Farmer in the Sky by Robert A. Heinlein Page A

miles in diameter. They say a man can come pretty close to jumping right off it. I asked George about it and he said, no, the escape speed was about five hundred feet per second and who had been filling me up with nonsense?
    I looked it up later; he was right. Dad is an absolute mine of useless information. He says a fact should be loved for itself alone.
    Callisto was behind us; we had passed her on the way in, but not very close. Europa was off to the right of our course nearly ninety degrees; we saw her in half moon. She was more than four hundred thousand miles away and was not as pretty a sight as the Moon is from Earth.
    Ganymede was straight ahead, almost, and growing all the time—and here was a funny thing; Callisto was silvery, like the Moon, but not as bright; Io and Europa were bright orange, as bright as Jupiter itself. Ganymede was downright dull!
    I asked George about it; he came through, as usual “Ganymede used to be about as bright as Io and Europa,” he told me. “It's the greenhouse effect—the heat trap. Otherwise we wouldn't be able to live on it.”
    I knew about that, of course; the greenhouse effect is the most important part of the atmosphere project When the 1985 expedition landed Ganymede had a surface temperature a couple of hundred degrees below zero—that's cold enough to freeze the milk of human kindness! “But look, George,” I objected, “sure, I know about the heat trap, but why is it so dark? It looks like the inside of a sack.”
    “Light is heat; heat is light,” he answered. “What's the difference? It's not dark on the ground; it goes in and doesn't come out—and a good thing, too.”
    I shut up. It was something new to me and I didn't understand it, so I decided to wait and not pound my teeth about it.
    Captain Harkness slowed her down again as we came up to Ganymede and we got in one good meal while she was under drive. I never did get so I could eat at free fall, even with injections. He leveled her off in a tight circular orbit about a thousand miles up from Ganymede. We had arrived—just as soon as we could get somebody to come and get us.
    It was on the trip down to Ganymede's surface that I began to suspect that being a colonist wasn't as glamorous and romantic as it had seemed back on Earth. Instead of three ships to carry us all at once, there was just one ship, the Jitterbug, and she would have fitted into one of the Bifrost's compartments. She could carry only ninety of us at a time and that meant a lot of trips.
    I was lucky; I had to wait only three days in free fall. But I lost ten pounds.
    While I waited, I worked, helping to stow the freight that the Jitterbug brought up each trip. At last it came our turn and we piled into the Jitterbug. She was terrible; she had shelves rather than decks—they weren't four feet apart. The air was stale and she hadn't been half way cleaned up since the last trip. There weren't individual acceleration couches; there were just pads covering the deck space and we covered the pads, shoulder to shoulder—and foot in your eye, for that matter.
    The skipper was a loud-mouthed old female they called “Captain Hattie” and she kept bawling us out and telling us to hurry. She didn't even wait to make sure that we were all strapped down.
    Fortunately it didn't take very long. She drove away so hard that for the first time except in tests I blacked out, then we dropped for about twenty minutes; she gunned her again, and we landed with a terrible bump. And Captain Hattie was shouting, “Out you come, you ground hogsl This is it.”
    The Jitterbug carried oxygen, rather than the helium-oxygen mix of the Mayflower. We had come down at ten pounds pressure; now Captain Hattie spilled the pressure and let it adjust to Ganymede normal, three pounds. Sure, three pounds of oxygen is enough to live on; that's all Earth has—the other twelve pounds are nitrogen. But a sudden drop in pressure like that is enough to make you gasp anyhow. You