Image: ExoMars Trace Gas Orbiter analyzes the atmosphere of Mars. (ESA/ATG Media Lab)
Planetary scientists have struggled for years with the question of why some measuring instruments detect methane on Mars and others not. For example, the American Mars explorer Curiosity has repeatedly detected large amounts of methane above the surface of Gale crater, while the European space probe TGO higher in the atmosphere of the red planet has found almost no methane.
Some experts have suggested that it may have been curiosity itself that released the methane, but it appears that a simpler gas has now been found for the notable difference.
The discrepancy between the two types of measurements is probably related to the Curiosity and TGO work tables. Because methane measurements use a lot of electricity, Curiosity takes measurements primarily at night. This occurs when the Martian atmosphere is at its calmest and measurable amounts of methane can accumulate above the surface.
On the other hand, the TGO space probe needs sunlight to detect methane high above the surface of Mars. During the day, the turbulence causes the current methane gas to spread throughout the atmosphere. That is why methane detectors at TGO detect practically no methane.
To test this hypothesis, devised by Canadian planetary scientist John E. Morris, Curiosity’s team has now taken both day and nighttime measurements of methane. It appears that the amount of methane actually drops to nearly zero during the day. In short, there is already methane from the bottom of Mars, but its average over the course of the day is not as much as suggested by the nighttime measurements.
The mystery of methane on Mars has not yet been fully resolved. It is not clear why the released methane does not accumulate in the atmosphere. Methane is a stable molecule that lasts on Mars for 300 years before being degraded by the sun’s radiation. Therefore, other explanations for the rapid collapse of methane are now being sought, including small electrical discharges in the Martian atmosphere. So that continues.