Nördlinger Ries
The calculation of depth of secondary crater can be formulated based on the target body's density. Studies of the Nördlinger Ries in Germany and of ejecta blocks circling lunar and martian crater rims suggest that ejecta fragments having a similar density would likely express the same depth of penetration, as opposed to ejecta of differing densities creating impacts of varying depths, such as primary impactors, i.e. comets and asteroids.