Abstract:
Earth is the only planet in the solar system with a climate that enables habitable surface conditions. Life on Earth also modifies the global environment, with an atmospheric composition that includes contributions from biological as well as technological sources. Some of these global-scale influences of life on climate could be could be observed remotely, manifesting as potential “biosignatures” that could be detectable across astronomical distances. This suggests the possibility of searching for exoplanets within the “habitable zone” of their host star, where liquid water could persist, and then further examining promising candidates for biosignatures. The search for habitable exoplanets and signs of extraterrestrial life has entered a new chapter with facilities like the James Webb Space Telescope now enabling the spectral characterization of exoplanet atmospheres. Exoplanet climate model calculations provide important guidance for selecting which planets to search, while observations of exoplanets are also showing promise for constraining the assumptions within such models.
In this presentation, I will discuss this interplay between exoplanet modeling and observations with a focus on Earth-sized planets in synchronous rotation around low mass stars. I highlight results showing a large parameter space of plausible climates for the planet TRAPPIST-1 e, which demonstrate the conditions under which the spectral features of carbon dioxide and methane could be detected. I also show results from ongoing exoplanet model intercomparison projects that seek to identify differences in exoplanet climate models and make ensemble predictions that can help guide or interpret observations. I discuss prospects for continuing the characterization of terrestrial exoplanets, and the search for biosignatures, with future mission concepts.