Abstract

The ejecta blankets of impact craters formed on a planetary body that is free of significant quantities of volatiles show substantial differences from those formed on a volatile-rich planetary body. Craters in volatile-rich environments often have layered ejecta blankets with lobe-like ramparts and long runout flows, as seen for Martian impact craters. Under volatile-free conditions, present on the Moon and Mercury, radial textures and patterns, and a gradational decrease in ejecta thickness with distance, can be observed. The Ries crater in Germany is one of the rare impacts on Earth with a preserved ejecta blanket. This crater was previously regarded as an analogue for impact formation on the Moon. Here we demonstrate for the first time that the recent Ries ejecta blanket contains a massive and continuous rampart structure at 1.45–2.12 crater radii from the crater center. Ejecta distribution and thickness, as well as the ejecta fabric, indicate the presence of fluids during the emplacement process. Although Mars differs in atmospheric pressure and water distribution from Earth, the Ries crater shows striking similarities to Martian craters; in particular, those with double-layered ejecta. Consequently, terrestrial impact craters can be better used as analogues for understanding impact formation on Mars than for planetary bodies with volatile-free conditions as seen on the Moon and Mercury.

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