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Evidence of flowing H20 on Mars
06/12/2006 20:48 - (SA)
Washington - Images taken by Nasa's Mars
Global Surveyor spacecraft suggest the presence of liquid water
on the Martian surface - a tantalising find for scientists
wondering if the Red Planet ever has harboured life.
The orbiting US spacecraft allowed scientists to detect
changes in the walls of two Martian craters that may have been
caused by the recent flow of water, a team of researchers saidin a paper appearing on Wednesday in the journal Science.
Scientists previously had established that two forms of
water - ice at the poles and water vapor - existed on Mars, but
liquid water is crucial to nurture life.
The scientists compared images of the Martian surface taken
seven years apart and found the existence of 20 newly-formed
craters caused by impact from space debris as well as the
evidence suggesting liquid water trickling down crater walls.
"These observations give the strongest evidence to date
that water still flows occasionally on the surface of Mars,"
Michael Meyer, lead scientist for Nasa's Mars exploration
programme, said. Close to surface
The paper said water seemed to have flowed down two gullies
in the past few years, even though liquid water cannot remain
long on the planet's frigid, nearly airless surface because it
would rapidly freeze or evaporate. This seemed to support the
notion that liquid water may exist close enough to the planet's
surface in some places that it can seep out from time to time.
The scientists proposed that water could remain in liquid
form long enough on the surface to transport debris downslope
before freezing. The two bright new deposits are each several
hundred meters long.
They cited a possible alternative explanation that these
features were caused by movement of dry dust down a slope.
Scientists long have wondered whether life ever existed on
Mars. Liquid water is an important part of the equation. On
Earth, all forms of life require water to survive.
Among the planets in our solar system, only Earth has a
more hospitable climate than Mars, and some scientists suspect
Mars once sheltered primitive, bacteria-like organisms.
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