"As soon as we start to eat them, those heavy metals can pose a problem for us," Wieger Wamelink, an ecologist working on the experiments, told The Washington Post in March.
After testing four of the 10 crops they harvested — radish, pea, rye and tomato — the scientists announced Friday that the plants don't contain concentrations of heavy metals that would be dangerous to humans.
"The four crops are therefore safe to eat," they said in a press release, "and for some heavy metals, the concentrations were even lower than in the crops grown in potting soil."
The radishes contained the most heavy metals, which include copper, lead and cadmium, though Wamelink said it wasn't clear if that's because they hadn't been properly cleaned.
"These remarkable results are very promising," Wamelink told Agence France Presse. "... I am very curious what they will taste like."
All this doesn't mean that we're suddenly ready to stage "The Martian" with real humans — for one thing, the results haven't been peer reviewed and published in a scientific journal yet, so they need to be viewed with some skepticism. For another, simulated Martian soil is not the same thing as actual soil from Mars. The scientists were working with a rough approximation based on chemical tests conducted by Mars orbiters and landers. They can't know for sure whether Martian agriculture will work until they try with dirt from the planet itself.
The team still needs to test the remaining six crops, and they have a crowdfunding campaign going to raise the money to do so. Once they have determined that all 10 plants are safe to eat, they hope to organize a meal for their funders made out of their faux-Martian crops.
Wamelink's research has been backed by MarsOne — the much-ballyhooed, privately-funded project that aims to send people on a one-way trip to Mars by 2020 (a goal that many scientists say is unrealistic) — and he believes that the findings could help people survive on Mars.
But his main interests are much closer to home. Wamelink says that the ability to cultivate crops in less-than-ideal soil could help address hunger here on Earth.
"There are over 7 billion people on the planet, and they have to be fed," Wamelink told The Post. "One solution is to grow crops in places where it's now basically impossible."