Images taken of sunlit craters on Mars seem to show water seeping from bedrock and flowing down before evaporating, U.S. researchers reported on Thursday. It is the first time water has been seen in motion on the dry, frozen planet and provides the strongest hint yet that life could exist there.
NASA’s Mars Reconnaissance Orbiter has recorded images of the flows in seven different places over as long as three Martian summers, the scientists report in the journal Science.
While there’s no proof the stuff moving around on the planet is water, there’s not much else it could be, said Alfred McEwen of the University of Arizona.
“These form and grow. They darken. Some of them start fading. Eventually they all fade and eventually they completely disappear,” McEwen told a news conference. “These flows appear to emanate from deep bedrock.”
Scientists have found water in several places on Mars – at the poles, in craters and just under the surface. They have even seen it snow. There’s also evidence of liquid water in the past – dry riverbeds and what are clearly dry lake beds. But never had liquid water been seen actively flowing.
“I think this is an eye-opening discovery that will really allow us to begin planning for future missions,” said Lisa Pratt, a biogeochemist at Indiana University who was not involved in the study.
The researchers said it is too warm in these places – up to 80 degrees Fahrenheit – for carbon dioxide ice to persist.
"By comparison with Earth, it's hard to imagine they are formed by anything other than fluid seeping down slopes,” said Mars Reconnaissance Orbiter project scientist Richard Zurek of NASA's Jet Propulsion Laboratory in Pasadena, Calif.
“We have followed the water and we have found repeated … evidence suggesting water flowing on Mars,” said Michael Meyer, the Mars exploration program's lead scientist at NASA headquarters. “What we have found on Earth is where there is water, there’s life.”
University of Arizona student Lujendra Ojha first spotted the dark features moving over time in repeated images sent back from the orbiting observatory.
“I was baffled when I first saw those features in the images after I had run them through my algorithm,” Ojha said in a statement. “We soon realized they were different from slope streaks that had been observed before. These are highly seasonal, and we observed some of them had grown by more than 200 meters in a matter of just two Earth months.”
There are robot explorers on Mars, but they are not close to the craters where the features were seen. NASA said it may take some time to figure out how to get a mission to the spots to directly sample them and see if there is water there – and if there are any signs of microbes or other life there.