DETAILED CHARACTERIZATION OF EUROPA'S RIDGE MORPHOLOGY

Ridges are the most common features on the surface of Europa, yet we do not have a viable mechanism to explain how they form. Based on previous observations, it has been hypothesized that ridges develop through a series of evolutionary stages: trough, raised rim trough, double ridge, and complex ridge, with double ridges seemingly the most prevalent. Ridge formation models frequently use an idealized morphology, however the simplification of these structures may in part explain the inadequacy of existing formation mechanisms. Similarly, ridge formation models cannot address the hypothesized genetic relationship of each ridge type. The diversity of ridge morphologies across Europa is not well understood, however previous models of ridge formation are based on detailed, local-scale observations. Thus existing ridge formation models are unable to produce the level of complexity observed by our detailed, regionally extensive mapping campaign. To better characterize ridge morphologies, and evaluate ridge formation mechanisms and evolution, we map ridges across images with resolutions of ~250m/pixel covering ~10% of Europa’s surface. We present preliminary mapping results from a mosaic located on Europa’s antijovian hemisphere, comprised of Galileo images (~250 m/pixel), which continuously covers latitudes from ~70˚ S to ~80˚ N. Initial observations suggest ridge structures are exceedingly diverse. We initially classify ridges into morphological categories of single, double, and complex. We also map troughs, bands, and transitions between features to enable future analysis of ridge evolution. Initial observations of ridge distribution suggest that single ridges become more common than double ridges closer to the poles. Further analysis is necessary to verify if this result is real, an observational bias, or related to low image resolutions.