Interpreting the Elliptical Crater Populations on Mars, Venus, and the Moon

摘要: Abstract Asteroids or comets striking a planetary surface at very shallow angles produce elliptical-shaped craters. According to laboratory impact experiments (D. E. Gault and J. A. Wedekind 1978, Proc. Lunar Planet. Sci. Conf. 9th , 3843–3875), elliptical craters result from within ∼5° of horizontal less than 1% projectiles with isotropic trajectories create This disagrees survey results which suggest that approximately 5% all kilometer-sized formed on Mars, Venus, the Moon have shapes. To explain this discrepancy, we examined threshold incidence angle necessary in experiments. Recent show aluminum targets elongated much steeper sand targets. suggests target properties are as important projectile's determining eventual ellipticity crater. Creating model interpolates between data produced using targets, derive new crater 12° for Moon. leads predicted proportion matches observations uncertainty given random projectile population. We conclude observed these bodies is natural by-product angles, no additional formation mechanisms needed.