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Published March 2017 | Published + Submitted
Journal Article Open

Sulfur Hazes in Giant Exoplanet Atmospheres: Impacts on Reflected Light Spectra

Abstract

Recent work has shown that sulfur hazes may arise in the atmospheres of some giant exoplanets, due to the photolysis of H_2S. We investigate the impact such a haze would have on an exoplanet's geometric albedo spectrum and how it may affect the direct imaging results of the Wide Field Infrared Survey Telescope (WFIRST), a planned NASA space telescope. For temperate (250 K < T_(eq) < 700 K) Jupiter-mass planets, photochemical destruction of H_2S results in the production of ~1 ppmv of S_8 between 100 and 0.1 mbar, which, if cool enough, will condense to form a haze. Nominal haze masses are found to drastically alter a planet's geometric albedo spectrum: whereas a clear atmosphere is dark at wavelengths between 0.5 and 1 μm, due to molecular absorption, the addition of a sulfur haze boosts the albedo there to ~0.7, due to scattering. Strong absorption by the haze shortward of 0.4 μm results in albedos <0.1, in contrast to the high albedos produced by Rayleigh scattering in a clear atmosphere. As a result, the color of the planet shifts from blue to orange. The existence of a sulfur haze masks the molecular signatures of methane and water, thereby complicating the characterization of atmospheric composition. Detection of such a haze by WFIRST is possible, though discriminating between a sulfur haze and any other highly reflective, high-altitude scatterer will require observations shortward of 0.4 μm, which is currently beyond WFIRST's design.

Additional Information

© 2017 The American Astronomical Society. Received 2016 November 11; revised 2017 January 30; accepted 2017 February 7; published 2017 March 3. M.S.M. acknowledges the support of the WFIRST preparatory science program and the NASA XRP program. P.G. acknowledges the support of the NASA Postdoctoral Program. In addition, we acknowledge and thank the Kavli Summer Program in Astrophysics and its sponsors for providing the opportunity and funding to conduct this research. We thank the Scientific Organizing Committee (J. Fortney, D. Abbot, C. Goldblatt, R. Murray-Clay, D. Lin, A. Showman, and X. Zhang) for putting together an enlightening series of lectures and activities that bolstered our research efforts both at Kavli and at home. We thank P. Garaud, the program coordinator, and others in the Local Organizing Committee (J. Scarpelli, Z. Kornberg, and S. Nasab) for ensuring that our stay at UC Santa Cruz was an amazing experience, being both conducive to research and fun. We thank the senior participants in the Kavli program, in particular D. Catling, K. Menou, and J. Bean, for giving such illuminating and interesting talks to start off our days. Last but far from the least, we thank the Kavli Fellows, A. Baker, C. Leung, C. Cadiou, D. Powell, G. McDonald, K. Feng, K. Ohno, L. Mayorga, M. Malik, N. Batalha, N. Espinoza, R. Garland, F. Ryan, R. MacDonald, T. Komacek, T. Louden, and Y. Kawashima, for creating an incredible atmosphere of camaraderie, friendship, adventure, and cake by the ocean. Software: FORTRAN, Python, IDL.

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Published - Gao_2017_AJ_153_139.pdf

Submitted - 1701.00318.pdf

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Additional details

Created:
August 19, 2023
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October 24, 2023