304 ANNUAL REPORT SMITHSONIAN INSTITUTION, 19 64 



nisms in a more completely simulated Martian environment. Two of 

 my colleagues and I have found that in every sample of soil tested, 

 some microorganisms could survive indefinitely the apparent rigors 

 of the Martian environment. Other experimenters have observed that 

 when a more plentiful supply of water is assumed (such as may occur 

 at the edge of the retreating polar ice caps) , many soil organisms grow 

 and reproduce. 



If biologically tractable mechanisms exist for the survival of ter- 

 restrial microorganisms, what may we not expect of the indigenous 

 biology ? We are almost entirely ignorant of the availability of water 

 in the Martian subsurface, and this remains the chief uncertainty 

 in assessing the possibility of life there. Nighttime ice crystallization 

 of tissue water would preclude the existence of larger plants and ani- 

 mals on Mars ; but one can envision a variety of adaptations to circum- 

 vent this difficulty. It seems premature to exclude, at the present time, 

 the presence of large organisms on Mars. 



These experiments also underscore the necessity for sterilization 

 of space vehicles intended for Mars landings. Suppose an unsterilized 

 space vehicle landed on Mars and the terrestrial microbiological con- 

 taminants which it contained then proliferated. If, several years 

 later, a life-detection experiment finds Mars populated with micro- 

 organisms of a familiar type, what shall we conclude ? That the evolu- 

 tion of life on Mars paralleled that on Earth ? That biological contact 

 between Mars and Earth had occurred in earlier times ? Or that the 

 previous space vehicle had not been sterilized ? 



Of the other planets in our solar system, serious direct evidence for 

 indigenous life exists only for Mars. That any evidence should exist 

 at all is in itself remarkable, a fact which perhaps can best be appreci- 

 ated by considering the circumstances reversed. Imagine that we 

 are situated on Mars, and provided with the same level of astronomical 

 instrumentation which exists on Earth today. Is there life on Earth ? 



The largest engineering works would be invisible. In 100,000 Tiros 

 photographs of Earth, of higher quality than could be obtained with 

 a 200-inch telescope from Mars, only one image showed any sign of 

 the works of man. Lights from large cities, such as Los Angeles, 

 would be marginally detectable, and interpretation would not be easy. 

 Seasonal color changes of deciduous forests and of crops — for example, 

 in the American midwest, or in the Ukraine — would be observed, but 

 here there would arise vexing questions on the reliability of Martian 

 color vision, and the chromatic aberration of telescopes. 



Occasionally, bright flashes of light might be discernible. Their 

 durations would be only several seconds, and there would be some 

 evidence of their recurrence only in a few restricted locales, such as 

 Eniwetok and Novaya Zemlya. It is doubtful whether they would 

 be considered evidence for life on Earth — ^much less, intelligent life. 



