211 Exploring the Third Zone: The Geology of Pluto, Charon, and the Kuiper Belt

Tuesday, 27 September 2016
1:30 PM - 5:30 PM
Mile High Ballroom 2A/3A

GEOPHYSICS OF THE PLUTO SYSTEM

Paper number: 211-5
Program: Technical Sessions
Time: 2:30 PM – 2:45 PM

Authors

Abstract

What are the internal structures of Pluto and Charon? How did they form and evolve? New Horizons data [1] provide the answer to some of these questions. Pluto and Charon have bulk densities differing by 9% and neither show fossil rotational bulges [2]. The different densities cannot be due simply to differential pore closure [3], and instead imply a different bulk composition, providing a constraint on how Pluto and Charon formed [4-5]. On both bodies the absence of a bulge and predominantly extensional tectonics [6] suggest an ancient ocean which re-froze [7,8]. A present-day ocean on Pluto implies that the shell is cold and conductive [7], perhaps because of the presence of ammonia. On Charon, an ocean would survive only if significant ammonia is present. Refreezing of an ice shell pressurizes the ocean [9], which may help explain apparently cryovolcanic features on both bodies [6].

The Sputnik Planum basin on Pluto may be an ancient impact feature. It is now buried with several km of solid N2 ice. This ice has a young surface age and appears to be convecting [10,11], driven by heat leaking out of the silicate interior. Sputnik Planum’s location close to the tidal axis may be a result of loading-driven reorientation [12-14]. Such reorientation likely requires a subsurface ocean and is also consistent with a thick elastic ice shell at present [13].

[1] Stern et al. Science 2015 [2] Nimmo et al., Icarus in press [3] Bierson et al., LPSC 2016 [4] Canup, Science 2005 [5] Desch et al., Icarus 2015 [6] Moore et al., Science 2016 [7] Robuchon & Nimmo, Icarus 2011 [8] Hammond et al., GRL 2016 [9] Manga & Wang, GRL 2007 [10] McKinnon et al., Nature 2016 [11] Trowbridge et al., Nature 2016 [12] Hamilton, Fall AGU 2015 [13] Nimmo et al., LPSC 2016 [14] Keane et al., LPSC 2016

Geological Society of America Abstracts with Programs. Vol. 48, No. 7

doi: 10.1130/abs/2016AM-279362

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