Extraction of topographic profiles of double ridges on Europa

Double ridges are a common linear feature on Europa’s surface. They can be identified by a central trough accompanied by two ridge crests. Usually, the elevation of double ridge crests is not higher than 300 meters (e.g. [1]). Some double ridges run almost perfectly straight for hundreds of kilometers, while others are curved, for example into a cycloidal shape. Several double ridge formation hypotheses exist, which can be separated into cryo-volcanism/-sedimentation and brittle deformation (an overview can be found in [2]). Each proposed formation mechanism results in a unique topographic profile, which allows these hypotheses to be tested. 

We extract topographic profiles of more than 1000 mapped double ridges (perpendicular to their orientation) from a shape-from-shading topographic map. The shape-from-shading topographical map and the double ridge map are based on regional mosaics of Europa (data by [3]), two north-south covering swaths of the trailing and leading hemispheres at the regional scale (~230 m/px). The two regional mosaics were obtained under consistent illumination angles by the solid-state imager (SSI) on the Galileo spacecraft. We map double ridges in the regional mosaics with the help of the deep-learning tool LineaMapper [4]. We manually inspect, adjust, and verify LineaMapper’s predictions while respecting disruptions caused by other cross-cutting surface features.  

With this methodology, we analyze topographic profiles of double ridges in the regional mosaics and match them with unique profiles predicted by cryo-volcanism/-sedimentation and brittle deformation hypotheses. By assuming that, for any lineament, the number of disruptions per kilometer length is a proxy for relative age, we can assess the evolution of double ridge profiles over time, with potential implications for the upcoming space missions Europa Clipper and JUICE. 

[1] F. Nimmo, R. T. Pappalardo, B. Giese. (2003). On the origins of band topography, Europa. Icarus, 166(1), 21-32. 
[2] A.C. Dameron & D. M. Burr. (2018). Europan double ridge morphometry as a test of formation models. Icarus, 305(1), 225-249. 
[3] M. T. Bland, L. A. Weller, B. A. Archinal, E. Smith, B. H. Wheeler, (2021). Improving the Usability of Galileo and Voyager Images of Jupiter's Moon Europa. Earth and Space Science, 8(12). 
[4] C. Haslebacher, N. Thomas, V. T. Bickel, (2024). LineaMapper: A deep learning-powered tool for mapping linear surface features on Europa. Icarus, 410(1).