Nasa's lunar exploration plans have been strongly endorsed by an influential panel of US scientists.
One of the first steps taken on the Moon in 1969
The Moon provided great opportunities for robotic and human space exploration, said a report by the National Academy of Sciences.
The 15-member panel was asked to evaluate and give advice on Nasa's lunar research programme.
President Bush vowed two years ago to return astronauts to the Moon, with the eventual goal of landing on Mars.
He told the US space agency (Nasa) to devote $12.5bn (£9.5bn) over five years for the early stages of the programme, with a goal of landing astronauts on the Moon between 2015 and 2020.
Some scientists have criticised the plans, saying they divert funds from research programmes that have no direct bearing on long-distance human spaceflight.
But a special National Research Council panel of the National Academy of Sciences said in an interim report that the Moon was "priceless to planetary scientists".
"Only by returning to the Moon to carry out new scientific exploration can we hope to close the gaps in understanding and learn the secrets that the Moon alone has kept for eons," it said.
The committee was made up of academics, a journalist and retired members of private industry involved in space programmes.
The experts outlined a number of priorities, including:
- determining the composition and structure of the interior of the Moon
- gaining a better understanding of the Moon's "atmosphere", the very thin whisps of gas at surface level
- evaluating the Moon's potential as a platform for studying Earth, the relationship of the Sun and Earth, and astronomy and astrophysics in general
The final version of the report is due to be released in mid-2007.
Nasa announced in August that the Lockheed Martin Corporation will build the next US spaceship to take humans to the Moon.
It awarded a multi-billion-dollar contract to the group to develop the Orion vehicle, which will replace the space shuttle when it retires in 2010.