Mars’s surface is much more toxic than we thought, study finds

With the discovery of organic molecules and evidence that liquid water once flowed (and may still be flowing) on Mars, many scientists believe that it’s only a matter of time until they find evidence of life on the Red Planet. A newly-published study, however, suggests otherwise.

Writing in the journal Scientific Reports, Jennifer Wadsworth and Charles S. Cockell from the UK Centre for Astrobiology at the University of Edinburgh reported that compounds in Martian soil become toxic to biological organisms when exposed to ultraviolet rays from the sun.

As Engadget explained, the compounds are known as perchlorates, and their existence on Mars was long speculated but was only confirmed by rovers four years ago. Since then, scientists have debated exactly how this discovery would affect the search for life on the Red Planet.

Some suggesting that arguing that their presence of actually increased the odds of finding life on Mars because perchlorates lower water’s freezing point and could be a potential source of energy for microbial lifeforms. In a series of experiments, however, Wadsworth and Cockell discovered that the presence of perchlorates would actually speed up the demise of Martian bacteria.

Findings underscore the need to search for life underground

Using Earth-based microbes, the duo mixed them with Martian perchlorates, then exposed them to UV rays similar to those found on Mars. They found that the bacteria died off twice as quickly as they would have without the perchlorates. Furthermore, adding other elements found in Mars’ soil to the equation caused them to die off even more rapidly.

Specifically, Wadsworth and Cockell explained, adding iron oxide and hydrogen peroxide to the perchlorates caused bacteria to be killed more than 10 times faster than they were when only the perchlorates were present, according to Engadget. Their conclusion? In its current condition, the surface of Mars is “more uninhabitable than previously thought.”

However, as Wadsworth told The Guardian, that doesn’t mean that all hope of discovering life on Mars is lost. Rather, it means that scientists will have to look below the surface if they hope to sometime discover microbes on the Red Planet. The best environment for such organisms, she told the UK newspaper, would be two to three meters below the planet’s surface, where they are more likely to be protected from the sun’s intense UV radiation.

The news isn’t all bad, though. As Chris McKay, a planetary scientist at NASA’s Ames Research Center in California, told The Guardian, the findings show that any microbes that hitch a ride to Mars onboard spacecraft launched from Earth are unlikely to survive conditions on the surface of the planet.

“This should greatly reduce planetary protection concerns as well as any concerns about infection of astronauts,” McKay explained. “But the bad news is that this means we have to dig to quite some depth to reach a biological record of early life that is not completely destroyed by the reactive UV-activated perchlorates.”

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Image credit: NASA/JPL/Cornell University

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