Abstract
The putative cryovolcanic terrains on Pluto described here are unique in morphology compared to other areas of Pluto and to any other imaged surface in the solar system. The region is a vast area of giant mounds (50+ km across and 1-7 km high) covered in undulating terrain (with a wavelength nearly equal 5-15 km across) with a rough surface at even smaller scales (boulders or ridges a few hundred meters across). This region has few if any impact craters. The area appears to be constructional, and not an erosional remnant. Although there are some depressions in the area, there are no structures that obviously resemble traditional collapse calderas at the summits of the mounds. We will present recent efforts (Singer et al. 2022, Nature Communications) to try to understand this enigmatic terrain through cryovolcanic modeling. We examined a number of models, including dome emplacement, to see if they could match the feature morphometry (e.g., dome aspect ratios). Given the low surface temperatures on Pluto (average 40 K), we assumed the flow was either solid-state but still mobile ice, or flow with a cooled carapace. We find that the aspect ratios of some of the large structures are similar to those predicted for building domes from a central vent located underneath the structure using material parameters for mobile ammonia-water ice. Not all of the large structures are dome shaped. We propose that some of the structures may have merged or overlapped as they formed to produce the variety of planforms. No volcanic or tectonic models have yet been a good match for producing the intermediate-scale undulating terrain. The existence of this terrain, which is likely endogenic, constructional, and composed of primarily water ice, implies an unexpected heat source in the subsurface of Pluto that allows extensive resurfacing late in Pluto history. Given the very low crater densities, it is possible this activity continues into the present day. We thank NASA's New Horizons Mission for funding.