It was billed as an official NASA headquarters briefing to space scientists — but turned into a powder-keg of emotion, with frustrated researchers demanding an explanation of the projected NASA budget cuts, mission deferrals and cancellations that could derail solar system exploration plans.

The collision between scientists and top NASA officials took place March 13 , here at the 37th Lunar and Planetary Science Conference.

The person squarely on the hot seat was Mary Cleave, NASA associate administrator for science, who told a standing-room-only crowd of scientists that NASA’s 2007 budget request has been impacted by “budget liens in the shuttle program … and those liens needed to be covered.”

Cleave stressed that while the five-year budget forecast for space science is not as good as it was in NASA’s 2006 budget request, the space science budget still is growing.

“We’re still going to grow … compared to a lot of other agencies in the discretionary budget. We are extremely fortunate to still be growing,” Cleave said. “We’re trying to build an executable program,” she added, one that can be accomplished on a schedule and given tight budget dollars. “We’re going to have to do some surgery, so to speak.”

Andrew Dantzler, director of NASA’s solar system division in Washington, acknowledged that the $1.8 billion budget the agency is seeking for solar system exploration in 2007 is smaller than the agency had anticipated it would be a year ago, but he stressed that is still a lot of money.

“The fact is … it’s sort of like stocks. At some point it doesn’t triple every time,” Dantzler said. “We had projected growth in the past. But this is more of a correction to that 45-degree angle growth, if you will. It’s a lot of money. If we use it correctly … if we use it smartly, we can do an awful lot.”

Dantzler said that space scientists have been very successful in the past “with this amount, and less.”

The response from space scientists attending the annual NASA briefing at the Lunar and Planetary Science Conference was highly charged. Several researchers characterized the agency’s 2007 budget request as the most serious threat to the space science community in a generation.

A concern — assuming that the NASA cuts do not increase — was the impact on the ability of researchers to reduce the science data gleaned from space missions. That’s tagged as research and analysis. Other scientists told the NASA officials that the budget hits translate into letting go university talent — graduate and post-doctoral students.

One scientist characterized the NASA officials as sitting around a conference table at the top floor of NASA headquarters in a “science vacuum,” a comment that sparked applause from the audience.

“I don’t understand why you’re so angry,” Cleave responded. “We come to work every day and we work hard. We really care about this program. “

The fury from the floor was not limited to those who work within U.S. borders. Scientists from Europe also cautioned that the NASA budget is damaging international cooperation. Several projects, including the now-scuttled Dawn mission to asteroids, involve non-U.S. partners.

Other scientists emphasized that there is no dialog between space researchers and space agency higher-ups to avoid what they characterized as the “train wrecks” that will result if NASA’s 2007 budget request is passed by Congress in anything like its current form.

One hot-button topic, for example, was the cut in funding for a mission to Europa, a moon of Jupiter that is considered important for the fiel d of exobiology.

“The Europa line is gone because we don’t have the money to do it now. We didn’t say that we’re never going to do it. It’s just that we don’t have it within this budget framework,” Cleave responded.

“If you want to do Europa, the money is going to have to come from somewhere,” Cleave said.

Cleave said that a new set of advisory subcommittees is being established at NASA. These new groups can help NASA discern what the proper budgetary mix should be, she said. “We may not have gotten this balance right … we’re hearing we didn’t get it right on R&A [research and analysis]. We will be talking to our science subcommittees,” she explained.

As “NASA night” at the conference drew to a close , one researcher added: “I hope you sense the mood of the audience … and reason with us.”

“The mood is really very obvious. It’s not hard to sense,” Cleave said. “We all really care about this program. We all work as hard as we can to maintain it … we really do.”