Absorption spectrum corresponding roughly to the surface Earth gas mixture (N2, H2O and CO2). Here we assume 1 bar of total pressure, including 370 ppm of CO2 and 0.01 bar of H2O at 285 K. The CO2 content corresponds to the Earth’s atmosphere conditions in 2000. — astro-ph.EP
A key challenge in modeling (exo)planetary atmospheres lies in generating extensive opacity datasets that cover the wide variety of possible atmospheric composition, pressure, and temperature conditions.
This critical step requires specific knowledge and can be considerably time-consuming. To circumvent this issue, most available codes approximate the total opacity by summing the contributions of individual molecular species during the radiative transfer calculation. This approach neglects inter-species interactions, which can be an issue for precisely estimating the climate of planets.
To produce accurate opacity data, such as correlated-k tables, chi factor corrections of the far-wings of the line profile are required. We propose an update of the chi factors of CO2 absorption lines that are relevant for terrestrial planets (pure CO2, CO2-N2 and CO2-H2O). These new factors are already implemented in an original user-friendly open-source tool designed to calculate high resolution spectra, named SpeCT.
The latter enables to produce correlated-k tables for mixtures made of H2O, CO2 and N2, accounting for inter-species broadening. In order to facilitate future updates of these chi factors, we also provide a review of all the relevant laboratory measurements available in the literature for the considered mixtures.
Finally, we provide in this work 8 different correlated-k tables and continua for pure CO2, CO2-N2, CO2-H2O and CO2-H2O-N2 mixtures based on the MT_CKD formalism (for H2O), and calculated using SpeCT. These opacity data can be used to study various planets and atmospheric conditions, such as Earth’s paleo-climates, Mars, Venus, Magma ocean exoplanets, telluric exoplanets.
G. Chaverot, M. Turbet, H. Tran, J.-M. Hartmann, A. Campargue, D. Mondelain, E. Bolmont
Comments: Accepted for publication in A&A: 18 August 2025
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:2508.18049 [astro-ph.EP] (or arXiv:2508.18049v1 [astro-ph.EP] for this version)
https://doi.org/10.48550/arXiv.2508.18049
Focus to learn more
Submission history
From: Guillaume Chaverot
[v1] Mon, 25 Aug 2025 14:07:33 UTC (2,879 KB)
https://arxiv.org/abs/2508.18049
Astrobiology,