Back in March, scientists from the Netherlands’ Wageningen University successfully grew ten different crops in Mars-like soil provided by NASA. But there was a catch: they couldn’t eat the food. They worried it contained heavy metals like cadmium and lead, which were present in the Mars soil stimulant. Well, good news: further research determined at least four of the crops do not contain dangerous heavy metal levels and are therefore edible, getting us one step closer to life on the Red Planet.

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The Wageningen team, led by ecologist Wieger Wamelink, tested radishes, tomatoes, rye, and peas. They tested the crops for cadmium, lead, aluminium, nickel, copper, chrome, iron, arsenic, manganese, and zinc. None of those compounds appeared in dangerous levels, and Wamelink said the results are “very promising.” Some of the heavy metal concentrations detected in the food were even less than those found in plants cultivated in regular potting soil. The plants were also tested for vitamins, alkaloids, and flavonoids.

Related: Scientists are growing ten different kinds of crops in Mars-like soil

While we don’t yet know whether NASA or Mars One will reach the red planet first, both entities support the research. NASA provided the soil stiumlant, mainly from a Hawaii volcano. Mars One co-founder and CEO Bas Lansdorp said in a press release, “Growing food locally is especially important to our mission of permanent settlement, as we have to ensure sustainable food production on Mars. The results of Dr. Wamelink and his team at Wageningen University & Research are significant progress towards that goal.”

A crowdfunding campaign is still going, and that money will allow Wamelink’s team to test the other six crops, including potatoes. You can donate here until the end of August. If all the vegetables grown contain heavy metal amounts lower than those stipulated by the FDA and the Dutch Food Agency, Wamelink’s team will host a “Martian dinner” at the Wageningen greenhouse.

+ Can we safely eat plants grown on Mars?

Images via Bryan Versteeg/Mars One and Food for mars and moon Facebook