Contemporaneous formation of self-secondaries and layered ejecta deposits on Mars

Abstract

Abstract Self-secondaries are secondary craters formed in cogenetic ejecta deposits. Bearing important information on cratering mechanics and the applicability of remote age-determination technique using crater statistics, the spatial distribution of self-secondaries on Mars and their potential effect on martian crater chronology remain uncharacterized. Here, we show that self-secondaries are scarce on Mars, possessing minor effect on crater chronology. Recognized self-secondaries primarily occur on rim deposits and are largely absent on layered ejecta deposits, suggesting that the emplacement of self-secondaries and layered ejecta deposits occurred in a narrow time window. Comparison with model-predicted distributions of self-secondaries suggests that fragments forming self-secondaries did not uniformly have near-vertical ejection angles and may have slightly larger angles than those of normal excavation flows, explaining their common occurrence on airless planetary bodies. The double-layered ejecta of Steinheim ceased emplacement earlier than single- and multiple-layered ejecta, possibly due to the higher volatile content in pre-impact target materials.