The Curiosity rover has detected seasonally varying levels of methane in Gale crater on Mars, which could have geological or astrobiological sources. The ExoMars Trace Gas Orbiter (TGO) spacecraft has detected no methane on Mars despite having better sensitivity than Curiosity, but had not yet examined the Gale location. Measurements from TGO were always for high altitudes during local dawn or dusk and those from Curiosity for the surface at midnight. Webster et al. used Curiosity to search for methane during the day, finding none and inferring a day–night cycle. Montmessin et al. performed TGO measurements at new locations, including close to Gale, ruling out methane with tight upper limits. Together, these two studies indicate that methane is released and trapped within Gale crater during the night and then rapidly dissipates or is destroyed during the day.
Astron. Astrophys. 650, A166, A140 (2021).
