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NASA Confirms Signs of Water Flowing on Mars, Possible Niches for Life

Scientists have for the first time confirmed liquid water flowing on the surface of present-day Mars, a finding that will add to speculation that life, if it ever arose there, could persist now.

“This is tremendously exciting,” James L. Green, the director of NASA’s planetary science division, said during a news conference on Monday. “We haven’t been able to answer the question, ‘Does life exist beyond Earth?’ But following the water is a critical element of that. We now have, I think, great opportunities in the right locations on Mars to thoroughly investigate that.”

That represents a shift in tone for NASA, where officials have repeatedly played down the notion that the dusty and desolate landscape of Mars could be inhabited today.

But now, John M. Grunsfeld, NASA’s associate administrator for science, talked of sending a spacecraft in the 2020s to one of these regions, perhaps with experiments to directly look for life.

“I can’t imagine that it won’t be a high priority with the scientific community,” he said.

Although Mars had rivers, lakes and maybe even an ocean a few billion years ago, the modern moisture is modest — small patches of damp soil, not pools of standing water.

In a paper published in the journal Nature Geoscience, scientists identified waterlogged molecules — salts of a type known as perchlorates — on the surface in readings from orbit.

“That’s a direct detection of water in the form of hydration of salts,” said Alfred S. McEwen, a professor of planetary geology at the University of Arizona, the principal investigator of images from a high-resolution camera on NASA’s Mars Reconnaissance Orbiter and one of the authors of the new paper. “There pretty much has to have been liquid water recently present to produce the hydrated salt.”

By “recently,” Dr. McEwen said he meant “days, something of that order.”

Scientists have long known that large amounts of water remain — but frozen solid in the polar ice caps. There have been fleeting hints of recent liquid water, like fresh-looking gullies, but none have proved convincing.

In 2011, Dr. McEwen and colleagues discovered in photographs from the orbiter dark streaks descending along slopes of craters, canyons and mountains. The streaks lengthened during summer, faded as temperatures cooled, then reappeared the next year.