The mountain that NASA's Mars rover Curiosity is exploring appears to have been the site of a large lake, one that likely filled and drained over tens of millions of years, scientists said Monday.
The discovery is based on data collected by Curiosity over the past 2.5 years, including findings of sediment beds of sandstones that are inclined toward Mount Sharp, a three-mile high mound rising from the center of a 96-mile wide impact crater.
ANALYSIS: Curiosity Surveys Wind-Rippled Sandy 'Sea' on Mars
"We can see a whole series of beds, of sandstones, with some pebble beds in there, that are actually inclined at a large scale toward the south," Curiosity scientist Sanjeev Gupta, with Imperial College in London, told reporters on a conference call.
Scientists believe that means that not only did Mount Sharp not exist at the time, but that Curiosity's Gale Crater landing site was once -- and possibly many times over -- a shallow lake.
Similar inclined beds are found on Earth at the mouths of river channels where they feed into lakes, Gupta said.
NEWS: Curiosity Finds Tantalizing Mineral Clues for Mars Habitability
The research indicates that Mount Sharp formed from sediments deposited in the center of the lakebed over millions of years. The sediments would have been carried in rivers originating from the crater rim highlands -- which may have been capped in snow or ice -- and ending in the waters that filled the crater basin. Scientists suspect that winds later eroded the deposits, eventually creating the mountain.
"We are beginning to think that maybe Mount Sharp formed in a series of episodes involving sedimentation and erosion, stacked by different processes," said lead Curiosity scientist John Grotzinger, with the California Institute of Technology in Pasadena.
Scientists suspect there were many cycles of wet and dry times at Gale Crater and that the cycle continued for millions or tens of millions of years, boosting chances that conditions were suitable for microbial life.
ANALYSIS: Curiosity Finds a Weird 'Ball' on Mars
"The size of the lake in Gale Crater and the length of time and series that water was showing up implies that there may have been sufficient time for life to get going and thrive," said NASA's Mars Exploration Program scientist Michael Meyer.
Curiosity landed inside Gale Crater to assess if the planet most like Earth in the solar system has or ever had the chemical ingredients and conditions for life. It found a life-friendly habitat almost immediately and spent the next 14 months driving to the base of Mount Sharp for additional studies and more ambitious experiments to try to find places where organic carbon may have been preserved.
Scientists have not yet released companion chemical data on the lakebed deposits.