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Last Updated: Friday, 22 August, 2003, 10:27 GMT 11:27 UK
Mars 'not a watery world'
Hopes that Mars once had vast oceans of water and perhaps microbial life have suffered a setback.

A US space agency (Nasa) spacecraft has failed to find evidence that the Red Planet was once a warm, watery world like the Earth.

Copyright Carlos Coimbra
This really points to a cold, frozen, icy Mars that has always been that way
Dr Philip Christensen, Arizona State University
Scientists have been searching for decades for signs of water-related carbonate minerals on the Martian surface.

Mars Global Surveyor, which is orbiting the planet, has at last come up with the goods.

But it has found only traces of carbonates in dust, which probably came from the atmosphere rather than rocky outcrops deposited by oceans.

"What we don't see is massive regional concentrations of carbonates, like limestone," said Dr Joshua Bandfield, a planetary geologist at Arizona State University, Tempe. "We're not seeing the white cliffs of Dover or anything like that."

Frozen planet

Some have argued that early in the 4.5 billion year history of Mars, its climate was much warmer and wetter.

Water flowed on Mars? Nasa
Geological features suggest water once flowed on Mars
If this was the case, oceans may have formed, producing extensive carbonate rock layers like those seen on Earth.

Mars Global Surveyor has been looking for signs of these rocks with its infrared spectrometer instrument.

The fact it has not found large quantities of carbonates suggests Mars is an icy wilderness that could never have supported life.

"This really points to a cold, frozen, icy Mars that has always been that way, as opposed to a warm, humid, ocean-bearing Mars sometime in the past," said co-researcher Dr Philip Christensen.

While the findings add weight to the view that Mars has always been a cold, inhospitable planet, they are unlikely to satisfy everyone.

Mars landings

Many scientists believe the argument will only be settled by landing robotic probes, and perhaps one day astronauts, on the Martian surface.

The European Space Agency's Mars Express space craft, carrying the Beagle 2 lander, is currently on the way to Mars.

Following close behind are two Nasa rovers that will search for geological evidence of water on Mars.

Beagle 2 and the Mars Exploration Rovers will land around Christmas, and more missions are planned for later in the decade.

Dr Jim Garvin, Nasa's lead scientist for Mars exploration, says the significance of the latest results may have to wait for the discoveries to be made by the Mars Exploration Rovers in 2004 and the Mars Reconnaissance Orbiter in 2006 and beyond.

"What's important is that we have found carbon-bearing minerals at Mars, which may be linked to the history of liquid water and hence to our quest to understand whether Mars has ever been an abode for life."

The research is published in the journal Science.




SEE ALSO:
Mars 'once warm and wet'
14 Feb 03  |  Science/Nature
Doubts over water on Mars
02 Apr 01  |  Science/Nature


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