Ejecta size velocity distributions and largest ejected fragment sizes from across the solar system

We have performed an extensive study of secondary craters associated with specific primary craters in order to understand the size and velocity of the ejecta fragments that formed them. This helps us understand the dynamics of the primary impact and the formation of fragments (or tightly bound clusters of fragments) and how they are ejected during the passage of the shock wave through a planetary surface. We now have data from icy Galilean satellites (Singer et al., 2013), the Moon (Singer et al., 2020 and continued work), Mercury (current work), and Mars (current work).

This study spans a range of crater diameters, on a range of target surface material types, on bodies with a range of gravities and primary impact velocities. We will present updates on all observed trends. We discovered a previously unrecognized trend where the size velocity distributions are dependent on the size of the impact (i.e., scale dependent).

This new empirical data can be: (1) used to help constrain analytical and numerical models of dynamic fragmentation, (2) provide information on the size of secondary craters across planetary surfaces, (3) place constraints on the largest ejecta fragments expected be ejected at escape velocity from a given body, and (4) used as inputs into models of regolith development and impact gardening.

Singer, K. N., McKinnon, W. B., & Nowicki, L. T. (2013). Secondary craters from large impacts on Europa and Ganymede: Ejecta size–velocity distributions on icy worlds, and the scaling of ejected blocks. Icarus, 226, 865-884. doi:10.1016/j.icarus.2013.06.034

Singer, K. N., Jolliff, B. L., & McKinnon, W. B. (2020). Lunar secondary craters and estimated ejecta block sizes reveal a scale-dependent fragmentation trend. J. Geophys. Res., 125(8), e2019JE006313. doi:10.1029/2019JE006313