MSR Science Planning Group 2 (MSPG2): Science & Curation Considerations for Time Sensitive Measurements That Should be Performed in Containment

The Perseverance rover is currently collecting samples on the martian surface for potential return to Earth and planning is underway to develop facilities to study these samples. Perseverance will collect up to 38 samples that will be sealed in TiN tubes. As long as the tubes remain sealed the samples will be metastable. However, as soon as a tube is opened, or headspace gas is extracted these samples will begin to re-equilibrate with their new surroundings. The MSPG2 time-sensitive science sub-group attempted to quantify the rates at which alteration is likely to occur assuming the samples are opened and stored in a nitrogen atmosphere at room temperature. The group also recommended ~20 instruments for inclusion in a sample receiving facility to allow the time sensitive properties of these samples to be measured before they are irreversibly altered. The team identified the following processes that may irreversibly alter the samples within months of opening the sample tubes: abiotic degradation of organic matter, modification of headspace gas composition, mineral-volatile exchange and oxidation or reduction of redox-sensitive elements. The team also identified several processes that would occur within hours to days of opening the sample tubes, and concluded that it may not be possible to make these measurements on this set of samples. These rapid alteration processes include: water loss from organic molecules, water desorption from sulfates, perchlorates and clay minerals, and dehydration driven phase transitions of sulfates, perchlorates, clay minerals and amorphous materials. Based on these findings the team recommend the following four goals for time-sensitive measurements inside containment: characterize 1) macromolecular material of biological origin 2) headspace gas composition 3) mineral-bound volatiles 4) solid-phase volatile hosts. 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.