Chapter I 

 Biology and the Space Sciences 



H. P. Klein 



It became more and more apparent, as data from the two Viking landers on 

 Mars began to accumulate during 1976 and 1977, that Mars is an inhospitable 

 planet for life. The excitement generated by initial, presumptive indications of 

 metabolic activity gave way under subsequent experimentation, both on the 

 Martian surface and in ground-based laboratories, to the realization that simple, 

 unanticipated, physico-chemical rather than biological processes were probably 

 the basis for the observed phenomena. To many this signaled an attenuation, if 

 not the end, of interest by biologists in conducting research in the space 

 sciences. From time to time "exobiology," i.e., the study of extraterrestrial 

 organisms, has been referred to as "an endeavor to study that which is nonexis- 

 tent," and the Viking results seemed to end any hope of studying the biota of 

 another planet. The conclusion was drawn, by some, that biologists involved 

 with such matters would now withdraw from participation in space exploration 

 and redirect their efforts to terrestrial biology. 



Proponents of this view were mistaken, however, because they did not under- 

 stand the biological context within which the search for life on Mars was carried 

 out. For the biologist, the Viking mission was an important test of ideas about 

 how life arises from relatively simple nonbiological materials. These ideas have as 

 their central theme the concept that living systems arise through a process of 

 chemical evolution, a process in which molecules of increasing complexity are 

 produced under the influence of natural energy sources until a stable, self- 

 reproducing system is established. According to this view, simple compounds 

 containing the "biogenic" elements— carbon, hydrogen, nitrogen, oxygen, sulfur, 

 and phosphorus— condense under appropriate conditions to form the direct pre- 

 cursors of living matter, ultimately resulting, with further chemical modifica- 

 tions, in replicating organisms. 



Once it became clear that direct analysis of other objects in the solar system 

 would become feasible through the use of spacecraft technology, attention 



The Martian surface, as seen by the Viking lander. 



