The methane mystery on Mars is exciting because the gas is known to break down in just 400 years.
The detections, therefore, suggest the gas was produced or released in the relative past.
In June 2019, NASA scientists behind the Curiosity rover mission detected about 21 parts per billion units by volume (ppbv) of methane – the largest amount of methane ever measured by the mission.
However, it was unclear what the source of the methane was and follow-up measurements a week later produced significantly lower results.
Paul Mahaffy of NASA’s Goddard Spaceflight Center said: “With our current measurements, we have no way of telling if the methane source is biology or geology, or even ancient or modern.”