Moon-forming impactor as a source of Earth’s basal mantle anomalies

A Giant Impact Origin for the First Subduction on Earth

“…The enrichment of heat-producing elements in LLSVPs can be created by Earth's internal differentiation process (Citron et al, 2020). If LLSVPs are made of Theia's mantle (Yuan et al, 2023), they are likely also enriched in heat-producing elements, given that the canonical MGI suggests Theia resembles Mars, which has been estimated to have higher heat-producing elements than Earth (Table S2 in Supporting Information S1). Thus, exploring the potential link between ancient plume-induced subduction sites and the location of LLSVPs may provide a powerful means to reconstruct global plate motions beyond 200 Ma.…”

“…The MGI is typically thought violent enough to melt a substantial portion or even the entire mantle, especially in scenarios involving high energy and high angular momentum (Lock & Stewart, 2017; Nakajima & Stevenson, 2015). Using two different giant impact computational methods with improved equations of state (Stewart et al., 2020) and at high (Deng et al., 2019) and ultra‐high (Kegerreis et al., 2022) resolution, our recent work (Yuan et al., 2023) demonstrates that the lower half of Earth's mantle would have remained mostly solid after a canonical MGI. It also suggests that large intact domains of Theia's likely Fe‐rich mantle are candidates of the two seismically‐observed large low‐shear velocity provinces (LLSVPs).…”

“… A schematic illustration of the path from the Moon‐forming giant impact (MGI) to plume‐induced subduction in the early Hadean. A canonical MGI (a) leads to a two‐layered mantle structure with a mostly solid lower mantle and an elevated core‐mantle boundary temperature (b) (Deng et al., 2019; Yuan et al., 2023). After solidification of the upper magma ocean within several million years (Hamano et al., 2013; Nikolaou et al., 2019), we assume a proto‐lithosphere gradually formed over 50–100 million years (c), which was then destabilized and segmented by a mantle plume from an large low‐shear velocity province made of the Theia mantle remnant (Yuan et al., 2023) (d).…”

“…A canonical MGI (a) leads to a two‐layered mantle structure with a mostly solid lower mantle and an elevated core‐mantle boundary temperature (b) (Deng et al., 2019; Yuan et al., 2023). After solidification of the upper magma ocean within several million years (Hamano et al., 2013; Nikolaou et al., 2019), we assume a proto‐lithosphere gradually formed over 50–100 million years (c), which was then destabilized and segmented by a mantle plume from an large low‐shear velocity province made of the Theia mantle remnant (Yuan et al., 2023) (d).…”

Mars's Crustal and Volcanic Structure Explained by Southern Giant Impact and Resulting Mantle Depletion

“…In this case, impact melt production is often a result of extreme pressure changes relevant to impact shock waves, leaving behind a thin layer of impact melt within the impact crater. On the other hand, hydrodynamical simulation methods show that giant impacts can warm up the planetary mantles on the impacted hemisphere by thousands of degrees (Ballantyne et al., 2023; Nakajima et al., 2021; Yuan et al, 2023; Zhu et al, 2019), creating magma oceans of various extents. In quest of the dichotomy formation mechanism, collision simulations demonstrate that a northern giant impact, within a range of impact angles and velocities, can strip the right amount of primordial crust necessary to form the thin lowland crust (Marinova et al., 2008; Nimmo et al., 2008).…”