A National Aeronautics and Space Administration (NASA) rover searching for signs of previous water on Mars has found the strongest evidence yet: a vein of gypsum, a mineral deposited by water, protruding from an ancient rock. The Opportunity rover and its twin, Spirit, arrived on opposite sides of Mars in early 2004. Over the years, the rovers, aided by several orbiting spacecraft, have returned a convincing body of evidence that Mars was not always as cold and dry as it is now. The most convincing proof, revealed this week at the American Geophysical Union conference in San Francisco, California, is the gypsum discovery. The substance, commonly known as plaster of Paris, typically forms from water flowing through rock. “This is the single most bullet-proof observation that I can think of that we've made this entire mission,” Steve Squyres, the lead researcher for NASA's Mars rover program, told Reuters. While Spirit, which is no longer operational, and Opportunity previously have found evidence of other water-deposited minerals, many questions remained. “They've been moved around by wind. They've been mixing with other materials. It's a big, jumbled, fascinating mess,” Squyres said. In contrast, the newly found gypsum is threaded into a rock. “This stuff formed right here. There was a fracture in the rock. Water flowed through it. Gypsum was precipitated from the water,” Squyres said, adding that both the chemistry and the geologic conditions indicate the presence of water. Water is considered by be a key condition for life. A new rover, named Curiosity, is en route to Mars to assess if another site, called Gale Crater, has or ever had water and other ingredients, including organics, necessary for life.
