As the search for life on Mars continues, orbital snapshots suggest a deep crater may have held a substantial lake.
The McLaughlin Crater, 92 km across with a depth of 2.2 km, may have been deep enough to allow underground water to flow into the crater's bed.
"The observations in McLaughlin Crater provide the best evidence for carbonate forming within a lake environment, instead of being washed in from outside," Joseph Michalski, the lead author of the paper presenting the latest findings, said in a statement.
Scans of the crater by NASA's Mars Reconnaissance Orbiter showed layered, flat rocks, containing carbonate and clay minerals that usually form in the presence of water.
The findings suggest the groundwater may have welled up into the crater, possibly providing a consistent wet environment that could have been home to life.
The search for signs of life on Mars has picked up speed since the Orbiter arrived at Mars in 2006.
On the planet surface, NASA's famed Curiosity rover has been making headlines since landing in 2012.
However, its quest has yielded a trove of data, but no conclusive evidence of life, after scans for methane
and organic compounds
came back negative.