A New Spectral Library for Modeling the Surfaces of Hot, Rocky Exoplanets
JWST’s MIRI LRS provides the first opportunity to spectroscopically characterize the surface compositions of close-in terrestrial exoplanets. Models for the bare-rock spectra of these planets often utilize a spectral library from R. Hu et al., which is based on room-temperature reflectance measureme...
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IOP Publishing
2025-01-01
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| Series: | The Astrophysical Journal |
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| Online Access: | https://doi.org/10.3847/1538-4357/ada9eb |
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| author | Kimberly Paragas Heather A. Knutson Renyu Hu Bethany L. Ehlmann Giulia Alemanno Jörn Helbert Alessandro Maturilli Michael Zhang Aishwarya Iyer George Rossman |
| author_facet | Kimberly Paragas Heather A. Knutson Renyu Hu Bethany L. Ehlmann Giulia Alemanno Jörn Helbert Alessandro Maturilli Michael Zhang Aishwarya Iyer George Rossman |
| author_sort | Kimberly Paragas |
| collection | DOAJ |
| description | JWST’s MIRI LRS provides the first opportunity to spectroscopically characterize the surface compositions of close-in terrestrial exoplanets. Models for the bare-rock spectra of these planets often utilize a spectral library from R. Hu et al., which is based on room-temperature reflectance measurements of materials that represent archetypes of rocky planet surfaces. Here we present an expanded library that includes hemispherical reflectance measurements for a greater variety of compositions, varying textures (solid slab, coarsely crushed, and fine powder), as well as high-temperature (500–800 K) emissivity measurements for select samples. We incorporate this new library into version 6.3 of the open-source retrieval package PLATON and use it to show that planetary surfaces with similar compositions can have widely varying albedos and surface temperatures. We additionally demonstrate that changing the texture of a material can significantly alter its albedo, making albedo a poor proxy for surface composition. We identify key spectral features—the 5.6 μ m olivine feature, the transparency feature, the Si-O stretching feature, and the Christiansen feature—that indicate silicate abundance and surface texture. We quantify the number of JWST observations needed to detect these features in the spectrum of the most favorable super-Earth target, LHS 3844 b, and revisit the interpretation of its Spitzer photometry. Lastly, we show that temperature-dependent changes in spectral features are likely undetectable at the precision of current exoplanet observations. Our results illustrate the importance of spectroscopically resolved thermal emission measurements, as distinct from surface albedo constraints, for characterizing the surface compositions of hot, rocky exoplanets. |
| format | Article |
| id | doaj-art-24339f78ff1e4c10b6f066aae2dcf10a |
| institution | OA Journals |
| issn | 1538-4357 |
| language | English |
| publishDate | 2025-01-01 |
| publisher | IOP Publishing |
| record_format | Article |
| series | The Astrophysical Journal |
| spelling | doaj-art-24339f78ff1e4c10b6f066aae2dcf10a2025-08-20T02:02:05ZengIOP PublishingThe Astrophysical Journal1538-43572025-01-01981213010.3847/1538-4357/ada9ebA New Spectral Library for Modeling the Surfaces of Hot, Rocky ExoplanetsKimberly Paragas0https://orcid.org/0000-0003-0062-1168Heather A. Knutson1https://orcid.org/0000-0002-5375-4725Renyu Hu2https://orcid.org/0000-0003-2215-8485Bethany L. Ehlmann3https://orcid.org/0000-0002-2745-3240Giulia Alemanno4Jörn Helbert5https://orcid.org/0000-0001-5346-9505Alessandro Maturilli6Michael Zhang7https://orcid.org/0000-0002-0659-1783Aishwarya Iyer8https://orcid.org/0000-0003-0971-1709George Rossman9Division of Geological and Planetary Sciences, California Institute of Technology , 1200 E California Boulevard, Pasadena, CA 91125, USA ; kparagas@caltech.eduDivision of Geological and Planetary Sciences, California Institute of Technology , 1200 E California Boulevard, Pasadena, CA 91125, USA ; kparagas@caltech.eduDivision