Simulated Phase-dependent Spectra of Terrestrial Aquaplanets in M Dwarf Systems

TL;DR

This study uses 3D climate simulations to analyze how phase-dependent spectral signals can reveal climate states of Earth-sized aquaplanets orbiting M dwarf stars, aiding in their characterization.

Contribution

It introduces a self-consistent 3D modeling approach to predict spectral signatures of different climate states on habitable zone planets around M dwarfs.

Findings

Icy, temperate, and runaway greenhouse states show distinct spectral phase signals.

Spectral variations depend on surface water, ice, and cloud distributions.

Phase-dependent spectra can help characterize planetary climate states.

Abstract

Orbital phase-dependent variations in thermal emission and reflected stellar energy spectra can provide meaningful constraints on the climate states of terrestrial extrasolar planets orbiting M dwarf stars. Spatial distributions of water vapor, clouds, and surface ice are controlled by climate. In turn, water, in each of its thermodynamic phases, imposes significant modulations to thermal and reflected planetary spectra. Here we explore these characteristic spectral signals, based on 3D climate simulations of Earth-sized aquaplanets orbiting M dwarf stars near the habitable zone. By using 3D models, we can self-consistently predict surface temperatures and the location of water vapor, clouds, and surface ice in the climate system. Habitable zone planets in M dwarf systems are expected to be in synchronous rotation with their host star and thus present distinct differences in emitted and reflected energy fluxes depending on the observed hemisphere. Here we illustrate that icy, temperate, and incipient runaway greenhouse climate states exhibit phase-dependent spectral signals that enable their characterization.