Ezt pedig nem is tudtam a Mentőexpedíció-val kapcsolatban:

(a könyvben meg van magyarázva, hogy tud Whitney termeszteni:)

The book does explain it. One of Watney's roles on the mission is botany. As part of his equipment, he has a small amount of Earth soil and various seeds for doing experiments. (I'm not sure how much he could have done in a 30-day mission, but never mind.) "Then I can sprinkle the Earth soil on top [of his bootleg Martian soil]. There are dozens of species of bacteria living in Earth soil, and they're critical to plant growth. They'll spread out and breed like ... well, like a bacterial infection. ... [After a week] I'll spread some of the live soil over [more Martian dirt]. It'll "infect" the new soild and I'll have double what I started with." Repeat, repeat, repeat.