Convection in a volatile nitrogen-ice-rich layer drives Pluto's geological vigor

Abstract

The vast, deep, volatile-ice-filled basin informally named Sputnik Planum is central to Pluto's geological activity[1,2]. Composed of molecular nitrogen, methane, and carbon monoxide ices[3], but dominated by N2-ice, this ice layer is organized into cells or polygons, typically ~10-40 km across, that resemble the surface manifestation of solid state convection[1,2]. Here we report, based on available rheological measurements[4], that solid layers of N2 ice approximately greater than 1 km thick should convect for estimated present-day heat flow conditions on Pluto. More importantly, we show numerically that convective overturn in a several-km-thick layer of solid nitrogen can explain the great lateral width of the cells. The temperature dependence of N2-ice viscosity implies that the SP ice layer convects in the so-called sluggish lid regime[5], a unique convective mode heretofore not definitively observed in the Solar System. Average surface horizontal velocities of a few cm/yr imply surface transport or renewal times of ~500,000 years, well under the 10 Myr upper limit crater retention age for Sputnik Planum[2]. Similar convective surface renewal may also occur on other dwarf planets in the Kuiper belt, which may help explain the high albedos of some of them.

References in corpus (1)

• On the Roles of Escape Erosion and the Relaxation of Craters on Pluto

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• 1I/'Oumuamua as an N2 ice fragment of an exo-Pluto surface: I. size and compositional constraints
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• Volatile transport modeling on Triton with new observational constraints
• A Search for Temporal Changes on Pluto and Charon
• New Constraints on Pluto's Sputnik Planitia Ice Sheet from a Coupled Reorientation-Climate Model
• N${}_2$ accretion, metamorphism of organic nitrogen, or both processes likely contributed to the origin of Pluto's N${}_2$
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• A Pluto--Charon Concerto II. Formation of a Circumbinary Disk of Debris After the Giant Impact
• A Pluto-Charon Sonata III. Growth of Charon from a Circum-Pluto Ring of Debris
• The New Astronomical Frontier of Interstellar Objects
• Nitrogen Loss from Pluto's Birth to the Present Day via Atmospheric Escape, Photochemical Destruction, and Impact Erosion
• Trans-Neptunian Space and the Post-Pluto Paradigm
• New Investigations of Dark Floored Pits in the Volatile Ice of Sputnik Planitia on Pluto