International treaty requires spacecraft landing on planetary surfaces that may have water present, or may have supported life in the past, to adhere to strict guidelines governing the microbial contaminants that are incidentally present in, and on, spacecraft hardware introduced to those environments. Precautions to prevent microbial contamination of flight hardware are taken throughout assembly, test, and launch operations to minimize transferring biological contamination to the planet. Effectiveness of these precautions is assessed by conducting bioassays of spacecraft surfaces and assembly areas to estimate the number of microorganisms present. Microorganisms discovered are preserved as a living document and compendium for the mission. The organisms that are of greatest concern are those that are highly resistant to desiccation and spacecraft sterilization by dry heat.

The collection of preserved microorganisms is important to scientific endeavors related to NASA’s stated goal of searching for life. The collection of microorganisms allows advances in the understanding of cleanliness levels of spacecraft throughout assembly operations and as a result of various sterilization approaches. It also provides a background for studying life signatures for future outbound and sample return missions.

The unique collection reported here was assembled during a specific period of time for a particular spacecraft mission — the Viking mission to Mars. It cannot be recreated or reproduced. The representative individual components, when viewed in their entirety, contain valuable information about the location and conditions in which the spacecraft was assembled. Each individual isolate is present because it possesses properties that allow it to survive in a harsh, dry environment. One subset of the collection, the “Teflon ribbon” collection, is composed of isolates, all of which are known to be resistant to dry heat. This dry heat resistance shaped the time and temperature requirements for the dry heat microbial reduction cycles and procedures currently applied to spacecraft and spacecraft components.

This collection has a total of 1,530 individual isolates (the Teflon ribbon collection and the Viking collection). The Viking collection consists of a total of 1,296 isolates, lyophilized and sealed in glass ampoules. This collection, held principally at the Jet Propulsion Laboratory, can be considered a biological resource for NASA. It has its own intrinsic value to biological research scientists. The collection can be used for future investigations into what makes these organisms uniquely important, including: the factors that allow these microbes to be associated with spacecraft; their resistance to sterilization procedures; their potential to survive harsh conditions on another planet; the potential for making a round-trip on a sample return mission; and the potential for being discovered by life-detection instruments carried on future missions.

This tech brief describes the historical origins of the collection, contributors to the original collection, and the integration into a more comprehensive microbial archive.

This work was done by Wayne W. Schubert, James N. Benardini, Sheryl L. Bergstrom, Karen L. Buxbaum, Norm D. Fields, C.M. Herring, Larry Kirschner, Robert C. Koukol, and John R. Puleo of Caltech; Martin S. Favero of Advanced Sterilization Products; Terry F. Foster of TFResearch; Michael J. Kempf of University of Tennessee; J. T. Peeler of FDA; and Pericles D. Stabekis of SETI Institute for NASA’s Jet Propulsion Laboratory. For more information, contact This email address is being protected from spambots. You need JavaScript enabled to view it.. NPO-48122