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- WASHINGTON (Reuters) - Water
on the surface of Mars is not found in bubbling springs or babbling brooks,
but in explosive bursts of mud and cold steam, scientists said on Thursday.
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- A pair of scientists examining images from NASA's orbiting
Mars Global Surveyor said they had found what look just like the gullies
formed on Earth by landslides and flash floods.
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- The most logical explanation, they say, is that water
flows up to the surface of the seemingly barren planet to make them.
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- ``We hypothesize that the thing that created all these
features is water coming out and running down a slope,'' Ken Edgett, a
staff scientist at Malin Space Science Systems in San Diego, told a news
conference.
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- Edgett and colleague Michael Malin admit they are still
puzzled by their findings. Although water is relatively common on Mars,
it was thought to be confined to the polar icecaps and perhaps found in
a few wisps in the thin atmosphere.
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- The best scientists had hoped for was perhaps an aquifer
far below the surface.
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- Dried-out beds suggest water was once abundant on Mars,
but all the evidence points to most water having disappeared billions of
years ago, along with most of Mars' atmosphere.
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- What the photographs seem to suggest, Edgett, Malin and
others told a NASA news conference, is that some of the water is still
there.
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- It shouldn't be.
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- The average temperature on the surface of Mars is far
below freezing, and it stays so cold that everything should be frozen hard
to the depth of several miles (kilometers), said Mike Carr, a planetary
geologist at the U.S. Geological Survey and an author of a book about water
on Mars.
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- ``We have conditions that seem to forbid that we have
flowing water close to the surface,'' Carr told the news conference, called
hastily after an Internet news site released news of the study by Malin
and Edgett a week before its scheduled publication.
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- ``The average temperature of Mars, particularly at these
high latitudes, is 70 to 100 degrees C (centigrade) below freezing. There
must be some mechanism by which water can flow through the near surface
that we don't understand.''
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- NASA came up with just such a mechanism.
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- Ed Weiler of the office of space science at NASA noted
that water does not last in the thin Martian atmosphere for long.
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- ``If you spit on Mars, it would probably evaporate instantly,''
Weiler said in an interview. ``But millions of gallons of water, backed
up, would burst out.''
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- NASA believes it is possible that water, warmed by geothermal
processes, seeps up toward the surface but freezes in an ice dam. This
blocks further flow, which builds up pressure behind the ice dam.
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- Finally, it bursts free in an explosion of mud, flash-frozen
ice, and vapor created by sublimation, a process seen on Earth when snow
dries up instantly into water vapor without melting first.
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- ``Some would sublimate, some would come crashing down
in a flow of mud, some would freeze instantly. You should think of these
things as flash floods. They are probably violent events, even faster than
a flash flood,'' Weiler said.
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- ``If you were an astronaut watching, preferably from
a safe distance, you would see the ice cover break, a cloud of steam, but
ice-cold steam, mud flowing downward.''
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- Malin and Edgett said they will watch the stream of photographs
being sent back by the Surveyor to see if they can catch this actually
happening.
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- ``One way we can do this is keep taking pictures. If
you see one that changes -- wow!'' Edgett said.
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- Having water on Mars makes it more likely that life might
exist there, but it also has implications for exploring the planet. Water
could be mined by astronauts not only for drinking, but to use to make
fuel.
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- Mining it could be complex, or it could be simple. ``I
might just pound a pipe into one of these layers and stand back,'' Edgett
said.
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- ``I warn you that the water might not be drinkable on
the first sip. There might be a lot of salt,'' he added.
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- There is also the possibility that a fluid other than
water caused the flows. Carr pointed to theories that an unstable compound
called clathrate, made up of carbon dioxide and water, exists under pressure
below the surface of Mars.
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- ``It could be benzene,'' added Edgett. ``But we do know
Mars has water. It doesn't have benzene polar caps.''
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