A simple 1‐D radiative‐convective atmospheric model designed for integration into coupled models of magma ocean planets

Abstract

In order to understand the early history of telluric interiors and atmospheres during the ocean magma stage, a coupled interior‐atmosphere‐escape model is being developed. This paper describes the atmospheric part and its first preliminary results. A unidimensional, radiative‐convective, H2O‐CO2 atmosphere is modeled following a vertical T(z) profile similar to Kasting (1988) and Abe and Matsui (1988). Opacities in the thermal IR are then computed using a k‐correlated code (KSPECTRUM), tabulated continuum opacities for H2O‐H2O and CO2‐CO2 absorption, and water or sulphuric acid clouds in the moist convective zone (whenever present). The first results show the existence of two regimes depending on the relative value of the surface temperature Ts compared to a threshold temperature Tc depending on the total gaseous inventory. For Ts < Tc, efficient blanketing results in a cool upper atmosphere, a cloud cover, and a long lifetime for the underneath magma ocean with a net thermal IR flux between 200 and 280 Wm−2. For Ts > Tc, the blanketing is not efficient enough to prevent large radiative heat loss to space through a hot, cloudless atmosphere. Our current calculations may underestimate the thermal flux in the case of hot surfaces with little gaseous content in the atmosphere.