A QUANTITATIVE MORPHOMETRIC ANALYSIS OF TERRESTRIAL PINGOS AND ANOMALOUS HILLS ON CERES

Dawn’s final extended mission at Ceres returned image data with spatial resolution as fine as ~3 m/pixel over Occator and Urvara craters. These high-resolution data revealed a myriad of morphological features populating the floors of these craters not previously discernable, including an abundance of small, hundred-meter scale, conical hills. A significant number of these hills exhibit morphological qualities, such as radial summit fractures, summit depressions, distinct aspect ratios, and substrate superposition, that are similar to those of ice-cored mounds found in terrestrial periglacial environments called pingos. Pingos primarily form through the injection and subsequent freezing of liquid water into the shallow subsurface either under hydrostatic or hydraulic conditions. Similar landforms have also been extensively documented on Mars although the degree of similarity between martian features and pingos remains relatively unknown. If these extraterrestrial hills are analogous to terrestrial pingo they represent high science-value ice-rich environment that are also attractive targets for future in situ resource utilization. We explore the hypothesis that crater-floor impact-melt systems in Occator and Urvara evolve in a similar fashion to freezing periglacial terrains on Earth and give rise to pingo-forming hydrological systems.

Using non-parametric clustering algorithms (e.g. OPTICS clustering), we established that these cerean hills occur in groups of similar morphology and that hill locations correlate with specific ice-rich geologic units. Additionally, we performed a quantitative morphometric comparison of cerean mounds to conical structures on Earth including pingos and volcanic cones. Our work indicates that these distinctive small hills on Ceres are morphometrically more similar to pingos than other common structures not formed by cryohydrologic processes in key metrics such as symmetry, curvature, and peak flank slope.

Building on this analysis, we will present a possible in situ geophysical framework for identifying pingo-like structures on other worlds. We will also discuss how investigations of terrestrial analogs can inform the search for shallow subsurface ice in the solar system.