The strange puzzle of methane on Mars continues. Previously, NASA’s Curiosity rover found something odd: It detected fluctuating levels of methane in the Martian atmosphere, even though an orbiting satellite, the European Space Agency’s (ESA) Trace Gas Orbiter, found no evidence of methane using its highly sensitive detection levels. It is theorized that life could exist beneath the Martian surface which is producing the gas, which then escapes up to the surface in plumes.