A Note on the "Various Atmospheres over Water Oceans on Terrestrial Planets with a One-Dimensional Radiative-Convective Equilibrium Model

TL;DR

This paper explores how different atmospheric compositions over water oceans affect the habitable zone limits, focusing on the Komabayashi-Ingersoll and Simpson-Nakajima limits using a one-dimensional radiative-convective model.

Contribution

It investigates the dependence of the KI-limit on atmospheric composition and initial pressure, extending previous models to include H$_2$, He, and N$_2$ atmospheres.

Findings

The KI-limit varies with atmospheric composition and initial pressure.

The SN-limit is independent of background atmospheric components.

Behavior of outgoing IR radiation shows peculiar dependence on surface temperature.

Abstract

It has been investigated the possibility of the various atmospheres over water oceans. We have considered the H$_2$ atmosphere and He atmosphere concerning to N$_2$ atmosphere over oceans. One of the main subjects in astrobiology is to estimate the habitable zone. If there is an ocean on the planet with an atmosphere, there is an upper limit to the outgoing infrared radiation called the Komabayashi-Ingersoll limit (KI-limit). This limit depends on the components of the atmospheres. We have investigated this dependence under the simple model, using the one-dimensional gray radiative-convective equilibrium model adopted by Nakajima et al. (1992). The outgoing infrared radiation ($F_{IRout}$) with the surface temperature ($T_s$) has shown some peculiar behavior. The examples for H$_2$, He, and N$_2$ background gas for H$_2$O vapour are investigated. There is another limit called the Simpson-Nakajima limit (SN-limit) mainly composed of vapour. This steam limit does not depend on the background atmosphere components. Under super-Earth case ($g=2\times$9.8 m/s$^2$), several cases are also calculated. The KI-limit dependence on the initial pressure is presented. The various emission rates by Koll & Cronin (2019) are investigated.