[P-CG19] Origin and evolution of materials in space

[PCG19-12] Assessing the potential of biogenic gases as exoplanet biosignatures

★Invited Papers

*Yuka Fujii¹, Yu Komatsu², Alexis Gilbert³, Sebastian Danielache⁴, Mayuko Nakagawa³ (1.National Astronomical Observatory of Japan, 2.Astrobiology Center, 3.Tokyo Institute of Technology, 4.Sophia University)

Keywords:Exoplanets, Earth-like planets, Planetary atmospheres

Searching for the signs of life on exoplanets is one of the major goals of modern astronomy. The proposed approaches such as transit spectroscopy, high-contrast imaging, and high-resolution spectroscopy will eventually allow us to access the spectra of a few nearby temperate terrestrial planets at the broad range of wavelengths from ultraviolet to mid-infrared ranges. A key to finding life on exoplanets is to detect the spectral features of biogenic gases. Earth’s biosphere emits various gases including O2, CH4, and C5H8. In this talk, we discuss their detectability and the challenges in identifying the biological origin.
Accumulation of a molecule in an atmosphere given the surface flux depends on the atmospheric properties (thickness, composition) and the boundary conditions including the ultraviolet spectrum. We examine the stability of O2 and CH4 as a function of surface flux under various conditions using a photochemical model (atmos; e.g. Kasting et al. 1984, Pavlov et al., 2001) and discuss the conditions in which their spectral features become detectable and how to distinguish from non-biological scenarios. We also qualitatively assess the stability of more complex volatile organic compounds and study their spectral fingerprints.