Conta:rination of the Moon and Planets. The Group decided at its meeting in February 1964 that a é as reproduced in Ann. 3 be immediately communicated AR behalf of the Group. This points out the extreme importance of undertaking for the time being only fly-by missions for the study of Mars. Following the compilation of available literature on the sub- ject a panel of the following specialists has met at Florence du- ring the COSPAR Symposium in May 1964: Prof, A. Brown, Dept. of Biology, Univ.of Pennsylvania Prof. A. Dollfus, Astrophysics Section, Paris Observatory. Prof. M, Florkin, Biochemical Laboratory, Univ. of Liége,. Dr. L, Hall, Bioscience Programs, NASA, Prof, C.-G.Hedén, Bacteriology Department, Karolinska Institutet (CONVENOR) Academician A,A, Imshenetskii, Inst. of Microbiology, USSR Academy of Sciences. Prof. C, Sagan, Harvard College Observatory (RAPPORTEUR) Dr. P.H.A.Sneath, British Medical Research Council. Additional Russian member (not present), The Panel has discussed the standards of sterilization which can be recommended for the protection of possible Life on Mars. Its report is enclosed in Annex 4. The Consultative Group has considered the report of the panel and wishes to make a statement whichis Annex 5, The re- port underlines the danger of contamination through accidental landing of fly-by missions and suggests definite steps to reduce this danger. The Group urges continued efforts in improving sterilization techniques and sharing of information concerning procedures designed to achieve space-craft with the desired degree of sterility. Annex 3. . Text of the preliminary statement on contamination as draf- ted by the Consultative Group at the Geneva meeting and later slightly amended. The text reads: "The COSPAR Consultative Group on Potentially Harmful Effects of Space Experiments has considered presently available scientific evaluations of the likely consequences of the biological contarnination of Mars. There is consen- sus of opinion among scientific workers of the extreme im- portance of not jeopardizing the value of information that can be gained from studies of this planet about many crucial problerns of biology and the evolution of life. Realizing that the technology of sterilization has many practical problems, the Group is endeavouring to estab- lish through consultation with competent biologists the limits of permissible contamination of objects that may land on iviars. The Group moreover recommends that early discussions be held between specialists of launching nations to discuss techniques of sterilization and problems of technology involved in launching steri- lized payloads. Inthe meantime, the Group urges these nations who presently have capability of attempting the exploration of Mars, to take steps to organize only fly-bye missions for the time being". -2- Anrex 4 Report of the Study Group on STANDARDS FOR SPACE PROBE STERILIZATION At the Florence meeting of COSPAR, the study group on Stan- dards for Space Probe Sterilization considered data and expres - sions of expert opinion from a variety of sources, including those listed in the appendices to this report. The following statements re- present a synthesis of the views of the members of the Study Group; itis suggested that they be made the basis of a position paper by COSPAR., We reaffirra the conviction that exobiology should be a primary Objective of activities in the space sciences. This view is justified for the following reasons: (1) The detection and subsequent investigation of extrater- restrial life has profound scientific significance. (2) Studies in planetary biology raust, in large part, be completed before contamination is effected by unsterili- zed devices used in physical or geophysical investiga- tions, The successful performance of physical experiments is primarily unaffected by previous biological experi- taents; because of contamination, the converse may be. false, (3) A study of the prebiological chersistry of a planet which proves to be sterile would nevertheless be of major bio- logical significance. We belicve that space probe sterilization and trajectory control of flyby spacecraft are essential until further information gives strong indication that such standards could be relaxed without jeopardizing planetary studies. This policy is justified for the following reasons: (1) A search for extraterrestrial life is essentially a search for materials with the properties of the known Organisms on the planet Earth. Therefore all life- detection experiments will be capable of detecting viable terrestrial contaminants. Consequently the introduction of such contarninants (for example, by inadequate space- craft sterilization) would render it i:possible to decide whether positive results of a life-detection experiment are significant or spurious. (2) Aside from such interference with remote life-detection experiments, biological contamination of a planct may lead to undesirable alterations of the planetary en- vironment from the standpoints of both exobiology and physical studies of planetary surfaces. If the pro- liferation of terrestrial contaminants -- at some time after their introduction, -- is not excluded, the extensive changes in the planetary environment which are possible as a conscquence could inhibit or destroy our opportunity to fa) identify and investigate the indigenous biota b) understand the ecological interactions of the Original indigenous biota, and (c) investigate the prebiological chemistry of a planct which proves to be sterile. It is difficult to estimate adequately the period of time which would pass before such undesirable consequences occur. As a simple cxamplo -3- of heuristic interest we note that a single viable organism deposited in an environment in which it slowly grows (general time, 30 ays) would in the course of eight years produce a population of 10°" organisms, a number equal approximately to the bacterial population of the arth. The calculation assumes zero death rate, and no interaction between indigenous planetary organisms and exogenous terrestrial contaminants. We believe . that the scientific desirability of sterility control is absolute; but the degree of sterilization required must be based on our judgements of the risks acceptable so planetary exploration will not be impossibly difficult. The probability that a single viable orga- nism is aboard any space vehicle intended for planetary impact can then be computed as the solution of a waiting time problem in probability theory. Adopting values for the acceptable risk during approximately