Hypervelocity impact simulations of DART on asteroid Dimorphos: Impact-generated porosity and gravity anomalies

The impact processes are ubiquitous in the solar system, as one of the fundamental mechanisms driving the evolution of asteroids and comets^[1]. From small meteorite impacts to gigantic Moon-forming collisions^[2], the impact cratering formation holds key insights pointing out the dynamic history of our solar system from 4.5 billion years ago. Thanks to the rapid progress in numerical modeling and computational resources, high-resolution numerical models offer a powerful framework for expanding our knowledge of the impact cratering phenomena. Meanwhile, planetary defense missions have steeply advanced in characterizing Near-Earth Objects (NEO), such as NASA's upcoming DART mission^[3], which will deflect the orbit of Dimorphos through a kinetic impactor. A few years after the DART impact, the Hera mission by European Space Agency (ESA)^[4] will rigorously portray the consequences of the collision, from cratering to exploring the interior and dynamics. Several numerical efforts have recently provided significant insights on impact cratering and ejecta dynamics in response to the DART impactor. Raducan et al. (2019)^[5], for example, have comprehensively reported several factors that affect the Dimorphos' response, from target layering and strength^[6] to the projectile obliquity^[7]. In the present study, after verifying our results using the impactor/target constraints^[5-7], we have further examined the consequences of DART impact, focusing more on the impact-generated porosity and gravity anomalies. To accomplish this, we performed hypervelocity impact simulations by the iSALE2D shock physics code^[8-10] set up for a variety of target scenarios, ranging from low-cohesion gravity-dominated to high-cohesion stress-dominated regimes. Our simulation results shed new light on the detailed picture of cratering formation in the aftermath of the DART impact.

Figure 1: DART impact-generated gravity and density distribution on asteroid Dimorphos.

References

^[1] Holsapple, K. A. (1993). The scaling of impact processes in planetary sciences. Annual review of earth and planetary sciences, 21(1), 333-373.

^[2] Wada, K., Kokubo, E., & Makino, J. (2006). High-resolution simulations of a Moon-forming impact and postimpact evolution. The Astrophysical Journal, 638(2), 1180.

^[3] Michel, P., Küppers, M., & Carnelli, I. (2018). The Hera mission: European component of the ESA-NASA AIDA mission to a binary asteroid. 42nd COSPAR Scientific Assembly, 42, B1-1.

^[4] Cheng, A. F., Rivkin, A. S., Michel, P., ... & Thomas, C. (2018). AIDA DART asteroid deflection test: Planetary defense and science objectives. PSS, 157, 104-115.

^[5] Raducan, S. D., Davison, T. M., Luther, R., & Collins, G. S. (2019). The role of asteroid strength, porosity and internal friction in impact momentum transfer. Icarus, 329, 282-295.

^[6] Raducan, S. D., Davison, T. M., & Collins, G. S. (2020). The effects of asteroid layering on ejecta mass-velocity distribution and implications for impact momentum transfer. PSS, 180, 104756.

^[7] Raducan, S. D., Davison, T. M., & Collins, G. S. (2022). Ejecta distribution and momentum transfer from oblique impacts on asteroid surfaces. Icarus, 374, 114793.

^[8] Amsden, A., Ruppel, H., and Hirt, C. (1980). SALE: A simplified ALE computer program for fluid flow at all speeds. Los Alamos National Laboratories Report, LA-8095:101p. Los Alamos, New Mexico: LANL.

^[9] Collins, G. S., Melosh, H. J., and Ivanov, B. A. (2004). Modeling damage and deformation in impact simulations. Meteoritics and Planetary Science, 39:217--231.

^[10] Wünnemann, K., Collins, G., and Melosh, H. (2006). A strain-based porosity model for use in hydrocode simulations of impacts and implications for transient crater growth in porous targets. Icarus, 180:514--527.