Assessing the Detectability of Europa’s Seafloor Topography from Europa Clipper’s Gravity Data

Abstract

Due to its size and tidal heating, Europa may potentially possess active volcanism and hydrothermal circulation at its seafloor. The upcoming Europa Clipper mission provides the opportunity to obtain global gravity maps over a range of spatial scales, up to degree l ≈ 10. We assess the ability of such gravity measurements to determine Europa’s seafloor topography, building on and extending previous work in this area. We create a suite of models that test the gravity signature of a wider range of possible topographies and lithospheric thicknesses, spacecraft close-approach altitudes, and the effect of a gypsum layer on the seafloor. Additionally, we model Europa’s seafloor scaled from other geologically active bodies, i.e., Earth, Venus, and Io, investigating the distinguishability of volcanic or plate tectonic features. We find that seafloor topography should be detectable at the resolution of Clipper, while the ice shell characteristics (e.g., via admittance analysis) are not resolvable globally. In our baseline scenario, seafloor topography dominates the total gravity signal up to degree l = 22, while for planetary analogs this proves true up to degree l = 11 for an Earth-scaled seafloor, as well as l = 42 and l = 54 for a Venus- or Io-scaled seafloor. Finally, we find that a putative layer of gypsum on the seafloor reduces the gravity signal by flattening out the seafloor, though its presence will not be detectable absent independent determination of its topographic amplitude.