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CHAPTER 22 THE IMPACT OF MANNED SPACEFLIGHT ON THE EXOBIOLOGY PROGRAM N. H. HOROWITZ It seems self-evident that the study of Martian life, assuming it exists, could be most effectively carried out by human investigators working in terrestrial laboratories on returned Martian samples. The resources of brains, of equipment, and of human intuition and judgment that could be brought to bear on the problems of Martian biology would, under such circumstances, be virtually limitless. By comparison, the information that could be obtained from automatic instruments landed on Mars and trans- mitting data by radio would be far inferior—not only in quantity and rele- vance, but also in reliability. It might well take many years of Martian exploration by automated spacecraft to discover what could be learned in a few months of study of returned samples in laboratories on the Earth. Until recently, the prospects of returning Martian samples to the Earth appeared so remote that it did not seem necessary to take these prospects into account in planning exobiological programs. Rather, the emphasis was on ingenious and ever more complicated machines. Recent engineering studies sponsored by NASA have changed the picture, however. It now appears that the sending of a manned mission to Mars and back will be technically feasible in the near future. For example, one estimate suggests that six or seven men could make the round-trip to Mars in the early 1980's if the current rate of NASA funding remains constant, or earlier if the funding is increased. It should be noted that forecasts such as this are 433

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434 MARTIAN LANDINGS: MANNED based on anticipated rocket capabilities and assume that men are physio- logically capable of making such a journey. Whether, in fact, the latter is correct or not cannot be decided until we have had more experience with prolonged manned space flights. The possibility of manned missions to Mars obviously has great signifi- cance for the exobiology program, since it implies that Martian samples may become available for terrestrial study in the foreseeable future. One of the major tasks is to arrive at a recommendation regarding the direction that the exobiology program should take in the light of this possibility; to wit, should it orient itself exclusively toward an unmanned sequence of missions, or should it prepare for the possibility that we may have Martian samples in our hands within twenty years? This question is not an academic one, since long-range plans have to be made, and the manned and un- manned programs will eventually be in direct competition for funds and priorities. In some ways, this competition has already begun. Although the advantages of returning Martian samples for study at home are very great and quite obvious, there are also possible disadvantages which the study has to evaluate. Among these are the risk of contaminating Mars with terrestrial microorganisms, a risk that is presumably greater with manned missions than with unmanned ones, and the risk of contaminating the Earth with returned Martian organisms. As regards the former, we do not have sufficient information to decide whether any terrestrial species could, in fact, take hold in the Martian environment and infect the planet in competition with whatever native organisms may exist there; present knowledge of the Martian environment indicates that it would be unrecep- tive to terrestrial species. As regards the risk of back contamination, the probability of finding organisms on Mars that are dangerous to man or other terrestrial species appears to be very remote, especially when one considers the fact that the pathogens we know have evolved in association with their hosts, or with a closely related species. In any case, precautions could be observed in introducing Martian samples to the Earth, with, for example, special facilities for quarantining such samples until an assess- ment of the actual hazard had been made. In any case, it is highly probable that if men can go to Mars, they will do so whether we like it or not. The path of wisdom, it seems to me, is therefore to anticipate the possibility of round-trip flights to Mars and to plan the exobiology program so that it can take full advantage of such missions in case they prove feasible; but also so that it will not be left high-and-dry if they prove to be impossible. The details of such a program cannot be stated here, but some general points can be made: 1. Whether manned missions are undertaken or not, the initial observa- tions of Mars will be by unmanned probes.

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Impact of Manned Spaceflight on Exobiology Program 435 2. The first objective of these probes would be to determine whether or not life exists on the planet. 3. If life is detected, the next tasks of the unmanned probes might be to discover the geological and ecological distribution of the organisms, i.e., where they are to be found in the greatest numbers. Also, information as to the size and gross morphology of the Martian biota, and some estimate of their numbers and variety would be among the first objectives. 4. The foregoing determinations and possibly others would be common to both the manned and unmanned programs. At some point, how- ever, these two programs would diverge in interest. The long-range objective of both programs would be to obtain a detailed description of the chemistry and biology of the Martian biota, but whereas one unmanned program would attempt to accomplish this in situ, the manned program would set about gathering the kinds of information necessary to insure the success of the anticipated manned landing. Meteorological and geological data, atmospheric and soil analyses, radiation flux measurements, etc., are some of the kinds of informa- tion that might be required. In summary, the technology of space flight is rapidly developing and changing. Goals that seemed out of the question a few years ago are now within the realm of possibility. The exobiology program should retain enough flexibility so that it can take full advantage of new advances in the art of space flight as they come along. Among these developments, none will be more significant for exobiology than the development of the means for prolonged manned missions.