With a poof, Mars methane is gone

Nasa's Curiosity rover on Mars on June 18, 2019. The rover detected a belch of natural gas on the red planet that has since dissipated. Photo / Nasa/JPL-Valtech via The New York Times

Last week, Nasa's Curiosity rover detected a belch of natural gas on the red planet. The gas has since dissipated, leaving only a mystery.

Mars gave a good burp last week, but the gas has come and gone, leaving scientists no closer to knowing whether there is life on or beneath the red planet.

On June 19, scientists grew excited when Nasa's Mars Curiosity rover, while testing the air of Gale Crater, detected high levels of methane, which on Earth can be produced by microbes or other living things.

Curiosity's keepers at the Jet Propulsion Laboratory, in Pasadena, California, cancelled the rover's weekend plans to repeat the experiment, hoping for clues that might point to the existence of life on the planet. But the second reading indicated that the methane had fallen to its normal level in the Martian air — less than 1 part per billion, all but nonexistent.

Only a few days earlier, the methane level had spiked to 21 parts per billion, according to the rover's Sample Analysis at Mars experiment.

"A plume came and a plume went," Paul Mahaffy, of Nasa's Goddard Space Flight Centre, said Sunday during a presentation at an astrobiology meeting in Bellevue, Washington.

"The methane mystery continues," Ashwin R. Vasavada, a mission project scientist, said in a statement from the Jet Propulsion Laboratory, where Curiosity was built. "We're more motivated than ever to keep measuring and put our brains together to figure out how methane behaves in the Martian atmosphere."

Methane, better known as natural gas, can be produced by microbes, including those that live in the guts of cows, or by purely geological processes. On Mars, sunlight and other chemical reactions should quickly destroy the molecule.

The fleet of robots orbiting and roving Mars has been on the lookout for methane, the breath of a possible something. And every once in a while, the planet has complied by emitting a puff of methane.

Scientists don't know for sure where the gas is coming from or what is producing it. The first indications that methane was present in the Martian atmosphere came from telescopes on Earth and from Mars Express, a European Space Agency satellite launched in 2003. In 2013, both Curiosity and Mars Express registered a spike in methane up to 7 parts per billion that lasted at least two months.

But a more recent satellite, the European Trace Gas Orbiter, which arrived at Mars in 2016, has not reported any methane. And Mars Express, which passed over Gale Crater the same day as Curiosity saw its recent spike, has not yet reported its own results from that day.

Scientists working on the two European orbiters are still analysing recent measurements.

"Until this is done we cannot say more," said Marco Giuranna, who is in charge of the Mars Express instrument that can measure methane.

Giuranna, however, says the event appeared not too different from the burst in 2013 that was observed by both Curiosity and Mars Express.