Astronomers have been talking about life on Mars for a century or more, but often without hard data. That situation has changed with the discovery of methane in the atmosphere. The presence of the gas there, as well as on Saturn's largest moon, Titan, might mean there is life there. Learn more in this article, "The Mystery of Methane on Mars and Titan", from the May 2007 edition of Scientific American.
©2007 Scientific American