Isn't the methane actually a bit mysterious though? IIUC, methane should be broken down by interaction with sunlight. So if there is trace methane in the Marti

Isn't the methane actually a bit mysterious though? IIUC, methane should be broken down by interaction with sunlight. So if there is trace methane in the Martian atmosphere, it's either coming from not-depleted sub-surface reserves (in which case: how did it get there?) or chemical processes are actively generating it in the Martian ecosystem somewhere.