2021/02/17 by Ramon Brasser, R. Brasser, S. J. Mojzsis +3 · 7 citations
Earth and Planetary Sciences · Physics and Astronomy · #Accretion (finance) #Astro and Planetary Science #Astrobiology #Astronomy #Astrophysics #Chronology #Crust #Geochemistry #Geological and Geochemical Analysis #Geology #Impact crater #Mantle (geology) #Mars Exploration Program #Paleontology #Physics #Planet #Planetary Science and Exploration #Planetesimal #Solar System #Terrestrial planet #astro-ph.EP
paper · pdf · doi:10.1016/j.icarus.2021.114389
published in Icarus 361, 114389 (Elsevier BV) · Accepted in Icarus after 5 rounds of review
arxiv created 2021/02/17 · openalex publication_date 2021/02/24 · openalex created_date 2021/03/01 · arxiv updated 2021/03/10 · openalex updated_date 2026/08/05
Subsequent to the Moon's formation, late accretion to the terrestrial planets strongly modified the physical and chemical nature of silicate crusts and mantles. This alteration came in the form of melting through impacts, as well as the belated addition of volatiles and the highly siderophile elements (HSEs). Current debate centres on whether the lunar HSE record is representative of its whole late accretion history or alternatively that these were only retained in the mantle and crust after a particular time, and if so, when. Here we employ improved Monte Carlo impact simulations of late accretion onto the Moon and Mars and present an updated chronology based on new dynamical simulations of leftover planetesimals and the E-belt. We take into account the inefficient retention of colliding material. We compute the crater and basin densities on the Moon and Mars, the largest objects to strike these planets and the amount of material they accreted. Outputs are used to infer the mass in leftover planetesimals at a particular time period, which is then compared to the lunar HSE abundance. From this estimate we calculate a preferred lunar HSE retention age of ca. 4450 Ma which means that the modelled lunar mantle HSE abundances trace almost all of lunar late accretion. Based on our results, the surface ages of the lunar highlands are at least 4370 Ma. We find that the mass of leftover planetesimals with diameters Di<300 km at 4500 Ma that best fits the crater chronology is approximately 2x10-3 Earth mass (ME) while the mass of the E-belt was fixed at 4.5x10-4 ME. We also find that a leftover planetesimal mass in excess of 0.01 ME results in a lunar HSE retention age younger than major episodes of lunar differentiation and crust formation, which in turn violates geochemical constraints for the timing and intensity of late accretion to the Earth (Mojzsis et al., 2019).