Volatile transport on inhomogeneous surfaces: I. Analytic expressions, with application to Pluto's day

TL;DR

This paper derives analytic expressions for temperature variations on volatile-covered planetary surfaces with nearly constant pressure, applying to bodies like Pluto and Triton, highlighting atmospheric buffering effects on diurnal timescales.

Contribution

It introduces new analytic formulas for surface and subsurface temperature variations considering atmospheric buffering and applies them to Pluto's current conditions.

Findings

Atmospheric buffering dominates temperature variation on Pluto.

Surface pressure remains nearly constant over a Pluto day.

Analytic expressions apply to other volatile-covered bodies with minimal horizontal heat flow.

Abstract

An analytic expression for the variation in surface and sub-surface temperature is developed for worlds whose surface pressures are nearly constant with latitude and longitude and whose atmospheres are in vapor-pressure equilibrium with the dominant surface volatiles. Such worlds include the current Pluto and Triton, and other volatile-covered Kuiper Belt Objects during some portion of their heliocentric orbit. The expressions also apply on worlds with negligible horizontal heat flow, such as asteroids. Temperature variations in volatile-covered or bare areas as a function of time is derived in terms of three thermal parameters relating to (1) the thermal wave within the substrate, (2) the energy needed to heat an isothermal volatile slab, and (3) the buffering by the latent heat needed to change the atmospheric surface pressure. For Pluto's current surface pressure (~17 microbar), atmospheric buffering dominates over subsurface effects on diurnal timescales, and should keep the surface pressure over a Pluto day constant to within 0.2%.