Mars rover's large methane discovery excites scientists

Curiosity's record-breaking measurement fuels speculation it is from microbial Martians

Nasa's Curiosity rover has detected its largest belch of methane on Mars so far, fuelling speculation that the robot may have trundled through a cloud of waste gas released by microbial Martians buried deep under the surface.

Mission scientists announced on Monday that Curiosity had measured a record-breaking 21 parts per billion (ppb) of methane in the air in Gale crater, the rover's landing site and area of exploration. The level is substantially more than the 5.8ppb it sensed on 16 June 2013.