WHILE the Bush administration sets its sights on a moon base and Mars exploration, space biologists shake their heads. The prospects for long-duration human expeditions to the moon and Mars within the next 15 years ``are nonexistent,'' says L. Dennis Smith of the University of California at Irvine. ``There are major problems with basic life processes under microgravity and heavy ion [cosmic particle] radiation,'' he warns.
Space medical scientist Francis Moore of Harvard Medical School notes that ``the radiological hazard [from solar protons and cosmic rays] is the highest hurdle to human habitation beyond low Earth orbit.'' Until this hazard is thoroughly understood and dealt with, he urges robotic - rather than human - exploration beyond the domain where Earth's magnetic field screens out much of the cosmic radiation.
He acknowledges that this advice ``is a bitter pill'' for planners devoted to human spaceflight. But he says it is the only realistic strategy given the magnitude of the biological uncertainties.
Drs. Moore and Smith reviewed their reservations about interplanetary flight during the recent annual meeting of the American Association for the Advancement of Science. The main problem, they explained, is that, in spite of more than three decades of spaceflight and space research, relevant biological knowledge is still minimal.
Only 29 astronauts in the old Apollo moon program have been beyond Earth's magnetic shield. None of them was exposed for more than 12 days.
Even the many years of human flight and biological research in low Earth orbit have done little more than emphasize that spaceflight is a formidable biological challenge for organisms that evolved on Earth.
Smith explained that much of the research data is essentially observation. There has been little controlled experimentation. By this he meant experiments in which organisms exposed to spaceflight conditions are compared to identical organisms treated in the same way but kept under gravity. These so-called ``control'' organisms could either be kept on Earth under normal gravity or under gravity simulated by a spinning centrifuge on the spacecraft.
Smith noted that what has been observed so far shows that weightlessness affects biological processes from major bodily functions and structure down to details of processes and structure in individual living cells.
Space biologists need to do extensive research, both on Earth and in space, to learn what it has meant for Earth's life forms to have evolved under our planet's gravity, Smith said. Then they must learn what it means for these organisms to live for extended periods with zero gravity or with some fraction of Earth's surface gravity.
This is the kind of basic knowledge needed to prepare for long-duration spaceflight. The fact that a few astronauts and cosmonauts have worked and survived for up to a year in low Earth orbit does necessarily mean that longer missions are safe.
Both Smith and Moore emphasized that such research is a justification for the US National Aeronautics and Space Administration (NASA) space station. They urged building the station on schedule and making sure it has adequate facilities for biological research, including a gravity-simulating centrifuge.
In 1988, NASA's Life Sciences Strategic Planning Study Committee drafted a comprehensive research program to provide the needed biological knowledge. But, so far, this has scarcely begun to be implemented. Smith noted that space biology is hampered by lack of funding, lack of facilities, and lack of scientists.