When Does Strength Matter? Assessing the Role of Material Strength in Planetary Impacts

Impact processes spanning in scale from cratering to that of catastrophic disruption determine both the development and ultimate habitability of terrestrial planets. Numerical simulations have played a key role in our understanding of these processes, demonstrating how impacts drive growth [1], deliver water [2], and lead to moon formation following giant impacts [3].

Most of these impact studies adopt the simplifying assumption that these collisions occur in the gravity-dominated regime, where material strength is relatively weak and so often simplified or neglected entirely. These approaches are motivated by a desire to limit the computational cost of simulations and hence maximise the number and resolution of simulations that can be performed. However, little work has been done to test this assumption and assess when the effects of material strength are important or negligible. Using the recent addition of strength models to the smooth particle hydrodynamics (SPH) code SWIFT [4], we can test the limits of these assumptions at high resolutions across a broad range of length scales.

We will present results from a suite of these simulations, comparing leading strength models [5] in this field with strengthless SPH, to provide detailed predictions for where scientific conclusions might be sensitive to the choice of strength model. We will investigate collisional outcomes such as the extent of melting in giant impacts and the catastrophic disruption threshold, assessing the scaling law relations commonly applied in planetary accretion models with implications for planetary habitability.

References:
[1] Crespi, S., et al., 2024, Protoplanet collisions: New scaling laws from smooth particle hydrodynamics simulations, Astronomy & Astrophysics, 685, A86
[2] Burger, C., et al., 2020, Realistic collisional water transport during terrestrial planet formation, Astronomy & Astrophysics, 634, A76
[3] Canup, R., 2004, Simulations of a late lunar-forming impact, Icarus, 168, 433-456
[4] Schaller, M., et al., 2024, Swift: a modern highly parallel gravity and smoothed particle hydrodynamics solver for astrophysical and cosmological applications, Monthly Notices of the Royal Astronomical Society, 530, 2378-2419
[5] Collins, G., et al., 2004, Modeling damage and deformation in impact simulations, Meteoritics & Planetary Science, 39, 217-231