Maggie McKee writes: "Venus, which is now hellishly hot, may have been cooler and wetter in the past, before a runaway greenhouse effect took over. Previous research suggests any oceans it had could have survived for 2 billion years, long enough for life to emerge. But scientists can't know for sure how long the water lasted until they have proof, and now David Grinspoon and Mark Bullock suggest the evidence may be locked in a hardy mineral called tremolite. Most of the planet appears to be covered with lava, but future robotic missions could target areas that may harbor the mineral. "We know at least locally and regionally where we have bits of older terrain that poke up through the volcanic plains," says Ellen Stofan of University College London. "All of a sudden, Venus may go from a place where we thought life never had a chance to take hold, to possibly a real player in the story of life in our solar system and the evolution of habitable planets.""