Year: 2022
Type: article
Abstract: The Moon is traditionally thought to have coalesced from the debris ejected by a giant impact onto the early Earth. However, such models struggle to explain the similar isotopic compositions of Earth and lunar rocks at the same time as the system’s angular momentum, and the details of potential impact scenarios are hotly debated. Above a high resolution threshold for simulations, we find that giant impacts can immediately place a satellite with similar mass and iron content to the Moon into orbit far outside Earth’s Roche limit. Even satellites that initially pass within the Roche limit can reliably and predictably survive, by being partially stripped and then torqued onto wider, stable orbits. Furthermore, the outer layers of these directly formed satellites are molten over cooler interiors and are composed of around 60% proto-Earth material. This could alleviate the tension between the Moon’s Earth-like isotopic composition and the different signature expected for the impactor. Immediate formation opens up new options for the Moon’s early orbit and evolution, including the possibility of a highly tilted orbit to explain the lunar inclination, and offers a simpler, single-stage scenario for the origin of the Moon.
Language: English
Topic: Astro and Planetary Science
Subfield: Space and Planetary Science
Field: Earth and Planetary Sciences
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $2,400
Awards: Cosmology and Cancer - Astronomical Statistics In Healthcare, DiRAC-3 Operations - 2022-23 extension - UCL, Durham DiRAC-2 petascale facility, G1468651527, STFC Durham Physics 2020 DTP, G1805294933, DiRAC-2.5 - the pathway to DiRAC Phase 3, DiRAC-3 Operations 2019-2022 - Edinburgh, G2843074508, DiRAC-3 Operations 2019-2022 - Cambridge [2020-06 resubmission], STFC DiRAC Project Office 2014-2017, DiRAC-2 Datacentric support grant, DiRAC SMP Facility: The Structure of the Universe, G472312141, DiRAC 2.5 Operations 2017-2020, DiRAC-3 Operations - 2022-23 extension - Leicester, DiRAC 2.5 Operations Bridging 2019 - Leicester, DiRAC 3 Operations, DiRAC-2: Recurrent Costs for Complexity@DiRAC Cluster at University of Leicester, WE WILL PERFORM A SERIES OF CALCULATIONS RELATING TO THE MOON-FORMING AND OTHER PLANETARY IMPACTS TO FOCUS ON TWO ISSUES. THE FIRST ISSUE IS THE EXTENT TO WHICH CONTAMINATION OF THE MOON BY THE EARTH S CRUST TOOK PLACE. THE SECOND IS THE AMOUNT OF WATER FROM TERRESTRIAL OCEANS THAT WAS INCORPORATED INTO THE PROTOLUNAR DISK OR WHICH ESCAPED DURING THE MOON-FORMING AND OTHER LARGE IMPACTS ON THE EARTH. WE WILL USE THE WELL-TESTED SPH/TREE-CODE OF FRYER AND WARREN (2004). SPH (SMOOTHED PARTICLE HYDRODYNAMICS) IS A LAGRANGIAN METHOD THAT REPRESENTS MATTER BY FREELY-MOVING PARTICLE ELEMENTS. IN COMBINATION WITH A TREE STRUCTURE FOR GRAVITY CALCULATION AND NEIGHBOR FINDING SPH/TREE-CODES ARE EXCEPTIONALLY WELL-SUITED FOR TRACKING MATERIAL PROVENANCE AND HAVE BEEN PARALLELIZED TO MAKE EFFICIENT USE OF MULTIPROCESSOR MACHINES WITH DISTRIBUTED MEMORY. THESE PROPERTIES MAKE THEM THE IDEAL CHOICE FOR THE CHALLENGE OF SIMULATING THE MOON-FORMING IMPACT. COMPLEMENTARY CALCULATIONS WILL BE PERFORMED USING THE EULERIAN CODE CTH FROM SANDIA NATIONAL LABORATORY TO INVESTIGATE IMPACTS AND ESCAPE ON SMALLER SCALES