arXiv subjects

Chaucer Langbert

Publications and source records attributed to Chaucer Langbert.

3 recordsLinked to original sources

arXiv2026

When Stabilizing Feedbacks Wreak Havoc in Habitable Planets: Chaos at the Freezing Point in a Four-Feedback Climate Model

The long-term habitability of Earth-like planets is governed by the balance of positive and negative climate feedbacks that regulate surface temperature and atmospheric composition. While some feedbacks, such as ice-albedo and silicate weathering, are thought to operate on many terrestrial planets, the number and strength of additional climate feedbacks may vary substantially from world to world. An important open question is whether and how the introduction of an additional climate feedback influences long-term climate evolution and complexity. To investigate this question, we extended a low-order climate model including outgoing longwave radiation, ice--albedo, and carbonate--silicate weathering, with an additional generalized feedback. Across 35,864 simulations, we characterized dynamical behavior using the largest Lyapunov exponent (LLE). While 10.4% of explored parameter combinations exhibited positive LLEs, indicating chaos, the fraction rose to 25.6% within the stabilizing, near-freezing regime. This suggests that chaotic behavior is preferentially concentrated where a strong stabilizing feedback operates in the same temperature regime as a strong destabilizing feedback, contrary to the expectation that additional negative feedbacks should increase climate stability. Increasing normalized volcanic outgassing shifts the chaotic regime toward lower stellar flux and partially suppresses chaos at high instellation.

astro-ph.EP↗

arXiv2026

Nautilus Space Observatory: The Evolution of Planets and their Atmospheres

We are just beginning to explore the billion-year evolution from nascent planets in disks to mature planetary systems. Recent discoveries hint at demographic and atmospheric differences between young planets and their Gyr-old counterparts, but current facilities are limited - particularly in their ability to conduct statistical atmospheric studies over a broad period range. This white paper outlines compelling science achievable with the Nautilus Space Observatory, a proposed constellation of large-diameter space telescopes. We identify four primary scientific objectives: (1) determining the timescales over which planets evolve into sub-Neptunes and super-Earths; (2) tracking the temporal evolution of atmospheric mass-loss rates; (3) characterizing the evolution of the atmospheric mean molecular weight and C/O ratio; and (4) identifying the emergence of Helium-dominated worlds. Answering these questions requires the high spatial resolution, broad-wavelength coverage, large effective area, and parallelized multiple units that Nautilus provides. By isolating the physical processes that govern the evolution of planets and their atmospheres, these science objectives directly support NASA's Cosmic Origins and Exoplanet Exploration Programs.

astro-ph.IM↗

arXiv2026

Not Earth-like Yet Temperate? More Generic Climate Feedback Configurations Still Allow Temperate Climates in Habitable Zone Exo-Earth Candidates

Earth's climate is influenced by over a dozen feedbacks, but only three dominate its long-term climate behavior. Models of the exoplanet habitable zone (HZ) assume that this is similar for other Earth-like planets. We used dynamical simulations to study Earth-like planets with a fourth, (potentially strong) generalized climate feedback. Across over 20,000 climate simulations, we find that the addition of the fourth feedback produces novel behaviors, including runaway and chaotic climate trajectories, that are more diverse than one would expect based on Earth's climate configuration. Non-negligible fourth feedbacks -- if negative -- would not lessen the probability of planets with temperate climates. However, positive fourth feedbacks decrease the fraction of exo-Earth candidates that are long-term habitable. Therefore, strong fourth feedbacks will alter (and mostly shrink) the boundaries of the classical habitable zone. When combined with occurrence rates of Earth-sized planets around sun-like stars, our results imply that the fraction of stars hosting rocky planets with temperate climates may be substantially lower than classical estimates under Earth-like climate assumptions. Our results are subject to the validity of the model assumptions and not intended to represent conclusive predictions about exoplanet populations but rather to demonstrate the potential climate diversity that emerges from non-Earth-like model configurations. Our conclusions provide context on sample sizes and science questions for next-generation exoplanet surveys.

astro-ph.EP↗