Atmospheres & Climate

Sporadic Spin-Orbit Variations in Compact Multi-planet Systems and their Influence on Exoplanet Climate

By Keith Cowing

Status Report

astro-ph.EP

February 22, 2023

Filed under Analog, astro-ph.EP, climate, Climate modeling, exoplanet, M-dwarf, TRAPPIST-1

Sporadic Spin-Orbit Variations in Compact Multi-planet Systems and their Influence on Exoplanet Climate — Timeseries of N-Rigid-Body simulation outcomes (a d) that are used as inputs to the climate model results for TRAPPIST-1 e and f. The top panels show the substellar point longitude and the bottom panels show global-mean surface temperatures and sea-ice thickness. The inclusion of sporadic planet interactions does not affect the mean climate of planet e, while increase pace of global glaciation is found for planet f with the inclusion of planet interactions. In the latter planet scenarios, as the location of maximum stellar heating moves away from the open ocean areas, the high surface albedo of the newly formed sea-ice makes deglaciation extremely difficult, and the planet rapidly transitions into a snowball state over ∼200 years. 180◦ is the substellar longitude for the 1 : 1 resonant state. — astro-ph.EP

Climate modeling has shown that tidally influenced terrestrial exoplanets, particularly those orbiting M-dwarfs, have unique atmospheric dynamics and surface conditions that may enhance their likelihood to host viable habitats.

However, sporadic libration and rotation induced by planetary interactions, such as that due to mean motion resonances (MMRs) in compact planetary systems may destabilize attendant exoplanets away from synchronized states (or 1:1 spin-orbit ratio).

Here, we use a three-dimensional N-Rigid-Body integrator and an intermediately-complex general circulation model to simulate the evolving climates of TRAPPIST-1 e and f with different orbital and spin evolution pathways. Planet f perturbed by MMR effects with chaotic spin-variations are colder and dryer compared to their synchronized counterparts due to the zonal drift of the substellar point away from open ocean basins of their initial eyeball states.

On the other hand, the differences between perturbed and synchronized planet e are minor due to higher instellation, warmer surfaces, and reduced climate hysteresis. This is the first study to incorporate the time-dependent outcomes of direct gravitational N-Rigid-Body simulations into 3D climate modeling of extrasolar planets and our results show that planets at the outer edge of the habitable zones in compact multiplanet systems are vulnerable to rapid global glaciations. In the absence of external mechanisms such as orbital forcing or tidal heating, these planets could be trapped in permanent snowball states.

Howard Chen, Gongjie Li, Adiv Paradise, Ravi Kopparapu

Comments: 14 pages, 6 figures, accepted to the Astrophysical Journal Letters
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:2302.11561 [astro-ph.EP] (or arXiv:2302.11561v1 [astro-ph.EP] for this version)
Submission history
From: Howard Chen
[v1] Wed, 22 Feb 2023 18:56:24 UTC (3,839 KB)
https://arxiv.org/abs/2302.11561
Astrobiology

Keith Cowing

SpaceRef co-founder, Explorers Club Fellow, ex-NASA, Away Teams, Journalist, Space & Astrobiology, Lapsed climber.

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