The Perchlorate Factor: Will Insidious Chemicals Slow Elon Musk’s Mars Plans?
published during a waning gibbous moon.

Guy Fleegman, crewmember of The NSEA Protector of Galaxy Quest expresses concern over the hostility of an alien world. YouTube.

“It’s an alien planet! Is there air? You don’t know!”

As Galaxy Quest’s crew touched down on an alien world, Guy Fleegman seemed to be the only one concerned about their environmental safety. Was there air? Or, perhaps, was there an insidious chemical that might—over prolonged exposure—lead to human fatalities? The later might be a reality for the nearby Red Planet.

That’s the fear of many Mars researchers and thinkers who have begun to express concern about potentially dangerous levels of the chemical perchlorate on the Martian surface. Perchlorates—cations consisting of a single chlorine atom bound to four oxygen atoms (ClO4)—are toxic to humans in high doses, interfering with the thyroid’s ability to absorb iodine.

Perchlorates were discovered on Mars by the Phoenix Lander in 2009, and they have since been found by the Mars Curiosity Rover as well. Phoenix Principle Investigator Peter Smith told “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.”


The instruments aboard NASA’s Curiosity Mars rover test the past and present habitability of Mars. Credit: NASA/JPL-Caltech/MSSS

Perchlorates getting into Mars habitats would be troubling for astronauts’ health, and based on our limited experience with lunar dust, such an outcome seems all but certain. Apollo astronauts dealt extensively with dust problems—even from inert Lunar regolith that posed no fundamental health risks. Moon dust got inside the guts of their equipment, blocking seals and causing irritation due to inhalation. Thus, airlock innovations that allow for the removal of Martian regolith from spacesuits may be essential for successful human colonization.

Paradoxically, while perchlorates pose risks to human health on the Martian surface, they may also provide some interesting benefits. As salts, perchlorates help lower the freezing temperature of water, possibly encouraging liquid brines to flow on the surface of Mars. These Martian brines may provide environments for microbial life, either extant today (but as yet undiscovered), or inoculated by humans during future terraforming efforts.


Evidence for percholate salts was found at the ‘Rocknest’ site studied by NASA’s Mars rover Curiosity. Credit: NASA/JPL-Caltech/MSSS

The chemicals also provide a potential source of oxygen, since they contain four times as many oxygen as chlorine atoms. Chemical digestion of perchlorates could, therefore, contribute to efforts to produce drinking water or rocket propellant.

In many plans to send humans to Mars, utilization of local resources figures prominently. For instance, the Mars Direct plan offered by Robert Zubrin, President of the Mars Society, utilizes local atmospheric carbon dioxide to produce oxygen for water and fuel. Many of the same techniques were recently featured in the hard-science-fiction novel, The Martian. However, few if any plans have been proposed to deal with potential chemical surface hazards, such as perchlorates.

SpaceX CEO Elon Musk recently announced the company’s intention to launch an unmanned Dragon capsule to the Martian surface in 2018, with a human mission to follow in 2024. Musk has yet specifically to address the potential risks of perchlorate toxicity to astronauts, but he may do so soon: Musk plans to reveal his humans-to-Mars architecture in late September.

Perhaps the innovator has a new chemical reaction up his sleeve?