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Samples returned from Mars would be placed under quarantine at a Sample Receiving Facility (SRF) until they are considered safe to release to other laboratories for further study. The process of determining whether samples are safe for release, which may involve detailed analysis and/or sterilization, is expected to take several months. However, the process of breaking the sample tube seal and extracting the headspace gas will perturb local equilibrium conditions between gas and rock and set in motion irreversible processes that proceed as a function of time. Unless these time-sensitive processes are understood, planned for, and/or monitored during the quarantine period, scientific information expected from further analysis may be lost forever. At least four processes underpin the time-sensitivity of Mars returned sample science: (1) degradation of organic material of potential biological origin, (2) modification of sample headspace gas composition, (3) mineral-volatile exchange, and (4) oxidation/reduction of redox-sensitive materials. Available constraints on the timescales associated with these processes supports the conclusion that an SRF must have the capability to characterize attributes such as sample tube headspace gas composition, organic material of potential biological origin, as well as volatiles and their solid-phase hosts. Because most time-sensitive investigations are also sensitive to sterilization, these must be completed inside the SRF and on timescales of several months or less. To that end, we detail recommendations for how sample preparation and analysis could complete these investigations as efficiently as possible within an SRF. Finally, because constraints on characteristic timescales that define time-sensitivity for some processes are uncertain, future work should focus on: (1) quantifying the timescales of volatile exchange for core material physically and mineralogically similar to samples expected to be returned from Mars, and (2) identifying and developing stabilization or temporary storage strategies that mitigate volatile exchange until analysis can be completed. Executive Summary Any samples returned from Mars would be placed under quarantine at a Sample Receiving Facility (SRF) until it can be determined that they are safe to release to other laboratories for further study. The process of determining whether samples are safe for release, which may involve detailed analysis and/or sterilization, is expected to take several months. However, the process of breaking the sample tube seal and extracting the headspace gas would perturb local equilibrium conditions between gas and rock and set in motion irreversible processes that proceed as a function of time. Unless these processes are understood, planned for, and/or monitored during the quarantine period, scientific information expected from further analysis may be lost forever. Specialist members of the Mars Sample Return Planning Group Phase 2 (MSPG-2), referred to here as the Time-Sensitive Focus Group, have identified four processes that underpin the time-sensitivity of Mars returned sample science: (1) degradation of organic material of potential biological origin, (2) modification of sample headspace gas composition, (3) mineral-volatile exchange, and (4) oxidation/reduction of redox-sensitive materials (Figure 2). Consideration of the timescales and the degree to which these processes jeopardize scientific investigations of returned samples supports the conclusion that an SRF must have the capability to characterize: (1) sample tube headspace gas composition, (2) organic material of potential biological origin, (3) volatiles bound to or within minerals, and (4) minerals or other solids that host volatiles (Table 4). Most of the investigations classified as time-sensitive in this report are also sensitive to sterilization by either heat treatment and/or gamma irradiation (Velbel et al., 2022). Therefore, these investigations must be completed inside biocontainment and on timescales that minimize the irrecoverable loss of scientific information (i.e., several months or less; Section 5). To that end, the Time-Sensitive Focus Group has outlined a number of specific recommendations for sample preparation and instrumentation in order to complete these investigations as efficiently as possible within an SRF (Table 5). Constraints on the characteristic timescales that define time-sensitivity for different processes can range from relatively coarse to uncertain (Section 4). Thus, future work should focus on: (1) quantifying the timescales of volatile exchange for variably lithified core material physically and mineralogically similar to samples expected to be returned from Mars, and (2) identifying and developing stabilization strategies or temporary storage strategies that mitigate volatile exchange until analysis can be completed. List of Findings FINDING T-1: Aqueous phases, and oxidants liberated by exposure of the sample to aqueous phases, mediate and accelerate the degradation of critically important but sensitive organic compounds such as DNA. FINDING T-2: Warming samples increases reaction rates and destroys compounds making biological studies much more time-sensitive. MAJOR FINDING T-3: Given the potential for rapid degradation of biomolecules, (especially in the presence of aqueous phases and/or reactive O-containing compounds) Sample Safety Assessment Protocol (SSAP) and parallel biological analysis are time sensitive and must be carried out as soon