Life Sciences in the Space Program 



Solar System Exploration 



The goal of this component of the program is to determine the extent to which 

 prebiological evolution has proceeded on other bodies in the solar system. This 

 goal is accomplished by conducting experiments and analyses with spaceborne 

 instruments to measure directly the elemental and chemical composition of 

 comets, asteroids, and the atmospheres and surfaces of other planets and their 

 satellites. 



Exploration of the solar system has made possible the comparative study of 

 planets (7,8). The knowledge gained indicates that even though some planets may 

 form by similar processes from common building blocks and share a common 

 early history, differences in size, location, composition, and other factors will 



eventually cause divergences in 

 their subsequent development. 

 For this reason, the prospects 

 for the emergence of life on a 

 planet are also inextricably tied 

 to that planet's development. 

 And data pertinent to the 

 history and properties of 

 planets and other objects in the 

 solar system should be sought 

 with spacecraft probes. 



As a result of information 

 returned from the Viking 

 mission, the importance of 

 seeking answers to questions 

 about the nature of chemical 

 evolution in ancient Martian 

 environments, the possible 

 origin and fate of life on Mars, 

 and the relationship between 

 the early histories of Mars and 

 Earth has been strongly 

 underscored. Missions to Mars 

 in the next several decades include opportunities to address these issues with 

 orbital observers and automated surface rovers and sample return. The Exobiology 

 Program should be actively involved in all these missions. In these forays, the 

 groundwork should be laid for conducting the future exploration of Mars by 

 humans. Even issues as speculative as the feasibility of making Mars habitable for 

 terrestrial organisms could be addressed by data provided by these opportunities (9). 



77ns montage of images was assembled from photographs of Saturn ami its moons taken 

 during the Voyager 1 mission. Clockwise, the moons arc Dionc (in front of Saturn), 

 Enceladus. Rhea, Titan, Mimas, and Tethys. A star background has been added by an 

 artist. 



The Voyager missions to the Outer Planets have stimulated exobiological interest in 

 several of their satellites. Europa, the second major satellite of lupiter, is covered 

 with ice, but its size and density suggest that it may have a subsurface ocean of 



146 



