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- Title
Heat Flux Constraints From Variance Spectra of Pluto and Charon Using Limb Profile Topography.
- Authors
Conrad, J. W.; Nimmo, F.; Beyer, R. A.; Bierson, C. J.; Schenk, P. M.
- Abstract
We derive a topography data set from images of Pluto and Charon that contain the body edge (i.e., limb profiles) which will help in understanding the comparative history of the binary system. We use the profiles to derive topographic variance spectra and find that while the variance spectrum of Pluto fits a single power law, Charon's spectrum displays a clear breakpoint at ∼150 km wavelength. Assuming the breakpoint is a result of topographic flexure, we find that Charon's elastic thickness must have been 20 ± 10 km during topography formation. A lack of a breakpoint for Pluto sets a minimum elastic thickness for Pluto of 60 km. We use these elastic thickness estimates to calculate a maximum heat flux of ∼13 m Wm−2 on Pluto during and after topography formation. On Charon, however, we find that the heat flux during topography formation was 35−15+44 m Wm−2. This range of values far exceeds the likely radiogenic heat production and is consistent with either heat released following the Charon‐forming impact event or (more likely) tidal heating during Charon's early history. Plain Language Summary: Studying the topography of planetary bodies provides key insights into the geologic processes of their surfaces and interiors. In this work we develop a topography data set for Pluto and Charon by mapping variations in the height along the worlds' edges in images from New Horizons. We analyze the data to determine roughness using the mean amplitude of mountains and valleys for a range of widths. Pluto shows the expected result of a single slope decreasing in roughness at shorter widths, but Charon has a change in the slope at ∼150 km. Mountains and valleys on Charon wider than this are respectively shorter and shallower than expected. This gives insight into how the landforms on Charon formed as well as the ability of Charon's crust to support variations in elevation. Charon's landforms must have formed at the observed size or decreased over time to have modern amplitudes. Either case implies that Charon had a thinner ice shell, and was relatively hotter, than Pluto in the ancient past. This extra heat is consistent with a Charon‐forming impact or (more likely) tidal heating during the Charon's initial history. Key Points: We derived new limb profile topography datasets of Pluto and Charon based on the body edge in imagesFor Charon, the topographic variance spectrum displays a distinct change in slope at ∼150 km wavelengthCharon's topography records high heat fluxes from either tidal heating or a giant impact
- Subjects
HEAT flux; PLUTO (Dwarf planet); CHARON (Satellite); TOPOGRAPHY; SPACE exploration
- Publication
Journal of Geophysical Research. Planets, 2021, Vol 126, Issue 2, p1
- ISSN
2169-9097
- Publication type
Article
- DOI
10.1029/2020JE006641