Normalmente, você não pode cultivar plantas em solo marciano ... mas adicionar nutrientes ao solo o torna perfeitamente utilizável.
Existe um ótimo artigo sobre isso em Modern Farmer :
And, yes, it is possible to grow plants on Mars—kind of. Alone, Martian soil doesn’t have the necessary elements for plant life. “The main thing that’s not in Martian soil is a bunch of nutrients and biological materials that plants rely on to grow,” Weir says. “It’s not there because, obviously, there’s no life on Mars.”
So to get biological material into Martian soil, Watney uses the only spare biological material he has: astronaut poop. He mixes it in with the Martian soil, plants some potatoes that NASA had sent up with his crew, and, voila, you have plant life on Mars.
Existem alguns pequenos problemas ...
Primeiro, no momento em que Weir escreveu o romance, ele não sabia que havia grandes quantidades de sal no solo, o que provavelmente mataria qualquer planta ou mataria qualquer humano que a comesse se não fosse removido primeiro:There’s just one problem that Weir didn’t address, because he didn’t know about when he wrote the novel: Martian soil has perchlorates, a type of salt that’s hazardous to the human body. The perchlorates would either make it more difficult for plants to grow, or would make the plants toxic. The solution is actually very simple, but it wasn’t included in the book or movie. “You can literally just rinse them out of the soil,” Weir says. “Wash the soil, soak it in water, and the water would wash the perchlorates away.”
Isso é um pouco problemático porque a falta de água também foi um problema para a Watney, mas é superável.
A outra questão é que o uso de resíduos humanos para adicionar nutrientes introduz agentes patogênicos que poderiam fazer com que qualquer pessoa os adoecesse. Weir aborda isso também, fazendo com que Watney use apenas o cocô que tem seus próprios patógenos. Todo o cocô de seus companheiros foi deixado de fora em temperaturas que matariam completamente os patógenos.Eating food grown from someone else’s poop, in other words, can get you sick. In Watney’s’s case, he uses his own poop, so he would contract only the pathogens he already has. “You can get away with it in a desperate survival situation, where you are a single person using your own manure to grow crops that only you eat,” Weir says.
But Watney also uses the crew’s leftover waste from the station’s toilet, which could mean that he could have contracted his crew members’ pathogens as well. (The movie isn’t as gross as it sounds, we promise.) This is addressed with a bit of explanation in the book, but isn’t said explicitly in the film.
“The crew’s waste was all completely desiccated, freeze-dried, and then dumped out on the surface of Mars and bagged,” Weir says. “Any pathogens in there would have been dead.”
Como nota, a maior parte da ciência em The Martian tem sido bastante sólida porque Weir fez um grande trabalho estudando a ciência e aprendendo o que ele precisava para que ele pudesse escrever um < href="http://www.iflscience.com/space/how-accurate-martian-9-things-movie-got-right-and-wrong"> história muito realista .
"The Martian" is hitting cinemas right about now, and already it is being heralded as one of the most scientifically accurate sci-fi films of all time. We’ve seen the movie, and we’ve got to say, it’s amazing how far we’ve come since "Armageddon" (shudder). NASA has been so impressed, they've been using the movie as a marketing campaign for their own, actual manned missions to Mars in the 2030s.
E, como um bônus, parece que alguns na NASA realmente acreditam que o solo pode ser usado como está:
In the movie, after becoming stranded on the surface, Watney resorts to using a combination of his own excrement, water, and Martian soil to grow potatoes. But would Martian soil actually be of any use? Isn’t it sterile and dead?
“In terms of basic mineral content and chemical content, yes it would be possible to grow plants in Martian soil,” said Lavery. “We actually have experiments going on right now using simulated Mars soil, and it indicates that’s a very realistic idea.”