New analysis of chemical signatures measured by NASA's Curiosity Rover gives a peek at Mars' past to a time, some 3.7 billion years ago, when it was warmer and wetter. Through measurements of isotopic ratios of oxygen, a team of collaborators, including researchers from Caltech's campus and NASA's Jet Propulsion Laboratory (JPL) have discovered that the lake which once existed in Mars' Gale Crater was undergoing significant evaporation earlier than the mineralogy and geochemistry of the lake