INVESTIGATING SIZE DISTRIBUTIONS OF CHAOS BLOCKS ON EUROPA, PLUTO, AND MARS

Chaos regions on Europa are thought to be some of the youngest features on the surface. Therefore, it is crucial to understand chaos formation in order to determine the current state of the ice shell and the potential for current geologic activity. If chaos formation is an ongoing process, it could be a target of further study by Europa Clipper. A possible window into chaos formation is the size distribution of blocks within chaos regions. Analogous work on other planetary bodies indicates that block size-frequency distributions (SFD) may be indicative of chaos morphology, level of deformation, and possible formation mechanisms. Here we construct a observational repository of the chaos blocks from mapping efforts in the Galileo SSI RegMaps where we first focus on the geomorphology comparisons and differences of chaos regions. We analyze the resulting SFD of the blocks and find least-squares fits to the data. These exponential fits may imply a quantitative measure for chaos morphology as well as possible processes occurring from region to region due to potential differences in formation energy or rheology. In addition to studying Europan chaos, we also compare previous work from Skjetne et al. (2021) that mapped chaos blocks on Pluto and Mars in order to understand if a unifying SFD exists to explain chaos block size distributions on any planetary body. Our results suggest that chaos morphology can be represented quantitively with an exponential fit for the block SFD for all planetary bodies. We find that platy chaos, or chaos that contains more blocks and less matrix material, could be described through SFDs that were more gently sloping which was most common on Mars and Pluto. The most matrix-dominated chaos regions, and therefore steeper SFD slopes, were found on Europa. A possible explanation of differences of the morphologies between the bodies could be the role of fractures and faults in chaos formation, which may range in associated energy as one moves along the chaos spectrum. Another explanation could be fundamentally different formation mechanisms, or differences in rheology between the bodies. We are also currently investigating potential further correlations between the SFDs and other values—such as geographical location, and chaos size—which may reveal further information on differences between chaos terrains.