Nasa is preparing to unveil a "major science finding" from its Mars exploration programme, amid speculation it could have found water flowing on the Red Planet. The space agency has scheduled a press conference for Monday, in which it promises to announce a "Mars Mystery Solved". While many are hoping for a discovery of alien life, the leading theory among those who follow research into Mars is an announcement of the presence of liquid water. The speculation has been driven by Nasa's disclosure that Lujendra Ojha, a PhD candidate who discovered possible signs of water as a 21-year-old undergraduate student...