Quantification of Impact‐Induced Melt Production in Numerical Modeling Revisited

Abstract

Melting and vaporization of rocks in impact cratering is mostly attributed to be a consequence of shock compression. However, other mechanism such as plastic work and decompression by structural uplift also contribute to melt production. In this study we expand the commonly used method to determine shock‐induced melting in numerical models from the peak shock pressure by a new approach to account for additional heating due plastic work and internal friction. We compare our new approach with the straight‐forward method to simply quantify melting from the temperature relative to the solidus temperature at any arbitrary point in time in the course of crater formation. This much simpler method does account for plastic work but suffers from reduced accuracy due to numerical diffusion inherent to ongoing advection in impact crater formation models. We demonstrate that our new approach is more accurate than previous methods in particular for quantitative determination of impact melt distribution in final crater structures. In addition, we assess the contribution of plastic work to the overall melt volume and find, that melting is dominated by plastic work for impacts at velocities smaller than 7.5–12.5 km/s in rocks, depending on the material strength. At higher impact velocities shock compression is the dominating mechanism for melting. Here, the conventional peak shock pressure method provides similar results compared with our new model. Our method serves as a powerful tool to accurately determine impact‐induced heating in particular at relatively low‐velocity impacts.

Plain Language Summary: During the collision of cosmic bodies such as planets and asteroids on various scales, the involved material is heated such that melting or vaporization can occur. The vast amount of heat is considered to be generated during shock compression, however recent studies found that plastic deformation during decompression also contribute to the heating process. In this study, we introduce a new approach to quantify impact‐induced melting more accurately under consideration of the latter heating mechanisms. We demonstrate that our approach is more accurate than previous attempts and quantify the contribution from plastic work on impact‐induced melting. We systematically study the effect of impact velocity and material strength on melt production and find, that it is dominated by plastic work for impact velocities up to 7.5–12.5 km/s in rocks, depending on the material strength.

Key Points:

We propose an improved method to quantify impact‐induced melt production for rocks.

We quantify impact‐induced melt production and separate between heating due to shock compression and plastic work.

Melting due to frictional heating (plastic work) dominates over shock melting for impact velocities below 7–13 km/s depending on strength.