NASA's Mars Curiosity rover landed in the Gale Crater when it touched down the Red Planet in August 2012. Had the robotic probe landed on the same site at some point in Mars' distant past, it would have landed on a pool of water.
Curiosity has found evidence indicating that the Gale Crater, now an arid and plain landscape, was once a huge lake of water that was able to support microbial life for a long period of time.
Mars Exploration Program lead scientist Michael Meyer said that this lake was large enough; it possibly lasted millions of years, a period that should be enough to jumpstart and sustain life on the Red Planet. This length of time is also sufficient for the lake sediments to build up and form Mount Sharp.
Observations made by Curiosity show that Mount Sharp, which forms the central peak within the 96-mile-wide Gale Crater, was built by sediments deposited in the lake bed over millions of years, suggesting that ancient Mars may have had a climate that could produce lakes that thrived for a long time at many spots on the Martian planet.
"To sustain a lake at Gale Crater for millions of years, Mars would need a vigorous hydrological cycle to keep the atmosphere humid," said Curiosity deputy project scientist Ashwin Vasavada. "The humidity could be explained by expanses of warmer ice at lower latitudes, or even better - by expanses of liquid water, like an ocean."
At the lower flanks of the 3 mile tall Mount Sharp are hundreds of rock layers with alternating lake, river and wind deposits that indicate repeated filling and evaporation of a large and long-lasting Martian lake.
Curiosity likewise spotted beds of sandstone that slope toward the 3 mile-tall Mount Sharp at a number of locations, and these inclined beds are seen on Earth at deltas where rivers once flowed into lakes. Since the deposits were observed at multiple elevations, this suggests that they were stacked up in multiple cycles.
"We found sedimentary rocks suggestive of small, ancient deltas stacked on top of one another," said Curiosity science team member Sanjeev Gupta. "Curiosity crossed a boundary from an environment dominated by rivers to an environment dominated by lakes."
Meyer said that by deciphering how Mount Sharp formed, scientists can gain insights on the environmental evolution of the Red Planet and this could help in planning out future missions that aim to look for signs of alien life in Mars.
