Spectral signatures from the Habitable Zone

Future observatories may enable the study of atmospheres of terrestrial planets from the habitable zones around various types of stars. Regardless of what will be found, this will provide major insights into planetary science, as well as doubtlessly result in profound paradigm shifts. In anticipation of these telescopes, much effort is going into simulating potential planets, atmospheres, and specific spectral signatures that may be expected to be observed. These include surface and atmospheric biosignatures, typically leveraging our Earth as a template for biology. In this talk, our teams’ efforts in simulating habitable planets around K and G stars will be presented.

Climate simulations
Climate simulation using both ROCKE-3D (Adams, PI Turnbull) and ExoCam (Wolf, PI: Lobo) are presented, with Earth-like planets but considering different types of host stars, rotation rates, obliquities, and thus widely varying climate states.

Spectral simulations
The Planetary Spectrum Generator is used to simulate 3D spectra from the planets (Villanueva et al., 2018). Following the recent developments described in Kofman et al., 2024, spectra, and RGB representations are simulated at different times of year and the detectability of different biomarkers is considered.

Critical in our spectral evaluations of the climate models are updated cloud parameterization strategies. Often, spectroscopic representations of GCMs employ simplified representation of clouds, or assume the planet is cloud-free. Particular effort is dedicated here to ensure accurate representation of clouds in the atmospheres, as this strongly affects the detectability of the spectroscopic features of interest.

The figure below provides an example from Kofman et al., 2024 of a simulation of Earth as an exoplanet, where the planet is observed in reflected light as might be seen with a future Habitable Worlds Observatory.