Jupiter Project

carried a bright orange balloon on top. If it melts its surroundings too fast and gets caught in a lake, it will float until a team can come to fish it out.

Given half a century, they’ll give us a thick atmosphere and burn away the toxic gases. Another twenty years and there will be Earth-style air and crops and people on Ganymede. I might live to see that—or maybe by that time I’ll be in a Walker on Titan. Saturn’s huge moon.

Not that Ganymede was all that cozy now. Our cabin heater ran constantly to fight off the chill that seeped in. Halfway through Monday morning we stopped in a narrow valley and I suited up; the sensor package I had to check out was a klick away, halfway up the side of a hill. The path was too dangerous for the Walker.

I was glad to get the exercise. Ammonia fog boiled up from the valley and wreathed the peaks ahead. I got so interested in the view I almost missed the package. It was a metal box with scoops and nozzles sticking out in all directions. I opened it up and took out the set of test tube samples I was to carry back. The map had carried a red tag at this one, so I looked it over.

The water collector had a pebble caught in the middle. Probably it had lodged there during one of the pint- sized quakes Ganymede has: tidal strains keep the rock and ice sheets butting each other. I replaced a defective bleeder valve in the oxygen sampler and hiked back to the Walker.

After I unsuited I made the mandatory hourly radio call back to the base. A familiar voice answered.

“Zak!” I said. “Don’t tell me you’re holding up your literary career to stand radio watch.”

“Funny man. There isn’t anything else to do, with a bum ankle. How are you and Yuri making out?”

“Okay. Say, would you monitor that package I just fixed?”

“Sure, just a minute. Yes, she’s sending an all clear now.”

We talked for several minutes. There wasn’t any important news from the Can and Zak seemed a little bored.

Yuri nudged me. “You guys going to talk forever?”

“Signing off, Zak.” I said, and replaced the mike. “What’s bugging you, Yuri?”

“Nothing. I just don’t think you guys should jam up the airwaves with idle chatter,” he said, not looking at me.

It seemed to me he was put out because Zak didn’t ask to speak to him. Even Yuri wanted to have some friends; there’s nothing like a few days out in the Ganymede wastelands to make you feel lonely.

We stopped several times that day to check out sensor packages. Most of them were at least a few hundred meters from any spot a Walker could reach. They’re set up high to keep them out of the gully-washers that sometimes come pouring down the valleys from some distant fusion caterpillar. Yuri and I took turns going out to them; somebody has to stay with the Walker at all times.

I found one package that had been the victim of a quake. The soil under one of its legs had dropped two feet and the package was teetering on the edge of a hole. All its sample tubes had broken.

The third time Yuri went out he came back empty-handed. He couldn’t find his package. I violated regs a little—the site was only a city block away from the Walker—and walked out to it with him.

“You know, I remember this spot,” I said. “We came by here a few years ago. The package is right around this ledge.”

“Well, it’s not here now,” We were standing by a shelf of yellow rock with boulders scattered around.

“What did the map say was wrong with it?”

Yuri looked around impatiently. “It stopped transmitting a few months ago. That’s all they know.”

I turned to go. “Well, there’s—wait a minute! Isn’t that a Faraday cup?”

I bent down and picked up a little bell-like scrap of metal that was lying in the dust. “One of these is usually attached to the top of a sensor package.”

I looked at the nearest boulder. It must have weighed a ton, even on Ganymede. “I bet I know where our package is.”

We found one other piece of metal wedged under the edge of boulder. I hiked back and got a replacement package. It took a while to set up and this time we put it away from any overhang.

Getting the package’s radio zeroed in on the base was a little tricky since we were down in a low trough and had to relay the signals from base through the Walker’s radio at first. It took a big chunk out of the day. The next package to be checked was a mile walk from our planned way station for the night. We elected to leave it for morning, but then I got restless and said I would walk out to the site myself.

Jupiter’s eclipse of the sun was just ending as I set out. I took a break to watch the sun slip out from behind Jupiter. Suddenly the planet had a rosy halo; we were looking through the outer fringes of the atmosphere. The Can was a distant twinkle of white. I walked along a stream bed and in a way it was like early morning on Earth—as the sun broke out from behind Jupiter things brightened, and the light changed from dull red to a deep yellow. Everything had a clean, sharp look to it. The sun was just a fierce, burning point and there were none of the fuzzy half-shadows you’re used to on Earth. Ganymede’s man-made atmosphere is still so thin it doesn’t blur things.

I felt a pop. I stopped dead. I stood still and quickly checked my suit. Nothing on my inboard monitors. My lightpipe scan showed nothing wrong on my back. Suit pressure was normal. I decided it must have been a low-energy micrometeoroid striking my helmet; they make a noise but no real damage.

The micrometeoroid was probably some uncharged speck of dust, falling into Ganymede’s gravity well. If it had been charged, the superconductor threads woven into my suit would have deflected it. Superconductors are a marvel. Once you run a current through them, they keep producing a magnetic field—forever. The field doesn’t decay because there’s no electrical resistance to the field-producing currents. So even a one-man suit can carry enough magnetic shield to fend off the ferocious Van Allen sleet. And inside the suit there’s no magnetic field at all to disturb your instrumentation, if the threads are woven in right. The vector integrals involved in showing that can get messy, especially if you don’t know Maxwell’s equations from a mud puddle. But the stuff works, and that’s all I needed to know.

When I found the sensor package it needed a new circuit module in its radio; the base had guessed the trouble and told me to carry one along on the walk out. That wasn’t what interested me, though. This particular package was sitting in the middle of a seeded area. Two years ago a team of biologists planted an acre of microorganisms around it. The organisms were specially tailored in the Lab to live under Ganymede conditions and—we hoped—start producing oxygen, using sunlight and ice and a wisp of atmosphere.

I was a little disappointed when I didn’t find a sprawling green swath. Here and there were patches of gray in the soil, so light you couldn’t really be sure they were there at all. Over most of the area there was nothing; the organisms had died.

The trouble with being an optimist is that you get to expect too much. The fact that anything could live out here was a miracle of bioengineering. I shrugged and turned back the way I had come.

I was almost halfway back to the Cat when I felt an itching in the back of my throat. My eyes flicked down at the dials mounted beneath my transparent viewscreen. The humidity indicator read zero. I frowned.

Every suit has automatic humidity control. You breathe out water vapor and the sublimator subsystem extracts some of it before passing the revived air back to you. The extra water is vented out the back of the suit. You’d think that if the microprocessor running the subsystem failed, you’d get high humidity.

But I had too little. In fact, none.

I flipped down my rear lightpipe and squinted at my backpack. Water dripped from the lower vent. I checked my—

Dripped? I looked at it again.

That shouldn’t happen. The suit should have been venting water slowly, so it vaporized instantly when it reached the extremely thin atmosphere outside. Dripping meant the relief valve was open and all my water had been purged.

I called up a systems review on my side viewplate, just below eye level inside my helmet. From the data train I guessed the humidity control crapout had been running for over half an hour. That was what had made the popping noise. And I had written it off as a micrometeoroid. Wishful thinking.

I stepped up my pace. The tickle at the back of my throat meant I might have suit throat. That’s the coverall name for anything related to breathing processed air. If you get contaminants in the mix, or just lose water vapor, your throat and nose soon dry out, or get irritated. A dry throat is a feasting ground for any bacteria hanging around. If you’re lucky, the outcome is just a sore throat that hangs around for a while.