The European Space Agencys Mars Express spacecraft should give scientists the best idea yet of where to find water on the Red Planet today.

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That information could aid follow-up spacecraft in targeting the places most likely to find life, as well as the resources that could provide future human missions with air to breathe, water to drink and fuel for the return trip home.

Just last week, NASA unveiled photographic evidence culled from the thousands of images snapped by its Mars Global Surveyor that there may be vast stores of liquid water near the planets surface.

The Mars Express will literally peer below the planets surface to map the extent of those reservoirs.

"Because these discoveries on Mars are very significant, this is actually one of our main goals: a subsurface sounding radar on the orbiter will look for water and ice under the surface of Mars," said Augustin Chicarro, the Mars Express project scientist.

The probe will study the planet for a full Martian year (687 days) with seven high-resolution instruments. The orbiters instruments include:

• A high-resolution stereo camera to make topographic maps with a resolution of 40-foot (12-meter).
• An infrared mapping spectrometer to conduct rock and soil analyses.
• A radio science experiment to measure Mars interior composition and shape.
• A sounding radar/altimeter to measure the depth and composition of the Martian surface, including the presence of subsurface water.
• An energetic-neutral-atom analyzer to study the upper atmosphere and examine the effects of the solar wind on it.
• A planetary Fourier spectrometer to study the atmosphere in infrared to produce three-dimensional charts of its temperature and pressure.
• An atmospheric spectrometer to measure the atmospheres composition and structure.

After a six-month journey, the Mars Express spacecraft will enter into orbit around Mars in December 2003. Although it will circle Mars for the duration of its mission, it will also dispatch a small lander called the Beagle 2 to the planets surface.

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From high in orbit, the satellite will use its instrument array to peel back the Martian surface to map the depth and extent of the aquifers that supplied the water that carved the gully features recently shown by the Global Surveyor.

 The Beagle 2 will also advance the cause: The tiny spacecraft will use its instruments, robotic arm and cameras to search the planets surface for water, minerals and organic materials.

Tempting as it may be, the spacecraft would have a difficult time reaching many of the sites that the recent Mars Global Surveyor images suggest held water, said Colin Pillinger, the missions lead scientist.

Although scientists have yet to pick its final destination, the lander cannot be reliably put down on Mars with the pinpoint accuracy necessary to investigate a specific site.

But, Pillinger said, the team would do its best to target a spot as near as possible to the places most likely to hold traces of water. To land near water, he said, is to land near life.

"We would like to be able to choose a site of recent water," said Pillinger, a professor at the Open University in the United Kingdom. "This would enhance our chances of discovering past life, and increase our chances of finding current life. It's a very big discovery."

 Rudi Schmidt, the missions project manager, said the best-case scenario would have the Beagle 2 land within an ellipse roughly 62 miles (100 kilometers) long by 12 miles (20 kilometers) wide.

"I think the generic approach we're taking is to make things as simple as possible," Schmidt said. "We have a 60-kilogram (132-pound) lander which is smaller compared to the NASA lander."

Meanwhile, the talk at NASA is of improving landing technology so that the U.S. can follow, or possibly match, the Europeans with a Martian lander of its own.

Due to the recent losses of the Mars Climate Orbiter and Polar Lander spacecraft, the American space agency has scaled back its plans to explore Mars. It cancelled a 2001 lander outright, opting instead to send just an orbiter to Mars. It may choose to do the same in 2003, again choosing to send only an orbiter, but not a lander.

Eventually, NASA hopes it can send small, versatile spacecraft to specific locations that larger landers could never reach. "The intent is to build the pieces that would allow us to go to the most interesting places on Mars," said James Garvin, NASA's Mars program scientist. "We need to make an investment. We're talking about precision landing."

Mars Express is scheduled to be launched in June 2003 on a Soyuz rocket at the Baikonur Cosmodrome in Kazakhstan.