Friday, January 26, 2007

Sun not responsible for no water on Mars

WASHINGTON (Reuters) - Scientists trying to find out where all the water on Mars went ruled out one culprit on Thursday -- new measurements show the Sun did not blow it away.
They measured ions -- charged particles -- being blown off the planet by the solar wind, itself a stream of charged particles.
Very little oxygen or carbon dioxide was blown off the planet during the year they measured it, the team at the Swedish Institute of Space Physics and Center d'Etude Spatiale des Rayonnements in Toulouse, France, reported.
"Mars was once wet but is now dry, and the fate of its ancient carbon dioxide atmosphere is one of the biggest puzzles in Martian planetology," they wrote in their report, published in the journal Science.
Several missions to Mars have found indirect evidence that water flowed relatively recently on its surface, and it seems fairly clear to experts that the dusty red planet was once covered with lakes, oceans and perhaps rivers.
There is also carbon dioxide ice, but very little -- much less than there must have been in the warm atmosphere that would have been needed to hold the water in place millions of years ago.
"What happened to the Martian water and carbon dioxide?" the researchers wrote.
One theory was that the solar wind, a steady stream of charged ions, carried it away. So the researchers, led by Stas Barabash in Sweden, measured this using a special instrument aboard the European Space Agency's Mars Express orbiter.
"We have measured the current loss rate due to the solar wind interaction," they wrote.
"The escape rate is low, and thus one has to continue searching for water reservoirs and carbon dioxide stores on or beneath the planetary surface and investigate other escape channels."
One other idea is an asteroid or some other large object hit Mars in the distant past and literally knocked off its atmosphere and large bodies of water.

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