Scientists have found evidence of an ancient freshwater lake on Mars well suited to support microbial life, the researchers said. The lake, located inside Gale Crater where the rover landed in August 2012, likely covered an area 31 miles long and 3 miles wide, though its size varied over time. Analysis of sedimentary deposits gathered by NASA's Mars rover Curiosity shows the lake existed for at least tens of thousands of years, and possibly longer, geologist John Grotzinger, with the California Institute of Technology in Pasadena, told reporters at the American Geophysical Union conference in San Francisco.
"We've come to appreciate that is a habitable system of environments that includes the lake, the associated streams and, at times when the lake was dry, the groundwater," he said. Analysis of clays drilled out from two rock samples in the area known as Yellowknife Bay show the freshwater lake existed at a time when other parts of Mars were dried up or dotted with shallow, acidic, salty pools ill-suited for life.
In contrast, the lake in Gale Crater could have supported a simple class of rock-eating microbes, known as chemolithoautotrophs, which on Earth are commonly found in caves and hydrothermal vents on the ocean floor, Grotzinger said. Scientists also reported that the clays, which form in the presence of water, were younger than expected, a finding that expands the window of time for when Mars may have been suited for life. The planet's surface is riddled with geologic features carved by water, such as channels, dried up riverbeds, lake deltas and other sedimentary deposits.
Scientists will continue to look for rocks that may have higher concentrations of organics or better chemical conditions for their preservation, Grotzinger said. "A key hurdle that we need to overcome is understanding how those organics may have been preserved over time, from the time they entered the rock to the time that we actually detect them," said Curiosity scientist Jennifer Eigenbrode with NASA's Goddard Space Flight Center in Greenbelt, Maryland.