Would the presence of methane on Mars suggest the presence of life on the Red Planet? Two Dartmouth College researchers don't think so. Mukul Sharma and Chris Oze have weighed in on the debate by suggesting that methane could just as readily have been produced by inorganic chemical processes as by putative bacteria. "Most methane on Earth is produced by bacteria, and methane has been cited as an indicator of life on other planets," explains Sharma. However, he and Oze explain in Geophysical Research Letters, that the mineral olivine can be altered in the presence of water and carbon dioxide to produce copious quantities of methane. "It's quite easy to do, and there is nothing bacterial about it. If there is life on Mars, I would like to see better evidence than methane," says Sharma.