Mars the water bearer

Scientists are beginning to see the telltale signs of warmth and wetness on Mars in the mineralogical studies made possible by data from the Reconnaissance Orbiter. In an article in the November issue of the journal Geology, spectroscopist Scott Murchie, of the Johns Hopkins Applied Physics Laboratory has analyzed opal evidence from Reconnaissance's data. Opals are hydrated silicas and their formation requires liquid water. According to Murchie and colleagues the opal deposits they have studied lie in regions formed just two billion years ago. Previously, water-bearing minerals in clays have been dated to 3.5 billion years. Water was obviously more widespread and extended to younger times than previous research suggested.