Richardson reported in late June, 2021 that an instrument attached to NASA’s Curiosity rover, called the Tunable Laser Spectrometer (TLS), has detected methane on Mars, but the traces found are inconsistent. On the back of this, an investigation by international space agencies was launched to look at why the gas is disappearing, and where it is going. While the Curiosity rover has repeatedly found traces of the gas that is associated with life above the surface of the Gale Crater, the European Space Agency’s ExoMars orbiter has yet to detect it higher in the planet’s atmosphere.
The TLS on the Curiosity rover has also had fluctuations in its readings of methane. The rover has typically found methane at one-half part per billion, which is the ‘equivalent to about a pinch of salt diluted in an Olympic-size swimming pool’. Nonetheless, a sharp spike was recorded in 2019 that wasn’t found by instruments used by other space agencies.
The differences in readings between sensors have inspired scientists to consider how methane is disappearing. Chris Webster, who leads the TLS instrument for NASA, noted that the team considered every possibility, even that the rover’s movement could be crushing rocks that may release methane. Eventually, the team discovered that because the TLS primarily operates at night, when the gases will remain on the calm surface it will be finding the gas undisturbed. However, when it is the day, the sunlight causes these intriguing gases to dissipate in the atmosphere. In a press release, NASA noted:
"Heat from the Sun churns the atmosphere as warm air rises and cool air sinks. Thus, the methane that is confined near the surface at night is mixed into the broader atmosphere during the day, which dilutes it to undetectable levels."
The researchers published their findings on the surprising gas phenomenon, and concluded that this atmosphere change is happening across the red planet. Chris Webster explained that the team now wants to investigate how the methane is disappearing so quickly:
"Very low-level electric discharges induced by dust in the Martian atmosphere could destroy methane, or whether abundant oxygen at the Martian surface quickly destroys methane before it can reach the upper atmosphere. We need to determine whether there’s a faster destruction mechanism than normal to fully reconcile the data sets from the rover and the orbiter."
While the study explains discrepancies in methane readings, it still leaves the mystery of where the gas is coming from. This will undoubtedly be researched further because of its connection to life on the planet.
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