as possible. FINDING T-4: If molecules or whole cells from either extant or extinct organisms have persisted under present-day martian conditions in the samples, then it follows that preserving sample aliquots under those same conditions (i.e., 6 mbar total pressure in a dominantly CO2 atmosphere and at an average temperature of -80°C) in a small isolation chamber is likely to allow for their continued persistence. FINDING T-5: Volatile compounds (e.g., HCN and formaldehyde) have been lost from Solar System materials stored under standard curation conditions. FINDING T-6: Reactive O-containing species have been identified in situ at the martian surface and so may be present in rock or regolith samples returned from Mars. These species rapidly degrade organic molecules and react more rapidly as temperature and humidity increase. FINDING T-7: Because the sample tubes would not be closed with perfect seals and because, after arrival on Earth, there will be a large pressure gradient across that seal such that the probability of contamination of the tube interiors by terrestrial gases increases with time, the as-received sample tubes are considered a poor choice for long-term gas sample storage. This is an important element of time sensitivity. MAJOR FINDING T-8: To determine how volatiles may have been exchanged with headspace gas during transit to Earth, the composition of martian atmosphere (in a separately sealed reservoir and/or extracted from the witness tubes), sample headspace gas composition, temperature/time history of the samples, and mineral composition (including mineral-bound volatiles) must all be quantified. When the sample tube seal is breached, mineral-bound volatile loss to the curation atmosphere jeopardizes robust determination of volatile exchange history between mineral and headspace. FINDING T-9: Previous experiments with mineral powders show that sulfate minerals are susceptible to H2O loss over timescales of hours to days. In addition to volatile loss, these processes are accompanied by mineralogical transformation. Thus, investigations targeting these minerals should be considered time-sensitive. FINDING T-10: Sulfate minerals may be stabilized by storage under fixed relative-humidity conditions, but only if the identity of the sulfate phase(s) is known a priori. In addition, other methods such as freezing may also stabilize these minerals against volatile loss. FINDING T-11: Hydrous perchlorate salts are likely to undergo phase transitions and volatile exchange with ambient surroundings in hours to days under temperature and relative humidity ranges typical of laboratory environments. However, the exact timescale over which these processes occur is likely a function of grain size, lithification, and/or cementation. FINDING T-12: Nanocrystalline or X-ray amorphous materials are typically stabilized by high proportions of surface adsorbed H2O. Because this surface adsorbed H2O is weakly bound compared to bulk materials, nanocrystalline materials are likely to undergo irreversible ripening reactions in response to volatile loss, which in turn results in decreases in specific surface area and increases in crystallinity. These reactions are expected to occur over the timescale of weeks to months under curation conditions. Therefore, the crystallinity and specific surface area of nanocrystalline materials should be characterized and monitored within a few months of opening the sample tubes. These are considered time-sensitive measurements that must be made as soon as possible. FINDING T-13: Volcanic and impact glasses, as well as opal-CT, are metastable in air and susceptible to alteration and volatile exchange with other solid phases and ambient headspace. However, available constraints indicate that these reactions are expected to proceed slowly under typical laboratory conditions (i.e., several years) and so analyses targeting these materials are not considered time sensitive. FINDING T-14: Surface adsorbed and interlayer-bound H2O in clay minerals is susceptible to exchange with ambient surroundings at timescales of hours to days, although the timescale may be modified depending on the degree of lithification or cementation. Even though structural properties of clay minerals remain unaffected during this process (with the exception of the interlayer spacing), investigations targeting H2O or other volatiles bound on or within clay minerals should be considered time sensitive upon opening the sample tube. FINDING T-15: Hydrated Mg-carbonates are susceptible to volatile loss and recrystallization and transformation over timespans of months or longer, though this timescale may be modified by the degree of lithification and cementation. Investigations targeting hydrated carbonate minerals (either the volatiles they host or their bulk mineralogical properties) should be considered time sensitive upon opening the sample tube. MAJOR FINDING T-16: Current understanding of mineral-volatile exchange rates and processes is largely derived from monomineralic experiments and systems with high surface area; lithified sedimentary rocks (accounting for some, but not all, of the samples in the cache) will behave differently in this regard and are likely to be associated with longer time constants controlled in part by grain boundary diffusion. Although insufficient information is available to quantify this at the present time, the timescale of mineral-volatile exchange in lithified samples is likely to overlap with the sample processing and curation workflow (i.e., 1-10 months; Table 