NASA scientists have said analysis of a rock sample collected on Mars shows the planet could have supported primitive life.
Sulphur, nitrogen, hydrogen, oxygen, phosphorus and carbon - some of the key chemical ingredients for life - were discovered in a tiny sample collected by the rover Curiosity after it drilled into a rock.
At a briefing at NASA's Washington headquarters on Tuesday, experts said the rock contained clay minerals that formed in a watery environment that may have been favourable for microscopic organisms.
Michael Meyer, lead scientist for NASA's Mars Exploration Programme, said: 'A fundamental question for this mission is whether Mars could have supported a habitable environment.
'From what we know now, the answer is yes.'
Curiosity had already found a hint of the site's watery past - an ancient streambed that the six-wheel rover crossed.
Paul Mahaffy, principal investigator at NASA's Goddard Space Flight Centre in Greenbelt, Maryland, said: 'The range of chemical ingredients we have identified in the sample is impressive, and it suggests pairings such as sulphates and sulphides that indicate a possible chemical energy source for micro-organisms.'
Scientists plan to work with Curiosity in the Yellowknife Bay area of Mars for several more weeks before beginning a long drive to Gale Crater's central mound, Mount Sharp.
The rover, which is carrying 10 science instruments, landed in August last year to begin a two-year mission.