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Geochronology Report In Situ Geochronology for the Next Decade Final Report Submitted in response to NNH18ZDA001N-PMCS: Planetary Mission Concept Studies August 10, 2020 Barbara Cohen Michael Amato Principal Investigator Planetary and Lunar Business Lead NASA Goddard Space Flight Center NASA Goddard Space Flight Center TABLE OF CONTENTS 1. SCIENTIFIC OBJECTIVES. .1 1.1 Science Questions and Objectives . 1 1.2 Science Traceability . 2 2. PAYLOAD DEFINITION AND SAMPLE ANALYSIS . 3 2.1 Instrument Descriptions . 4 2.2 Sample Analysis Concept of Operations . 6 3. HIGH-LEVEL MISSION CONCEPT . 8 3.1 Overview . 8 3.2 Technology Maturity and Technology Development Plan . 9 3.3 Risks. 10 4. LUNAR GEOCHRONOLOGY LANDER MISSION . 10 5. VESTA GEOCHRONOLOGY HOPPER MISSION. .16 6. MARS GEOCHRONOLOGY LANDER MISSION . 20 7. DEVELOPMENT SCHEDULES AND COSTS . 22 APPENDICES A – ACRONYMS . A-1 B1 – SCIENCE TEAM STUDY REPORT. .B1-1 B2 – PAYLOAD. .B2-1 B3 – DESIGN TEAM STUDY REPORT . .B3-1 B4 –DETAILED COST AND SCHEDULE . .B4-1 C – SPECIAL TECHNICAL ANALYSIS – MOBILITY TRADES. C-1 D – REFERENCES . D-1 i PROPRIETARY INFORMATION Use or disclosure of data contained on this sheet is subject to the restriction on the title page of this proposal. STUDY AUTHORS SCIENCE DEFINITION TEAM Barbara Cohen (PI), GSFC Juliane Gross, Rutgers University Kelsey Young (DPI), GSFC Jennifer Grier, PSI Nicolle Zellner, Albion College John Grant, Smithsonian Kris Zacny, Honeybee Robotics Caleb Fassett, MSFC R. Aileen Yingst, PSI Ken Farley, Caltech Ryan Watkins, PSI Ben Farcy, U of Maryland Sarah Valencia, GSFC Bethany Ehlmann, Caltech Tim Swindle, U of Arizona Darby Dyar, PSI Stuart Robbins, SwRI Natalie Curran, GSFC Noah Petro, GSFC Carolyn van der Bogert, University Westfalische Dan Moriarty, GSFC Ricardo Arevalo, U of Maryland Stephen Indyk, Honeybee Robotics Scott Anderson, SwRI GSFC ENGINEERING TEAM GSFC MISSION DESIGN LAB TEAM Mike Adams Maryam Bakhtiari-Nejad Ginger Bronke Grant Barrett Eric Cardif Bob Beaman John Crow Emily Beckman Amani Ginyard Kaitlyn Blair Kyle Hughes Jennifer Bracken Stephen Indyk Thomas Carstens Cameron Jerry Angel Davis Andrew Jones Paul Earle Richard Lynch Luis Gallo Stephen Meyer Camille Holly Ryo Nakamura Frank Kirchman Anthony Nicoletti Steve Levitski Dave Palace Blake Lorenz Miguel Benayas Penas Mike Machado Glenn Rakow Dick McBirney Bruno Sarli Khashy Parsay Marcia Segura Sara Riall Thomas Spitzer Russ Snyder David Steinfeld David Steinfeld John Zuby James Sturm Huaizu You John Young LOCKHEED MARTIN (MARS LANDER CONCEPT) Richard Warwick Noble Hatten Mark Johnson Scott Francis Madeline O’Neil Tim Linn EXECUTIVE SUMMARY Geochronology, or determination of absolute ages for geologic events, underpins many inquiries into the formation and evolution of planets and our Solar System. The bombardment chronology inferred from lunar samples has played a significant role in the development of models of early Solar System and extrasolar planet dynamics, as well as the timing of volatile, organic, and siderophile ele- ment delivery. Absolute ages of ancient and recent magmatic products provide strong constraints on the dynamics of magma oceans and crustal formation, and the longevity and evolution of interior heat engines and distinct mantle/crustal source regions. Absolute dating also relates habitability markers to the timescale of evolution of life on Earth. The importance of constraining the planetary history via absolute dating has been reaffirmed in multiple community documents, including the last two Planetary Science Decadal Surveys. For ex- ample, Vision and Voyages advocates efforts to “Determine the chronology of basin-forming impacts and constrain the period of late heavy bombardment in the inner solar system and thus address fun- damental questions of inner solar system impact processes and chronology.” For both the Moon and Mars, sample-return missions are being planned where samples can be returned to terrestrial labora- tories and examined in depth. But the number of geochronologically-significant terrains across the inner Solar System far exceeds our ability to conduct sample return to all of them. Accordingly, the Vision and Voyages document also recommended technology development of in situ geochronology experiments that have now advanced; several such instruments will be TRL 6 by the time of the next Decadal Survey. We formulated a set of medium-class (New Frontiers) mission concepts to three different locations (the Moon, Mars, and Vesta) where sites that record Solar System bombardment, magmatism, and habitability are uniquely preserved and accessible. We developed a notional payload consisting of two instruments capable of measuring radiometric ages, an imaging spectrometer and optical cameras to provide site geologic