NASA's mission: Can we live on the moon?

The administration's recent decision ordering a review of the future of human spaceflight stirred anxieties in the passionate space community. Some observers wonder whether Obama is setting the stage for a pullback from Bush's grand vision to a much more limited one -- similar to the one that led NASA to abandon the moon in the '70s in favor of the much-derided space shuttle program.

In his May 19 testimony to a Senate science subcommittee, Christopher Scolese, acting NASA administrator, indicated that he was well aware the long-term plan for humans to colonize other worlds could be in danger. He took note of the fact that "the administration will provide an updated request for exploration activities, as necessary."

"In the meantime," he said, "NASA is proceeding as planned with current exploration activities, including . . . lunar systems."

An hour after launch on Wednesday, the 4,000-pound reconnaissance orbiter will separate from the crater-sensing satellite and rocket portions of the spacecraft. After a nearly five-day cruise, it will use a dozen guidance thrusters to settle into orbit about 30 miles above the lunar surface, which is much more of a mystery than many might think.

Other than the equatorial area explored by the Apollo missions, "images of the rest of the moon are pretty poor," Tooley said. "We have much better images of Mars than the moon."

The problem is particularly acute at the poles, where the current maps can be off as much as 10 miles, even though the current NASA plan calls for establishing the outpost at one of the poles.

The poles have areas of perpetual sunlight and perpetual shade. The sunlight would be useful as a source of solar power for colonists. The shaded areas may feature deposits of ice that have been locked up for billions of years.

Such ice could be used not just as a source of water. Through electrolysis, it could be broken down into hydrogen and oxygen. The oxygen could be used both for respiration and to make rocket fuel for trips back and forth to Earth. But there's no definitive proof ice is there. The possible presence of water on the moon "is a hotly and passionately debated topic," Tooley said.

Tantalizing clues point in both directions. One of the most persuasive came from the 1998 Lunar Prospector mission, which detected large stores of hydrogen in sunken craters, where the temperature never rises above minus 270 degrees. Yet, recent efforts to find water with other international satellites orbiting the moon have failed.