THE RELEVANCE OF MARS SAMPLES TO PLANNING FOR POTENTIAL FUTURE IN-SITU RESOURCE UTILIZATION.

Considerable recent planning has focused on the potential importance of Mars in-situ resources to support future human missions. While atmospheric CO2 provides a source of oxygen [1], the regolith offers other potential resources [2]. The most significant surface asset is water, which could be used for propellant generation [3], life support, habitat sustainment, and agriculture [4]. In regard to the latter, the regolith could also provide a source of nutrients to supplement terrestrial fertilizers and/or act as a substrate to buffer plant roots. Local material could also be used as feedstock for construction, including for structures, roads, and additive manufacturing [5]. Native salts (e.g. perchlorates or chlorides) in the Martian regolith could be used as water absorbents for closed loop life support systems or for capture of the limited atmospheric water. Any of these in-situ processes would require definition of the resources to influence equipment design and resource budgeting. Exploration via orbital and landed surveys as well as technical demonstrations would be necessary. Mars sample return could play a key role in supporting this planning, especially when considering possible long-term human presence. The goal of the International MSR Objectives & Samples Team (iMOST) is to define the objectives that could be met using returned martian samples, and identify the types of samples needed to meet those objectives. In-Situ Resource Utilization (ISRU) is one of the six iMOST objectives, and this document summarizes the needs specified therein

Developing atom probe tomography of phyllosilicates in preparation for extra-terrestrial sample return

Hydrous phyllosilicate minerals, including the serpentine subgroup, are likely to be major constituents of material that will be bought back to Earth by missions to Mars and to primitive asteroids Ryugu and Bennu. Small quantities (< 60 g) of micrometre sized, internally heterogeneous material will be available for study, requiring minimally destructive techniques. Many conventional methods are unsuitable for phyllosilicates as they are typically finely crystalline and electron beam sensitive resulting in amorphisation and dehydration. New tools will be required for nanoscale characterisation of these precious extra‐terrestrial samples. Here we test the effectiveness of atom probe tomography (APT) for this purpose. Using lizardite from the Ronda peridotite, Spain, as a terrestrial analogue, we outline an effective analytical protocol to extract nanoscale chemical and structural measurements of phyllosilicates. The potential of APT is demonstrated by the unexpected finding that the Ronda lizardite contains SiO‐rich nanophases, consistent with opaline silica that formed as a by‐product of the serpentinisation of olivine. Our new APT approach unlocks previously unobservable nanominerals and nanostructures within phyllosilicates owing to resolution limitations of more established imaging techniques. APT will provide unique insights into the processes and products of water/rock interaction on Earth, Mars and primitive asteroids

The Importance of Mars Samples in Constraining the Geological and Geophysical Processes on Mars and the Nature of its Crust, Mantle, and Core.

In situ compositional and mineralogical measurements on the Martian surface, combined with analyses of Martian meteorites, indicate that most igneous rocks are lavas and volcaniclastic rocks of basaltic composition and cumulates of ultramafic composition [1]. Alkaline rocks are common in Early Hesperian terranes and tholeiitic rocks dominate younger Amazonian martian meteorites [1]. Very uncommon feldspathic rocks represent the ultimate fractionation products, while granitoid rocks have not been identified [1]. The impact-driven delivery mechanism for the Martian meteorites [2] biases in favor of more competent samples – young, igneous rocks [e.g., 3] – and against rocks that are more representative of the Martian crust [e.g., 4]. Comparisons of rock types found among the meteorites to those documented by landed missions demonstrates this bias unequivocally [1]; furthermore, of the over 100 martian lithologies represented by the martian meteorites, only one (NWA 7034 and pairs) is a regolith breccia [e.g., 1, 5]. While the meteorites provide important insights into the nature of the silicate portion of Mars, including the origin of mantle components with differing geochemical characteristics [e.g., 6], they do not provide information on the composition of the original crust Mars, nor the nature of the mantle sources from which rocks at the Martian surface have been derived (e.g., igneous rocks at Gusev and Gale craters). Thus, there is much to be learned from the study of carefully selected samples from the martian surface

Sample Quality Standards for Returned Martian Samples

Summary of sample quality standards for Mars Sample Return as defined by the Mars 2020 Returned Sample Science Board

POTENTIAL HIGH PRIORITY SUBAERIAL ENVIRONMENTS FOR MARS SAMPLE RETURN.

Subaerial environments of interest for Mars Sample Return include surface or near-surface sites not covered by a body of water, but having direct access to water from precipitation, snow melt, or ambient-temperature groundwater [1]. This includes soils, wetlands, ephemeral ponds, cold springs, and periglacial/glacial environments, with paleosol profiles as a high priority collection site. Such soils can be topped by aqueously deposited sediments and precipitates from wetlands, ephemeral ponds, and springs. The composition and morphology of paleosols preserve evidence of past climate, aqueous conditions, and life

CONSTRAINING OUR UNDERSTANDING OF THE ACTIONS AND EFFECTS OF MARTIAN VOLATILES THROUGH THE STUDY OF RETURNED SAMPLES.

