Two years ago, President Bush's call for America's return to the moon after a three-decade absence stirred about as much enthusiasm as simultaneous invasions of Iran and North Korea.

Responding to Mr. Bush's mandate for a vigorous return to manned space exploration, NASA Administrator Michael Griffin announced this week an ambitious plan for human habitation of the moon by 2020. He said the effort to build a fully-functioning moon base capable of hosting astronauts for months at a time will cost $100 billion, not counting the additional billions needed to maintain the base annually.

By 2024, four-person crews could be living in solar-powered encampments at the lunar north or south poles. NASA hopes that enough liquid in the form of ice can be culled from yet-to-be-discovered craters to replenish the mission's water and fuel needs. In other words, a lot of things have to go right before American astronauts are hitting golf balls on the moon again.

As of now, NASA has nowhere near the money it needs to pull off such a technically daunting mission without endangering every other program it has in the pipeline. Though glamorous and inspiring, another manned mission to the moon has little scientific value beyond national vanity and bragging rights.

NASA's annual budget is $17 billion. Out of this relatively small pool of funds, the space agency has to squeeze out dollars for unmanned satellites, deep-space probes, the Hubble telescope and its share of the load for building the International Space Station, already woefully behind schedule. Somewhere along the line, NASA would have to find money for the new Orion space ships and Ares rockets that will presumably take the astronauts to the moon -- and beyond.

The Congressional Budget Office and the Government Accountability Office believe NASA's cost estimates might as well be made out of green cheese because the space agency has no visible means of fully funding the mission.

A faith-based approach to financing a moon base and maintaining it is bad science and even worse economics. If the debacle in Iraq has taught America anything, it's the importance of counting the cost of every venture.

Returning to the moon would be America's most ambitious space adventure since the moon landings of the early 1970s. In an ideal universe where a moon base could be funded without robbing programs with tangible scientific value, returning to the moon would be a wonderful thing.

Attempting to do so on the cheap would be a disastrous undertaking from beginning to end. NASA can't afford to proceed with stardust in its eyes.