Space Studies Board Annual Report 2006 (2007)

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64 Space Studies Board Annual Report—2006 6.1 Assessment of Planetary Protection Requirements for Venus Missions On February 8, 2006, Jack W. Szostak, chair of the Ad Hoc Committee on Planetary Protection Requirements for Venus Missions, sent the following letter report to John D. Rummel, Planetary Protection Officer, NASA Headquarters. As originally written in your letter of February 7, 2005, to Space Studies Board (SSB) Chair Lennard Fisk and reiterated at the February 9-11, 2005, meeting of the SSB’s Committee on the Origin and Evolution of Life (COEL), you asked for advice on planetary protection concerns related to missions to and from Venus. In particular, you asked that the National Research Council (NRC) address three issues in terms of their implications for planetary protection: 1. Assess the surface and atmospheric environments of Venus with respect to their ability to support Earth- origin microbial contamination, and recommend measures, if any, that should be taken to prevent the forward contamination of Venus by future spacecraft missions; 2. Provide recommendations related to planetary protection issues associated with the return to Earth of samples from Venus; and 3. Identify scientific investigations that may be required to reduce uncertainty in the above assessments. In response to your request, the Task Group on Planetary Protection Requirements for Venus Missions was formed (the membership of the task group is listed in Attachment 1) and met at the Southwest Research Institute in Boulder, Colorado, on October 3-5, 2005. The task group’s deliberations and discussions relating to the conclusions and recommendations contained in this letter report were confined to the Boulder meeting. To set the context for and define the scope of this study, presentations were given and discussions were held at two meetings of COEL earlier in 2005—the February 9-11 and May 31-June 2 meetings at the National Academies’ Keck Center in Washington, D.C., and its Jonsson Center in Woods Hole, Massachusetts, respectively. These preliminary presentations and discussions were conducted under the aegis of COEL’s standing oversight of NASA’s Astrobiology program and in its role as the organizing committee for the SSB’s astrobiological activities. And, since all but two members of the task group are also members of COEL, the majority of the authoring group of this letter report participated in all three meetings and heard the following presentations relevant to this study: • At the meeting in Washington, D.C., you briefed the committee on the topic “Planetary Protection Classifica- tion of Venus,” and Dirk Schulze-Makuch (Washington State University) spoke on the question “A Case for Life on Venus?” • At the meeting in Woods Hole, Massachusetts, you presented an updated version of “Planetary Protection Classification of Venus,” and Linda Amaral Zettler (Marine Biological Laboratory) addressed the topic “Acidophiles in the Rio Tinto.” In addition, Martha Gilmore (Wesleyan University) and James W. Head III (Brown University) gave presentations respectively entitled “NASA Planning for Venus Sample-Return Missions” and “Origin and Evolution of Venus’s Environment.” • At the meeting in Boulder, Colorado, D. Kirk Nordstrom (U.S. Geological Survey) gave a talk titled “Nega- tive pH, Efflorescent Mineralogy and Consequences for Environmental Restoration at Iron Mountain.” Mark Bull- ock (Southwest Research Institute) gave the presentation “Origin and Evolution of Venus’s Environment,” and task group member David Grinspoon gave the summary presentation entitled “The Astrobiology of Venus.” In addition, individual task group members held extensive discussions in open and closed sessions. The task group consulted related reports issued by the SSB and other NRC committees (e.g., Recommendations on Quarantine Policy for Mars, Jupiter, Saturn, Uranus, Neptune, and Titan [1978], An Integrated Strategy for the Planetary Sciences: 1995-2010 [1994], Evaluating the Biological Potential in Samples Returned from Planetary Satellites and Small Solar System Bodies [1998], A Science Strategy for the Exploration of Europa [1999], and Preventing the Forward Contamination of Europa [2000]1). NOTE: Attachments are not reprinted in this annual report. 1These reports were published by the National Academy Press, Washington, D.C. 

Short Reports 65 In its deliberations, the task group examined planetary protection considerations affecting Venus missions. The known aspects of the present-day environment of Venus offer compelling arguments against there being significant dangers of forward or reverse biological contamination, regardless of the unknowns. Full details are contained in the attached “Assessment of Planetary Protection Requirements for Venus Missions.” Because of the extreme temperature at the Venus surface, the fact that concentrated H2SO4 is sterilizing for all known Earth organisms, the consideration that the Venus cloud environment is extremely dehydrating and oxidiz- ing, and the realization that any life forms adapted to the Venus clouds would not survive in Earth conditions, with respect to planetary protection issues, the task group concluded as follows: • No significant risk of forward contamination exists in landing on the surface of Venus; • No significant forward-contamination risk exists regarding the exposure of spacecraft to the clouds in the atmosphere of Venus; • No significant back-contamination risk exists concerning the return of atmospheric samples from the clouds in the atmosphere of Venus; and • No significant risk exists concerning back contamination from Venus surface sample returns. Currently, NASA classifies Venus missions under planetary protection Category II, which “includes all types of missions to target those bodies where there is significant interest relative to the process of chemical evolution and the origin of life, but where there is only a remote chance that contamination carried by a spacecraft could jeopardize future exploration,”2 rather than under the less restrictive Category I assigned by the Committee on Space Research (COSPAR) of the International Council for Science. The task group recommends that the Category II planetary protection classification of Venus be retained. Although there are many important scientific investigations to be carried out to improve understanding and knowledge of Venus, the task group does not recommend any scientific investigations for the specific purpose of reducing uncertainty with respect to planetary protection issues. The considerations that led to the above conclusions are presented in the attached assessment. Signed by Jack W. Szostak Chair of the Ad Hoc Committee on Planetary Protection Requirements for Venus Missions 2This explanation of Category II and of the other categories is given at the web site <planetaryprotection.nasa.gov/pp/about/categories.htm>. Last accessed February 7, 2006. The explanation of these categories is also reprinted in this letter report in Attachment 2, “COSPAR Categories for Planetary Protection.”