The surface and atmosphere of Mars (NASA)The chances of discovering life on Mars have fallen following the discovery that the soil on the Red Planet contains toxic chemicals capable of wiping out living organisms. Experiments show that when exposed to ultraviolet (UV) radiation from the Sun, chlorine compounds in the Martian soil are “activated”, turning them into bacteria killers. A more hospitable environment for microbes may lie two or three metres beneath the surface, where the soil is shielded from intense radiation. "At those depths, it’s possible Martian life may survive," said Jennifer Wadsworth, an astrobiologist carrying out the research along with Charles Cockell at Edinburgh University, Scotland.
Streaks on Mars seen in summer months (NASA)
These chlorine compounds, known as perchlorates, were first discovered in the Martian soil some years ago, and confirmed by NASA’s Curiosity rover in 2012–13. In 2015, the Mars Reconnaissance Orbiter detected signs of perchlorates in what look like damp streaks that were observed seeping down Martian gullies. Scientists now think that perchlorates are widespread across the surface of Mars.
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