4). This underscores the need to prioritize measurements targeting mineral-hosted volatiles within biocontainment. FINDING T-17: The liberation of reactive O-species through sample treatment or processing involving H2O (e.g., rinsing, solvent extraction, particle size separation in aqueous solution, or other chemical extraction or preparation protocols) is likely to result in oxidation of some component of redox-sensitive materials in a matter of hours. The presence of reactive O-species should be examined before sample processing steps that seek to preserve or target redox-sensitive minerals. Electron paramagnetic resonance spectroscopy (EPR) is one example of an effective analytical method capable of detecting and characterizing the presence of reactive O-species. FINDING T-18: Environments that maintain anoxia under inert gas containing <

The most important single element of the "ground system" portion of a Mars Sample Return (MSR) Campaign is a facility referred to as the Sample Receiving Facility (SRF), which would need to be designed and equipped to receive the returned spacecraft, extract and open the sealed sample container, extract the samples from the sample tubes, and implement a set of evaluations and analyses of the samples. One of the main findings of the first MSR Sample Planning Group (MSPG, 2019a) states that "The scientific community, for reasons of scientific quality, cost, and timeliness, strongly prefers that as many sample-related investigations as possible be performed in PI-led laboratories outside containment." There are many scientific and technical reasons for this preference, including the ability to utilize advanced and customized instrumentation that may be difficult to reproduce inside in a biocontained facility, and the ability to allow multiple science investigators in different labs to perform similar or complementary analyses to confirm the reproducibility and accuracy of results. It is also reasonable to assume that there will be a desire for the SRF to be as efficient and economical as possible, while still enabling the objectives of MSR to be achieved. For these reasons, MSPG concluded, and MSPG2 agrees, that the SRF should be designed to accommodate only those analytical activities that could not reasonably be done in outside laboratories because they are time- or sterilization-sensitive, are necessary for the Sample Safety Assessment Protocol (SSAP), or are necessary parts of the initial sample characterization process that would allow subsamples to be effectively allocated for investigation. All of this must be accommodated in an SRF, while preserving the scientific value of the samples through maintenance of strict environmental and contamination control standards. Executive Summary The most important single element of the "ground system" portion of a Mars Sample Return (MSR) Campaign is a facility referred to as the Sample Receiving Facility (SRF), which would need to be designed and equipped to enable receipt of the returned spacecraft, extraction and opening of the sealed sample container, extraction of the samples from the sample tubes, and a set of evaluations and analyses of the samples-all under strict protocols of biocontainment and contamination control. Some of the important constraints in the areas of cost and required performance have not yet been set by the necessary governmental sponsors, but it is reasonable to assume there will be a desire for the SRF to be as efficient and economical as is possible, while still enabling the objectives of MSR science to be achieved. Additionally, one of the main findings of MSR Sample Planning Group (MSPG, 2019a) states "The scientific community, for reasons of scientific quality, cost, and timeliness, strongly prefers that as many sample-related investigations as possible be performed in PI-led laboratories outside containment." There are many scientific and technical reasons for this preference, including the ability to utilize advanced and customized instrumentation that may be difficult to reproduce inside a biocontained facility. Another benefit is the ability to enable similar or complementary analyses by multiple science investigators in different laboratories, which would confirm the reproducibility and accuracy of results. For these reasons, the MSPG concluded-and the MSR Science Planning Group Phase 2 (MSPG2) agrees-that the SRF should be designed to accommodate only those analytical activities inside biocontainment that could

The Mars Sample Return Planning Group 2 (MSPG2) was tasked with identifying the steps that encompass all the curation activities that would happen within the MSR Sample Receiving Facility (SRF) and any anticipated curation-related requirements. An area of specific interest is the necessary analytical instrumentation. The SRF would be a Biosafety Level-4 facility where the returned MSR flight hardware would be opened, the sample tubes accessed, and the martian sample material extracted from the tubes. Characterization of the essential attributes of each sample would be required to provide enough information to prepare a sample catalog used in guiding the preparation of sample-related proposals by the world's research community and informing decisions by the sample allocation committee. The sample catalog would be populated with data and information generated during all phases of activity, including data derived concurrent with Mars 2020 sample-collecting rover activity, sample transport to Earth, and initial sample characterization within the SRF. We conclude that