Leveraging Eutectic Interfaces in Geodynamic models of Europa’s Ice shell to constrain Physical Parameters

Kurzfassung

Jupiter’s moon Europa is one of the prime targets for planetary exploration due to its high astrobiological potential. Slightly smaller than Earth’s moon, Europa harbors a liquid water ocean beneath an ice shell. The thickness of Europa’s ice shell is poorly constrained and values of less than 1 km to up to 90 km have been suggested in previous studies that investigated shell thickness via a combination of thermal, impact, and mechanical models [2,3]. Low thickness values were derived from mechanical models, which can generally only estimate the thickness of the brittle layer. Thermal and impact models can consider the entire ice shell and estimates using such models suggest the higher thickness end-member values. Ice-penetrating radars on NASA’s Europa-CLIPPER (REASON, [4]) and ESA’s JUICE (RIME, [5]) missions aim to determine the thickness of Europa's ice shell. Recent studies have suggested that constraints on the thickness of Europa’s ice shell can be obtained through the detection of eutectic interfaces, defined as the depth where brine becomes thermodynamically stable in the ice shell [6]. In fact, previous studies have shown that the detection of eutectic horizons within an ice shell is likely easier than detecting the ice-ocean interface, given their shallower depths and therefore lower total signal attenuation [7,8,9]. The depth of the eutectic interfaces depends on the thermal state of the ice shell, which is closely linked to the ice shell viscosity and large-scale dynamics [7]. As suggested by previous authors [6,7], detection of eutectic interfaces therefore represents a promising strategy to constrain the thermophysical properties of the ice shell through characterization of its convective pattern.