Habitable Zones & Global Climate

Habitability in 4-D: Predicting the Climates of Earth Analogs across Rotation and Orbital Configurations

By Keith Cowing

Status Report

astro-ph.EP

January 7, 2025

Filed under astro-ph.EP, Circumstellar Habitable Zone, Earth, exoplanet, general circulation model, Habitable Zone, Latin Hypercube Sampling, ROCKE-3D

Habitability in 4-D: Predicting the Climates of Earth Analogs across Rotation and Orbital Configurations — Time averages of the surface temperature for the 1st quintile of the training and test models in rotation period, ordered fastest to slowest. While the rotation periods are organized in increasing order from top left to bottom right, the remaining spin and orbital parameters (obliquity, eccentricity, and longitude of periapse) vary according to the configuration from the Latin Hypercube Sampling algorithm, and are themselves not in any particular order. — astro-ph.EP

Earth-like planets in the circumstellar habitable zone (HZ) may have dramatically different climate outcomes depending on their spin-orbit parameters, altering their habitability for life as we know it.

We present a suite of 93 ROCKE-3D general circulation models (GCMs) for planets with the same surface conditions and average annual insolation as Earth, but with a wide range of rotation periods, obliquities, orbital eccentricities, and longitudes of periastra.

Our habitability metric fHZ is calculated based on the temperature and precipitation in each model across grid cells over land. Latin Hypercube Sampling (LHS) aids in sampling all 4 of the spin-orbit parameters with a computationally feasible number of GCM runs. Statistical emulation then allows us to model fHZ as a smooth function with built-in estimates of statistical uncertainty.

We fit our emulator to an initial set of 46 training runs, then test with an additional 46 runs at different spin-orbit values. Our emulator predicts the directly GCM-modeled habitability values for the test runs at the appropriate level of accuracy and precision. For orbital eccentricities up to 0.225, rotation period remains the primary driver of the fraction of land that remains above freezing and with precipitation above a threshold value.

For rotation periods greater than ∼20 days, habitability drops significantly (from ∼70% to ∼20%), driven primarily by cooler land temperatures. Obliquity is a significant secondary factor for rotation periods less than ∼20 Earth days, with a factor of two impact on habitability that is maximized at intermediate obliquity.

Arthur D. Adams, Christopher Colose, Aronne Merrelli, Margaret Turnbull, Stephen R. Kane

Comments: Accepted for publication in the Astrophysical Journal
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:2412.19357 [astro-ph.EP] (or arXiv:2412.19357v1 [astro-ph.EP] for this version)
https://doi.org/10.48550/arXiv.2412.19357
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Submission history
From: Arthur Adams
[v1] Thu, 26 Dec 2024 21:39:04 UTC (25,140 KB)
https://arxiv.org/abs/2412.19357
Astrobiology,

Keith Cowing

Explorers Club Fellow, ex-NASA Space Station Payload manager/space biologist, Away Teams, Journalist, Lapsed climber, Synaesthete, Na’Vi-Jedi-Freman-Buddhist-mix, ASL, Devon Island and Everest Base Camp veteran, (he/him) 🖖🏻

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