Distribution of chaotic terrain on Europa

The locations of chaotic terrain are mapped over all regions of Europa for which we have adequate resolution (∼200 m or better) and appropriate lighting geometry (Sun angle <35° from the local horizontal), comprising 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 covered by small chaos features. The largest contiguous area of chaotic terrain is ∼1300 km across. Chaotic terrain displays variations in freshness of appearance, probably because of aging by fine-scale tectonics. Resurfacing of previous chaotic terrain by larger-scale tectonics or disruption by newer chaos are common. Chaos formation is not necessarily recent relative 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 terrain that occupies more than half of the surface of Europa.