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NATIONAL RESEARCH COUNCIL COMMISSIOi\;ON PHYSICALSCIE;\;CES.~tATHE~tATICS.A:'\:DRESOURCES :1111(,'n-mUII"n ,' \\dshln~t(ln. D C :"41~ OFFICE LOCATIOS: SPACESCIESCE 80AaD IOUI'M HEsa.. II;ILDISC ::ST STaUT ASD PESSSYLVASIA "\~S\:I, S '" June 6~ 1985 Arnauld E. Nicogossian~ M.D. Director~ Life Sciences Division Code EBR National Aeronautics and Space Administration Washington~ D.C. 20545 Dear Arnauld: In response to your letter requesting advice on categorization of the M~rs Orbiter Mission~ from the point of view of planetary protection~ the Committee on Planetary Biology and Chemical Evolution of the Space Science Board considered this issue at its latest meeting on May15 and 16~ 1985. For its deliberations~ the Convnittee 'solicited information and opinions from a number of specialists~ all of whomare~ or have been involved in studies related to this subject (I. Friedman~ Fla. State univ.; N. Horowitz~ Cal Tech; R. Huguenin~ University of Massachusetts; B. Jakosky~ Colorado U; T. Jukes~ UC Berkeley; P. Mazur, ORNL; and C. Sagan~ Cornell). In addition~ the Committee was briefed by personnel of the MOproject~ who presented an overview of themission~ with particular emphasis on the status of their planning efforts to meet NASAls planetary protection guidelines. In arriving at a reconvnended Category for this mission~ the Committee strongly reaffirms the position~ taken by previous sse convnittees~ that Mars is the prime extraterrestrial target for the study of planetary biology and chemical evol~tion (cf.: Space Science Board~ "Opportunities and Choices in Space Sciences~ 1974~II NAS1975~ Space Science Board~ IIPost-Viking Biological Investigations of Marsll~ NAS1977). As a result of the Viking. mission~ it appears that the likelihood of an indigenous biota on Mars is very remote. Nonetheless~ the limited scope of the Viking investigations leaves open the possibility that future studies may show this initial assessment to be incorrect. Viking also raised a myriad of~ as yet~ unanswered Questions - regarding the chemical and physical environment of that planet Questions such as the nature and distribution of the putative lIoxidantll imputed to be present in the regolith~ and whether liquid water and/or organic compounds exist at or near the surface of Mars in any regions of the planet. The Committee is sensitive to the incompleteness of our understanding of - the Martian environment especially on the scale of IImicro-environments" that might be adequate to sustain some potential terrestrial contaminants. Furthermore~ we are mindful of the diversity and adaptive capabilities of terrestrial microorganisms (of which only a fraction has~ as yet~ been characterized~) These considerations~ together with our strong desire to minimize the chances for ambiguity in future studies of Martian surface samples dictated a conservative approach as the most prudent course to. follow in connection with the MOcategorization. Tlte N/ltioft/ll Rne/lrcll Cauftcil i, Ille /I"ftCl/l/l1 a,,~r/lllftg /lg~ftcy af tlt~ N/Illaft/ll AC/ldelftyaf SCI'ftcn /lftd III, N/Illaft/ll AC/ld",,!' af £ftglft,mftg , ta Strtl, gw,rftlft,ftt /lftd allt" arg/lftl:/Illaft'

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Arnauld E. Nicogossian, M.D. June 6, 1985 Accordingly, the Committee judges the MO mission to be properly assigned a Category III designation. Wefurther recommendthat the MOProject carry out all of the precautions that the Project personnel described as being necessary to meet the stringent requirements inherent in this category. These include: assembly of the spacecraft in Class cleanrooms; biasing the injection lOOK aimpoint of the spacecraft to assure a probability of <10-5 of impact of the launch vehicle, and a probability of <10-4 of impact of the spacecraft; selecting a mapping orbit such that the probability of remaining in orbit until the year 2009 is >0.9999; and, raising the orbit of the spacecraft upon completion of the nominal mission to an orbit with a probability of >0.95 of remaining stable until the year 2039. With regard to the prospects of implementing these requirements, the Committee is pleased to note the considerable effort that has already gone into these matters on the part of the MOProject. Wetherefore expect that meeting these planetary protection objectives will pose no insuperable problems for them. Please note that the Project personnel expressed a sense of urgency, since their plans call for the "sign-off" on their final "Planetary Protection Plan" in September of this year. Finally, the Committee expressed its willingness and interest to assist NASA categorizing additional solar system missions. in In these cases, it would seem most expedient to consider the issues involved for each proposed - mission at an earlier stage than was done for the MOmission that is, before . concepts for the mission(s) become "hardened" and at a time when additional requirements are less likely to be burdensome. Yours sincerely, ? k~/:Ht ~eJ Harold P. Klein, Chairman Committee on Planetary Biology and Chemical Evolution, SSB cc: Or. Tom Donahue, SSB