NASA Administrator Sean O'Keefe announced yesterday the first installment of an agency "transformation" designed to create a more supple organization to implement the Bush administration's call for renewed human exploration of the moon and Mars.

O'Keefe said NASA's seven "strategic enterprises" will shrink to four "mission directorates," a change that will take effect Aug. 1. He said he does not envision any job losses or extra expenditures from the changes. The four subdivisions are: aeronautics; science; exploration, which includes physical and biological research; and operations, which will handle spaceflight.

In a widely expected move, O'Keefe said NASA will merge its Earth science and space science programs into the science directorate, but he insisted that the agency has no plans to diminish the importance of Earth science.

"The range of activities within Earth science have applications in other areas," O'Keefe said at a NASA headquarters news conference. "There is no intent, design or objective to reduce the scope of these activities in any way."

Earth science involves using satellites to study Earth's atmosphere, environment and weather and to facilitate mapping and other tasks. NASA's proposed budget for the next five years would reduce funding for Earth science, raising concern in Congress that NASA planned to raid Earth science to fund the moon-Mars initiative.

"We're looking at that very carefully," House Science Committee Chairman Sherwood L. Boehlert (R-N.Y.) said. "But the bottom line for us on the Hill, I think, is that if he wants to restructure NASA, let him do it."

The plan responds to recommendations by a presidential commission on how NASA could facilitate the Bush administration plan, but O'Keefe was markedly lukewarm toward the commission in other areas.

The transformation is "a work in progress," he said, noting that NASA has been bombarded with criticism since the space shuttle Columbia tragedy last year. "When something doesn't work," he said, "it's surprising how many people become expert in why it didn't."

He said NASA would look at the commission's recommendation that NASA put its various centers under private management and make a decision "in the next weeks or months."