Geochemical Constraints on the Origin of the Moon and Preservation of Ancient Terrestrial Heterogeneities
- PDF / 1,828,789 Bytes
- 46 Pages / 439.37 x 666.142 pts Page_size
- 69 Downloads / 245 Views
Geochemical Constraints on the Origin of the Moon and Preservation of Ancient Terrestrial Heterogeneities Simon J. Lock1 · Katherine R. Bermingham2,3 Rita Parai4 · Maud Boyet5
·
Received: 26 November 2019 / Accepted: 26 August 2020 © Springer Nature B.V. 2020
Abstract The Moon forming giant impact marks the end of the main stage of Earth’s accretion and sets the stage for the subsequent evolution of our planet. The giant impact theory has been the accepted model of lunar origin for 40 years, but the parameters of the impact and the mechanisms that led to the formation of the Moon are still hotly debated. Here we review the principal geochemical observations that constrain the timing and parameters of the impact, the mechanisms of lunar formation, and the contemporaneous evolution of Earth. We discuss how chemical and isotopic studies on lunar, terrestrial and meteorite samples relate to physical models and how they can be used to differentiate between lunar origin models. In particular, we argue that the efficiency of mixing during the collision is a key test of giant impact models. A high degree of intra-impact mixing is required to explain the isotopic similarity between the Earth and Moon but, at the same time, the impact did not homogenize the whole terrestrial mantle, as isotopic signatures of pre-impact heterogeneity are preserved. We summarize the outlook for the field and highlight the key advances in both measurements and modeling needed to advance our understanding of lunar origin. Keywords Earth · Moon · Impacts · Formation · Geochemistry · Isotopes
Reading Terrestrial Planet Evolution in Isotopes and Element Measurements Edited by Helmut Lammer, Bernard Marty, Aubrey L. Zerkle, Michel Blanc, Hugh O’Neill and Thorsten Kleine
B S.J. Lock
[email protected]
1
Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125, USA
2
Department of Earth and Planetary Sciences, Rutgers University, Piscataway, NJ 08854, USA
3
Department of Geology, University of Maryland, College Park, MD 20742, USA
4
Department of Earth and Planetary Sciences, Washington University in St. Louis, Saint Louis, MO 63130, USA
5
Laboratoire Magmas et Volcans, Université Clermont Auvergne, CNRS, IRD, OPGC, 63000 Clermont-Ferrand, France
109
Page 2 of 46
S.J. Lock et al.
1 Introduction The terminal event in the main stage of Earth’s accretion is thought to be the Moon-forming giant impact (Hartmann and Davis 1975; Cameron and Ward 1976). A planetary body (often referred to as Theia) collided with the proto-Earth, injecting material into orbit from which the Moon formed. The giant impact melted and vaporized much of Earth and set the initial conditions for the subsequent evolution of our planet. The giant impact theory has been the accepted model of lunar origin for 40 years, yet the parameters of the impact and the mechanisms that led to the formation of the Moon are intensely debated (see reviews by Asphaug 2014; Barr 2016). Lunar origin is one of the best characterized problem
Data Loading...
