http://news.bbc.co.uk/hi/english/sci/tech/newsid_801000/801086.stm
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By BBC News Online science editor Dr David Whitehouse
Water could still be flowing on Mars, Nasa scientists believe.
The announcement follows two days of speculation that evidence exists
that recent running water has cut channels into the flanks of craters,
something previously considered impossible.
The lack of small craters superimposed on the channels and apron
deposits indicates that the features are geologically young
Images of steep-sided gullies, sinuous channels, and deltas of debris
have been captured by Mars Global Surveyor, the satellite currently in
orbit around the Red Planet.
These suggest that liquid water may be lurking just below the Martian
surface, say researchers Dr Michael Malin and Dr Kenneth Edgett in a
paper published in the journal Science.
It is a discovery that will change the direction of Mars exploration and
boost demands for a lander to be sent to investigate the water and look
for signs of life.
"If it is true that there is water on Mars near the surface, it has
profound implications for the prospect of life on Mars," said Ed Wieler,
with the office of space science at Nasa.
Short-lived torrents
The Science paper does not say that water itself has been detected -
only structures that, if found on Earth, would have been formed by water
seeping up from underground.
Material flowing down a channel covers sand dunes
The formations are unblemished by impact craters, freeze cracks, or
windblown deposits.
"These gullies could be on the order of a million years old, or they
could have formed yesterday," says Dr Malin, who with Dr Edgett works
out of Malin Space Science Systems, Inc.
The images are stunning and convincing: banked, winding, and often
branching channel paths, with final fans of debris.
They suggest that the water could exist in a porous layer of rock buried
a few hundred meters below the Martian surface, kept liquid by the
pressure exerted by overlying rock.
Cooler areas
The researchers suggest that the formation of the Martian gullies may be
linked to their location. More than 90% of them occur in the planet's
southern hemisphere, almost all of them are found on the pole side of 30
degrees latitude.
What is happening on Mars?
Compared with the rest of the Martian surface, the pictured channels
appear to be extremely young
Some of the channels are free of dust, suggesting they were only
recently washed clean
Malin and Edgett's idea is that sudden floods have cut the grooves
Atmospheric pressure is so low on Mars that liquid water will rapidly
boil away
Any evaporating seepage would be likely to freeze the ground and dam
waters building up behind
These waters might burst out, flooding down the side of cliffs
Each flood could contain as much as 2,500 cubic metres of water - enough
water to fill seven community-sized swimming pools
Volcanic heating could be driving the whole process
"These are cooler areas, areas further away from the sunlight and higher
temperatures that you get on slopes that are near to the equator or face
the equator," says Dr Edgett.
Water on Mars could be widespread. About 200 of the 60,000 images
produced by the Mars Global Surveyor are said to show evidence of
grooves carved by rivers flowing down the sides of craters in fan-shaped
patterns.
Some scientists will find this discovery unsettling because it does not
fit into what is understood about Mars. They know that water must be
there but it had been thought that it was in the form of subsurface ice
and not running water on its surface.
Liquid water is the key ingredient for life so finding it on the surface
represents a significant boost for those who think there may be
micro-organisms still living on the Red Planet.
This discovery will set the direction for the exploration of Mars in the
future.
In the next few months, scientists will closely examine new pictures
from Mars - any changes in the landforms would confirm water is flowing.
In the next few years, placing a lander in the watery region will be
what every Mars scientist wants to do.
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Warm regards
Blunderov
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