NASA says samples taken by its "Curiosity" rover on the surface of Mars show the red planet could have supported life long ago.
Scientists from the U.S. space agency released their findings on March 12, seven months after "Curiosity" landed on Mars and a month after the rover used its robotic arm to dig deep inside a rock.
And what "Curiosity" found, NASA scientists say, are some of the building blocks of life, including evidence that liquid water was once present, as well as clays, sulfates, and other minerals.
"You can imagine [our] relief, landing there and then almost right off the bat we do find evidence of water and we see an ancient riverbed," said NASA scientist Michael Myer. "We're now finding an environment in the near sub-surface -- not too far beneath the oxidized layer -- of finding sort of a neutral rock. All the things that we were really hoping for to find a place that could have been habitable in its past.
"As far as I'm concerned, this is fantastic. All the rest is gravy in terms of how the rover is going to go about looking around this area because it definitely [has] all the indications of being an inhabitable environment at one point in time."
Scientist John Grotzinger described the water that once flowed through the area, known as Yellowknife Bay.
"I think we have found a habitable environment that is so benign and supportive of life that probably if this water was around, and if you had been on the planet, you would have been able to drink it," he said.
Scientist David Blake spelled out the impact of the findings.
"What's the take-home message about this?" he said. "I think this is probably the only definitively habitable environment that we've described and recorded. There are places we would suggest could be habitable, but we haven't measured there."
In May, NASA says "Curiosity" will drill a second hole into the Gale Crater rock to look for organic compounds.
Earlier, NASA's other Mars rovers -- "Opportunity" and "Spirit" -- also found evidence that Mars once flowed with water. But at the time, NASA scientists judged the water was likely too acidic to support microbes, single-cell organisms.
With reporting by AP and Reuters