Projects Principal Investigator Paul Mahaffy says that "With our current measurements, we have no way of telling if the methane source is biology or geology, or even ancient or modern."
Scientists found methane in late 2013 and 2014. The amount of methane found had a ten-fold increase compared to earlier measurements. The gas has also been found on Pluto. On Saturn’s giant moon Titan, methane appears in liquid form, filling lakes and seas.