BANDS ON JUPITER'S MOON EUROPA: GEOMETRIES, MORPHOLOGIES, CLASSIFICATION, AND FORMATION MECHANISMS

The surface of Jupiter's moon Europa is disrupted by multiple types of geologic features. Bands form prominent extensional, tabular features with contrasting albedo and/or surface texture to the surrounding terrain. They represent sites of new crustal creation through plate-like opening or spreading. The surface of Europa is geologically young (perhaps no more than ~90 my), indicating that some combination of processes must rapidly resurface this icy moon. Bands may be a major contributor to this process. Nonetheless, how and why bands form remains an open question. This study utilizes the USGS Europa global mosaic and Galileo spacecraft images to map and characterize bands from nine regions: Argadnel Regio, Yelland Linea, Argiope Linea, Castalia Macula, Echion Linea, Sarpedon Linea, Libya Linea, Astypalaea Linea, and Falga Regio. We have developed a new classification system for bands focused on geometry in relation to the breadth of morphologies observed and infer a range of potential top-driven (i.e., not endogenic) formation mechanisms. Bands may change morphology across the width or along the length of the band. Geometric elements include band shapes, association with other structures, opening vectors, and the ratio of dilation to band length. By matching piercing points of older features along the margins of the bands and accounting for internal morphology changes, we reconstruct the dilation phases from initial opening of a pre-existing fracture to the current state of maximum dilation (up to ~30-40 km). We identify patterns where the morphology of a band changes from smooth to lineated in response to the opening vector becoming highly oblique (<45^o as measured relative to the margin of the band), resulting in primarily lateral motions. This obliquity could have implications for the rate or mechanism by which material is transported to the surface. Understanding the driving mechanisms behind band formation will shed insight into how the surface of Europa was formed and possibly is still being resurfaced. If bands are a conduit through which material is transported to the surface from deeper and warmer portions of the ice shell, they may provide key sites for the search for life on Europa and priority targeting by future missions to this icy moon, such as NASA’s Europa Clipper mission.