Volatiles have clearly played a key role in the evolution of Mars’ atmosphere, hydrosphere and geosphere, with effects ranging from the geomorphological evidence for outflow channels and valley networks early in Mars’ history to formation of alteration products in rocks to the current seasonal changes in the polar caps. It is clear that the absolute and relative abundances of various volatiles have changed through time via volcanic degassing, atmospheric loss, and interactions with the crust. In addition to studying the current Martian atmosphere and ancient trapped gasses in Martian sedimentary, igneous and impact samples, there is considerable knowledge to be gained by examining the compositions of sedimentary rocks, regolith and secondary minerals that are especially sensitive to climatic influences such as obliquity-driven changes. For example, results from the Curiosity rover indicate that it is possible to obtain high resolution chemostratigraphic climate records from rhythmically bedded sedimentary rocks using in situ measurements [1]. Analysis of selected returned samples from such in situ records would be extremely important in confirming and fully understanding such records. In addition, there is growing capability of applying a variety of radiometric techniques to dating of the time of sedimentation and obtaining such dates from climate-sensitive sedimentary sequences would greatly help to tie down the timescales of past climate changes. This is a provisional report from the iMOST subteam on key samples needed to understand volatiles

SEEKING SIGNS OF LIFE ON MARS: THE IMPORTANCE OF SEDIMENTARY SUITES AS PART OF A MARS SAMPLE RETURN CAMPAIGN.

Seeking the signs of life on Mars is often considered the “first among equal” objectives for any potential Mars Sample Return (MSR) campaign [e.g., ref. 1]. Among the geological settings considered to have the greatest potential for recording evidence of ancient life or its pre-biotic chemistry on Mars are lacustrine (and marine, if ever present) sedimentary depositional environments. This potential, and the possibility of returning samples that could meaningfully address this objective, have been greatly enhanced by investigations of an ancient redox stratified lake system in Gale crater by the Curiosity rover [2]

HIGH PRIORITY SAMPLES TO CHARACTERIZE THE HABITABILITY OF GROUNDWATERS AND SEARCH FOR ROCK-HOSTED LIFE ON MARS WITH SAMPLE RETURN.

Objective 1.1 of the iMOST sample return objectives is to establish the geologic context, interpret the potential habitability, and evaluate the potential for biosignature preservation in samples from an environment hypothesized to have had elevated potential for Martian life [1]. Here, we describe the strategies required to understand the geologic context and habitability of Martian groundwater aquifers and to search for evidence of life in the Martian subsurface using samples

WHAT COULD BE LEARNED ABOUT THE GEOCHRONOLOGY OF MARS FROM SAMPLES COLLECTED BY M-2020.

Based on meteoritic evidence, Mars accreted as early as 2 Ma after the formation of the first solids in the solar system [1] from material with an OTi-Cr-Ni isotopic provenance distinct from the EarthMoon system [2]. It likely formed a magma ocean within ~100 Ma after solar system formation [3], from which the martian core last equilibrated with its mantle at pressures of ~14 GPa [4]. The formation of most of the mass of the Martian crust is constrained to have occurred by 4.35 Ga [5,6]. Remanent magnetization in martian meteorite ALH 84001 demonstrates a dynamo had initiated on Mars at or before 4.1 Ga [7]. Sample return is necessary because meteorites lack geologic context and their orientation with respect to the paleomagnetic field is not known [8]

SEEKING SIGNS OF LIFE ON MARS: A STRATEGY FOR SELECTING AND ANALYZING RETURNED SAMPLES FROM HYDROTHERMAL DEPOSITS.

Highly promising locales for biosignature prospecting on Mars are ancient hydrothermal deposits, formed by the interaction of surface water with heat from volcanism or impacts [1-3]. On Earth, they occur throughout the geological record (to at least ~3.5 Ga), preserving robust mineralogical, textural and compositional evidence of thermophilic microbial activity [e.g., 3-5]. Hydrothermal systems were likely present early in Mars’ history [6], including at two of the three finalist candidate landing sites for M2020, Columbia Hills [7-9] and NE Syrtis Major [10 & refs. therein]. Hydrothermal environments on Earth’s surface are varied, constituting subaerial hot spring aprons, mounds and fumaroles; shallow to deep-sea hydrothermal vents (black and white smokers); and vent mounds and hot-spring discharges in lacustrine and fluvial settings. Biological information can be preserved by rapid, spring-sourced mineral precipitation [1,2,9], but also could be altered or destroyed by postdepositional events [5,11,12]. Thus, field observations need to be followed by detailed laboratory analysis to verify potential biosignatures