Viscous relaxation of Oort and Edgeworth craters on Pluto: Possible indicators of an epoch of early high heat flow

Journal of Geophysical Research: Planets
By: , and 



Impact craters, with their well-defined initial shapes, have proven useful as heat flow probes of a number of icy bodies, provided characteristics of viscous relaxation can be identified. For Pluto's numerous craters, such identifications are hampered/complicated by infilling and erosion by mobile volatile ices, but not in every case. Large craters offer relatively deep probes of rheological structure, and on Pluto two large old craters in a major dark (volatile-ice free) region are probably the best examples for possible viscous relaxation: Oort (115-km diameter) and Edgeworth (140-km diameter). They are similar in size, location, and apparent age (morphological preservation), but may or may not be coeval. Edgeworth is particularly shallow and its floor appears bowed up above the original ground plane, a classic hallmark of viscous relaxation in which viscosity decreases sharply with depth. Oort is less relaxed, but may be somewhat younger and less affected by an early epoch of high heat flow. Finite element calculations show that this heat flow would have to have been substantial to explain Edgeworth's upbowed floor by viscous relaxation, several times steady-state radiogenic values for present-day surface temperatures. We expect Pluto's brittle ice lithosphere to be fractured and porous, however, markedly reducing thermal conductivity and increasing temperatures at depth and relaxation for a given heat flow. We find that most relaxation occurs well within 100 Myr after impact for Edgeworth and Oort, and focus attention on a temporal (and/or regional) epoch of elevated heat flow, possibly tied to the serpentinization of Pluto's rocky core.

Publication type Article
Publication Subtype Journal Article
Title Viscous relaxation of Oort and Edgeworth craters on Pluto: Possible indicators of an epoch of early high heat flow
Series title Journal of Geophysical Research: Planets
DOI 10.1029/2023JE007831
Volume 128
Issue 9
Year Published 2023
Language English
Publisher American Geophysical Union
Contributing office(s) Astrogeology Science Center
Description e2023JE007831, 25 p.
Other Geospatial Pluto
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