a decade of planetary exploration by landing vehicles, and for the bio- logical and spacecraft reliability parameters involved -- values which we consider conservative -- we conclude that (1) the probability that a single viable organism be aboard any vehicle intended for planctary landing must be less than 4 1x10", . and that (2) the probability of accidental planetary impact by an unsterilized flyby or arbiter must be less than 3 x 10 during the interval terminating at the end of the initial period of planetary exploration by landing vehicles (approx. one decade). We appreciate the considerable technical difficultics involved in realizing these probabilities in practice, but we consider that they are attainable by known means. The probabilities also apply to con- tamination by spacecraft propulsion and attitude-control systems. The probability of contamination by accidental impact of flybys and or- biters can be minimized by 1) = initial trajectory control, 2) initial spacecraft sterilization, or by (3) inclusion of programmed or commanded terminal precautionary systems for assuming non-intercept trajectories or for initiating destruction sterilization. The probabilities given above are obviously subject to future revision as our knowledge of planetary environments, raicrobial ecology, and spacecraft design improves. We feel that while our recommendations apply immediately to flyby, orbiter, and lander missions planned for Mars, the same recommendations should apply to any planet, which, on the basis of current information, cannot firmly be excluded as a possible abode of extraterrestrial life. The standards of space vehicle sterilization are, we believe, unrelated to the probability of indigenous life on the planet in question; except in the limiting case that indigenous life and the proliferation of terrestrial contaminants can both be firmly excluded. While there is a sizable probability that the surface tempcratures of Venus are too high for either indigenous or exogenous organisrnas, this conclusion is based on indirect lines of argument. Also, we cannot entirely exclude the possibility of biological contamination of the cloudes of Venus. Until unambiguous astronomical information is available, we recommend that Martian standards of sterility control should alse apply to Venus. In the case of the Moon, the surface -4- conditions are rigorous enough to reliably exclude biological contamina - tion of the surface. We cannot exclude the possibility that conditions several tens of meters below the lunar surface will permit microbial replication, Such depths, however, are unlikely to be reached uninten- tionally during lunar landings. Accordingly, we recommend such less rigorous sterilization techniques as biocleanroom assembly and terminal gaseous sterilization of all spacecraft intended for lunar landings; but rigorous sterilization of drills designed for lunar sub- surface boring. Our information about the conditions on other plancts is insufficient to form a basis for definitive recommendations at this time. To encourage broader consideration of the diverse means which can be employed to neet these recommended standards of sterility, it is suggested that an international conference be sponsored by COSPAR, possibly in cooperation with one or more other appropriate international scientific groups, to consider the technology of sterilization, and ste- rilization testing. To implement this suggestion, it will be necessary for COSPAR to endorse the proposed conference and to supply a budget for bringing it about, It is suggested further than the conference be held as soon as feasible, preferably in early 1965, Annex 5. Action suggested by the Consultative Group on Potentially Harmful Effects of Space Experiments concerning the contamination of planets: Having studied the available information, which includes corn:nents by specialists and a report on contacts established with the National Microbiological Societies in 37 _ countries, taking into account the discussions of the Consultative Group in Warsaw (June 1963) and in Geneva (Febr. 1964) and the report by a special study group charged with re- commending standards for space craft ste rilization (Florence, May, 1964), and considering firstly the conceivable risks of interfering with possible extraterrestrial ecologies, secondly the importance of avoiding any action which may jeo- pardize future biological and chemical surveys, thirdly that the techniques available for space craft sterilization are continually improving, fourthly that there is a need for an advancement in this art before specimens can be returned frorn other planets, the CONSULTATIVE GROUP ON POTENTIALLY HARMFUL EFFECTS OF SPACE EXPERIMENTS, recommends the following action by the EXECUTIVE COUNCIL OF COSPAR: 1, that it requests the UN to ‘declare Mars a Temporary Biological Preserve. Jhis will mean that in the exploration of this planet considerations of biological research receive priority over all other, and that the planet must be approached only by spacecrafts subjected to certified (see below) sterilization procedures. The declaration should remain in force until information returned from outer space will permit a change in policy on biological grounds, - ~5- _2. that it recommends to launching nations that they plan only fly-bye 3, os . yissions, in the case of Mars, for the tirne being. that it recommends to nations capable of launching moon probes that th » ct | such probes are prepared and handled in such a way as to keep contamination to a feasible minireura and to give technical expe- rience so that - in the future - no important planetary experi- ment will have to be rejected for lack of suitable sterilization techniques. it establishes a Study Group on Techniques for Space Craft Sterilization and instructs this group to: make possible an international comparison of sterilization tech- niques by devising an easily reproducible "mock capsule", incor- porating basic probe elernents suitable for standardized conta- ‘nination - for instance by specified spores distributed on and between surfaces, under grease and paint films, in liquids, entrapped in solids and provided with different degrees of thermal protection. defining the term "certified", used in the first recommendation above draft an international code for space craft sterilization, based on the standards proposed by the special study group (Florence, May 1964) propose approaches to the problems involved in controlling the sterility level of space probes | report to the Executive Council before a fixed date.