On the biological problems to be attacked with a series of U.S. satellites in 1966.

In the opinion of interested biologists in the U.S. the search for extraterrestrial life is by far the outstanding biological task that can be undertaken with the new technology of spacecraft. And it is their hope that the bulk of the national effort put into biology in space will be directed towards the biological exploration of Mars. There are, however, many other issues that the biologist can and should pursue in orbiting laboratories, or satellites. 1) Some of these are in the areas of the cardiovascular and neurophysiology of primates, and derive their importance from the need to put man into the weightless state for prolonged durations. 2) Other questions, similarly prompted by the prospect of prolonged space flight, concern the radiation hazard. Many experiments are planned for a single satellite in which it is hoped to discover whether the weightless state significantly affects biological responses to radiation. If, as is expected, there is no synergism between weightlessness and radiation, it will be possible to pursue all other questions about radiation effects in space by experimentation on the ground. 3) Two other classes of questions that satellite experiments may answer have deeper roots in theoretical and cellular physiology. The first of these concerns weightlessness itself. A long list of experiments involving a diversity of material from animal eggs to higher plants will seek to determine whether or not the absence of a gravitational input to the system significantly affects its general performance. Special interest in the U.S. attaches to suggestions from ground based experiments that normal morphogenesis may fail in plant systems that are exposed to less than about 10(-5) g. 4) It is also hoped that satellite experiments will help resolve the long-standing debate on the cause of persistent daily rhythmicity in organisms. One school of workers in the U.S. continues to believe that such rhythmicity is caused by organisms sensing an unidentified physical variable with a 24 hr period and hence presumably caused by the earth's rotation. It is proposed to assay the persistence and stability of such rhythms in organisms orbiting the earth with a period of about 90 min. Persistence of the rhythm in such orbital conditions would dispose of the theory of external causation; failure of such rhythms to persist would, however, constitute strong though not crucial support in its favor.