Distribution of chaotic terrain on Europa

The locations of chaotic terrain are mapped over all regions of Europa for which we have adequate resolution (similar to 200 m or better) and appropri ate lighting geometry (Sun angle <35 degrees from the local horizontal), co mprising 9% of the total surface of the satellite. Nearly 30% of the mapped area is occupied by chaotic terrain recognizable at 200 m resolution, and sampling at higher resolution suggests that at least 10% more may be covere d by small chaos features. The largest contiguous area of chaotic terrain i s similar to 1300 km across. Chaotic terrain displays variations in freshne ss of appearance, probably because of aging by fine-scale tectonics. Resurf acing of previous chaotic terrain by larger-scale tectonics or disruption b y newer chaos are common. Chaos formation is not necessarily recent relativ e to tectonics; both types of process appear to have gone on diachronously, The size distribution shows no dominant or characteristic size and appears to have been controlled by competition from tectonics, which has created t errain that occupies more than half of the surface of Europa.