Appendix B
Request from NASA

National Aeronautics and Space Administration

Headquarters
Washington, DC 20548-0001

Reply to Attn of: SR

MAR 13 1998

Dr. Claude Canizares

Space Studies Board

National Academy of Sciences

2101 Constitution Avenue, N.W. Washington, DC 20418

Dear Dr. Canizares:

The investigation of the ancient Martian meteorite ALH84001 for evidence of life has revealed and highlighted a large degree of uncertainty in the possible existence of extremely small microorganisms here on Earth. The question of minimal microbial size is debated within the scientific community and there is no widely accepted theoretical minimum size for microorganisms. The Space Studies Board (SSB) has been a primary group advising NASA and seeks the Space Studies Board's advice concerning the size limits to life.

NASA has an interest in determining the current state of knowledge of the size limits to life on Earth, for microorganisms past and present, and in the theoretical limits. To understand the origin, evolution and distribution of life in the universe, a fundamental understanding of the size limits to life is needed. Scientists need to know what to look for and how to interpret the results. Considering the infancy of this research area and the continual advance in laboratory techniques, NASA also seeks recommendations concerning fertile research directions to explore the size limits to life.

In addition to considering the size below which life is not possible, there are related issues that should be addressed. What is the relationship between minimal size and the environment? Are very small microorganisms primitive or is their size a derived characteristic? What are the implications to the search for life on other planets?

Your help in addressing the questions about the size limits to life is greatly appreciated. Dr. Michael Meyer will be working with you and the SSB staff to finalize a Statement of Task for this study effort. Please contact him (202-358-0307) if you need further information about this request.

Sincerely,

Wesley T. Huntress, Jr.

Associate Administrator for Space Science



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Appendix B Request from NASA National Aeronautics and Space Administration Headquarters Washington, DC 20548-0001 Reply to Attn of: SR MAR 13 1998 Dr. Claude Canizares Space Studies Board National Academy of Sciences 2101 Constitution Avenue, N.W. Washington, DC 20418 Dear Dr. Canizares: The investigation of the ancient Martian meteorite ALH84001 for evidence of life has revealed and highlighted a large degree of uncertainty in the possible existence of extremely small microorganisms here on Earth. The question of minimal microbial size is debated within the scientific community and there is no widely accepted theoretical minimum size for microorganisms. The Space Studies Board (SSB) has been a primary group advising NASA and seeks the Space Studies Board's advice concerning the size limits to life. NASA has an interest in determining the current state of knowledge of the size limits to life on Earth, for microorganisms past and present, and in the theoretical limits. To understand the origin, evolution and distribution of life in the universe, a fundamental understanding of the size limits to life is needed. Scientists need to know what to look for and how to interpret the results. Considering the infancy of this research area and the continual advance in laboratory techniques, NASA also seeks recommendations concerning fertile research directions to explore the size limits to life. In addition to considering the size below which life is not possible, there are related issues that should be addressed. What is the relationship between minimal size and the environment? Are very small microorganisms primitive or is their size a derived characteristic? What are the implications to the search for life on other planets? Your help in addressing the questions about the size limits to life is greatly appreciated. Dr. Michael Meyer will be working with you and the SSB staff to finalize a Statement of Task for this study effort. Please contact him (202-358-0307) if you need further information about this request. Sincerely, Wesley T. Huntress, Jr. Associate Administrator for Space Science cc: S/Dr. C. Pilcher S/Dr. G. Soffen S/Dr. E. Weiler SR/Dr. M. Meyer NRC/Dr. Alexander