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

Abstract. 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 eleva-tions and formed by destruction of lineated plains, while the remainder consists of 139 fragmented polygons of linear-textured background plains. Using through-trending linear fea-tures, we reconstruct he 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-11ø). Movement of poly-gons appears to be inward from the chaos margins and clock-wise in the center, while polygon rotation is evenly clockwise and counterclockwise. Chaos formation in this region thus in-volves destruction of over half of the pre-existing terrain, and mobilization, translation, and rotation of the remaining poly-gons, implying elevated near-surface temperatures and a highly mobile substrate over lateral scales of--100 km