“A plume came and a plume went,” Paul Mahaffy, of NASA’s Goddard Space Flight Center, said about Curiosity’s detection of a methane spike during a presentation at an astrobiology meeting in Bellevue, Wash.
“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.”
“The fleet of robots orbiting and roving Mars has been on the lookout for methane, the breath of a possible something,” writes Dennis Overbye in The New York Times. “And every once in a while, the planet has complied by emitting a puff of methane.”
The Curiosity rover’s follow-up experiment this weekend found the methane had returned to background levels, NASA said Tuesday, suggesting the temporary spike while testing the air of Gale Crater was caused by one of a number of transient plumes observed by Curiosity in the past.
NASA’s Curiosity Rover last week detected the highest ever levels of the colorless, odorless gas over the course of its seven year mission on the Red Planet, raising hopes it could be evidence of the existence of microbial life. Scientists have tracked a seasonal rise and fall in background methane levels but haven’t been able to establish a pattern for the transient plumes.
Curiosity’s team conducted a follow-on methane experiment this past weekend. The results came down early Monday morning: The methane levels have sharply decreased, with less than 1 part per billion by volume detected. That’s a value close to the background levels Curiosity sees all the time.
The finding suggests last week’s methane detection — the largest amount of the gas Curiosity has ever found — was one of the transient methane plumes that have been observed in the past. While scientists have observed the background levels rise and fall seasonally, they haven’t found a pattern in the occurrence of these transient plumes.
Curiosity doesn’t have instruments that can definitively say whether the source of the methane is biological or geological. A clearer understanding of these plumes, combined with coordinated measurements from other missions, could help scientists determine where they’re located on Mars.