hitching a ride and ruining the mission. Maybe the ponies did something similar, or maybe magic pony arm-stealing germs don’t like the taste of poor mundane Mark.

But accepting unavoidable risk is one thing, and tempting fate is another. Even if all the bacteria we have left are the happy healthy kind, the good kind in the wrong place can be just as bad as the bad kind. Since the air in the Hab was full of ‘em today, my burned arm got a fresh sterile dressing and Starlight and I decamped for the cave.

My flight suit is wrecked- no surprise. The right arm is gone completely except for the electronics. Same deal with most of the torso. The helmet might still be good, and my left glove would be salvageable if there were some point to it without the right. The life support systems are charred and probably wrecked, but I might be able to use it for spare parts if I get that desperate. I still have my EVA suit, which was built more rugged to deal with being on a planet instead of a spaceship. I also have several other EVA suits, if it comes to that.

There’s still a good bit of perchlorate left scattered around. The eruption scattered the stuff enough that it dropped below decomposition temperature rapidly once the fuel was gone. What’s left should be easy to clean up. About a quarter of what we dumped down the hill is already blown away or sloughed into the soil. I say good riddance. If I think of some insanely suicidal plan for our survival that requires me to make solid rocket fuel I’ll ask Starlight to revive that spell. Until then I don’t want to see even a speck of pure perchlorate salts ever again.

That wasn’t the reason we went, though. We already knew that from the report Cherry and Fireball gave us. Today was about making the cave airtight.

When we went into the cave we took a magic battery and two ten-liter tanks full of compressed liquid CO₂, produced by the MAV descent stage’s fuel plant. Of course, this wasn’t a fart in the wind so far as pressurizing the cave was concerned. The open space inside could be anything from 10,000 to 50,000 cubic meters, and twenty liters of liquid CO₂ would only fill forty cubic meters to one atmosphere’s worth of pressure. Releasing it all in the cavern at once would raise the existing air pressure by about one-tenth- call it 0.1 pounds per square inch instead of 0.09 psi. (The Hab’s one atmosphere internal pressure, the same as on Earth at sea level, is 14 psi.)

But Starlight said it was enough, and I guess she was right. She used the battery to create two airtight force fields, sealing off the cave in both directions just far enough for the two of us to stand between. I opened and closed the valves on the CO₂ tanks and watched the pressure readings on my suit to keep the area in our slice of cave at one-tenth of an atmosphere (1.4 psi, or fourteen times Mars’s normal pressure).

We walked the length of the cave doing this. Starlight was wobbly on her feet to begin with, and by the time we got to the end of the dirt floor she was ready to pass out again. Still, she used one last burst of magic and all the remaining CO₂ in the tanks to get a reading clear to the far end of the cave. I ended up carrying her and the battery back to the rover; I’ll go back for the empty tanks tomorrow.

The news is actually pretty good. In fact, I’d call it suspiciously good. The cave leaks like a sieve at the entrance, but Starlight says she can fix that when the ponies put the airlock in place, ideally tomorrow. And there’s another substantial leak way at the back, almost in the middle of the hill. But most of the cave is actually airtight. I don’t know if the permafrost or compacted soil on top of the cave is creating a seal, or if the air leaking is too low for Starlight or my suit to detect it, or what. But it does mean that, after a couple of magical welding jobs, the cave will hold air.

And doing the math, it’s just now sinking in to me how much air it would require. NASA provided us with 350 liters of compressed oxygen and nitrogen. That’s enough for one atmosphere pressure for the rovers, the space suits, and the approximately 240 cubic meter interior space of the Hab, plus a significant reserve, but it’s not a drop in the bucket for the cave.

Assuming 25,000 cubic meters from entrance to rear, it would require 12,500 liters of compressed liquid air to fill the space to one atmosphere. The most oxygen I can safely transport at a time is fifty liters, and replacing that requires seventy-five hours of run time on the MAV fuel plant plus whatever time the oxygenator needs to turn carbon dioxide into oxygen. If I had to fill it myself, I’d run out of food long before there was enough air for my crops.

Luckily I don’t need to. The pony ship’s environmental system is back up and running, complete with its direct connection to their home world’s atmosphere. What would take me over a year will take them a matter of hours. Best yet, their system also provides Earth-levels of carbon dioxide (well, almost- 0.028% CO₂ instead of our global-roasting 0.045%, but that’s still plenty for plants). That limits the amount of Mars atmosphere we’ll have to bring in for our farm to thrive.

(Fun fact: plants give off almost as much CO₂ at night as they absorb during the day! Photosynthesis turns CO₂ and water into oxygen and sugar, but at night plant metabolisms reverse the process and use the sugar to live and grow on. That’s why Earth still has so many green things without requiring CO₂ atmospheric levels that would kill most animal life on the planet. But once we really get going with the plants that little difference will swamp whatever the aliens and I contribute with our own lungs, so the occasional hit off a Mars bong will be required to keep our crop nice and mellow.)

Anyway, we’re back at the Hab now, and the dirt doubling is over- probably the last one we’re going to do here. Dragonfly, bless her perforated heart, has just sweet-talked Spitfire away from doing her vulture imitation over Starlight’s bed. I’ve gotta do something nice for that bug soon. But first my three-quarters of a dinner, and then tonight’s line-up of fine quality viewing.

Leading off with The Electric Company. Of course, my mind is still blown by the fact that Morgan Freeman was once young. And, apparently, a hippie. Or a beatnik. Or a hippie beatnik. Or something. I wonder if the bug will write a sequel to her fanfic that has the Duke boys rescue Easy Reader from one of Boss Hogg’s schemes. I’m sure there could never be anything problematic with that idea whatever.

That’s sarcasm, by the way.

Author's Notes:

No time for an author's note.