initial sample characterization can best be planned as a set of three sequential phases, which we have called Pre-Basic Characterization (Pre-BC), Basic Characterization (BC), and Preliminary Examination (PE), each of which requires a certain amount of instrumentation. Data on specific samples and subsamples obtained during sample safety assessments and time-sensitive scientific investigations would also be added to the catalog. There are several areas where future work would be beneficial to prepare for the receipt of samples, which would include the design of a sample tube isolation chamber and a strategy for opening the sample tubes and removing dust from the tube exteriors. Executive Summary All material collected from Mars (gases, dust, rock, regolith) would need to be carefully handled, stored, and analyzed following Earth return to minimize the alteration or contamination that could occur on Earth and maximize the scientific information that can be attained from the samples now and into the future. A Sample Receiving Facility (SRF) is where the Earth Entry System (EES) would be opened and the sample tubes opened and processed after they land on Earth. Samples should be accessible for research in biocontainment for time-sensitive studies and eventually, when deemed safe for release after sterilization or biohazard assessment, should be transferred out of biocontainment for allocation to scientific investigators in outside laboratories. There are two main mechanisms for allocation of samples outside the SRF: 1) Wait until the implementation of the Sample Safety Assessment Protocol (Planetary Protection) results concludes that the samples are non-hazardous, 2) Render splits of the samples non-hazardous by means of sterilization. To make these samples accessible, a series of observations and analytical measurements need to be completed to produce a sample catalog for the scientific community. Specialist members of the Mars Sample Return Planning Group Phase 2 (MSPG2), referred to here as the Curation Focus Group, have identified four curation goals that encompass all of the activities within the SRF: 1.Documentation of the state of the sample tubes and their contents prior to opening, 2.Inventory and tracking of the mass of each sample, 3.Preliminary assessment of lithology and any macroscopic forms of heterogeneity (on all the samples, non-invasive, in pristine isolators), 4.Sufficient characterization of the essential attributes of each sample to prepare a sample catalog and respond to requests by the sample allocation committee (partial samples, invasive, outside of pristine isolators). The sample catalog will provide data for the scientific community to make informed requests for samples for scientific investigations and for the approval of allocations of appropriate samples to satisfy these requests. The sample catalog would be populated with data and information generated during all phases of activity, including data derived from the landed Mars 2020 mission, during sample collection and transport to Earth, and reception within the Sample Receiving Facility. Data on specific samples and subsamples would also be generated during curation activities carried out within the Sample Receiving Facility and during sample safety assessments, time-sensitive studies, and a series of initial sample characterization steps we refer to as Pre-Basic Characterization (Pre-BC), Basic Characterization (BC), and Preliminary Examination (PE) phases. A significant portion of the Curation Focus Group's efforts was to determine which instrumentation would be required to produce a sample catalog for the scientific community and how and when certain instrumentation should be used. The goal is to provide enough information for the PIs to request material for their studies but to avoid facilitating studies that target scientific research that is better left to peer-reviewed competitive processes. We reviewed the proposed scientific objectives of the International MSR Objectives and Samples Team (iMOST) (Beaty

International audience; Dust transported in the martian atmosphere is of intrinsic scientific interest and has relevance for the planning of human missions in the future. The MSR Campaign, as currently designed, presents an important opportunity to return serendipitous, airfall dust. The tubes containing samples collected by the Perseverance rover would be placed in cache depots on the martian surface perhaps as early as 2023-24 for recovery by a subsequent mission no earlier than 2028-29, and possibly as late as 2030-31. Thus, the sample tube surfaces could passively collect dust for multiple years. This dust is deemed to be exceptionally valuable as it would inform our knowledge and understanding of Mars' global mineralogy, surface processes, surface-atmosphere interactions, and atmospheric circulation. Preliminary calculations suggest that the total mass of such dust on a full set of tubes could be as much as 100 mg and, therefore, sufficient for many types of laboratory analyses. Two planning steps would optimize our ability to take advantage of this opportunity: (1) the dust-covered sample tubes should be loaded into the Orbiting Sample container (OS) with minimal cleaning and (2) the capability to recover this dust early in the workflow within an MSR Sample Receiving Facility (SRF) would need to be established. A further opportunity to advance dust/atmospheric science using MSR, depending upon the design of the MSR Campaign elements, may lie with direct sampling and the return of airborne dust.

