Saturday, 22 July, 2017

Toxic Cocktail to the surface of Mars

Why life on Mars may be impossible Mars Is Even Less Hospitable Than We Thought
Garry Little | 08 July, 2017, 00:28

Martian soil is laced with perchlorates, an ion composed of one chlorine and four oxygen atoms, and which binds to a number of different elements to form various compounds. If they can't survive there, it significantly lowers our chances of finding life on Mars - life that looks similar to organisms on Earth at least.

Wadsworth: We irradiated bacteria with UV in the presence of perchlorate at Martian concentrations.

Their experiments showed that when magnesium perchlorate was exposed to UV radiation similar to that on Mars, it became capable of killing bacteria much more effectively than UV light alone.

The researchers also suggest that two other components on the Martian surface - iron oxides and hydrogen peroxide - may act alongside the perchlorates resulting in a 10 times increase in bacteria death.

The impact of the radiation, combined with certain types of compounds in the soil, resulted in sterilizing the upper layers. In turn, they made a decision to delve deeper on its effect on Bacillus subtilis - a common bacteria often found on spacecrafts (via Daily Mail).

"We need to be able to be drilling maybe 20 centimetres, maybe metres, down below the Martian regolith [the mixture of dust, soil and broken rocks] and be looking for life in the rocks and the sediments below the surface, out of the way of this UV radiation", he said.

"I can't speak for life in the past", said Wadsworth.

This was a bit surprising for the researchers because the strain of bacteria used, Bacillus subtilis, belongs to a genus that actually does fine in the presence of perchlorates, as studies of the microbes in terrestrial environments have confirmed. They had a pretty generous prerequisite for the bacteria to be considered viable - anything more than zero cells that survived. "This should greatly reduce planetary protection concerns as well as any concerns about infection of astronauts", he said. Perchlorates have some characteristics that would appear to boost the Red Planet's habitability. "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".

There still remains some hope for surface microbes. Although we have our own problems with perchlorate here on Earth - too much of it can mess with the thyroid gland - the new paper suggests that perchlorate is particularly nasty on Mars.

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