Post contributed by Helle L. Skjetne, PhD candidate, Department of Earth and Planetary Sciences, University of Tennessee, Knoxville, USA.

Chaos terrain is formed by disruption of preexisting surfaces into irregularly shaped blocks with a “chaotic” appearance (Image 1). This typically occurs through fracturing (that can be induced by a variety of mechanisms), and the subsequent evolution of these blocks can follow several paths (Image 2). These distinctive areas of broken terrains are most notably found on Jupiter’s moon Europa, Mars, and Pluto. Although chaos terrains on these bodies share some common characteristics, there are also distinct morphological differences between them (Image 1). The geologic evolution required to shape this enigmatic terrain type has not yet been fully constrained, although several chaos formation models have been proposed. We studied chaotic terrain blocks on Pluto, Europa and Mars to infer information about crustal lithology and surface layer thickness (Skjetne et al. 2020).

Image 1: Examples of chaotic terrain “blocks” (referring to each mountain-like topographic feature). Chaos on Pluto in a) Tenzing Montes and b) Al-Idrisi Montes, respectively (New Horizons image at ~315 m px^–1), c) Hydraotes Chaos on Mars (Mars Odyssey THEMIS daytime infrared global mosaic at 100 m px^–1), and d) Conamara Chaos on Europa (Galileo 210–220 m px^–1 East and West RegMaps).