Europe's Mars orbiter has detected water molecules vaporizing from the Red Planet's south pole, scientists announced on January 24, calling it the most direct evidence yet of water in the form of ice on the Martian surface.

The quest for water on Mars -- which could indicate life -- has fascinated scientists for centuries. Mars watchers have long believed that the planet's poles contain frozen water, but previous scientific findings -- including NASA's Mars Odyssey orbiter's evidence of large amounts of ice -- were based more on inferences, European Space Agency scientists said.

While Mars Odyssey has been able to indirectly show the presence of water at the pole using temperature monitors, the European camera has for the first time been able to "literally map the polar cap" using infrared technology that shows where water molecules are present, said scientist Jean-Pierre Bibring.

"You look at the picture, look at the fingerprint, and say this is water ice," said agency scientist Allen Moorehouse. "This is the first time it's been detected on the ground. This is the first direct confirmation."

If Mars once had surface water, it had the potential to support life, although members of the European project have stressed that it remains too early to draw conclusions.

NASA's Mars Odyssey, which has orbited the planet for two years, previously turned up evidence of lots of ice mixed with the soil, as little as 40 centimeters from the surface.

James Garvin, lead scientist for NASA's Mars exploration program, told The Associated Press that Mars Express had offered further confirmation of what scientists have long known: "Mars is a water planet."

"They've seen another way of looking at it," Garvin added.

At a news conference earlier, he said the Express' results were "not unexpected."

"In terms of the impact, that's wonderful results. It's instant science, and I think the science community is going to want some time to think about what that means in the context of what we're learning."

As far back as 1940, scientists using telescopes saw vapors they believed indicated the presence of water. But in the 1960s the first Mars mission revealed the planet to be frozen, dry and covered with craters and deep ravines.

Conflicting and inconclusive information has been coming in ever since.

The latest round of Martian exploration, including Mars Express and NASA's twin rovers, Spirit and Opportunity, are using highly sophisticated instruments to map the mineralogical makeup of the planet's surface and search for evidence of past water activity.

While the infrared camera on Mars Express, called OMEGA, analyses reflections of sunlight to map the surface and determine its mineralogical and atmospheric composition, the rovers are physically on the ground searching for indications that water once flowed on the surface.

After two days of silence, NASA picked up a signal from Spirit on January 24, ending worries that the mission had come to a calamitous end.

In the coming months, European scientists will switch on Mars Express' powerful radar, which is capable of searching below the surface, beyond the range of the infrared camera. The radar will be probing for carbonates -- contained in limestone -- that would help prove whether water once flowed.

Information from all the instruments, as well as high-resolution images captured by another camera on the orbiter that has already sent back detailed pictures of Mars, will be pooled to provide a more complete overall picture.

The data, including Martian atmospheric weather patterns, will be crucial for planning future Martian missions, including the possibility of landing a human on the planet, said Michael McKay, European flight operations director.

The European Space Agency's Mars Express orbiter is part of Europe's first mission to Mars. Mars Express hit orbit on Christmas Day and began transmitting its first data from the planet this month.

However, no signal has yet been picked up from its surface probe, the British-made Beagle II.

(China Daily January 24, 2004)