CHICAGO – NASA’s evolving plans for building a permanent moon base by 2024 portray the facility as a scientific outpost where astronauts will build telescopes, forage for rare minerals and prepare for future Mars missions to be launched from the lunar surface.

But the reality is likely to be far more modest, many scientists say, with few tangible scientific benefits in the short term. Some researchers who support the return to the moon argue that the National Aeronautics and Space Administration should downplay any potential scientific payoff and focus instead on the sheer adventure of people exploring and living on new worlds.

The rationale – and cost – of President Bush’s proposed moon base will be among the first priorities for the new Democratic leaders of the congressional committees that oversee NASA’s budget and goals. The Democrats say the administration must explain how it will pay for the base, expected to cost around $200 billion over 20 years, without raiding other missions such as unmanned probes and studies of the Earth.

What supporters and opponents of a moon base fear most is a repeat of the International Space Station, widely considered one of NASA’s worst failures. That facility has not delivered on promised research benefits and brought few inspiring images of exploration from its perch in low Earth orbit.

“This [moon base] is the space station writ large. It’s building something just for the purpose of having something for people to do in space,” said astrophysicist Steven Weinberg of the University of Texas, a Nobel laureate and frequent critic of the manned space program.

The researchers with the most to gain from a permanent moon outpost are experts in lunar geology, who see a chance to finally glimpse the moon’s full history.