Unknown artist, SCIENCE@NASA





Larger illustration.





Ancient Mars had a thick

atmosphere and abundant

surface water (more).



Breaking News On May 30, 2012, scientists published a paper suggesting that a large portion of the atmospheric methane detected on Mars may have been generated by ultraviolet radiation of fallen carbonaceous meteorites. They based their hypothesis from experiments using samples from the Murchison meteorite (which has a high carbon content), which gave off methane when exposed to levels of ultraviolet radiation equivalent to sunlight falling on Mars' surface and varies seasonally and by latitude (matching the observed methane). As Mars experiences a higher rate of meteorites landing on its surface, the scientists provide a non-biological explanation for much, if not most, of its detected methane (University of Edinburgh press release; and Keppler et al, 2012).