March 7, 2006— NASA has canceled a mission to explore two asteroids, setting off an angry backlash by scientists who fear the agency's emphasis on human space flight will irreparably harm the country's robotic space science programs.

NASA last year ordered a review to determine if the mission, called Dawn, was technically sound enough to warrant spending an additional $40 million, as program managers had requested. The original budget for the project, which planned to send a spacecraft to two large and unusual asteroids, was $373 million.

Despite a favorable recommendation by the independent assessment team, NASA last week suddenly canceled Dawn.

"This was a very odd that that happened," Dawn principal investigator Christopher Russell, with the University of California at Los Angeles, said in an interview with Discovery News on Monday. "There was no process involved. It was just out of the blue. It came as a total surprise."

Russell said he was told only that NASA does not have the money for Dawn. The agency already has spent between 80 percent and 90 percent of the mission costs, including a launch services agreement a launch for Dawn aboard an unmanned heavy-lift Delta rocket.

"This was not a cost-effective decision. It was a very expensive decision," Russell said.

The team decided Monday to ask NASA to reconsider its decision before taking any further action, such as appealing directly to Congress for funding.

"I think there is a move afoot to move money for science and robotic missions into the human exploration program and this is just part of it," Russell said. "There is a strong push to reduce the number of missions."

NASA is juggling expensive propositions to return the shuttle fleet to flight, finish construction of the International Space Station and develop a new vehicle to replace the shuttles, which are to be retired in 2010.

The president's budget request for the year beginning Oct. 1 does not provide enough money to cover NASA's commitments, forcing agency administrator Michael Griffin to slice into funds earmarked for future space science missions to pay for human space programs.

"Cuts to basic research and analysis programs and the cancellation of Dawn are merely harbingers of things to come as NASA continues to raid its science programs to pay for under-funding and cost overruns associated with human space flight. In a few years there may be little of these science programs left," Mark Sykes, director of the Arizona-based Planetary Science Institute and member of the Dawn science team, wrote in a letter to legislators serving on a NASA oversight committee.

The Dawn mission was supposed to investigate the two largest known asteroids in the main asteroid belt that lies between Mars and Jupiter.

The first, Vespa, is a rocky asteroid with an iron core. The second, Ceres, is entirely different, with what appears to be a thick coating of water ice and perhaps a liquid sea beneath.

"It could be an important to astrobiology as Europa, and it's much easier to get to," said Russell, referring to a moon of Jupiter that is believed to harbor a liquid ocean and perhaps some form of life.

The spacecraft includes about $40 million worth of equipment built by German and Italy and researchers from both countries are part of the Dawn science team.

"Needless to say, the Europeans are furious with the U.S. at this peremptory action by NASA," Sykes said.