NASA's Curiosity rover has found evidence that the area in Gale crater it is traveling through once had vigorously flowing water for perhaps thousands or millions of years.A shallow river once coursed through a great crater on Mars, according to the latest surface images, which suggest the dusty planet was more hospitable in ancient times.
Photographs from Nasa's Curiosity rover revealed clear signs of an ancient waterway winding from the northern edge of the Gale crater towards the base of Mount Sharp, a mountain that rises 5km from the crater floor.
Several pieces of evidence attest to this hypothesis, but the key feature was a strange rock sticking out of the Martian regolith that Curiosity spotted two weeks ago. The rock (above), nicknamed Hottah, â€œlooked like someone came to the surface of Mars with a jackhammer," said John Grotzinger of Caltech, project scientist for the mission, during a NASA press conference on Sept. 27, adding that it wouldn't look out of place as a slab of concrete in downtown L.A.
The $2.5bn (£1.6bn) mobile science laboratory began its work on Mars after a dramatic arrival last month in which the rover was winched to the surface from a spacecraft hovering overhead on rocket thrusters.
Curiosity is not searching for signs of past or present life, but for evidence that Mars was once habitable. Scores of earlier missions have found evidence of water on the red planet. Snapshots from spacecraft in orbit around Mars have beamed back images of ancient lakes and gullies. The north and south poles are largely frozen water.
These pictures are the first to show stones and gravel that had been dragged along the Martian surface by a river. Nasa geologists said the rounder shape of some of the pebbles suggests they had travelled long distances from above the crater rim.
Curiosity's next step is to pull out its vast array of sophisticated instruments to chemically analyze this area on Mars. The rover is currently on its way to an area named Glenelg, where it will search for further confirmation of water. Along the way, it will stop and scoop some Martian sand to run through its internal laboratory. It will look for evidence of organic carbon that might indicate the presence of ancient life.