Conamara Chaos Region, Europa: Reconstruction of mobile polygonal ice blocks

New Galileo images of Europa reveal regions of chaotic terrain in otherwise highly-lineated background plains. Examination of Conamara Chaos shows that 59% of the region is composed of fine-textured matrix material lying at low elevations and formed by destruction of lineated plains, while the remainder consists of 139 fragmented polygons of linear-textured background plains. Using through-trending linear features, we reconstruct the original positions of chaos polygons and find that significant lateral translation and rotation have occurred: 78% of the polygons have undergone horizontal translations with most moving between 1 and 5 km, and 81% have rotated (average rotation of ∼11°). Movement of polygons appears to be inward from the chaos margins and clockwise in the center, while polygon rotation is evenly clockwise and counterclockwise. Chaos formation in this region thus involves destruction of over half of the pre-existing terrain, and mobilization, translation, and rotation of the remaining polygons, implying elevated near-surface temperatures and a highly mobile substrate over lateral scales of ∼100 km.