The potential science and engineering value of samples delivered to Earth by Mars sample return

Abstract

Executive Summary Return of samples from the surface of Mars has been a goal of the international Mars science community for many years. Affirmation by NASA and ESA of the importance of Mars exploration led the agencies to establish the international MSR Objectives and Samples Team (iMOST). The purpose of the team is to re‐evaluate and update the sample‐related science and engineering objectives of a Mars Sample Return (MSR) campaign. The iMOST team has also undertaken to define the measurements and the types of samples that can best address the objectives. Seven objectives have been defined for MSR, traceable through two decades of previously published international priorities. The first two objectives are further divided into sub‐objectives. Within the main part of the report, the importance to science and/or engineering of each objective is described, critical measurements that would address the objectives are specified, and the kinds of samples that would be most likely to carry key information are identified. These seven objectives provide a framework for demonstrating how the first set of returned Martian samples would impact future Martian science and exploration. They also have implications for how analogous investigations might be conducted for samples returned by future missions from other solar system bodies, especially those that may harbor biologically relevant or sensitive material, such as Ocean Worlds (Europa, Enceladus, Titan) and others. Summary of Objectives and Sub‐Objectives for MSR Identified by iMOST This objective is divided into five sub‐objectives that would apply at different landing sites. 1.1 Characterize the essential stratigraphic, sedimentologic, and facies variations of a sequence of Martian sedimentary rocks. 1.2 Understand an ancient Martian hydrothermal system through study of its mineralization products and morphological expression. 1.3 Understand the rocks and minerals representative of a deep subsurface groundwater environment. 1.4 Understand water/rock/atmosphere interactions at the Martian surface and how they have changed with time. 1.5 Determine the petrogenesis of Martian igneous rocks in time and space. This objective has three sub‐objectives: 2.1 Assess and characterize carbon, including possible organic and pre‐biotic chemistry. 2.2 Assay for the presence of biosignatures of past life at sites that hosted habitable environments and could have preserved any biosignatures. 2.3 Assess the possibility that any life forms detected are alive, or were recently alive. Summary of iMOST Findings Several specific findings were identified during the iMOST study. While they are not explicit recommendations, we suggest that they should serve as guidelines for future decision making regarding planning of potential future MSR missions. The samples to be collected by the Mars 2020 (M‐2020) rover will be of sufficient size and quality to address and solve a wide variety of scientific questions. Samples, by definition, are a statistical representation of a larger entity...

In-situ preservation of nitrogen-bearing organics in Noachian Martian carbonates

“…The 4 Ga aqueous fluids, from which ALH carbonates precipitated, must have provided non-destructive environments for organic matter (i.e., moderate pH, Eh, UV, and cosmic-ray irradiation). Strong oxidants, such as chlorine oxides (ClO x − ) and nitrogen oxides (NO x − ), which are known to degrade organics and oxidize the Martian surface 37 , have been reported in both current Martian regolith and in Amazonianaged young Martian meteorites 30,[38][39][40] . In contrast, our ALH carbonates do not show the XANES features of nitrate.…”

Probing space to understand Earth

“…The Mars 2020 rover, in particular, will acquire a series of samples to be returned to Earth through a Mars sample-return mission orchestrated by NASA and the ESA. These samples could provide critical constraints on the timing and magnitude of Solar System events that directly impacted Earth's history, including, possibly, the origins of life 118,209 . NASA's Psyche orbiter will launch in 2022 to explore the metal-rich 16 Psyche asteroid, seeking to answer fundamental questions about planetary cores and possibly offering our first direct look at a protoplanetary core fragment.…”

“…Mars, in particular, is an ideal target to test this idea, as its sedimentary record is longer than Earth's and it has thick sequences of quasiperiodically layered sediments at its surface that might reflect an astronomical forcing 207,208 . The feasibility of measuring the signals on Mars will strongly depend upon the chronometers that will be sent to the planet in the future and, perhaps more critically, on the success of sample return to Earth 209 . Proposed atmospheric compositions thought to be characteristic of the early Earth hinge critically upon Solar insolation 197 .…”

Transport of impact ejecta from Mars to its moons as a means to reveal Martian history

“…Mars rovers, such as Curiosity and Mars 2020, are ongoing and planned 27,28 . They are designed to acquire specific detailed information about Martian geology near their landing sites.…”