We don’t need nitrogen to breathe and ordinarily we don’t think much about it. But it takes nitrogen to make protein—muscle. Most plants take it out of the ground; some plants, like clover and alfalfa and beans, take it out of the air as well and put it back into the ground. Ganymede’s soil was rich in nitrogen; the original scanty atmosphere was partly ammonia—but the day would come when we would have to put the nitrogen back in that we were taking out. So the atmosphere project was now turned to making nitrogen.
This wasn’t as simple as breaking up water; it called for converting stable isotope oxygen-16 into stable isotope nitrogen-14, an energy consuming reaction probably impossible in nature—or so the book said—and long considered theoretically impossible. I hadn’t had any nucleonics beyond high school physics, so I skipped the equations. The real point was, it could be done, in the proper sort of a mass-energy converter, and Ganymede would have nitrogen in her atmosphere by the time her fields were exhausted and had to be replenished.
Carbon dioxide was no problem; there was dry ice as well as water ice on Ganymede and it had evaporated into the atmosphere long before the first homesteader staked out a claim.
Not that you can start farming with oxygen, carbon dioxide, and a stretch of land. That land was dead. Dead as Christopher Columbus. Bare rock, sterile, no life of any sort—and there never had been any life in it. It’s a far piece from dead rock to rich, warm, black soil crawling with bacteria and earthworms, the sort of soil you have to have to make a crop.
It was the job of the homesteaders to make the soil.
See how involved it gets? Clover, bees, nitrogen, escape speed, power, plant-animal balance, gas laws, compound interest laws, meteorology—a mathematical ecologist has to think of everything and think of it ahead of time. Ecology is explosive; what seems like a minor and harmless invasion can change the whole balance. Everybody has heard of the English sparrow. There was the Australian jack rabbit, too, that darn near ate a continent out of house and home. And the Caribbean mongoose that killed the chickens it was supposed to protect. And the African snail that almost ruined the Pacific west coast before they found a parasite to kill it.
You take a harmless, useful insect, plant, or animal to Ganymede and neglect to bring along its natural enemies and after a couple of seasons you’ll wish you had imported bubonic plague instead.
But that was the chief ecologist’s worry; a farmer’s job was engineering agronomy—making the soil and then growing things in it.
That meant taking whatever you came to—granite boulders melted out of the ice, frozen lava flows, pumice, sand, ancient hardrock—and busting it up into little pieces, grinding the top layers to sand, pulverizing the top few inches to flour, and finally infecting the topmost part with a bit of Mother Earth herself–then nursing what you had to keep it alive and make it spread. It wasn’t easy.
But it was interesting. I forgot all about my original notion of boning up on the subject just to pass a merit badge test. I asked around and found out where I could see the various stages going on and went out and had a look for myself. I spent most of one light phase just looking.
When I got back to town I found that George had been looking for me. “Where in blazes have you been?” he wanted to know.
“Oh, just out and around,” I told him, “seeing how the ‘steaders do things.”
He wanted to know where I had slept and how I had managed to eat? “Bill, it’s all very well to study for your merit badges but that’s no reason to turn into a tramp,” he objected. “I guess I have neglected you lately—I’m sorry.” He stopped and thought for a moment, then went on, “I think you had better enter school here. It’s true they haven’t much for you, but it would be better than running around at loose ends.”
“George?”
“Yes, that’s probably the best-huh?”
“Have you completely given up the idea of home-steading?”