"It really strengthens the evidence for an ocean and that the ocean is liquid today," said Margaret Kivelson of the University of California Los Angeles and the principal investigator of Galileos magnetometer during an interview on Sunday. "Nobody has come up with an idea that you can carry the currents weve seen with any other conductor."

The new readings suggest not only that the ocean is there, but that it is currently liquid or, at most, a slurry of ice and water.

Along with Mars, Europa stands to become one of NASAs primary targets in the search for life beyond the planet Earth. Scientists assume that liquid water is necessary for life to develop and flourish, whether here or elsewhere in the universe.

The Europa Orbiter mission, scheduled for launch in 2003, will attempt to further characterize the jovian moons ocean.

A later mission, still on the drawing board, could send a "hydrobot" beneath the moons icy surface to plumb the depths of that ocean. NASA has already tested an early version of that robotic craft, the Lo'ihi Underwater Volcanic Vent Mission Probe, deep in the Pacific Ocean off Hawaii.

Scientists first proposed an ocean on Europa following the Voyager encounters in 1979. Since then, the evidence has mounted, based largely on interpretations on the crack patterns on the icy moons surface.

But the crack evidence could be eons old; the new magnetometer readings suggest not only that the ocean is there, but that it is currently liquid or, at most, a slurry of ice and water.

During five previous encounters close enough to Europa to get good readings, Galileo always passed by the moon when it was in one hemisphere of Jupiters magnetic field. During the January 3 pass, however, the moon which is about the size of Earths own moon was in the opposite hemisphere.

Scientists had theorized that Europas magnetic field was not intrinsically generated, like the Earths, but induced by its proximity to Jupiter.

If that were the case, magnetic north on Europa would flip to the south each time the moon moved between the two hemispheres of Jupiters magnetic field but only if the moon were covered in a substance conductive enough. That now seems all but certainly to be the case.

"If there was another source of the field, it was not going to change in time and we would have seen the north pole in the same place as before," Kivelson said of the January 3 flyby, which brought Galileo within 218 miles (351 kilometers) of Europa.

With the flyby complete, Galileo concludes the first extended portion of its decade-old mission. NASA has tentatively agreed to further extend the mission through this year.

The Galileo Millennium Mission will take the unmanned spacecraft past the moons Io on February 22 and Ganymede on May 30 and December 28.

Preliminary plans also call for Galileo and the Saturn-bound Cassini probe to make joint observations of Jupiter when the latter spacecraft flies by for a gravity assist in December.

In a previous interview, project manager Jim Erickson said he doubted the spacecraft could do much more after December since it will have exhausted all but about 20 pounds (9 kilograms) of its propellant.