On the possibility of viscoelastic deformation of the large south polar craters and true polar wander on the asteroid Vesta

Abstract

The asteroid Vesta, located within the inner asteroid belt, is a differentiated body with a prominent rotational bulge. NASA's Dawn mission revealed the presence of two large, relatively shallow impact craters in the south polar region, one with a high‐standing central peak. The shallowness and prominent central peak are reminiscent of large craters on some icy satellites that may have experienced strong topographic relaxation. The location of these basins near the south pole is also unusual and suggests true polar wander, which requires relaxation of the rotational bulge. Thus, we use the finite element method and a viscoelastic rheology to examine the feasibility of relaxation processes operating on Vesta. Given the plausible thermal state of Vesta by the decay of long‐lived radioactive elements, we find that the lithosphere is not compliant enough to allow strong relaxation of the large south polar craters, and thus the peculiar morphology is possibly a product of the formation of these large basins at a planetary scale. Additionally, the asteroid has not been warm enough to permit the relaxation of the rotational bulge. Consequently, these craters both happened to form near the south pole, as unlikely as that is.

Martian Mantle Heat Flow Estimate From the Lack of Lithospheric Flexure in the South Pole of Mars: Implications for Planetary Evolution and Basal Melting

“…The viscoelastic response of the Martian lithosphere to the SPLD was modeled using the finite element package Marc‐Mentat. Here, we only summarize the methodology, and interested readers are referred to several previous works (e.g., Karimi & Dombard, 2016; Karimi et al., 2016; Ojha et al., 2019) for a detailed description.…”

Depletion of Heat Producing Elements in the Martian Mantle

“…Given the relatively small wavelength of our topographic loads (<10°), we use a planar mesh instead of a spherical mesh. Spherical mesh is only important when modeling the effects of topographic loads with large wavelength for which planetary curvature may play a role (Karimi & Dombard, 2016). We fit the observed stress profiles of PB and GL with cosine curves and use the fitted stress profiles as an axisymmetric distributed load in our finite element method models (Figure 1; Figure S1).…”

Large‐Scale Troughs on Asteroid 4 Vesta Accommodate Opening‐Mode Displacement

“…Although the established crater statistics in Cheng et al (2021) neither confirm nor refute the simultaneous formation of the Divalia Fossae and Rheasilvia Basin, their large uncertainties allow for the Divalia Fossae to have formed long before or after the Rheasilvia impact (Cheng et al, 2021). Taking together the established age relationships and the crosscutting relationships between troughs and basins, it is plausible for the Divalia Fossae to have formed as a long-term consequence of the Rheasilvia impact (Cheng and Klimczak., 2022), perhaps tied to changes in the orientation or rotation of the asteroid (Karimi & Dombard, 2016;Mao and McKinnon., 2020). This newly proposed formation hypothesis contradicts with the leading hypothesis of the impact directly triggering the troughs and is yet to be tested by, and incorporated into other research.…”