NASA finds evidence of recent flowing water on Mars

A NASA spacecraft circling Mars has found evidence of water on the Red Planet’s surface — liquid that flowed in our lifetime, not in some dim and more verdant past.

New data reveal that Earth’s close neighbor boasts multiple seeps of salt-laden water that were wet, or at least damp, as recently as last year. The water may be many times saltier than Earth’s ocean, but there could be enough to provide a bonanza for humans exploring the surface.

“Mars is not the dry, arid planet we thought of in the past,” NASA planetary science chief Jim Green said Monday. “Under certain circumstances, liquid water has been found on Mars.”

Until now, “we thought of the current Mars as a barren, extremely dry and cold desert,” SETI Institute planetary scientist Janice Bishop, who did not take part in the research, said via email. “What is new and exciting here is that this provides evidence for liquid water on Mars in the current environment.”

Eons ago, Mars had enough water to fill enormous lakes and rivers. Scientists prospecting for the wet stuff in recent decades, however, had to content themselves with ice at the planet’s poles, small amounts of water vapor in the atmosphere and water locked up in minerals in the Martian soil. The wet Mars of billions of years ago seemed to have become a desiccated world.

But five years ago, researchers spotted mysterious dark streaks running down the warm slopes of Martian craters and mountains. The lines disappeared in the cold season and reappeared in the warm season, like spring freshets on Earth. They looked tantalizingly like a sign of liquid water, but landslides or dust couldn’t be ruled out, said study co-author Scott Murchie of the Applied Physics Laboratory.

So Murchie and his colleagues had NASA’s Mars Reconnaissance Orbiter take a closer look. Along the mysterious lines, the spacecraft detected the signature of waterlogged molecules of perchlorate, chemicals made up of chlorine and oxygen, the scientists report in this week’s Nature Geoscience. Something is moistening Mars' ample deposits of perchlorate, said study leader Lujendra Ojha, a graduate student at the Georgia Institute of Technology. And that something must be liquid water.

Maybe the perchlorate itself is pulling water vapor out of the Martian atmosphere. Or maybe water from melting ice flows down hillsides and soaks the perchlorate in the soil. Or maybe water is trickling out of an aquifer. The amount of water could be huge: the scientists estimated that one dark line contains, at a minimum, enough water to fill 40 of the enormous swimming pools used for international competitions.

“That sounds like a lot,” study co-author Alfred McEwan of the University of Arizona, Tucson, said Monday, but that amount of water spread over a large area amounts to a “thin layer of wet soil, not standing water.”

Each wet place may be less of a stream and “more of a sludge,” said planetary scientist David Vaniman of the Planetary Science Institute, who was not a part of the study team. Even if there were ponds, perchlorates are toxic.

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“Water is the elixir of life,” said Mars expert Ray Arvidson of Washington University in St. Louis, who wasn’t part of the study either. Still, “I wouldn’t particularly want to live in a perchlorate fluid.” Ojha concedes that the briny water spotted by his team would not be hospitable to living creatures.

All the same, the seeps could be “an important source of water for a future human mission to Mars,” Bishop said via email, and its presence in a wide variety of Martian terrains indicates there are water cycles on Mars that Earthlings don’t fully understand. However, humans have sent a fleet of sophisticated satellites and rovers to scour the planet.

“Mars is being Mars,” Vaniman said. “It’s always throwing curves at you.”