Characterizing extrasolar terrestrial planets with reflected, emitted and transmitted spectra

Area of Science:

• Exoplanetary Science
• Astrobiology
• Planetary Science

Background:

• NASA and ESA are planning missions (Terrestrial Planet Finder, DARWIN) for direct detection and characterization of exoplanets.
• These missions will enable spectroscopic study of exoplanet atmospheres and surfaces, searching for habitability and biosignatures.
• Stellar occultation may also detect atmospheric signatures of Earth-size exoplanets.

Purpose of the Study:

• To model observational sensitivity to atmospheric and surface property changes on Earth-like exoplanets.
• To assess the detectability of surface biosignatures, specifically vegetation's spectral signature.
• To explore the detectability of hypothetical exo-vegetation with shifted spectral signatures.

Main Methods:

• Utilized spatially and spectrally-resolved models of Earth's globally averaged spectra and light-curves.
• Simulated observational conditions including atmospheric composition, cloud cover, and stellar type.
• Analyzed the detectability of specific spectral features, such as the vegetation red-edge.

Main Results:

• Earth's land vegetation red-edge signature is potentially detectable in disk-averaged spectra, even with clouds and daily averaging.
• Marine vegetation signatures are significantly more challenging to detect.
• Simulations explored the detectability of exo-vegetation with spectral signatures red-shifted compared to Earth's vegetation.

Conclusions:

• Direct detection and characterization of Earth-like exoplanets are feasible with upcoming missions.
• Vegetation, a key biosignature, may be detectable on exoplanets, though challenges like cloud cover and marine signatures exist.
• Further research is needed to refine detection strategies for various biosignatures and exoplanetary environments.