Search for life on Mars set back

Salt minerals present kill organisms.

Hopes of finding life on Mars, at least on the surface, were dealt a blow this week by a study revealing that salt minerals present on the Red Planet kill bacteria.

In lab tests on Earth, the compounds known as perchlorates killed cultures of the bacteria Bacillus subtilis, a basic life form, a research duo from the University of Edinburgh’s School of Physics and Astronomy reported.

Perchlorates, stable at room temperature, become active at high heat. Mars is very cold.

In the new study, Jennifer Wadsworth and Charles Cockell showed the compound can also be activated by UV light, without heat, in conditions mimicking those on the martian surface. It killed bacteria within minutes, they said, implying the planet was “more uninhabitable than previously thought”.

“If we want to find life on Mars, we have to take this into consideration and look at trying to find sub-surface life that wouldn’t be exposed to these conditions,” Wadsworth said.

Perchlorates are natural and man-made on Earth, but are more abundant on Mars. The fact that perchlorates killed B. subtilis in the presence of UV radiation did not necessarily mean that all other life forms would similarly die.

Perchlorates presence was presented as evidence by scientists in 2015 of liquid water on the Red Planet. But the new study said brine seeps, “although they represent local regions of water availability, could be deleterious to cells” if they contain perchlorates. The findings contain good news – that organic contaminants left on Mars by robotic exploration, of which B. subtilis is a common one, are unlikely to survive long. –