A Gas Could Hint at Signs of Life on Mars. Why Hasn’t a New Spacecraft Found It?
The newer spacecraft entered orbit around Mars in 2017 and carries more sensitive instruments than Mars Express, which arrived in 2003. While the Trace Gas Orbiter has so far failed to find methane, that does not mean Mars Express and the Curiosity rover were wrong. Methane, if it is there in the thin Martian air, is significant, because sunlight and chemical reactions would break up the molecules within a few centuries. Thus any methane detected now must have been released recently. On Earth, almost all methane is produced by living organisms, although it is also generated by geothermal reactions devoid of biology.