of Geological and Planetary Sciences, California Institute of Technology , 1200 E California Boulevard, Pasadena, CA 91125, USA ; kparagas@caltech.edu; Jet Propulsion Laboratory , 4800 Oak Grove Drive, Pasadena, CA 91101, USADivision of Geological and Planetary Sciences, California Institute of Technology , 1200 E California Boulevard, Pasadena, CA 91125, USA ; kparagas@caltech.eduInstitute of Planetary Research, German Aerospace Center (DLR) , Rutherfordstrasse 2, 12489, Berlin-Adlershof, GermanyInstitute of Planetary Research, German Aerospace Center (DLR) , Rutherfordstrasse 2, 12489, Berlin-Adlershof, GermanyInstitute of Planetary Research, German Aerospace Center (DLR) , Rutherfordstrasse 2, 12489, Berlin-Adlershof, GermanyDepartment of Astronomy & Astrophysics, University of Chicago , 5640 S Ellis Avenue, Chicago, IL 60637, USANASA Goddard Space Flight Center , 8800 Greenbelt Road, Greenbelt, MD 20771, USANASA Goddard Space Flight Center , 8800 Greenbelt Road, Greenbelt, MD 20771, USAJWST’s MIRI LRS provides the first opportunity to spectroscopically characterize the surface compositions of close-in terrestrial exoplanets. Models for the bare-rock spectra of these planets often utilize a spectral library from R. Hu et al., which is based on room-temperature reflectance measurements of materials that represent archetypes of rocky planet surfaces. Here we present an expanded library that includes hemispherical reflectance measurements for a greater variety of compositions, varying textures (solid slab, coarsely crushed, and fine powder), as well as high-temperature (500–800 K) emissivity measurements for select samples. We incorporate this new library into version 6.3 of the open-source retrieval package PLATON and use it to show that planetary surfaces with similar compositions can have widely varying albedos and surface temperatures. We additionally demonstrate that changing the texture of a material can significantly alter its albedo, making albedo a poor proxy for surface composition. We identify key spectral features—the 5.6 μ m olivine feature, the transparency feature, the Si-O stretching feature, and the Christiansen feature—that indicate silicate abundance and surface texture. We quantify the number of JWST observations needed to detect these features in the spectrum of the most favorable super-Earth target, LHS 3844 b, and revisit the interpretation of its Spitzer photometry. Lastly, we show that temperature-dependent changes in spectral features are likely undetectable at the precision of current exoplanet observations. Our results illustrate the importance of spectroscopically resolved thermal emission measurements, as distinct from surface albedo constraints, for characterizing the surface compositions of hot, rocky exoplanets.https://doi.org/10.3847/1538-4357/ada9ebExoplanet surface compositionExoplanet surface characteristicsExoplanet surfacesExoplanetsExtrasolar rocky planetsSuper Earths |
| spellingShingle | Kimberly Paragas Heather A. Knutson Renyu Hu Bethany L. Ehlmann Giulia Alemanno Jörn Helbert Alessandro Maturilli Michael Zhang Aishwarya Iyer George Rossman A New Spectral Library for Modeling the Surfaces of Hot, Rocky Exoplanets The Astrophysical Journal Exoplanet surface composition Exoplanet surface characteristics Exoplanet surfaces Exoplanets Extrasolar rocky planets Super Earths |
| title | A New Spectral Library for Modeling the Surfaces of Hot, Rocky Exoplanets |
| title_full | A New Spectral Library for Modeling the Surfaces of Hot, Rocky Exoplanets |
| title_fullStr | A New Spectral Library for Modeling the Surfaces of Hot, Rocky Exoplanets |
| title_full_unstemmed | A New Spectral Library for Modeling the Surfaces of Hot, Rocky Exoplanets |
| title_short | A New Spectral Library for Modeling the Surfaces of Hot, Rocky Exoplanets |
| title_sort | new spectral library for modeling the surfaces of hot rocky exoplanets |
| topic | Exoplanet surface composition Exoplanet surface characteristics Exoplanet surfaces Exoplanets Extrasolar rocky planets Super Earths |
| url | https://doi.org/10.3847/1538-4357/ada9eb |
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