B
Recommendations from Two Previous NRC Reports on Forward Contamination

TABLE B.1 Recommendations from Two Previous National Research Council (NRC) Reports on Forward Contamination of Planetary Bodies

Category

Recommendation

Report

Pre-Launch and Pre-Cursor Studies

Techniques for assessing the existence of microorganisms have advanced dramatically since pre-Viking days. These advances will have a strong impact both on bioburden assessment procedures and on future life-detection experiments. New methods have been developed with increasingly greater sensitivity and specificity. The task group strongly recommends that efforts be made to explore current analytical methods for use in bioburden assessment and inventory procedures before spacecraft assembly and launch.

Biological Contamination of Mars: Issues and Recommendations,

NRC, SSB, 1992, p. 5.

 

The task group recommends a number of studies that would improve knowledge of Europa and that would better define the issues related to minimization of forward contamination. These include studies on the following topics:

Preventing the Forward Contamination of Europa,

NRC, SSB, 2000, p. 5.

 

 

  • Ecology of clean room and spacecraft-assembly areas, with emphasis on extremophiles such as radiation-resistant microbes;

  • Detailed comparisons of bioload assay methods;

  • Desiccation- and radiation-resistant microbes that may contaminate spacecraft during assembly;

  • Autotroph detection techniques; and

  • Europa’s surface environment and its hydrologic and tectonic cycles.

 



The National Academies | 500 Fifth St. N.W. | Washington, D.C. 20001
Copyright © National Academy of Sciences. All rights reserved.
Terms of Use and Privacy Statement



Below are the first 10 and last 10 pages of uncorrected machine-read text (when available) of this chapter, followed by the top 30 algorithmically extracted key phrases from the chapter as a whole.
Intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text on the opening pages of each chapter. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.

Do not use for reproduction, copying, pasting, or reading; exclusively for search engines.

OCR for page 135
Preventing the Forward Contamination of Mars B Recommendations from Two Previous NRC Reports on Forward Contamination TABLE B.1 Recommendations from Two Previous National Research Council (NRC) Reports on Forward Contamination of Planetary Bodies Category Recommendation Report Pre-Launch and Pre-Cursor Studies Techniques for assessing the existence of microorganisms have advanced dramatically since pre-Viking days. These advances will have a strong impact both on bioburden assessment procedures and on future life-detection experiments. New methods have been developed with increasingly greater sensitivity and specificity. The task group strongly recommends that efforts be made to explore current analytical methods for use in bioburden assessment and inventory procedures before spacecraft assembly and launch. Biological Contamination of Mars: Issues and Recommendations, NRC, SSB, 1992, p. 5.   The task group recommends a number of studies that would improve knowledge of Europa and that would better define the issues related to minimization of forward contamination. These include studies on the following topics: Preventing the Forward Contamination of Europa, NRC, SSB, 2000, p. 5.     Ecology of clean room and spacecraft-assembly areas, with emphasis on extremophiles such as radiation-resistant microbes; Detailed comparisons of bioload assay methods; Desiccation- and radiation-resistant microbes that may contaminate spacecraft during assembly; Autotroph detection techniques; and Europa’s surface environment and its hydrologic and tectonic cycles.  

