Scientists using instruments aboard the Curiosity rover now say there is methane in the atmosphere of Mars — though its odd behaviour and uncertain origin have raised fresh questions about the Red Planet.
The presence of the gas, considered to be a potential sign of life, in the Martian atmosphere has been reported and seemingly refuted before. Earth-based observatories reported seeing large “plumes” of methane in 2003 but, following its arrival in 2012, Curiosity turned up nothing.
Now, according to a paper published Tuesday in the journal Science, scientists say there is a faint hint of methane — about one part per billion — near the Gale Crater where Curiosity landed.
The strange thing is, that reading unexpectedly jumped, at least once, to almost ten times that amount. The methane levels then returned to normal.
“We’ve really been racking our brains,” about the jump, said Prof. John Moores of York University in Toronto, one of the team members that co-authored the study. “What does it all mean?”
Curiosity sends back data about once a month, Moores said. Over the last two years, the readings were providing a clearer picture of the Martian atmosphere and its methane content — until one set revealed a spike to about seven parts per billion.
Leading theories
The leading theories about why the level spiked have some significant problems, he said.
A carbon-rich meteorite might have struck the surface near Curiosity, and that carbon could have broken down into methane. But there are no fresh craters in the neighbourhood.
Methane could also be created by a chemical interaction with the Martian surface, but lab work suggests this is “not very likely.”
The methane could also be produced underground and occasionally vented to the surface.
“That makes you wonder why it happened at that time,” said Moores. “But we certainly can’t rule it out.
“Maybe there’s something about the atmosphere on Mars we don’t understand and this is our hint.”
Methane can be produced geologically though on Earth it also made by a class of bacteria known as methanogens. Its presence on Mars could be a sign of life.
But, if so, that does not necessarily mean there is life on Mars now, Moores said. Today’s methane could be left over from biological activity that took place billions of years ago, when the Red Planet is thought to have been more hospitable. Or it could be purely geological.
“It’s a bit of a puzzle,” Moores said.
