Washington: Led by a team of scientists of Indian-origin, NASA's Curiosity rover has found new evidence of water on Mars, indicating that the planet most like Earth in the solar system was suitable for microbial life.
Pictures and other data collected by NASA's Mars rover Curiosity show that rivers once flowed into a lake or lakes at the bottom of Gale Crate, an enormous dimple carved out by an incoming space rock.
NASA said its interpretation of Curiosity's finds in Gale Crater suggests ancient Mars maintained a climate that could have produced long-lasting lakes at many locations on the Red Planet.
The American space agency said Mars's Mount Sharp was built by sediments deposited in a large lake bed over tens of millions of years.
"If our hypothesis for Mount Sharp holds up, it challenges the notion that warm and wet conditions were transient, local, or only underground on Mars," said Indian-American Ashwin Vasavada, who is the Curiosity deputy project scientist at NASA's Jet Propulsion Laboratory in Pasadena.
The thickness of the rock outcrops indicates that the lake or lakes must have sloshed around the bottom of 154-km Gale Crater over the course of millions of years, though the lake probably dried up and then reappeared a number of times, the researchers said.
"A more radical explanation is that Mars' ancient, thicker atmosphere raised temperatures above freezing globally, but so far we don't know how the atmosphere did that," he added.
Mount Sharp stands about three miles (5 kilometers) tall, its lower flanks exposing hundreds of rock layers.
The rock layers -- alternating between lake, river and wind deposits -- bear witness to the repeated filling and evaporation of a Martian lake much larger and longer-lasting than any previously examined close-up.
In a statement NASA said why this layered mountain sits in a crater has been a challenging question for researchers.
"We are making headway in solving the mystery of Mount Sharp," said Curiosity Project Scientist John Grotzinger of the California Institute of Technology in Pasadena, California. "Where there's now a mountain, there may have once been a series of lakes."
Curiosity currently is investigating the lowest sedimentary layers of Mount Sharp, a section of rock 500 feet (150 meters) high dubbed the Murray formation.
Rivers carried sand and silt to the lake, depositing the sediments at the mouth of the river to form deltas similar to those found at river mouths on Earth.
This cycle occurred over and over again.
"The great thing about a lake that occurs repeatedly, over and over, is that each time it comes back it is another experiment to tell you how the environment works," Grotzinger said.
On the 5-mile (8-kilometer) journey from Curiosity's 2012 landing site to its current work site at the base of Mount Sharp, the rover uncovered clues about the changing shape of the crater floor during the era of lakes.
"We found sedimentary rocks suggestive of small, ancient deltas stacked on top of one another," said Curiosity science team member Sanjeev Gupta of Imperial College in London.
"Curiosity crossed a boundary from an environment dominated by rivers to an environment dominated by lakes," he said.
