Fenn • The Challenge of Space Biology 119 



tain limits of temperature, oxygen, and any event, a primeval surface would 



carbon dioxide pressures, nutrient sup- offer more points of scientific interest 



ply, radiation intensity, etc. If these are than one more or less disturbed by pre- 



adequatelv monitored and kept within vious human intervention, 



acceptable limits any failure of growth Surely landings on the moon are 



or survival can onlv mean the presence far in the future but not too far for 



of some unpredicted environmental scientific interest. Among the many 



factor. However unlikelv this may ap- difficult biological problems involved 



pear to be, the demonstration that life is the effect of gravity. On the take-off 



is actually possible in a satellite for fortunately the acceleration is within 



long periods of time would be very re- tolerable limits provided the occupant 



assuring. For a biologist also it would can orient the long axis of his body 



provide a real thrill to be in continual transverse to the line of thrust. The 



communication, of a sort, with any complete absence of gravity when the 



living cell circumnavigating the earth satellite is in orbit will pose a still more 



above the atmosphere. The effects of serious and in some respects perhaps a 



radiation could be tested in this way more amusing problem, 



if yeast could remain exposed in a non- For the maintenance of man over 



growing state in the satellite for var\'ing long periods in a satellite the nitrogen 



periods of time before the initiation of of the inspired air will presumably be 



growth by the automatic influx of completely eliminated and pure oxygen 



nutrients. While there are many varia- at a pressure of perhaps 15-21% of an 



tions of this plan which would be of atmosphere will be substituted. This 



interest, most of the results could prob- will minimize the pressure differential 



ably be predicted from terrestrial ex- on the walls of the satellite and will 



periments if physical measurements provide an adequate oxygen tension for 



were available of the radiation intensity survival. The effect of removing all the 



in the environment of the satellite. nitrogen from the ambient atmosphere 



Another point to explore is the pos- has not yet been adequately determined 

 sibility of the existence of variable although some have claimed that it 

 spores or virus particles in space. While tends to inhibit oxidations to some ex- 

 this is highly unlikely because of the tent. Some decrease in basal meta- 

 intense ultraviolet light to which such bolic rate may also result from de- 

 cells would be exposed, direct proof of creased tone of the anti-gravity muscles, 

 the complete sterility of space would The diet should be designed for mini- 

 still be useful. It would help to dispose mum weight and possibly also for 

 of the old panspermia theory of minimum indigestible residue. At best 

 Arrhenius which supposed that living it will have to be a survival menu of 

 spores could be widely disseminated spartan simplicity. A new diurnal 

 throughout the universe by the pressure rhythm will be imposed upon the occu- 

 of light rays. Possibly spores could be pants, with night occurring perhaps 

 found in space on their radiation wings every hour or half hour as in the pres- 

 even though they might not be any ent orbiting satellites. It will be inter- 

 longer viable. esting to discover how long the 24-hour 



A related problem is the possibility rhythm will persist under these condi- 



of testing the surface of the moon for tions and indeed in which direction it 



the presence of living cells. However, may become modified. For intcrplane- 



if the moon is once hit by a missile tary flights the problem is still different 



fired from the earth the interpretation with perpetual daylight— or at least a 



of such data might be ambiguous. In bright sun in a black sky. 



