On the 2,440th Martian day at Gale Crater, the Curiosity rover detected a large spike in the presence of the gas methane. It was by far the largest plume detected by the rover, and parallels an earlier ground-based discovery of an even larger plume of the gas. (NASA, JPL-Caltech, MSSS)
The presence — and absence — of methane gas on Mars has been both very intriguing and very confusing for years. And news coming out last week and then on Monday adds to this scientific mystery.
To the great surprise of the Curiosity rover team, their Sample Analysis on Mars instrument sent back a measurement of 21 parts per billion of methane on Thursday — by far the highest measurement since the rover landed at Gale Crater.
As Paul Mahaffy, principal investigator of the instrument that made the measurement, described it yesterday at a large astrobiology conference in Seattle, “We were dumbfounded.”
And then a few days later, all the methane was gone. Mahaffy, and NASA headquarters, reported that the readings went down quickly to below 1 part per billion.
These perplexing findings are especially important because methane could — and also could not — be a byproduct of biology. On Earth, more than 90 percent of methane is produced via biology. On Mars — at this point, nobody knows. But the question has certainly gotten scientists’ attention.
The most recent finding of a return to low methane levels suggests that last week’s methane detection was one of the transient methane plumes that have been observed in the past. While Curiosity scientists have noted background levels rise and fall seasonally, they haven’t found a pattern in the occurrence of these transient plumes.
“The methane mystery continues,” said Ashwin Vasavada, Curiosity’s project scientist at NASA’s Jet Propulsion Laboratory in Pasadena, California. “We’re more motivated than ever to keep measuring and put our brains together to figure out how methane behaves in the Martian atmosphere.”
This image was taken by the left Navcam on the Curiosity Mars rover on June 18, 2019, the day when a methane plume was detected. It shows part of “Teal Ridge,” which the rover has been studying within a region called the “clay-bearing unit.” (NASA/JPL-Caltech)
The nature and size of this most recent methane plume will, by chance, be the most widely observed so far.
That’s because the Mars Express orbiter happened to be performing spot tracking observations at the Gale Crater right around the time Curiosity detected the methane spike. … Read more