In all the discussion about colonising Mars, I don't see much about how the soil is poisonous to us. This was only discovered in 2008. It contains perchlorates, which are environmental toxins here on Earth. Any human contact with Mars dust? Bad news in the long run. 1/

That's basically *the entire surface of the planet* being poisonous - not just to us, but plant life too. Even if the temperature, pressure, radiation and various other human biology problems are solved, this alone will be a super-hard thing to fix: sciencedirect.com/science/ar… 2/