Determining the roles of active, passive, and compositional support mechanisms in the formation of bands and complex ridges on Europa utilizing topography

It has been suggested that band topography observed in limited stereo coverage of Europa could result from lateral density variations created through active thermal (e.g., shear heating), passive thermal (e.g., thermal buoyancy), or compositional (e.g., compositional buoyancy) mechanisms. More extensive topographic data has been produced using stereo photogrammetry and '2d' photoclinometry and is being used to test the applicability of these support mechanisms to explain the formation of bands and complex ridges. Previously, three regions on Europa were examined (i.e., E4. E12 Wedges, and Rhadamanthys) and, in the latter two regions, topography indicates that young bands appear to be elevated above older ones, possibly suggesting that passive support mechanisms (i.e., thermal buoyancy) play a role in the formation of the most recent bands. We are currently examining additional regions of the surface utilizing DEMs and topographic profiles of Europa's surface to further characterize the likelihood of passive support mechanisms (e.g., thermal buoyancy) as a means of accounting for age relationships of bands with respect to each other and the surrounding terrain. We are also looking in more detail at complex ridges to determine their relationship, if any, to bands and to the surrounding terrain.