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NASA's Curiosity rover finds signals of possible life on Mars

NASA’s Curiosity rover has detected bursts of methane gas on Mars, suggesting the existence of past or present life on the planet.

While methane is present consistently at low levels (about 0.7 parts per billion by volume (ppbv), the discovery of short-lived spikes registering 10 times or higher than background levels has had some scientists speculating as to its origin.

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95 per cent of all methane present on Earth originated from microbial organisms, leading some researchers to hope the bursts are connected to Martian life. However, scientists have stressed that the most probable origin of the gas is underground stores known as clathrates.

"These are molecular cages of water-ice in which methane gas is trapped. From time to time, these could be destabilised, perhaps by some mechanical or thermal stress, and the methane gas would be released to find its way up through cracks or fissures in the rock to enter the atmosphere," Professor Sushil Atreya of the University of Michigan told the BBC.

Even if clathrates are found to be the source, the question of how the methane gas got there remains unanswered. It could still be the result of organic life or geological processes such as serpentinisation, but further analysis is required to form a definitive conclusion.

Curiosity is capable of analysing “enriched samples” of Martian air, where the most abundant molecule, carbon dioxide, is removed to enable more accurate analysis of trace gases like methane. If a particular isotope of carbon (carbon-12) is more prevalent in the methane, this is likely to suggest a biological origin.

The methane spikes were recorded four times over a two-month period and are likely to have occurred nearby the rover.

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After also discovering organic compounds in some of its rock samples, the Curiosity team have experienced a momentous week, described by project scientist Professor John Grotzinger as the “crowning moment of 10 years of hard work.”