Heat Flux Constraints From Variance Spectra Of Pluto And Charon Using Limb Profile Topography

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 similar to 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 similar to 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.