MSR Science Planning Group 2 (MSPG2): Planning Implications Related to Sterilization-Sensitive Science Investigations Associated with Mars Sample Return (MSR)

The NASA/ESA Mars Sample Return (MSR) Campaign seeks to establish whether life on Mars existed where and when allowed by environmental conditions. Laboratory measurements on the returned samples would be useful if what is measured is evidence of phenomena on Mars that has not been degraded or altered by sterilization. Sterilization kills living microorganisms and inactivates complex biological structures by breaking chemical bonds. It also breaks bonds in non-biological compounds, including abiotic or pre-biotic reduced carbon compounds, and hydrous minerals and amorphous solids. We considered effects of dry heat under two specific temperature-time regimes and of -irradiation. This report finds categories of measurements that can be fruitful despite sample sterilization and other categories that cannot. Many measurements of volatile-rich materials are sterilization-sensitive they would be compromised by either dehydration or radiolysis upon sterilization. The sterilization modes considered differ somewhat in their effects but affect the same chemical elements. Sterilization-sensitive measurements include the abundances and oxidation-reduction states of redox-sensitive elements, and isotope abundances and ratios of most of them. All organic molecules, and most minerals and naturally occurring amorphous materials that formed under habitable conditions, contain at least one such element. Thus, evidence of ancient life on Mars and its relationship to its ancient environment would be severely compromised if the MSR samples cannot be analyzed in an unsterilized condition. To ensure that sterilization-sensitive measurements can be made effectively, instruments and capabilities necessary to make these measurements would need to be present in a MSR Sample Receiving Facility. Investigations using analogs of MSR-relevant returned-sample types should be undertaken to fill knowledge gaps about sterilization effects on important scientific measurements, especially if the sterilization regimens eventually chosen differ from those considered here. Disclaimer: The decision to implement Mars Sample Return will not be finalized until NASAs completion of the National Environmental Policy Act (NEPA) process. This document is being made available for planning and information purposes only.