Executive summary provided in lieu of abstract., SCOPUS: no.j, info:eu-repo/semantics/published

Autonomous exploration requires the use of movable platforms that carry a payload of instruments with a certain level of autonomy and communication with the operators. This is particularly challenging in subsurface environments, which may be more dangerous for human access and where communication with the surface is limited. Subsurface robotic exploration, which has been to date very limited, is interesting not only for science but also for cost-effective industrial exploitation of resources and safety assessments in mines. Furthermore, it has a direct application to exploration of extra-terrestrial subsurface environments of astrobiological and geological significance such as caves, lava tubes, impact or volcanic craters and subglacial conduits, for deriving in-situ mineralogical resources and establishing preliminary settlements. However, the technological solutions are generally tailor-made and are therefore considered as costly, fragile and environment-specific, further hindering their extensive and effective applications. To demonstrate the advantages of rover exploration for a broad-community, we have developed KORE (KOmpact Rover for Exploration); a low-cost, re-usable, rover multi-purpose platform. The rover platform has been developed as a technological demonstration for extra-terrestrial subsurface exploration and terrestrial mining operations pertaining to geomorphological mapping, environmental monitoring, gas leak detections and search and rescue operations in case of an accident. The present paper, the first part of a series of two, focuses on describing the development of a robust rover platform to perform dedicated geomorphological, astrobiological and mining tasks. KORE was further tested in the Mine Analogue Research 6 (MINAR6) campaign during September 2018 in the Boulby mine (UK), the second deepest potash mine in Europe at a subsurface depth of 1.1 km, the results of which will be presented in the second paper of this series. KORE is a large, semi-autonomous rover weighing 160 kg with L × W × H dimensions 1.2 m × 0.8 m × 1 m and a payload carrying capacity of 100 kg using 800 W traction power that can power to a maximum speed of 8.4 km h−1. The rover can be easily dismantled in three parts facilitating its transportation to any chosen site of exploration. Presently, the main scientific payloads on KORE are: (1) a three-dimensional mapping camera, (2) a methane detection system, (3) an environmental station capable of monitoring temperature, relative humidity, pressure and gases such as NO2, SO2, H2S, formaldehyde, CO, CO2, O3, O2, volatile organic compounds and particulates and (4) a robotic arm. Moreover, the design of the rover allows for integration of more sensors as per the scientific requirements in future expeditions. At the MINAR6 campaign, the technical readiness of KORE was demonstrated during 6 days of scientific research in the mine, with a total of 22 h of operation., The authors thank the University of Isfahan (Isfahan, Iran) and the Instituto Andaluz de Ciencias de la Tierra (IACT, Granada, Spain) for their support in field work and sample preparation and for providing geochemical analyses facilities. We are grateful to Prof. Kristoffer Szilas, Prof. Tomo Morishita and two anonymous reviewers for their useful and constructive comments that improved the manuscript.