context and sample characterization, a trace-element analyzer to augment sample contextualization, and a sample acquisition and handling system. A Vesta hopper and single-site lunar and Mars landers to advance Solar System chronology would likely fit into the New Frontiers cost cap in our study. Such missions would also enable a broad suite of geologic investigations such as basic geo- logic characterization, geomorphologic analysis, establishing ground truth for remote sensing analyses, analyses of major, minor, trace, and volatile elements, atmospheric and other long-lived monitoring, organic molecule analyses, and soil and geotechnical properties. These investments have made possible New Frontiers-class missions that would carry multiple, complementary instruments to conduct in situ dating with the precision needed to meet community- identified science goals. Allowing proposals for missions that improve Solar System chronology by in situ dating could take advantage of both recent advances in science and creative implementation solutions emerging from the planetary science community. The study team believes smart proposal teams and organizations would likely be able to fit competing versions of these missions into a New Frontiers-class mission. We urge the Decadal Survey panel to include missions in the New Frontiers list that address compelling problems in geochronology by either sample return or in situ dating. MAIN REPORT 1. SCIENTIFIC OBJECTIVES 1.1 Science Questions and Objectives Geochronology, or the determination of absolute ages for geologic events, underpins many inquiries into the formation and evolution of planetary bodies and our Solar System (Figure 1). Geochronology can drive major advances in planetary science in the next decade, including calibrating body-specific chronologies and creating a framework for understanding Solar System formation, illuminating the effects of impact bombardment on life, and revealing the evolution of planetary surface environments and interiors. Longstanding geochronology-driven science goals are to: • Determine the chronology of basin-forming impacts to constrain the time period of heavy bom- bardment in the inner Solar System and thus address fundamental questions related to inner Solar System impact processes and chronology. • Reduce the uncertainty for inner Solar System chronology in the “middle ages” (1-3 Ga) to improve models for planetary evolution, including volcanism, volatiles, and habitability. • Establish the history of habitability across the Solar System. Absolute ages of potentially habitable terrains would help resolve when localized environments within the inner Solar System could have supported biological activity. • Calibrate body-specific chronologies. Geologic epochs on different planetary bodies have been de- fined by events that have little apparent relationship to each other. Calibrating body-specific chro- nologies is critically important for comparing planetary histories, contextualizing Solar System dynamics, and developing an interplanetary perspective on the evolution of planetary surfaces, inte- riors, and habitable environments. When did the outer planets migrate and what was the ux of early bombardment? When was Mars warm and wet? How much time did organisms have to thrive in this environment? How long were planetary heat engines active? When did planets dierentiate? How long have surfaces been exposed to and changed by the space environment? What else was going on in the solar system at these times? GN047 Figure 1: Geochronology would create a framework uniting processes across the inner Solar System. In the last two decades, NASA has invested in developing innovative in situ dating techniques that will be TRL 6 by the time of the next Decadal Survey. These instruments are less precise than their terrestrial laboratory counterparts, but sufficient to answer a wide range of questions related to Geo- chronology Science Goals (Appendix B2). The team developed Objectives through which in situ dating would resolve Science Objectives specific to the Moon, Mars, and Vesta, tracing to Lunar Exploration Analysis Group (LEAG), Mars Exploration Program Analysis Group (MEPAG), and Small Bodies Analysis Group (SBAG) goals documents. See Appendix B1 for fuller descriptions of the Science Goals and Objectives. 1 Moon 1: Establish the chronology of basin-forming impacts by measuring the radiometric age of samples di- rectly sourced from the impact melt sheet of a pre-Imbrian lunar basin. In situ dating of an impact-melt sheet of a lunar basin thought to be significantly older than the Imbrium basin would place it either within the canonical cataclysm (3.9 Ga) or as part of a declining bombardment in which most impacts are 4.2 Ga or older. Moon 2: Establish the
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