Antipodal Deposits on Europa from the Pwyll Impact?

Abstract:

Pwyll is considered one of the youngest craters on Europa’s surface based on superposition relationships and its bright crater rays. Secondary craters from Pwyll have been clearly identified as far away as 30 degrees (>1000 km) from the primary impact. Approximately antipodal to Pwyll, Trumbo et al. (2018) have identified a high thermal inertia anomaly based on ALMA observations of Europa. Additionally, recent regional mapping of Europa by Leonard et al. (2020) has identified a terrain with a unique morphology at 40^oN, 260^oE—near Pwyll’s antipode. These observations suggest that ejecta from Pwyll may have been focused at its antipode. This scenario would be analogous to the Tycho impact on Earth’s moon where analysis of thermal infrared and high-resolution image data returned by Lunar Reconnaissance Orbiter, combined with ballistic modeling, has revealed the presence of high thermal inertia antipodal deposits consisting of melt pools and rocky debris. We aim to determine the feasibility of antipodal deposit formation on Europa from the Pwyll impact through modeling and analogy to the Tycho deposits. It is then important to understand whether other, older large impacts on Europa (e.g., Manannán) may have produced antipodal deposits. It could be possible that the signature of an antipodal deposit has faded over the visible surface history (~60 Ma). Additionally, if the Pwyll impact is capable of creating antipodal deposits, it could imply that ejecta from this impact would have been distributed all over Europa’s surface. Determining the feasibility and lifetime of antipodal deposits on Europa could allow us to constrain the surface processes active on Europa and potentially further constrain the age and characteristics of the Pwyll impact.