In this study, three simulations by the Mars Weather Research and Forecasting Model are compared: two 10 Martian year (MY) 2° × 2° simulations with (i) fully radiatively active dust and (ii) a prescribed dust scenario, and a (iii) 1 MY 0.5° × 0.5° simulation with prescribed dust as in (ii). From comparing (i) and (ii), we found that the impact of dust-radiation feedback is individually different for any region. The most striking evidence are major dust lifting activities to the south of Chryse Planitia (S-CP) seen in (i) but not in (ii). By contrast, dust lifting and deposition on the southern slopes and inside the Hellas Basin are similar in both simulations. The latter, in turn, points toward a similar near-surface atmospheric circulation. In (iii), the total global amount of wind stress lifted dust is by a factor of ∼8 higher than in (ii), with S-CP being a major lifting region as in (i). Nonetheless, the surface dust lifting by wind stress in (iii) may be also reduced regionally, as seen at the peak of Elysium Mons because of its unique topography. The zonal mean circulation in (i) is generally of a comparable strength to that in (ii), with exceptions in global dust storm years, when it is clearly stronger in (i), in line with a dustier atmosphere. The differences in the zonal mean circulation between (ii) and (iii) are mostly at lower altitudes and may arise because of differences in the representation of the topography., M.-P. Z. has been partially funded by the AEI (MDM-2017-0737, Unity of Excellence “María de Maeztu” - Centro de Astrobiología (CSIC-INTA)) and the Spanish Ministry of Science and Innovation (PID2019-104205GB-C219)

Geomorphological studies of the hidden and protected subsurface environments are crucial to obtain a greater insight into the evolution of planetary landforms, hydrology, climate, geology and mineralogy. From an astrobiological point of view subsurface environments are of interest for their potential habitability as they are local environments that are partially or fully shielded from the high levels of space and solar radiation. Furthermore, in the case of Mars, there is an increasing interest in searching for the presence of past or extant life in its subsurface. These applications make it mandatory to investigate equipment and instrumentation that allow for the study of subsurface geomorphology, as well as organic chemical biomarkers, such as biomolecules, carbon, nitrogen and sulphur isotopes, and other biologically significant minerals and gases. Mines on Earth can be used as analogues to investigate the geomorphology of Martian subsurface environments and perform astrobiology studies. With that goal, we have developed a low-cost, robust, remotely operable subsurface rover called KORE (KOmpact Rover for Exploration). This work illustrates the studies of a terrestrial analogue for the exploration of Mars using KORE during the Mine Analogue Research 6 (MINAR 6) campaign with the low-cost 3D mapping technology InXSpace 3D (In situ 3D mapping tool eXploration of space 3D). InXSpace 3D utilizes an RGB-D camera that captures depth information in addition to the RGB data of an image, operating based on the structured light principle capable of providing depth information in mm scale resolution at sub 3 m mapping range. InXSpace 3D is used to capture point clouds of natural and artificial features, thereby obtaining information about geologically relevant structures and also to incorporate them in earth mining safety. We tested two of the dense simultaneous localization and mapping (SLAM) algorithms: Kintinuous and Real-Time Appearance-Based Mapping (RTAB-Map) to check the performance of InXSpace 3D in a dark mine environment. Also, the air accumulation of volatiles such as methane and formaldehyde due to thermogenic and mining process was measured with the environmental station payload on the rover platform, which caters to both astrobiological significance and mine safety. The main conclusions of this work are: (1) a comparison made between the RTAB-Map algorithm and Kintinuous algorithm showed the superiority of Kintinuous algorithm in providing better 3D reconstruction; although RTAB-Map algorithm captured more points than the Kintinuous algorithm in the dark mine environment; (2) a comparison of point cloud images captured with and without lighting conditions had a negligible effect on the surface density of the point clouds; (3) close-range imaging of the polygonal features occurring on the halite walls using InXSpace 3D provided mm-scale resolution to enable further characterization; (4) heuristic algorithms to quickly post-process the 3D point cloud data provided encouraging results for preliminary analyses; (5) we successfully demonstrated the application of KORE to mine safety; and (6) the multi-sensors platform on KORE successfully monitored the accumulated volatiles in the mine atmosphere during its operation. The findings obtained during this KORE campaign could be incorporated in designing and planning future subsurface rover explorations to potential planetary bodies such as Mars with synergistic applications to subsurface environments in mines on Earth., The authors of this paper would like to thank Kempe Foundation for its generous funding support to develop KORE, the workshop at the Teknikens Hus, Luleå, for their invaluable and unconditional support in helping with the fabrication of the KORE components and the organizers of the MINAR campaign comprising the UK Centre of Astrobiology, ICL Boulby Mine and STFC Boulby Underground Laboratory, UK. MPZ has been partially funded by the Spanish State Research Agency (AEI) Project No. MDM-2017-0737 Unidad de Excelencia ‘María de Maeztu’- Centro de Astrobiología (INTA-CSIC).

