Effect of UV Radiation on the Spectral Fingerprints of Earth-like Planets Orbiting M dwarfs
Rugheimer et al
We model the atmospheres and spectra of Earth-like planets orbiting the entire grid of M dwarfs for active and inactive stellar models with Teff = 2300K to Teff = 3800K and for six observed MUSCLES M dwarfs with UV radiation data. We set the Earth-like planets at the 1AU equivalent distance and show spectra from the VIS to IR (0.4μm - 20μm) to compare detectability of features in different wavelength ranges with JWST and other future ground- and spaced-based missions to characterize exo-Earths. We focus on the effect of UV activity levels on detectable atmospheric features that indicate habitability on Earth, namely: H2O, O3, CH4, N2O and CH3Cl.
To observe signatures of life - O2/O3 in combination with reducing species like CH4, we find that early and active M dwarfs are the best targets of the M star grid for future telescopes. The O2 spectral feature at 0.76μm is increasingly difficult to detect in reflected light of later M dwarfs due to low stellar flux in that wavelength region. N2O, another biosignature detectable in the IR, builds up to observable concentrations in our planetary models around M dwarfs with low UV flux. CH3Cl could become detectable, depending on the depth of the overlapping N2O feature.
We present a spectral database of Earth-like planets around cool stars for directly imaged planets as a framework for interpreting future lightcurves, direct imaging, and secondary eclipse measurements of the atmospheres of terrestrial planets in the HZ to design and assess future telescope capabilities.
Monday, August 24, 2015
Detectable Effects of UV on Earth-like Terrestrial World's Atmospheres
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