DARMSTADT, Germany - A European spacecraft has found the most direct evidence yet of water in the form of ice on Mars, detecting molecules vaporizing from the Red Planet's south pole, scientists said Friday.

The quest for water on Mars - which could indicate life - has fascinated scientists for centuries.

The Mars Express, launched last year by the European Space Agency, made the discovery with its infrared camera while circling the planet's south pole.

Scientists have long believed the planet's poles contain frozen water, but previous findings - including NASA's Mars Odyssey orbiter's evidence of large amounts of ice - were based more on inferences, European scientists said.

While the Mars Odyssey has indirectly shown 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."

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

At a news conference earlier, he said the Europeans' findings were "not unexpected."

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

In 2001, NASA's Mars Odyssey turned up evidence of lots of ice mixed with the soil, as little as 18 inches from the surface.

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 analyzes reflections of sunlight to map the surface and determine its mineralogical and atmospheric composition, the rovers are on the ground searching for indications that water once flowed.

In 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 probe 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 together to provide a more complete overall picture.

The data, including martian weather patterns, will be crucial for planning future 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 entered on Dec. 25 and began transmitting its first data from the planet this month. It has failed to pick up a signal from its surface probe, the British-made Beagle II, which had been scheduled to land Dec. 25.