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Post-impact gravity anomalies on asteroid Dimorphos following the Double Asteroid Redirection Test (DART)

Presentation #310.08 in the session Asteroids: Dynamics (Oral Presentation)

Published onOct 23, 2023
Post-impact gravity anomalies on asteroid Dimorphos following the Double Asteroid Redirection Test (DART)

Impacts are frequent in our Solar System, emerging as one of prime mechanisms governing the evolution of asteroids and comets. From small-scale Martian meteorites to larger biosphere-forming collisions, e.g., the Chicxulub cataclysm at the end of the Cretaceous Period, impact processes are vital in understanding the dynamic history of planetary bodies. In recent years, asteroid missions have made major advancement in characterizing in-situ the Near-Earth Objects (NEOs), from JAXA’s sample-return mission on asteroid Ryugu to NASA’s recent DART space mission that performed the first kinetic deflection on asteroid Dimorphos. The upcoming Hera mission by the European Space Agency (ESA) will assess the DART impact from a unique close point of view, during a rendezvous with Dimorphos in 2026. Meanwhile, several numerical simulations have studied the likely impact cratering [1] and ejecta plume outcomes in response to the DART-scale impactor, depending on the surface strength, target layering, boulder distribution, and the shape of the projectile. In this study, we further analyze the impact cratering processes, focusing on impact-generated gravity anomalies. We conduct a series of hypervelocity impact simulations through the iSALE2D shock physics code [2-3], with recently validated parameters for regolith-like materials [4]. In our model setup, we assume the DART impact falls into the low-to-intermediate strength regime (50 Pa - 1 kPa) with a wide porosity range (10 - 50%). The impactor is approximated to be a solid aluminum sphere with 579 kg mass, and vertically impacts into Dimorphos with a speed of 6.145 km/s. To compute the gravity anomalies, we combine the output of impact cratering simulations with our in-house gravity model based on the polyhedron method [5] in a series of post-impact scenarios, depending on the crater and subsurface morphology. Our modeling results provide predictions of the geophysical signatures from the DART impact crater and the subsurface characteristics of asteroid Dimorphos, which might be verified by the Hera spacecraft.

[1] Stickle et al. (2022). Planetary Science Journal, 3(11), 248. [2] Collins et al. (2004). Meteoritics and Planetary Science, 39:217-231 [3] Wünnemann et al. (2006). Icarus, 180:514-527. [4] Luther et al. (2022). Planetary Science Journal, 3(10), 227. [5] Werner et al. (1996). Celestial Mechanics and Dynamical Astronomy, 65, 313-344.

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