"We're trying to simulate what kind of mechanisms are possible and are active on Mars in order to see this behavior," Guiseppe Marzo, a researcher with ENEA, the Italian National Agency for New Technologies, Energy and Sustainable Economic Development, told Discovery News.
Marzo and colleagues found three regions in the planet's northern hemisphere with consistently higher concentrations of methane -- Tharsis, Elysium and Arabia Terrae. Tharsis and Elysium are home to Mars' most massive volcanoes and Arabia Terrae has large quantities of subterranean frozen water.
Methane concentrations are highest in autumn and tail off dramatically in winter. Levels build up again in spring and climb rapidly during summer, causing the gas to spread across the planet, the researchers found.
Lead researcher Sergio Fonti, with Italy's Universita del Salento, says the seasonal pattern rules out the possibility that the methane is due to cosmic ray bombardment or meteorite impacts.
"It could be geology or biology, but it is not coming from another source. There is a seasonal pattern, so it could only be a local origin," Fonti told Discovery News.