Impact crater scaling and inner solar system bombardment

Impact crater scaling and inner solar system bombardment

DiRAC resource used: DiAL 2.5

PI: G.S. Collins

The relationship between impact crater size and impactor properties, such as size and speed, is key to comparing impactor and crater populations on different planets and dating planetary surfaces. Most of our understanding of this relationship, however, comes from numerical simulations of vertical-incidence impacts, and laboratory impact experiments at relatively low speed, which are comparatively rare in nature.

In this project, we have run shock physics simulations of large crater formation on Earth and the Moon, for a range of oblique impact angles and speeds more typical of planetary scale impacts. We have generated an extensive dataset of high-resolution, oblique-impact complex crater simulations which would not have been possible without the DiRAC facility.

We find that while crater size decreases as the impact angle becomes shallower, crater diameter, depth and volume are all affected by impact angle in different ways. Most importantly, we find that crater diameter depends less on impact angle than previously thought, especially for steeply inclined impacts. This implies that typical asteroid impacts on planetary surfaces form larger craters, and large craters are formed more frequently, than is currently assumed.

Davison, T. M., & Collins, G. S. (2022). Complex crater formation by oblique impacts on the Earth and Moon. Geophysical Research Letters, 49, e2022GL101117.

Fig 1: Snapshots from a simulation of a 14 km diameter projectile, hitting at 20 km/s and an angle of 45° from the horizontal, on Earth. The frames are slices along the symmetry plane of the simulation, and show (a) the initial conditions, (b) the crater at its maximum depth (c) maximum volume and (d) final morphology. The arrow in (a) shows the projectile’s trajectory. Transient (e) and final (f) crater surface profiles taken along the symmetry plane, for simulations with a projectile diameter of 14 km and velocity of 20 km/s on Earth, for impact angles 30–90°. Note in (f), the z-axis scale is exaggerated by a factor of 2.