Last year, NASA's Curiosity Rover confirmed something discovered by multiple previous Martian landers: the surface of the red planet is full of reactive chlorinated hydrocarbons known as perchlorates. That's great news for the search for life on Mars, but it could be a disaster for any new life hoping to travel there.

As Leonard David explains over at, perchlorates are frequently used as a food source by microbes on Earth, and the unusually high concentration of the chemicals on Mars could provide microbes with all the energy they need to survive on the barren world. But perchlorates can be toxic to humans, particularly with respect to the thyroid. David quotes the University of Arizona's Peter Smith, the principal researcher for NASA's Phoenix mission, who explains just why the presence of perchlorates could be so problematic for future human missions to Mars:

"Perchlorate is not a common word in the English language; all of us had to go and look it up. Perchlorate has become an important component of the soil … and half a percent is a fair amount... Anybody who is saying they want to go live on the surface of Mars better think about the interaction of perchlorate with the human body. At one-half percent, that's a huge amount. Very small amounts are considered toxic. So you'd better have a plan to deal with the poisons on the surface. It'll get into everything… certainly into your habitat."

It's not all bad news — some perchlorates are a component of rocket fuels, and they might even be used to obtain oxygen on the Martian surface. It's well worth checking out David's entire column, as he argues that this represents a real concern for future missions, but definitely not an insoluble problem. For more, head over to



Top image via NASA.