Ongoing resurfacing of KBO Eris by volatile transport in local, collisional, sublimation atmosphere regime

Abstract

Kuiper belt object (KBO) Eris is exceptionally bright with a greater visible geometric albedo than any other known KBO. Its infrared reflectance spectrum is dominated by methane, which should form tholins that darken the surface on timescales much shorter than the age of the Solar System.Thus one or more ongoing processes probably maintain its brightness. Eris is predicted to have a primarily nitrogen atmosphere that is in vapor pressure equilibrium with nitrogen-ice and is collisional (not ballistic). Eris's eccentric orbit is expected to result in two atmospheric regimes: (1) a period near perihelion when the atmosphere is global (analogous to the atmospheres of Mars, Triton, and Pluto) and (2) a period near aphelion when only a local * Corresponding author.

Photometry of Kuiper belt object (486958) Arrokoth from New Horizons LORRI

“…The map for the CA01 image geometry is also included to show some regions of the surface that were imaged by New Horizons but are not apparent in the CA06 geometry, albeit at lower spatial resolution (Table 1) The brightest regions of Arrokoth are correlated to depressions, suggesting that the topography influences the albedo and/or vice versa. A possible explanation is that volatiles have accumulated in the depressions, but we consider this explanation unlikely since the normal reflectances are not as high as that of known volatile-rich surfaces in the Kuiper belt (e.g., Buratti et al, 2017;Hofgartner et al, 2019) and the surface temperatures of these regions should differ from their surroundings by only a few Kelvin (Grundy et al, accepted). Another possible explanation is that topographic shielding of energetic radiation that would chemically modify the surface toward dark-red material (similar to tholins produced in terrestrial laboratories) inhibits this processing in Louisiana Maryland depressions.…”

Surface properties of large TNOs: Expanding the study to longer wavelengths with the James Webb Space Telescope

“…CO has only been detected on Pluto to this point (e.g., Owen et al, 1993), due to strong overlapping CH4 absorption features. The presence of an atmosphere around Pluto is firmly established (e.g., Elliot et al, 1989), and the presence of volatile CH4 and N2 on Eris and Makemake make them good candidates to support an atmosphere, at least during part of their orbits (Young and McKinnon, 2013;Hofgartner et al, 2018). The lack of detectable atmospheres in the present-day combined with these objects' high albedos provides very strong evidence for ongoing resurfacing on both of these dwarf planets (Sicardy et al, 2011;Ortiz et al, 2012).…”

Volatile evolution and atmospheres of Trans-Neptunian objects

“…• Models such as Hofgartner et al (2018) can be used to investigate the transition between global and collisional atmospheres. Atmospheric searches:…”

“…Supersonic winds certainly flow and transport volatiles, even if they are not effective at equalizing pressures and temperatures (e.g., Walker et al 2012). Recently, Hofgartner et al (2018) used the Ingersoll et al (1985) meteorological model developed for Io study the transport of N 2 on Eris at aphelion, when it is a local, collisional atmosphere, and found significant transport of N 2 ice. Even for more tenuous "surface-bounded exospheres," the loss of volatiles can modify landforms (see review by Mangold 2011).…”