Issues involved in a Martian sample return: Integrity preservation and theCuration and Analysis Planning Team for extraterrestrial materials (CAPTEM) position

Returning geological samples from Mars is the next logical step as part of an integrated exploration program and is the critical subsequent stage in t he search for evidence of life on the red planet. Analysis of such samples on Earth will generally produce data of superior accuracy and precision tha n can be accomplished in situ on the Martian surface, and such data will be invaluable in providing ground truth for remotely sensed observations. How ever, obtaining meaningful data requires that the samples returned to Earth suffer little (or preferably no) compositional or morphological changes du ring collection on Mars, transit to Earth, entry into Earth's atmosphere, i mpact on the surface, and long-tenn curation. This paper presents recommend ations from NASA's committee for Curation and Analysis Planning Team for Ex traterrestrial Materials (CAPTEM) for preserving the integrity of Martian s amples during a return mission. Potential contaminants include dead bacteri a on the outbound spacecraft and materials that come into contact with the samples during collection and storage. Therefore it is recommended that the spacecraft be sterilized and cleaned at least to Pathfinder standards, wit h the components that interact with the samples having a higher degree of c leanliness. Furthermore, it is recommended that only pure, homogeneous mate rials should be used for components that come into contact with the samples . The adverse effects of temperature on the samples are explored, and it is demonstrated that heat sterilization or undue temperature increases in tra nsit or reentry have the potential to destroy important mineralogical and g eochemical information. Concomitant with this will be degassing of the samp les and stable isotopic fractionation. Therefore it is recommended that sam ples be kept at 240 K or below during transit, reentry, and curation. It is further recommended that heat sterilization not be used, except in extreme circumstances, and other sterilization techniques, such as radiation, be e xplored. While the purpose of this paper is not to design a sample return m ission, the recommendations presented here are intended to act as guideline s for returning Martian samples in their pristine state. In essence, any pr ocedure or piece of equipment that has the potential to compromise the pris tinity of Martian samples during the collection, transportation, or curatio n needs to be fully evaluated by a scientific committee with the requisite expertise prior to implementation. CAPTEM is willing to serve in such a cap acity if requested by NASA.