NASA rover Opportunity finds signs Mars once had fresh water

NASA's decade-old Mars rover, Opportunity, has found evidence that life-friendly fresh water once pooled on the red planet's surface, reinforcing similar discoveries made by newcomer Curiosity on the other side of the planet, scientists said on Thursday. Opportunity, along with its now-defunct twin, Spirit, landed 10 years ago for concurrent 90-day missions to look for clues of the past existence of water. In August 2012, Curiosity, equipped with an onboard chemistry lab, arrived for follow-up investigations to determine if Mars had other ingredients essential for supporting life. On the other side of the planet, meanwhile, Opportunity has been analyzing water-bearing rocks at the rim of an ancient impact crater called Endeavour.