“Yuri,” I said, “check and be sure we got our tanks filled with air and water. It’s a long way to the next—”
“Bohles, you may be sick but that doesn’t mean you can start ordering me around. I will get us there.”
I rolled over and tried to go to sleep. I heard Yuri suit up and go out. A little later there were two faint thunks as the hoses disconnected from the way station. Then Yuri came back in, unsuited and sat down in the driver’s chair.
The Cat lurched forward and then settled down to a steady pace. I decided to stop worrying and let Yuri handle things for a while. I was feeling better every minute, but another forty winks wouldn’t do any harm. I let the gentle swaying of the Walker rock me to sleep.
I woke around noon; I must have been more tired than I thought. Yuri tossed me a self-heating can of corned beef; I opened it and devoured the contents immediately.
I passed the next hour or so reading a novel. Or rather, I tried. I dozed off and woke up in mid-afternoon. There was a lot of sedative in that medicine.
I got up, pulled on my coveralls and walked over to the control board. “Walked” isn’t quite the right word—with my bunk and the table down, the Cat resembled a roomy telephone booth.
I sat down next to Yuri. We were making good time across a flat, black plain. There was an inch or so of topsoil—dust, really—that puffed up around the Cat’s feet as they stepped. The dust comes from the cycle of freezing and thawing of ammonia ice caught in the boulders. The process gradually fractures the Ganymede rock, breaking it down from pebbles to shards to BB shot to dust. In a century or so somebody will grow wheat in the stuff.
Some of the soil is really specks of interplanetary debris that has fallen on Ganymede for the last three billion years. All over the plain were little pits and gouges. The bigger meteors had left ray craters, splashing white across the reddish-black crust. The dark ice is the oldest stuff on Ganymede. A big meteor can crack through it, throwing out bright, fresh ice. The whole history of the solar system is scratched out on Ganymede’s ancient scowling face, but we still don’t know quite how to read all the scribblings. After the fusion bugs have finished, a lot of the intricate, grooved terrain will be gone. A little sad, maybe—the terraced ridges are beautiful in the slanting yellow rays of sunset—but there are others like them, on other moons. The solar system has a whole lot more snowball moons like Ganymede than it has habitable spots for people. Just like every other age in human history, there are some sad choices to make.
Yuri sidestepped a thick-lipped crater, making the servos negotiate the slope without losing speed. He had caught the knack pretty fast. The bigger craters had glassy rims, where the heat of impact had melted away the roughness. Yuri could pick his way through that stuff with ease. I leaned back and admired the view. Io’s shadow was a tiny dot on Jupiter’s eternal dancing bands. The thin little ring made a faint line in the sky, too near Jupiter to really see clearly. You had to look away from it, so your side vision could pick it out. There was a small moon there, I knew, slowly breaking up under tidal stresses and feeding stuff into the ring. It’s too small to see from Ganymede, though. You get the feeling, watching all these dots of light swinging through the sky, that Jupiter’s system is a giant clockwork, each wheel and cog moving according to intricate laws. Our job was to fit into this huge cosmic machine, without getting mashed in the gears.
I yawned, letting all these musings drop away, and glanced at the control board. “You do a full readout this morning?”
Yuri shrugged. “Everything was in order last night.”
“Huh. Here—” I punched in for a systems inventory. Numbers and graphs rolled by on the liquid display. Then something went red.
“Hey. Hey. B and C tanks aren’t filled,” I said tensely.
“What? I put the system into filling mode last night. The meter read all right this morning.”
“Because you’ve got it set on A tank. You have to fill each independently, and check them. For Chrissakes—!”
“Why is that? Was that your idea? It’s stupid to not combine the entire system. I—”
“Look.” I said rapidly, “the Cat sometimes carries other gasses, for mining or farming. If the computer control automatically switched from A to B to C, you could end up breathing carbon dioxide, or whatever else you were carrying.”
“Oh.”
“I showed you that a couple days back.”
“I suppose I forgot. Still—”
“Quiet.” I did a quick calculation. With only a third of our oxy capacity filled—correction, we’d used some already—and on our present course—
“We won’t make it to our next station,” I announced.
Yuri kept his eyes on his driving. He scowled. “What about our suits?” he asked slowly. “They might have some air left.”
“Did you recharge yours when you came back in?”
“Ah…no.”
“I didn’t either.” Another screw-up.
I checked them anyway. Not much help, but some. I juggled figures around on the clipboard, but you can’t sidestep simple arithmetic. We were in deep trouble.
Yuri stepped up the Cat’s pace. It clanked and bounced over slabs of jutting purple ice. “I conclude,” he said, “that we should call the base and ask for assistance.”
I frowned. “I don’t like to do it.”
“Why? We must.”
“Somebody will have to fly out here and drop air packs. There’s always some risk, because even Ganymede’s thin air has winds in it. We don’t understand those winds yet.”
“I see.” Yuri gave me a guarded look. “An extra mission. It would not sit well with Commander Aarons, would it?”
“Probably not.” I could tell Yuri was thinking that when the report came to be written, he’d get the blame. “But look, the real point is that somebody back at base would have to risk his neck, and all because of a dumb mistake.”
Yuri was silent. The Walker rocked on over the broken ground. A thin pink ammonia stream flowed in the distance.
“You may not like it,” he said, “but I do not intend to die out here.” He reached for the radio, turned it on, and picked up the microphone.
“Wait,” I said. “I may…”
“Yah?”
“Let’s see that map.” I studied it for several minutes. I pointed out a spot to Yuri and said, “There, see that gully that runs off this valley?”
“Yes. So what?”
I drew a straight line from the gully through the hills to the next broad plain. The line ran through a red dot on the other side of the hills. “That’s a way station, that dot. I’ve been there before. We’re slated to check it in two days, on our way back. But I can reach it by foot from that gully, by hiking over the hills. It’s only seven kilometers.”
“You couldn’t make it.”
I worried over the map some more. A few minutes later I said, “I can do it. There’s a series of streambeds I can follow most of the distance; that’ll cut out a lot of climbing.” I worked the calculator. “Even allowing for the extra exertion, our oxy will last.”
Yuri shrugged. “Okay, boy scout. Just so you leave me enough to cover the time you’re gone, plus some extra so a rocket from the base can reach me if you crap out.”
“Why don’t you walk yourself?”
“I’m in favor of calling the base right now. But I’ll wait out your scheme if you want, right here, without budging an inch. I don’t like risks.”