TERRESTRIAL PINGOS AS MORPHOMETRIC AND GEOPHYSICAL ANALOGS FOR SMALL HILLS ON CERES

The NASA Dawn mission revealed that the floor of Occator crater on the dwarf planet Ceres is populated with many small quasi-conical hills. Many of these features exhibit morphometric properties that are like those of ice-cored periglacial hills on Earth called pingos. Alternatively, some of these Cerean hills have also been hypothesized to be cryovolcanic in origin. If these hills are analogous to pingos, they represent ice-rich environments that are attractive targets for future exploration. Here we directly test how morphologically similar the hills in Occator are to pingos and volcanic cones on Earth using comparative statistical analyses. Using a novel application of kernel density estimation and Markov chain Monte Carlo methods we show that the morphologies of terrestrial pingos and volcanic cones are quantifiably distinct, and that the Cerean hills share significant morphometric similarities with pingos on Earth. Our findings indicate that a statistical treatment of morphometry alone can be a powerful tool for classifying and comparing planetary surface features, and that the majority of the resolved Cerean hills are morphometrically more similar to pingos than to small terrestrial volcanic cones.

Recognizing that morphology alone is insufficient to unambiguously determine a ground ice origin for these Cerean hills, we also report findings from electrical and electromagnetic geophysical field studies of hydraulic and hydrostatic pingos in the North American Arctic. These analog surveys were conducted to better constrain the 3D subsurface cryohydrology of pingos with variable surface morphologies and to identify potential pathways for future in situ geophysical studies of ground ice rich planetary environments. Our initial surveys indicate that existing commercial geophysical instrumentation is more than capable of resolving the ground ice structure of large pingos, and that contactless electrical and electromagnetic methods are ideally suited for future landed robotic explorers on Ceres or other icy worlds.