Evolution and Spectral Response of a Steam Atmosphere for Early Earth with a Coupled Climate–Interior Model

Abstract

The evolution of Earth's early atmosphere and the emergence of habitable conditions on our planet are intricately coupled with the development and duration of the magma ocean phase during the early Hadean period (4 to 4.5 Ga). In this paper, we deal with the evolution of the steam atmosphere during the magma ocean period. We obtain the outgoing longwave radiation using a line-by-line radiative transfer code GARLIC. Our study suggests that an atmosphere consisting of pure H 2 O, built as a result of outgassing extends the magma ocean lifetime to several million years. The thermal emission as a function of solidification timescale of magma ocean is shown. We study the effect of thermal dissociation of H 2 O at higher temperatures by applying atmospheric chemical equilibrium which results in the formation of H 2 and O 2 during the early phase of the magma ocean. A 1-6% reduction in the OLR is seen. We also obtain the effective height of the atmosphere by calculating the transmission spectra for the whole duration of the magma ocean. An atmosphere of depth 100 km is seen for pure water atmospheres. The effect of thermal dissociation on the effective height of the atmosphere is also shown. Due to the difference in the absorption behavior at different altitudes, the spectral features of H 2 and O 2 are seen at different altitudes of the atmosphere. Therefore, these species along with H 2 O have a significant contribution to the transmission spectra and could be useful for placing observational constraints upon magma ocean exoplanets.

TRAPPIST-1: Global results of theSpitzerExploration Science Program Red Worlds

“…The most likely yet plausible atmosphere to maximize thermal flux in the 4-5 µm spectral range is a thick H 2 O dominated atmosphere, due to a gap between two infrared absorption bands of H 2 O near 4 µm (Miller-Ricci et al 2009;Hamano et al 2015;Katyal et al 2019). This is one of the most likely scenarios for the atmospheres of the innermost planets of the TRAPPIST-1 system if the planets formed water-rich (rich enough that they A&A 640, A112 (2020) Notes.…”

“…This demonstrates how decisive JWST occultation observations of the two TRAPPIST-1 inner planets must be to be able to constrain different realistic scenarios about the nature of these planets. Additional gases are also likely to quantitatively change these numbers (Marcq et al 2017;Katyal et al 2019). Specifically, there is a very strong CO 2 absorption band around 4.3 µm which implies that even a small amount of CO 2 in the atmospheres of both planets (if any) could mitigate their 4-5 µm brightness, which would limit the ability of the Spitzer/IRAC channel 2 to detect any signal.…”

Venusian Habitable Climate Scenarios: Modeling Venus through time and applications to slowly rotating Venus-Like Exoplanets

“…An outstanding unsolved and understudied problem is what happened in the epoch of Venus' MO as it cooled, as this may greatly affect the long-term water inventory of the planet. The timescale of the MO crystallization could be of order a few million years (M yr) as for Earth (e.g., Katyal et al, 2019;Nikolaou et al, 2019) or greater than 100 M yr (Hamano et al, 2013;Lebrun et al, 2013). The longevity of the MO and associated hot steam and CO 2 atmosphere is vital to understanding the volatile history of Venus (e.g.…”

Vertically Resolved Magma Ocean–Protoatmosphere Evolution: H2, H2O, CO2, CH4, CO, O2, and N2as Primary Absorbers

“…In Figure 4a, we compare the outgoing thermal radiation (  th F ) for all volatiles for surface pressures of 260 bar and 1 bar, which capture the instantaneous state of the atmosphere near the end and start of outgassing, respectively. For the H 2 O-260 bar case we recover the tropospheric radiation limit (Nakajima et al, 1992;Simpson, 1929) Katyal et al (2019). For 260 bar, H 2 shows a strong depression in the outgoing radiation below the H 2 O radiation limit for T surf ≲ 1700 K which appears to be due to its strongly pressure-dependent opacity.…”