WASHINGTON - Spending cuts President Bush proposed for NASA science projects will cause far more harm than the administration has acknowledged, top scientists warned a congressional panel Thursday.

If it passes, the Bush budget will turn out the lights on a whole generation of young scientists and researchers, said Joseph Taylor Jr., a Princeton University physics professor.

"These budget cuts . . . will be disproportionately felt by the younger members of the (science) community -- the assistant professors, post-doctoral trainees, and graduate students," said Taylor, co-chairman of the National Academy of Sciences Decadal Survey for Astrophysics.

The Bush administration budget request provides $3.1 billion less for science through 2010 than was promised in last year's spending request.

Much of the burden would fall on smaller, low-cost missions that conduct experiments in astronomy, Earth science, physics and other fields.

Also cut significantly would be funding for scientists to do research on data already collected by NASA missions.

Both categories are important sources of funding for academic scientists and their students.

NASA leaders said the funding shift was necessary to pay for the shuttle's final missions before scheduled retirement of the three remaining orbiters in four years.

"We're trying to maintain a balance," said Mary Cleave, associate administrator for NASA's science mission directorate.

Cleave reminded lawmakers that about 30 percent of NASA's budget would remain devoted to science pursuits under the Bush proposal, as it is now.

The cuts NASA and White House managers plan could usher in a dark new age for some aspects of American science, other experts told the House Science Committee.

For example, the NASA proposed budget cuts would delay the Europa Orbiter mission, a robotic observer designed to answer tantalizing questions about one of Jupiter's most interesting moons.

"For the first time in four decades, there will be no solar system flagship mission at all," said Wesley Huntress Jr., director of the Geophysical Laboratory at the Carnegie Institution of Washington. "For science, we will remain ignorant that much longer of Europa's deep ocean and the potential for life within it."

In order to reverse the science cuts proposed in the Bush budget, Congress would have to shift money from elsewhere in NASA's annual spending plan or take the funding from another federal agency's budget.

Given the tight budget climate on Capitol Hill, that will be a difficult task, said Rep. Sherwood Boehlert, R-N.Y, chairman of the House Science Committee.

Two years ago, President Bush unveiled his exploration initiative and promised "a robust science program" at NASA, said Rep. Bart Gordon, of Tennessee, the senior Democrat on the committee.

"As we now know, that's not what happened," Gordon said.

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