WASHINGTON -- Some of the most ballyhooed missions on NASA's scientific agenda would be postponed indefinitely or perhaps canceled under the agency's new budget proposal, despite its administrator's vow to Congress six months ago that not "one thin dime" would be taken from space science to pay for President Bush's plan to send astronauts to the moon and Mars.
The cuts come to $3 billion over the next five years, as NASA's total spending grows by 3.2 percent this year, to $16.8 billion.
Among the casualties in the budget, released last month, are attempts to look for habitable planets and perhaps life elsewhere in the galaxy, an investigation of the dark energy that seems to be ripping the universe apart, bringing a sample of Mars back home to Earth and exploring for life under the ice of Jupiter's moon Europa -- as well as numerous smaller programs and individual research projects that astronomers say are the wellsprings of new science and new scientists.
The administrator, Michael D. Griffin, says the agency needs the money to keep the space shuttle fleet aloft, complete the International Space Station and build a new crew exploration vehicle to replace the shuttle.
That transition has produced an unexpected shortfall of funds but, he told the House Science Committee last month, to postpone it would be more damaging than to put off some science projects.
"We're delaying some missions," he told the panel, "but we're not abandoning them."
Yesterday, Mary Cleave, NASA's associate administrator for science, said she took Griffin at his word that the cuts were a one-time event. "There was no money available anyplace else," Cleave said. "We took a hit."
The programs could still be saved if Congress voted to increase the budget. NASA has powerful allies in both parties, and some have expressed alarm at the proposed cuts, which will be discussed today at a hearing of the House Science Committee.
But as fiscal conservatives are placing intense pressure on the Republican leadership to rein in government spending, programs that were previously considered sacrosanct are now vulnerable.
The cuts have alarmed and outraged many scientists, who have long feared that NASA will have to cannibalize its science program to carry out the president's vision of human spaceflight.
The new cuts, they say, will drive young people from the field, ending American domination of space science and perhaps ceding future discoveries to Europe.
"The bottom line: Science at NASA is disappearing -- fast," said Donald Lamb, an astrophysicist at the University of Chicago and chairman of a committee on space science for the Association of American Universities.
Rep. Sherwood Boehlert, a New York Republican who is chairman of the science committee, called the new budget "bad for space science, worse for earth science," adding, "It basically cuts or de-emphasizes every forward-looking, truly futuristic program of the agency to fund operational and development programs to enable us to do what we are already doing or have done before."
As a result of the new cuts, NASA's expenditures for space and earth science will grow about 1 percent a year from now until 2011, far less than inflation, even as the administration promotes its effort to bolster American competitiveness by doubling the research budgets at the National Science Foundation, the Department of Energy and the National Institute of Standards and Technology over the next 10 years.
Pete V. Domenici, a New Mexico Republican, and 56 other senators have introduced a bill mandating, among other things, a 10 percent increase per year in NASA's science budget through 2013.
Astronomers and planetary researchers say that space science has provided NASA's brightest and most inspirational moments in recent years: the landing on Saturn's moon Titan, the exploits of the Mars rovers, and the stream of cosmic postcards from the Hubble Space Telescope.
Despite Griffin's assurances, they say that delaying space missions can be a death sentence if there is not money in the budget to continue developing technology and to keep teams together until the mission is ready to fly again.
That is the case, said Charles Beichman of NASA's Jet Propulsion Laboratory, with the Terrestrial Planet Finder missions, which are intended to produce images of Earth-like planets around other stars.
They are the culmination of a line of missions devoted to hunting for planets around other stars and investigating whether they are habitable or perhaps already harbor life -- a goal, planetary scientists point out, that is explicitly endorsed in Bush's space vision.
"We're getting ready to fire all the people we've built up," said Beichman, who is the project scientist for the second of the two spacecraft once scheduled for about 2020. Once those scientists have found other jobs, he said, they are not likely to come back.
"What I feel bad about is turning away a generation," he said, explaining that planet finding has been one of the hottest fields in science lately, attracting, in particular, young scientists into astronomy. "We were the new kid on the block," he said.
Much of the concern among scientists is for the fate of smaller projects such as the low-budget spacecraft called Explorers. Designed to provide relatively cheap and fast access to space, they are usually developed and managed by university groups. Lamb referred to them as "the crown jewels in NASA's science program."
In recent years, one such mission, the Wilkinson Microwave Anisotropy Probe, produced exquisite baby pictures of the "big bang," while another, the Swift satellite, has help solve a 30-year-old mystery, linking distant explosions called gamma ray bursts to the formation of black holes.
Explorers, Lamb said, often give graduate students and young professors their first taste of space science. Until recently about one mission was launched per year, but under the new plan, none is scheduled from 2009 to 2012.
In a letter to Cleave last fall, 16 present and former Explorer scientists wrote: "Such a lengthy suspension would be a devastating blow to the program and the science."