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Science team finds methane in meteorites from Mars

Paul Sutherland, Feature writer
Jun 18, 2015, 0:30 UTC

Sen—Controversy over whether microbial life might exist today on Mars has been fuelled by the detection of methane in the planet’s atmosphere in recent years.

Now an international team of scientists has revealed that it has found the gas trapped within martian meteorites that fell to Earth, indicating that it was in the air on Mars in historic times.

Chunks of Mars came to Earth after being blasted out of its surface by asteroid impacts many millions or billions of years ago. After orbiting the Sun for aeons, they crossed our planet’s path providing a home delivery service of martian rock samples.

Scientists have been able to tell they originate from the Red Planet because the gases trapped within the rock, which melted then resolidified during the asteroid impacts, match the known chemical composition of Mars’ atmosphere.

The latest research was led by the University of Aberdeen in Scotland, together with the Scottish Universities Environmental Research Centre, the University of Glasgow, Brock University in Ontario, and the University of Western Ontario.

The team studied samples from six meteorites made up of volcanic rock from Mars. They held gases in the same proportion and with the same isotopic composition as the martian atmosphere. But all six martian samples also contained methane. Two other meteorites which were not from Mars were checked for comparison and found to contain less methane.

The researchers say that their findings suggest that methane on Mars could be providing a food source for simple forms of life beneath the martian surface, just as it does for microbes on Earth in a range of environments. It is generally accepted that life could not live on the surface of Mars as it would be exposed to deadly levels of radiation.

The team is not suggesting that the methane was itself produced by organisms. In 2009, NASA scientists reported that plumes of methane had been detected with Earthbound telescopes as well as orbiting spacecraft raising the question of whether it was being emited by microbes.

Of the meteorite research, Professor John Parnell, of Aberdeen University, who directed the study, told Sen: “I think that the methane comes from normal chemical (non-biological) reactions between unstable minerals in martian volcanic rocks and water. The same happens on Earth and it would be odd if it didn’t happen on Mars.

“We might get a handle on this from isotopic analysis of the carbon in the methane, which we will be attempting this autumn. We tried once before, without success, but I think we have a better chance this year.”

Co-author of the study Sean McMahon, a Yale University postdoctoral associate in the Department of Geology and Geophysics, said in a statement: “Our findings will likely be used by astrobiologists in models and experiments aimed at understanding whether life could survive below the surface of Mars today.

“Even if Martian methane does not directly feed microbes, it may signal the presence of a warm, wet, chemically reactive environment where life could thrive.”

The presence of methane on Mars today has been confirmed by NASA’s Mars Science Laboratory, also known as Curiosity. Since it should only exist for around 300 years after being produced, it is thought to have been produced in relatively recent times.

Some previous studies of rocks that have fallen from Mars have led to claims that they contain signs of organisms, or “fossils”. But Professor Parnell told Sen: “No credible fossils have been found in martian meteorites.”