A One-Dimensional Energy Balance Model Parameterization for the Formation of CO2 Ice on the Surfaces of Eccentric Extrasolar Planets

Eccentric planets may spend a significant portion of their orbits at large distances from their host stars, where low temperatures can cause atmospheric CO2 to condense out onto the surface, similar to the polar ice caps on Mars.
The radiative effects on the climates of these planets throughout their orbits would depend on the wavelength-dependent albedo of surface CO2 ice that may accumulate at or near apoastron and vary according to the spectral energy distribution of the host star.
To explore these possible effects, we incorporated a CO2 ice-albedo parameterization into a one-dimensional energy balance climate model. With the inclusion of this parameterization, our simulations demonstrated that F-dwarf planets require 29% more orbit-averaged flux to thaw out of global water ice cover compared with simulations that solely use a traditional pure water ice-albedo parameterization.
When no eccentricity is assumed, and host stars are varied, F-dwarf planets with higher bond albedos relative to their M-dwarf planet counterparts require 30% more orbit-averaged flux to exit a water snowball state. Additionally, the intense heat experienced at periastron aids eccentric planets in exiting a snowball state with a smaller increase in instellation compared with planets on circular orbits; this enables eccentric planets to exhibit warmer conditions along a broad range of instellation.
This study emphasizes the significance of incorporating an albedo parameterization for the formation of CO2 ice into climate models to accurately assess the habitability of eccentric planets, as we show that, even at moderate eccentricities, planets with Earth-like atmospheres can reach surface temperatures cold enough for the condensation of CO2 onto their surfaces, as can planets receiving low amounts of instellation on circular orbits.

The instellations required for warm-start planets to transition into a snowball state are shown in Ys, pluses, and crosses. The instellations required by cold-start planets to deglaciate at e = 0, 0.5, and 0.9 are displayed by circles, squares, and triangles. The orbit-averaged flux currently received by Earth and Mars, which is 100% and 43% of the orbit-averaged solar constant, respectively, is also shown for context. — astro-ph.EP
Vidya Venkatesan (1), Aomawa L. Shields (1), Russell Deitrick (2), Eric T. Wolf (3,4,5), Andrew Rushby (6) (1)Department of Physics, Astronomy, University of California, Irvine, California, USA (2)School of Earth, Ocean Sciences, University of Victoria, Victoria, Canada (3)Laboratory for Atmospheric, Space Physics, University of Colorado Boulder, Boulder, Colorado, USA (4)Sellers Exoplanet Environment Collaboration (SEEC), NASA Goddard Space Flight Center, Greenbelt, Maryland, USA (5)Blue Marble Space Institute of Science, Seattle, Washington, USA (6)Department of Earth, Planetary Sciences, Birkbeck University of London, London, United Kingdom
Comments: 18 pages, 14 figures
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:2501.11667 [astro-ph.EP] (or arXiv:2501.11667v1 [astro-ph.EP] for this version)
https://doi.org/10.48550/arXiv.2501.11667
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Journal reference: Astrobiology 2025
Related DOI:
https://doi.org/10.1089/ast.2023.0103
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Submission history
From: Vidya Venkatesan
[v1] Mon, 20 Jan 2025 18:48:29 UTC (1,987 KB)
https://arxiv.org/abs/2501.11667
Astrobiology