AND TO ASSESS THE ROBUSTNESS OF THE SPH RESULTS. THE RESOLUTION OF THE PROPOSED SPH SIMULATIONS WILL FOR THE FIRST TIME MAKE IT POSSIBLE TO INCLUDE PLANETARY CRUSTS AND OCEANS SELFCONSISTENTLY FOR WHICH 20 KM RESOLUTION IS THE MINIMUM REQUIREMENT TO RESOLVE THE SHOCK AT THE PLANET'S SURFACE. BECAUSE THE EARTH S PROTO-CRUST WAS ENRICHED IN INCOMPATIBLE ELEMENTS ADDITION OF TOO MUCH CRUSTAL MATERIAL TO THE PROTOLUNAR DISK WOULD VIOLATE THE AVAILABLE CONSTRAINTS ON LUNAR TRACE ELEMENT BULK CONCENTRATIONS. THIS CRITERION PROVIDES A NOVEL ADDITIONAL TEST OF MOON-FORMING MODELS. ZIRCON EVIDENCE SUGGESTS THE PRESENCE OF LIQUID WATER AT THE SURFACE OF THE HADEAN EARTH. ALTHOUGH SURFACE OCEANS CAN NOT YET BE FULLY RESOLVED WE WILL CARRY OUT PRELIMINARY STUDIES TO INVESTIGATE HOW MUCH WATER IS TRANSFERRED FROM THE SURFACE TO THE PROTOLUNAR DISK. DOING SO IS IMPORTANT BECAUSE OF ABUNDANT RECENT EVIDENCE FOR AT LEAST LOCALLY HIGH WATER CONCENTRATIONS IN LUNAR MAGMA SOURCE REGIONS. THE SPH SIMULATIONS WILL USE 10^8 TO 10^9 PARTICLES AND ACHIEVE SPATIAL RESOLUTIONS ON THE ORDER OF 10 KM IN THE EARTH AND 100 KM IN THE MOON-FORMING DISK. THESE RESOLUTIONS ARE 10 TIMES FINER THAN THOSE IN STATE-OF-THE-ART SIMULATIONS PUBLISHED TO DATE WHICH TYPICALLY DEPLOY ONLY 10^5-10^6 PARTICLES. OUR SIMULATIONS WILL ALSO PROVIDE A QUALITATIVELY AND QUANTITATIVELY BETTER DESCRIPTION OF THE MOON-FORMING DISK BY VERTICALLY RESOLVING THE DISK AND REDUCING NUMERICAL VISCOSITY INTO THE ESTIMATED RANGE OF PHYSICAL VISCOSITIES. PRELIMINARY CALCULATIONS DONE BY US USING 10^8 PARTICLES HAVE SHOWN THAT THE PROPOSED RESEARCH USING HUNDRED-MILLION AND BILLION PARTICLE SIMULATIONS IS NOT ONLY TIMELY BUT CAN PROVIDE A QUANTITATIVE IMPROVEMENT IN OUR UNDERSTANDING OF THE ORIGIN OF THE MOON RELEVANCE TO THE EMERGING WORLDS PROGRAM: THIS PROPOSAL IS RELEVANT TO THE GOALS OF THE EMERGING WORLDS RESEARCH PROGRAM AS LAID OUT IN SECTION C.2 SECTION 2 OF THE ROSES 2017 DOCUMENT. SPECIFICALLY UNDER THE PROGRAM SCOPE OUR PROPOSAL ADDRESSES THEORETICAL AND MODELING INVESTIGATIONS OF FORMATION AND GLOBAL DIFFERENTIATION OF SOLAR SYSTEM BODIES AND PROCESSES THAT OCCUR DURING THAT EVENT. THE PROPOSED WORK IS CONCERNED WITH COLLISION PROCESSES THAT HAD SIGNIFICANT EFFECT ON THE STRUCTURE OF THE TARGET BODIES (EARTH AND MOON) AND WILL ADDRESS KEY GEOCHEMICAL AND GEOPHYSICAL PROCESSES IN EARLY PLANETARY EVOLUTION AND TERRESTRIAL HISTORY IN TERMS OF GENERAL SOLAR SYSTEM PROCESSES., DiRAC Bridging Grant 2019 - Cambridge, G629320885, DiRAC-2.5 DC - Operations 2017-2020, STFC Durham Physics 2019 DTP, Dirac-3 Operations 2019-2022- Durham, G653891685, Resources for DiRAC2 at HPCs, DiRAC-3 Operations - 2022-23 extension - EDinburgh, Dirac 2.5 Operations, DiRAC2.5 Operations: The DiRAC Project Office 2017-2020, DiRAC-3 Operations - 2022-23 extension - Cambridge, DiRAC 2.5y Bridging Funding - UCL, Edinburgh DiRAC Resource Grant, DiRAC SMP Facility: Revealing the Structure of the Universe, G7937591081, DiRAC: Memory Intensive 2.5y, Durham Astronomy Consolidated Grant 2017-2020, DiRAC Bridging Grant 2019, Astronomy at Durham 2020-2023, Software development support for DiRAC, STFC Centre for Doctoral Training in Data Intensive Science, DiRAC 2.5 Operations 2017-2020, DiRAC: Memory Intensive 2.5x
OpenAlex ID: W4301395651