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. Last Updated: 07/27/2016

Evidence of Water Clashes With Mars Theory




WASHINGTON -- The standard description of Mars as cold, desolate and dry may have to be revised slightly. It now appears that Mars may have reservoirs of liquid water hidden under parts of its icy surface, a finding that could profoundly affect the search for life there, scientists said Thursday.


Pictures taken from orbit by NASA's Mars Global Surveyor spacecraft have disclosed features in numerous locations that look like gullies formed by flowing water carrying rocks and debris to the bottom of craters, according to a study released Thursday.


The report, by Dr. Michael Malin and Dr. Kenneth Edgett of Malin Space Science Systems in San Diego, said evidence suggested these water flows happened in recent geological time, perhaps just a few hundreds, thousands or millions of years ago instead of billions of years in the past. And the researchers said it may still be occurring.


"We see features that look like gullies formed by flowing water and the deposits of soil and rocks transported by these flows,'' said Malin, whose company built the spacecraft camera that made the images. "These features appear to be so young that they might be forming today.''


At a news conference on Thursday in the headquarters of the National Aeronautics and Space Administration, the researchers said there was ample evidence that water once flowed on Mars, leaving ancient river beds and the markings of huge oceans. One of the big questions about Mars, Edgett said, has been, "Where did the water go?''


"The new pictures from Global Surveyor tell us part of the answer,'' he said. "Some of that water went underground, and quite possibly it's still there.''


The researchers, whose study will be published next week in the journal Science, said they found evidence for the flow of liquid water in 150 of 65,000 photos taken by the Surveyor's high resolution camera over the last two years. The evidence of water movement, in the form of gullies and channels terminating into fan-like deltas, appears recent because surfaces around these features are smooth and relatively light in color. Older areas on the planet are pocked with craters and covered with a dark dust, they said.


Both researchers said they were surprised by evidence of possible present-day water because the finding does not fit into current models of what Mars is like. Most of the spots that appear to be the source of flowing water are on slopes with exposed rock layers, they said, raising the possibility that liquid water is trapped below these layers and is freed by a surface shift.


Dr. Michael Carr, a planetary geologist with the U.S. Geological Survey in Menlo Park, Calif., called the images "exciting,'' saying the gullies and channels looked like water-worn features seen when flying over the western United States. However, he said he was skeptical about the researchers' theory that there was liquid water in layers 300 to 1,300 feet below the surface that occasionally burst out from the walls of certain craters and canyons.


Carr, author of "Water on Mars," said Mars that any water near the surface, which has an average temperature of minus 51 Celsius, should be frozen. Carr said that while the new pictures show important features, he is skeptical. "Either this interpretation is wrong or there is some mechanism we don't know of to keep water liquid under these conditions,'' he said.


Edgett said a possible explanation for the features was that water, kept liquid by a still-unknown means, would freeze and form an ice dam as it flowed from an underground source. The ice dam would retard the flow until there was enough force to break through the barrier, sending the water in a cascade down the slope, like a flash flood. The water would quickly freeze as its motion slowed and then quickly sublimate into gas because of the planet's low atmospheric pressure, he said, but not before spreading rocks and mud down the slope.


While the theory is "very compelling,'' Carr cautioned it is possible that the features were not caused by liquid water, but by dry avalanches or rock flows lubricated by carbon dioxide emissions from the planet.


Other scientists were excited by the finding, but remained perplexed.


"It's kind of like we have a crime scene and a really strong suspect f but the suspect has a good alibi. The alibi is that physics doesn't allow liquid water on Mars,'' said John Callas, a research scientist on the Mars exploration team at the Jet Propulsion Laboratory in Pasadena, Calif.


Mars scientists are fixated on finding liquid water because it is a major prerequisite for life on Earth and is thought to be a requirement for extraterrestrial life. While the new finding does not suggest vast pools of water at the surface, it does indicate there is enough water near the surface to support some forms of life, Jakosky said.


Dr. Edward Weiler, NASA's chief scientist, said if there was liquid water on Mars, it would have profound implications for the question of life on the planet, both in the past and today, and where to search for it. "If life ever did develop there, and if it survives to the present time, then these landforms would be great places to look,'' he said.


On Earth, some forms of life can survive repeated freezing and thawing and can exist within ice, he said. The discovery of so-called "extremophiles'' has scientists moving away from the "Goldilocks theory of biology'' where conditions must be "just right'' for life to exist, Weiler said.


Weiler said that the findings would have to be verified and explained if they were to become widely accepted. And he cautioned against exaggerating the discovery, alluding to some news reports on the find in recent days. "There is possible evidence of liquid water,'' he said. "They have not found lakes or rivers flowing on Mars. They have not found hot springs. They certainly have not found hot tubs with Martians in them.''


Excitement over the finding led to immediate speculation over whether NASA would redirect or speed up plans to explore Mars and whether the discovery would justify a manned mission to the Red Planet.


If the presence of subsurface water was proved, Weiler said, it could fuel a desire to send humans to Mars. A new orbiter is scheduled to be launched to Mars in April, and NASA is currently deciding whether to send an orbiter or a lander to the planet in 2003. NASA will continue, Weiler said, with its "follow the water'' approach.