DETECTING AND CONSTRAINING N{sub 2} ABUNDANCES IN PLANETARY ATMOSPHERES USING COLLISIONAL PAIRS

Schwieterman, Edward W.; Meadows, Victoria S.; Misra, Amit; Robinson, Tyler D.; Domagal-Goldman, Shawn

doi:10.1088/0004-637X/810/1/57

Title: DETECTING AND CONSTRAINING N{sub 2} ABUNDANCES IN PLANETARY ATMOSPHERES USING COLLISIONAL PAIRS

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Abstract

Characterizing the bulk atmosphere of a terrestrial planet is important for determining surface pressure and potential habitability. Molecular nitrogen (N{sub 2}) constitutes the largest fraction of Earth's atmosphere and is likely to be a major constituent of many terrestrial exoplanet atmospheres. Due to its lack of significant absorption features, N{sub 2} is extremely difficult to remotely detect. However, N{sub 2} produces an N{sub 2}–N{sub 2} collisional pair, (N{sub 2}){sub 2}, which is spectrally active. Here we report the detection of (N{sub 2}){sub 2} in Earth's disk-integrated spectrum. By comparing spectra from NASA's EPOXI mission to synthetic spectra from the NASA Astrobiology Institute's Virtual Planetary Laboratory three-dimensional spectral Earth model, we find that (N{sub 2}){sub 2} absorption produces a ∼35% decrease in flux at 4.15 μm. Quantifying N{sub 2} could provide a means of determining bulk atmospheric composition for terrestrial exoplanets and could rule out abiotic O{sub 2} generation, which is possible in rarefied atmospheres. To explore the potential effects of (N{sub 2}){sub 2} in exoplanet spectra, we used radiative transfer models to generate synthetic emission and transit transmission spectra of self-consistent N{sub 2}–CO{sub 2}–H{sub 2}O atmospheres, and analytic N{sub 2}–H{sub 2} and N{sub 2}–H{sub 2}–CO{sub 2} atmospheres. We show thatmore »« less

Authors:

Schwieterman, Edward W.; Meadows, Victoria S.; Misra, Amit ^[1]; Robinson, Tyler D.; Domagal-Goldman, Shawn ^[2]

Astronomy Department, University of Washington, Seattle, WA 98115 (United States)
NAI Virtual Planetary Laboratory, Seattle, WA 98115 (United States)

Publication Date:: Tue Sep 01 00:00:00 EDT 2015

OSTI Identifier:: 22525503

Resource Type:: Journal Article

Journal Name:: Astrophysical Journal

Additional Journal Information:: Journal Volume: 810; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0004-637X

Country of Publication:: United States

Language:: English

Subject:: 79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; CARBON DIOXIDE; COMPARATIVE EVALUATIONS; ELEMENT ABUNDANCE; HYDROGEN; MIXING RATIO; NITROGEN; PARTIAL PRESSURE; PLANETARY ATMOSPHERES; PLANETS; RADIANT HEAT TRANSFER; SATELLITE ATMOSPHERES; SATELLITES; STARS; WATER

Citation Formats


                    Schwieterman, Edward W., Meadows, Victoria S., Misra, Amit, Robinson, Tyler D., and Domagal-Goldman, Shawn. DETECTING AND CONSTRAINING N{sub 2} ABUNDANCES IN PLANETARY ATMOSPHERES USING COLLISIONAL PAIRS.  United States: N. p., 2015. 
        Web.  doi:10.1088/0004-637X/810/1/57.

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                    Schwieterman, Edward W., Meadows, Victoria S., Misra, Amit, Robinson, Tyler D., & Domagal-Goldman, Shawn. DETECTING AND CONSTRAINING N{sub 2} ABUNDANCES IN PLANETARY ATMOSPHERES USING COLLISIONAL PAIRS.  United States.  https://doi.org/10.1088/0004-637X/810/1/57

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                    Schwieterman, Edward W., Meadows, Victoria S., Misra, Amit, Robinson, Tyler D., and Domagal-Goldman, Shawn. 2015.  
        "DETECTING AND CONSTRAINING N{sub 2} ABUNDANCES IN PLANETARY ATMOSPHERES USING COLLISIONAL PAIRS".  United States.  https://doi.org/10.1088/0004-637X/810/1/57.

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@article{osti_22525503,

  title        = {DETECTING AND CONSTRAINING N{sub 2} ABUNDANCES IN PLANETARY ATMOSPHERES USING COLLISIONAL PAIRS},

  author       = {Schwieterman, Edward W. and Meadows, Victoria S. and Misra, Amit and Robinson, Tyler D. and Domagal-Goldman, Shawn},

  abstractNote = {Characterizing the bulk atmosphere of a terrestrial planet is important for determining surface pressure and potential habitability. Molecular nitrogen (N{sub 2}) constitutes the largest fraction of Earth's atmosphere and is likely to be a major constituent of many terrestrial exoplanet atmospheres. Due to its lack of significant absorption features, N{sub 2} is extremely difficult to remotely detect. However, N{sub 2} produces an N{sub 2}–N{sub 2} collisional pair, (N{sub 2}){sub 2}, which is spectrally active. Here we report the detection of (N{sub 2}){sub 2} in Earth's disk-integrated spectrum. By comparing spectra from NASA's EPOXI mission to synthetic spectra from the NASA Astrobiology Institute's Virtual Planetary Laboratory three-dimensional spectral Earth model, we find that (N{sub 2}){sub 2} absorption produces a ∼35% decrease in flux at 4.15 μm. Quantifying N{sub 2} could provide a means of determining bulk atmospheric composition for terrestrial exoplanets and could rule out abiotic O{sub 2} generation, which is possible in rarefied atmospheres. To explore the potential effects of (N{sub 2}){sub 2} in exoplanet spectra, we used radiative transfer models to generate synthetic emission and transit transmission spectra of self-consistent N{sub 2}–CO{sub 2}–H{sub 2}O atmospheres, and analytic N{sub 2}–H{sub 2} and N{sub 2}–H{sub 2}–CO{sub 2} atmospheres. We show that (N{sub 2}){sub 2} absorption in the wings of the 4.3 μm CO{sub 2} band is strongly dependent on N{sub 2} partial pressures above 0.5 bar and can significantly widen this band in thick N{sub 2} atmospheres. The (N{sub 2}){sub 2} transit transmission signal is up to 10 ppm for an Earth-size planet with an N{sub 2}-dominated atmosphere orbiting within the habitable zone of an M5V star and could be substantially larger for planets with significant H{sub 2} mixing ratios.},

  doi          = {10.1088/0004-637X/810/1/57},

  url          = {https://www.osti.gov/biblio/22525503},
  journal      = {Astrophysical Journal},

  issn         = {0004-637X},

  number       = 1,

  volume       = 810,

  place        = {United States},

  year         = {Tue Sep 01 00:00:00 EDT 2015},

  month        = {Tue Sep 01 00:00:00 EDT 2015}

}

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