Someday, perhaps not too far in the distant future if Elon Musk gets his way, there will be humans on Mars. Although we can take resources with us, it will be far more sensible in the long run to grow our own crops there. Although The Martian makes it seem almost easy to do this, the reality is that very few experiments in this regard have been conducted in real life.

Fortunately, Dutch scientists this week have announced that four varieties of vegetables and cereals grown on soil very similar to that found on the Red Planet have been found safe to eat. Radishes, peas, rye, and tomatoes were found to contain no dangerous levels of heavy metals – such as lead, copper, and cadmium – which can be harmful to human health.

“These remarkable results are very promising,” said the project’s senior ecologist Wieger Wamelink, a researcher at the Wageningen University in the Netherlands, as reported by the Guardian. “It’s important to test as many crops as possible, to make sure that settlers on Mars have access to a broad variety of different food sources.”

Since 2013, the university has managed to raise 10 different crops on simulated Martian soil, but some of them may still be unsafe to consume. Further tests are being conducted on these additional crops – which include potatoes, garden rocket, and water cress – to make sure they also do not preferentially absorb any dangerous heavy metals.

Testing if crops can be grown on Martian soil is just one part of a huge effort to understand whether or not agriculture on Mars is currently plausible. In the long term, it has been suggested that geoengineers could initiate a global warming program on the surface, which will aim to warm the atmosphere, melt the ice caps, and perhaps flood parts of the planet with a mixture of fresh and somewhat briny water.

Even in the short term, though, a lot of water will still need to be produced on site in order to keep the crops satiated. There are several ways to do this on a small scale, but it’s most likely that the first manned missions to Mars will bring the water with them on cargo shuttles. Either that, or they can dredge up ice from the caps or the subsurface reservoirs to keep them going for a while.