The Mars Odyssey spacecraft has uncovered preliminary yet tantalizing evidence for water near the surface of Mars and away from the permanently frozen north polar ice cap.

Scientists already know there is water ice in the polar cap. But water ice near the surface in warmer regions of the planet would be a remarkable and long-sought finding that would have broad implications in the search for extraterrestrial life and for the possibility of human exploration of Mars.

The data, collected during tests of Odyssey's neutron spectrometer, show signs of hydrogen, which may or may not mean there is water. Hydrogen is one component of water but also exists alone and in other substances.

The detection of hydrogen points to the possibility that there is water ice within 3 feet (1 meter) of the surface, said James Garvin, lead scientist for the Mars Exploration Program at NASA Headquarters in Washington, D.C.

"Is this a real science result? Maybe," Garvin told SPACE.com. "But whatever it is, it bodes very well for finding hydrogen in the upper few feet of Mars, and the most likely culprit is water ice."

Such ice might melt in summer months and would be reachable by robotic or human explorers. It might even support microbial life, as researchers have found on Earth that wherever there is water, there is life.

Bill Feldman, the principal investigator of Odyssey's neutron spectrometer and a researcher at Los Alamos National Lab, first revealed the findings Wednesday at the AGU meeting.

The quantity of hydrogen detected was so startling -- suggesting a huge concentration relative to what Feldman saw with a similar instrument on Lunar Prospector, which surveyed the Moon -- that researchers may task Odyssey to begin mapping crustal water ice during the first week January, Garvin said.

But Garvin said a great story may be about to unfold.

The hydrogen detection was made during the first test of Odyssey's neutron spectrometer, a subsystem of a gamma ray spectrometer instrument.

The test pass covered an area from the equator to the north pole. The resolution of the observations were at 100 kilometers or more.

Garvin explained that the speculation of water ice is based on comparing observations over the permanent ice cap with observations farther south. Scientists know that the polar cap contains both water ice and carbon dioxide ice, commonly thought of as dry ice.

"This pass suggested that hydrogen was enriched in a high-latitude region extending from around 55 degrees North to near to the edge of the north polar cap, and that it was not enhanced over the north polar permanent cap," Garvin said. "This suggests, in a most preliminary sense, that if the hydrogen in the northern high latitudes is water, that there is ice in the upper meter or so of this region ... and that it is masked by a carbon dioxide frost cover on the permanent cap."

Garvin and others expect a flurry of findings from Odyssey early next year. The craft will also map Mars in visible and infrared light, and is expected to produce a picture a day beginning in February. But it is the search for water that will be Odyssey's top priority.

All that seems to have changed now.

"We're not there yet, but getting close. So stay tuned," Garvin said. "We should be reporting on definitive water mapping by sometime in early February 2002. My bet is that we will see lots of new 'water stories' once Odyssey is mapping."