OCR for page 135
Preventing the Forward Contamination of Mars Category Recommendation Report Sterilization and Pre-sterilization Based on the MESUR [Mars Environmental Survey, later renamed Mars Pathfinder] group’s consensus and the task group’s agreement with it, the task group makes the following recommendations for control of forward contamination, each tied to specific mission objectives. Biological Contamination of Mars: Issues and Recommendations, NRC, SSB, 1992, p. 7.   Landers carrying instrumentation for in situ investigation of extant martian life should be subject to at least Viking-level sterilization procedures. Specific methods for sterilization are to be determined. Viking technology may be adequate, but requirements will undoubtedly be driven by the nature and sensitivity of the particular experiments. The objective of this requirement is the reduction, to the greatest feasible extent, of contamination by terrestrial organic matter and/or microorganisms deposited at the landing site.     Spacecraft (including orbiters) without biological experiments should be subject to at least Viking-level presterilization procedures—such as clean-room assembly and cleaning of all components—for bioload reduction, but such spacecraft need not be sterilized.     The task group’s recommendation to reduce bioload on all spacecraft and to sterilize those spacecraft used in life-detection missions assumes the use of Viking procedures. However, the task group recommends that the Viking protocols for assessment of spacecraft bioloads be upgraded to include state-of-the-art methods for the determination of bioload. It is critical that methods for assessing bioload be compatible with methods used to detect life, with methods for both assessment and detection reflecting the same limits and sensitivity. Data on bioloads of Viking components and spacecraft are not relevant to current life-detection procedures. Modern methods of bioburden assessment should be developed for and applied to spacecraft destined for future Mars missions, especially those carrying in situ extant life-detection experiments. Biological Contamination of Mars: Issues and Recommendations, NRC, SSB, 1992, p. 9.   … the bioload of each Europa-bound spacecraft must be reduced to a sufficiently low level at launch that delivery of a viable organism to a subsurface ocean is precluded at a high level of probability. This approach allows mission planners to take advantage of the bioload reduction likely to occur en route, particularly while in Jupiter’s radiation environment. One consequence of this view is that Europa must be protected from contamination for an open-ended period, until it can be demonstrated that no ocean exists or that no organisms are present. Thus, we need to be concerned that over a time scale on the order of 10 million to 100 million years (an approximate age for the surface of Europa), any contaminating material is likely to be carried into the deep ice crust or into the underlying ocean. Preventing the Forward Contamination of Europa, NRC, SSB, 2000, p. 2.   The task group therefore recommends the following standard: for every mission to Europa, the probability of contaminating a europan ocean with a viable terrestrial organism at any time in the future should be less than 10–4 per mission. This standard calls for explicit calculation of the probability of contamination posed by each particular mission. It allows spacecraft designers to take advantage of the bioload reduction that occurs from radiation in the jovian environment. The value of 10–4 was chosen because of its historical precedents in the planetary protection resolutions issued by COSPAR. Preventing the Forward Contamination of Europa, NRC, SSB, 2000, p. 22.   NASA must devise a method for carrying out this calculation. An example of how such a calculation might be done is given in Appendix A. The task group’s suggested methodology subdivides the bioload into common microorganisms, spores, radiation-resistant spores, and highly radiation-resistant nonspore microorganisms (e.g., Deinococcus radiodurans; see Chapter 3). Preventing the Forward Contamination of Europa, NRC, SSB, 2000, p. 22.

OCR for page 135
Preventing the Forward Contamination of Mars Category Recommendation Report Piloted Versus Unpiloted Missions The task group strongly recommends that a sequence of unpiloted missions to Mars be undertaken well in advance of a piloted mission. Any future changes in recommendations to ensure planetary protection, especially for piloted or sample return missions, will depend on the acquisition of new data. Biological Contamination of Mars: Issues and Recommendations, NRC, SSB, 1992, p. 8.   With regard to these missions, the task group recommends that a broad spectrum of martian sites be examined, with emphasis on measurements that provide data most likely to contribute to models that provide for a better understanding of the probability of life on Mars and where best to go to find it. Biological Contamination of Mars: Issues and Recommendations, NRC, SSB, 1992, p. 8. Societal Issues A substantial number of active national and international organizations are on the alert for environmental abuse. There is every reason to take seriously the concern (already expressed in some cases) about contamination of Mars and almost certainly about the issue of back contamination of Earth by martian samples. Although public concern over such issues is often sincere and productive, it at times becomes distorted and exaggerated in the media, leading to public misunderstanding and opposition. The task group recommends that NASA inform the public about current planetary protection plans and provide continuing updates concerning Mars exploration and sample return. Biological Contamination of Mars: Issues and Recommendations, NRC, SSB, 1992, p. 9. Legal Issues There are also legal issues that must be addressed, involving international restrictions as well as federal, state, and local statutes that may come into play. There are currently no binding international agreements concerning forward or back contamination. The task group recommends as essential that efforts be made (1) to assess the legal limits (and implied liabilities) in existing legislation that relates to martian exploration and (2) to pursue the establishment of international standards that will safeguard the scientific integrity of research on Mars. Furthermore, the task group recommends that NASA make a strong effort to obtain international agreement for a planetary protection policy. Biological Contamination of Mars: Issues and Recommendations, NRC, SSB, 1992, pp. 9-10. NASA Planetary Protection Program Although a planetary protection officer currently exists at NASA, there is no budgeted program (as there was during the Viking Program) to implement needed planetary protection research, a public education program, examination of legal and international issues, and the like. The task group recommends that NASA redefine the responsibilities and authority of its planetary protection officer and provide sufficient resources to carry out the recommendations made in this report. Biological Contamination of Mars: Issues and Recommendations, NRC, SSB, 1992, p. 10.