Morphological Comparison of Blocks in Chaos Terrains on Pluto, Europa, and Mars

TL;DR

This study compares the morphology of chaos terrain blocks on Pluto, Europa, and Mars to understand their formation and surface layer properties, revealing different size-height relationships and implications for crustal composition.

Contribution

It provides a detailed morphological comparison of chaos terrain blocks across three planetary bodies, linking block features to crustal and surface layer characteristics.

Findings

Positive size-height relationship on Pluto and Mars

Flat size-height trend on Europa

Block heights inform about crustal and surface layer thicknesses

Abstract

Chaos terrains are characterized by disruption of preexisting surfaces into irregularly arranged mountain blocks with a chaotic appearance. Several models for chaos formation have been proposed, but the formation and evolution of this enigmatic terrain type has not yet been fully constrained. We provide extensive mapping of the individual blocks that make up different chaos landscapes, and present a morphological comparison of chaotic terrains found on Pluto, Jupiter's moon Europa, and Mars, using measurements of diameter, height, and axial ratio of chaotic mountain blocks. Additionally, we compare mountain blocks in chaotic terrain and fretted terrain on Mars. We find a positive linear relationship between the size and height of chaos blocks on Pluto and Mars, whereas blocks on Europa exhibit a flat trend as block height does not generally increase with increasing block size. Block heights on Pluto are used to estimate the block root depths if they were floating icebergs. Block heights on Europa are used to infer the total thickness of the icy layer from which the blocks formed. Finally, block heights on Mars are compared to potential layer thicknesses of near-surface material. We propose that the heights of chaotic mountain blocks on Pluto, Europa, and Mars can be used to infer information about crustal lithology and surface layer thickness.