THE MICROBIOLOGY OF THE ATMOSPHERE 



were so, a planet might leave a trail of dust in space, and large particles 

 might move in the sun's gravitational field; but the smallest iDacterial 

 spores (o-2 [x) would move away from the sun with high velocities under 

 radiation pressure, even crossing interstellar space and entering planetary 

 atmospheres. Arrhenius's hypothesis now appears improbable. Conditions 

 in space seem inimical to the survival of a spore (Oparin, 1957); and our 

 increasing knowledge, as we probe beyond the confines of our atmosphere, 

 of the intense radiation to which a nucleo-protein would there be exposed, 

 raises serious doubts about this speculation. However, this negative 

 conclusion should not prevent us from making attempts to sample Space 

 for microbes in the wake of this planet — an experiment which seems 

 already within reach of an artificial satellite. Knowledge so gained could be 

 used for sampling in outer space near other planets, to discover whether 

 there is a microbiology of Space. 



The techniques of aerobiology would probably not solve the novel 

 problems that would arise in sampling in Space, but present knowledge 

 will need thorough exploitation when we begin to probe the atmospheres 

 of other planets. Many problems will arise, such as: (i) the necessity of 

 studying any atmospheric spore-flora of another planet; (2) the moral 

 obligation to avoid contaminating its atmosphere; and (3) the practical 

 necessity to avoid contaminating our own atmosphere with completely 

 unknown organisms which might be carried on a returning space-vehicle. 

 We must explore any atmospheric spora of other planets less inefficiently 

 than we have done our own, and for this much developmental work re- 

 mains to be done. 



FUTURE STUDY OF OUR ATMOSPHERE 



Our knowledge of the terrestrial air-spora is fragmentary in the extreme. 

 The air has never been systematically explored simultaneously in different 

 parts of the world by comparable methods. There is a heap of accumulated 

 data, from which Chapters IX to XII attempt to sort out a few principles. 

 Here and there are intriguing suggestions of phenomena; but many of the 

 data are uninterpretable, and we need a fresh study of aerobiology as 

 part of a vast terrestrial process. 



Before starting, aims must be clearly defined, and the needs of three 

 separate analyses formulated — concentration in air, concentration in 

 precipitation, and surface deposition. Methods must then be worked out, 

 based on visual examination of the whole air-spora, and supplemented by 

 cultural and other methods for the taxonomically diverse components. 

 Equipment must be tested and calibrated in wind-tunnels and in the open 

 air, including sampling during flight at high altitudes. 



When methods have been developed, international co-operation will 

 be necessary to organize a chain of routine sampling stations and to co- 

 ordinate programmes. Routine sampling stations should cover a wide 



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