Life Sciences in the Space Program 



Recommendations 



• The Life Sciences and Solar System Exploration Divisions of OSSA should 

 support the search for relatively unmetamorphosed Archean and Proterozoic 

 sedimentary sequences; analogous samples from Mars should be acquired by 

 unmanned missions and returned to Earth. 



• The Exobiology Program should sponsor concerted studies of rock compo- 

 nents of entire Precambrian sedimentary basins in which chemical, isotopic, 

 paleontological, and paleoenvironmental information is simultaneously 

 acquired on a common set of rocks. 



• In the Exobiology Program, research on contemporary organisms aimed at 

 unraveling the evolutionary history of life should focus on the following 

 areas: 



— The abundance, physiology, and environment of the microorganisms in 

 modern homologues of ancient microbial communities 



— Models of the simplest components of the apparatus required by 

 microorganisms to carry out the indispensable energy harvesting, 

 metabolic, and reproductive functions of life 



— The phylogeny and physiology of uncultivated organisms that inhabit 

 hot springs, hydrothermal vents, and planktonic environments 



— The nature of the common ancestor of contemporary life as characterized 

 by molecular phylogeny. 



Evolution of Advanced Life 



Research on the evolution of advanced life seeks to understand the influence of 

 both intrinsic planetary processes and astrophysical processes on the course of 

 biological evolution from unicellular to advanced forms of life. Such fundamental 

 understanding will provide a basis for predicting the distribution of advanced life 

 forms among other star systems throughout the galaxy. A direct search for 

 technologically advanced life in the galaxy can be conducted by means of the 

 Microwave Observing Project of the Search for Extraterrestrial Intelligence 

 Program (6). 



Studies of the evolution of metazoans and metaphytes during the most recent 600 

 million years show that the complexity of advanced life has not accumulated .it a 

 steady rate but rather episodically in surges that are rapid on a geological time 

 scale (t) During this period, major environmenta] fluctuations occurred, including 

 changes in the areas of shallow marine and continental habitats, regional climatic 

 shifts, alteration of the geographic continuity of oceans and continents, onsets of 

 glacial and thermal intervals, and variations in atmospheric and oceanic chem- 

 istries. These changes, due in part to the internal dynamics ot the Earth, are 

 expected to have influenced the course ol evolution, but the causal relationships 

 remain to be established. 



foremost among the possible extraterrestrial influences on biological evolution are 

 the environmental perturbations resulting from impacts of asteroids and comets 



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