The NASA/ESA Mars Sample Return (MSR) Campaign seeks to establish whether life on Mars existed where and when environmental conditions allowed. Laboratory measurements on the returned samples are useful if what is measured is evidence of phenomena on Mars rather than of the effects of sterilization conditions. This report establishes that there are categories of measurements that can be fruitful despite sample sterilization and other categories that cannot. Sterilization kills living microorganisms and inactivates complex biological structures by breaking chemical bonds. Sterilization has similar effects on chemical bonds in non-biological compounds, including abiotic or pre-biotic reduced carbon compounds, hydrous minerals, and hydrous amorphous solids. We considered the sterilization effects of applying dry heat under two specific temperature-time regimes and the effects of γ-irradiation. Many measurements of volatile-rich materials are sterilization sensitive—they will be compromised by either dehydration or radiolysis upon sterilization. Dry-heat sterilization and γ-irradiation differ somewhat in their effects but affect the same chemical elements. Sterilization-sensitive measurements include the abundances and oxidation-reduction (redox) 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 redox-sensitive element. Thus, sterilization-sensitive evidence about ancient life on Mars and its relationship to its ancient environment will be severely compromised if the samples collected by Mars 2020 rover Perseverance cannot be analyzed in an unsterilized condition. To ensure that sterilization-sensitive measurements can be made even on samples deemed unsafe for unsterilized release from containment, contingency instruments in addition to those required for curation, time-sensitive science, and the Sample Safety Assessment Protocol would need to be added to the Sample Receiving Facility (SRF). Targeted investigations using analogs of MSR Campaign-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 are different from those considered in this report., Astrobiology, 22 (S1), ISSN:1531-1074, ISSN:1557-8070

The Sample Analysis at Mars (SAM) instrument onboard the Mars Science Laboratory Curiosity rover measures the chemical composition of major atmospheric species (CO2, N2, 40Ar, O2, and CO) through a dedicated atmospheric inlet. We report here measurements of volume mixing ratios in Gale Crater using the SAM quadrupole mass spectrometer, obtained over a period of nearly 5 years (3 Mars years) from landing. The observation period spans the northern summer of MY 31 and solar longitude (LS) of 175° through spring of MY 34, LS = 12°. This work expands upon prior reports of the mixing ratios measured by SAM QMS in the first 105 sols of the mission. The SAM QMS atmospheric measurements were taken periodically, with a cumulative coverage of four or five experiments per season on Mars. Major observations include the seasonal cycle of CO2, N2, and Ar, which lags approximately 20¿40° of LS behind the pressure cycle driven by CO2 condensation and sublimation from the winter poles. This seasonal cycle indicates that transport occurs on faster timescales than mixing. The mixing ratio of O2 shows significant seasonal and interannual variability, suggesting an unknown atmospheric or surface process at work. The O2 measurements are compared to several parameters, including dust optical depth and trace CH4 measurements by Curiosity. We derive annual mean volume mixing ratios for the atmosphere in Gale Crater: CO2 = 0.951 (±0.003), N2 = 0.0259 (±0.0006), 40Ar = 0.0194 (±0.0004), O2 = 1.61 (±0.09) x 10-3, and CO = 5.8 (±0.8) x 10-4. ©2019. The Authors., All MSL data used in this manuscript (REMS and SAM) are freely available on NASA's Planetary Data System (PDS) Geosciences Node, from within 6 months after receipt on Earth (http://pds‐geosciences.wustl.edu/missions/msl/). The mixing ratios developed and presented in this paper are available at a publicly available archive (dataverse.org: doi.org/10.7910/DVN/CVUOWW) as cited within the manuscript. The successful operation of the Curiosity rover and the SAM instrument on Mars is due to the hard work and dedication of hundreds of scientists, engineers, and managers over more than a decade. Essential contributions to the successful operation of SAM on Mars and the acquisition of SAM data were provided by the SAM development, operations, and test bed teams. The authors gratefully thank the SAM and MSL teams that have contributed in numerous ways to obtain the data that enabled this scientific work. We also thank NASA for the support of the development of SAM, SAM data analysis, and the continued support of the Mars Science Laboratory mission. The contribution of F. Lefèvre was supported by the Programme National de Planétologie (PNP). R. Navarro‐Gonzalez acknowledges support from the Universidad Nacional Autónoma de México (PAPIIT IN111619). LPI is operated by USRA under a cooperative agreement with the Science Mission Directorate of the National Aeronautics and Space Administration. We thank members of the SAM and larger MSL team for insightful discussions and support. In particular, we thank R. Becker and R. O. Pepin for careful review of data analysis and interpretation. We thank M. D. Smith for discussion of CRISM CO measurements. We thank A. Brunner, M. Johnson, and M. Lefavor for their development of customized data analysis tools used here and in other SAM publications.