In Situ Geochronology for the Next Decade: Mission Designs for the Moon, Mars, and Vesta

B A Cohen ,S J Robbins ,T D Swindle ,Dan P Moriarty ,Amani Ginyard ,S N Valencia ,Juliane Groß ,Benjamin Farcy ,Richard J.m Lynch ,K Zacny ,J A Grier ,R Warwick ,Ricardo Arévalo ,C I Fassett ,K E Young ,N M Curran ,Anthony Nicoletti ,Kenneth A Farley ,N E B Zellner ,M D Dyar ,Ryan Watkins ,N E Petro ,J A Grant ,C H Van Der Bogert ,B L Ehlmann ,Gerard Daelemans ,R A Yingst ,Stephen Indyk ,F S Anderson

doi:10.3847/psj/abedbf

Abstract

Abstract Geochronology is an indispensable tool for reconstructing the geologic history of planets, essential to understanding the formation and evolution of our solar system. Bombardment chronology bounds models of solar system dynamics, as well as the timing of volatile, organic, and siderophile element delivery. Absolute ages of magmatic products provide constraints on the dynamics of magma oceans and crustal formation, as well as 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. However, the number of terrains important to date on worlds of the inner solar system far exceeds our ability to conduct sample return from all of them. In preparation for the upcoming Decadal Survey, our team 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 to directly date planetary surfaces, consisting of two instruments capable of measuring radiometric ages, an imaging spectrometer, 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. Landers carrying this payload to the Moon, Mars, and Vesta would likely fit into the New Frontiers cost cap in our study (∼$1B). A mission of this type would provide crucial constraints on planetary history while also enabling a broad suite of complementary investigations.

Highlights

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
Bombardment chronology inferred from lunar samples has played a significant role in the development of models of early Solar System and extrasolar planetary dynamics, as well as the timing of volatile, organic, and siderophile element delivery
Terrestrial laboratory radiometric and cosmic ray exposure dating of lunar samples, paired with crater size-frequency distributions (CSFDs) of the geologic units associated with the samples, have enabled the calibration of lunar cratering chronology functions

Summary

Introduction

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. Terrestrial laboratory radiometric and cosmic ray exposure dating of lunar samples, paired with crater size-frequency distributions (CSFDs) of the geologic units associated with the samples, have enabled the calibration of lunar cratering chronology functions. These functions allow the determination of model ages for unsampled geological units across the Moon and have been adapted for application on other terrestrial planetary bodies for which no samples of known provenance currently exist. Major advances in planetary science can be driven by geochronology in the decade, calibrating body-specific chronologies and creating a framework for understanding Solar System formation, the effects of impact bombardment on life, and the evolution of planetary surface environments and interiors

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Conclusion