First 'Unambiguous' Signs Of Water On Mars

Researchers using data from a NASA satellite orbiting Mars said Monday they have found clear evidence of intermittent flows of salty water on the red planet, the first "unambiguous" signs of liquid water on the surface and a possible indicator of microbe-friendly environments in the frigid soil.

"This is a significant development, as it appears to confirm that water -- albeit briny -- is flowing today on the surface of Mars," John Grunsfeld, an astronomer and former shuttle astronaut who heads up NASA's space science operations, said in a statement.

The apparent flows were first noticed in 2010 by Lujendra Ojha, then a student at the University of Arizona, studying photographs taken by the Mars Reconnaissance Orbiter. Dark streaks were apparent in the walls of steep craters near the equator that faced the sun during the warmer summer months.

The streaks appeared to brighten and darken over the martian year, fading away during the cold winter months and showing back up in warmer weather when the temperature climbed back above minus 10 degrees Fahrenheit.

Scientists came up with a variety of explanations for the branching channel-like streaks, arguing they could have been caused by brief rushes of sub-surface water, dust slides or other non-liquid phenomena. The water hypothesis appeared to be a stretch given the low pressure of the martian atmosphere and constant, below-freezing temperatures.

But spectroscopic data from the Mars Reconnaissance Orbiter has revealed telltale signatures of hydrated salts, known as perchlorates, around numerous crater wall channel sites known as "recurring slope lineae," or RSLs.

The hydrated minerals are consistent with magnesium perchlorate, magnesium chlorate and sodium perchlorate. Found on Earth in desert environments, perchlorates have been shown in the laboratory to keep liquids from freezing at temperatures as low as minus 94 degrees Fahrenheit.

On Mars, the hydrated salts "would lower the freezing point of a liquid brine, just as salt on roads here on Earth causes ice and snow to melt more rapidly," NASA said in a statement.

Researchers said a sub-surface flow of briny water could allow enough liquid to "wick" its way to the surface to explain the recurring slope lineae.

"We found the hydrated salts only when the seasonal features were widest, which suggests that either the dark streaks themselves or a process that forms them is the source of the hydration," said Ojha, now at the Georgia Institute of Technology and lead author of a paper publishedMonday by Nature Geoscience.

"In either case, the detection of hydrated salts on these slopes means that water plays a vital role in the formation of these streaks," he said in the NASA statement.

Data from a variety of spacecraft have shown that Mars once hosted a warmer, wetter environment with a thicker atmosphere, flowing rivers and large bodies of water on the surface.

While Mars was once habitable for life as it's known on Earth -- water, organic compounds and energy from sunlight were present -- it's not clear how long those conditions persisted or whether life ever had a chance to evolve. Mars today is a cold, desert world.

But the discovery that liquid water still flows on the red planet, even intermittently, bolsters the odds that microbial life of some sort could, in theory, still exist on the red planet.

"When most people talk about water on Mars, they're usually talking about ancient water or frozen water," Ojha said. "Now we know there's more to the story. This is the first spectral detection that unambiguously supports our liquid water-formation hypotheses for RSL."

Said Michael Meyer, NASA's lead Mars scientist: "It seems that the more we study Mars, the more we learn how life could be supported and where there are resources to support life in the future."

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