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Reflected Spectroscopy of Small Exoplanets II: Characterization of Terrestrial Exoplanets

Damiano, Mario and Hu, Renyu (2022) Reflected Spectroscopy of Small Exoplanets II: Characterization of Terrestrial Exoplanets. Astronomical Journal, 163 (6). Art. No. 299. ISSN 0004-6256. doi:10.3847/1538-3881/ac6b97.

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A space telescope capable of high-contrast imaging has been recognized as the avenue toward finding terrestrial planets around nearby Sun-like stars and characterizing their potential habitability. It is thus essential to quantify the capability of reflected light spectroscopy obtained through direct imaging for terrestrial exoplanets, and existing work focused on planetary analogs of modern Earth. Here we go beyond Earth analogs and use a Bayesian retrieval algorithm, ExoReLᴿ, to determine what we could learn about terrestrial exoplanets from their reflected light spectra. Recognizing the potential diversity of terrestrial exoplanets, our focus is to distinguish atmospheric scenarios without any a priori knowledge of the dominant gas. We find that, while a moderate-resolution spectrum in the optical band (0.4−1.0 μm) may sufficiently characterize a modern Earth analog, it would likely result in incorrect interpretation for planets similar to Archean Earth or having CO₂-dominated atmospheres. Including observations in the near-infrared bands (1.0−1.8 μm) can prevent this error, determine the main component (N₂, O₂, or CO₂), and quantify trace gases (H₂O, O₃, and CH₄) of the atmosphere. These results are useful to define the science requirements and design the wavelength bandwidth and observation plans of exoplanet direct imaging missions in the future.

Item Type:Article
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URLURL TypeDescription Paper
Damiano, Mario0000-0002-1830-8260
Hu, Renyu0000-0003-2215-8485
Additional Information:© 2022. The Author(s). Published by the American Astronomical Society. Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. Received 2022 March 9; accepted 2022 April 25; published 2022 May 31. We thank Charles Lawrence, Bertrand Mennesson, Keith Warfield, and Rhonda Morgan for helpful discussion. This work was supported in part by the NASA WFIRST Science Investigation Teams grant #NNN16D016T and Exoplanets Research Program grant #80NM0018F0612. This research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration.
Funding AgencyGrant Number
Subject Keywords:Exoplanet atmospheric composition; Exoplanet atmospheres; Bayesian statistics; Bayes' Theorem; Posterior distribution; Prior distribution; Extrasolar rocky planets
Issue or Number:6
Classification Code:Unified Astronomy Thesaurus concepts: Exoplanet atmospheric composition (2021); Exoplanet atmospheres (487); Bayesian statistics (1900); Bayes’ Theorem (1924); Posterior distribution (1926); Prior distribution (1927); Extrasolar rocky planets (511)
Record Number:CaltechAUTHORS:20220531-844272000
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Official Citation:Mario Damiano and Renyu Hu 2022 AJ 163 299
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:114973
Deposited By: George Porter
Deposited On:01 Jun 2022 17:30
Last Modified:01 Jun 2022 17:30

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