Washington ? When the international space station was initially proposed by President Ronald Reagan, its central mission was conceived as providing the most innovative and unusual research center that mankind had ever created. The station would be a laboratory for developing medicines, for learning how single cells, plants and animals adapt to life in space, and for discovering technologies for processing metals and other materials in a gravity-free environment.

Twenty-two years later, the space station is half-built and can carry out some experiments, but the U.S. view of its science mission has greatly changed. The primary U.S. goal is no longer basic research, but to support President Bush’s initiative of manned missions to the moon and to Mars by learning about how astronauts can live for long periods in space.

The morphing of the space station’s role has not been without controversy. Some scientists fret that critical research in medicine and on atmospheric change is being de-emphasized in favor of splashy projects that will have little earthly benefit.

the space shuttle Discovery's nose and the International Space Station can be seen during the second spacewalk Monday in this image made from NASA TV.

This refocusing does not mean basic science on the space station has ended or that planning for more elaborate and dramatic research is over.

Rather, NASA’s partners in the space station – most notably Japan, 11 European nations and Canada – will do substantial research of their own.

Despite the cutbacks and disappointments, NASA’s Thomas said more than 100 journal articles have been published based on space station data. He said researchers have made important discoveries by growing protein crystals in space that could not be grown on Earth – research that could lead to new drugs.