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A bimodal distribution of haze in Pluto’s atmosphere

Fan, Siteng and Gao, Peter and Zhang, Xi and Adams, Danica J. and Kutsop, Nicholas W. and Bierson, Carver J. and Liu, Chao and Yang, Jiani and Young, Leslie A. and Cheng, Andrew F. and Yung, Yuk L. (2022) A bimodal distribution of haze in Pluto’s atmosphere. Nature Communications, 13 . Art. No. 240. ISSN 2041-1723. PMCID PMC8752795. doi:10.1038/s41467-021-27811-6.

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Pluto, Titan, and Triton make up a unique class of solar system bodies, with icy surfaces and chemically reducing atmospheres rich in organic photochemistry and haze formation. Hazes play important roles in these atmospheres, with physical and chemical processes highly dependent on particle sizes, but the haze size distribution in reducing atmospheres is currently poorly understood. Here we report observational evidence that Pluto’s haze particles are bimodally distributed, which successfully reproduces the full phase scattering observations from New Horizons. Combined with previous simulations of Titan’s haze, this result suggests that haze particles in reducing atmospheres undergo rapid shape change near pressure levels ~0.5 Pa and favors a photochemical rather than a dynamical origin for the formation of Titan’s detached haze. It also demonstrates that both oxidizing and reducing atmospheres can produce multi-modal hazes, and encourages reanalysis of observations of hazes on Titan and Triton.

Item Type:Article
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URLURL TypeDescription ItemNew Horizons observations ItemPython package Itemdphere pixelation tool CentralArticle Paper
Fan, Siteng0000-0002-3041-4680
Gao, Peter0000-0002-8518-9601
Zhang, Xi0000-0002-8706-6963
Adams, Danica J.0000-0001-9897-9680
Kutsop, Nicholas W.0000-0001-7188-9044
Bierson, Carver J.0000-0002-6840-7187
Yang, Jiani0000-0003-0037-2413
Young, Leslie A.0000-0002-7547-3967
Yung, Yuk L.0000-0002-4263-2562
Additional Information:© The Author(s) 2022. This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit Received 22 September 2021; Accepted 22 November 2021; Published 11 January 2022. We thank William M. Grundy for sharing the LEISA data, Michael L. Wong and Xue Feng for improving figure representations, and Yan Wu for comments. P.G. is supported by NASA Hubble Fellowship grant HST-HF2-51456.001-A awarded by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., for NASA, under contract NAS5-26555. X.Z. is supported by NASA Solar System Workings Grant 80NSSC19K0791. A.F.C. is supported by NASA under the New Horizons Project. Data availability: The New Horizons observations are available on NASA PDS ( The measured haze optical properties are in Khare et al. 38. The processed observations, including the extinction and scattering intensities, are attached in the Supplementary Information. The retrieved parameters describing haze morphology and corresponding scattering properties are also attached in the Supplementary Information. Source data are provided with this paper. Code availability: The data processing procedure is described step by step in the Methods. The Python package emcee for implementing MCMC is available at The haze scattering model is described in the appendix of Tomasko et al.10. The sphere pixelation tool is available at Author Contributions: S.F. conducted the data analysis, performed the calculations, and wrote the manuscript. S.F., P.G., X.Z., and Y.L.Y. conceived and designed the research. P.G. and D.J.A. provided the microphysical model. P.G. and C.L. provided the aggregate scattering model. X.Z. originated the idea of bi-modality. N.W.K. and C.J.B. contributed to the analysis of MVIC data. J.Y. contributed to interpreting and presenting the retrieval results. L.A.Y. and A.F.C provided insights into interpreting New Horizons observations. All authors contributed to the manuscript writing. The authors declare no competing interests. Peer review information: Nature Communications thanks Kathleen Mandt and the anonymous reviewer(s) for their contribution to the peer review of this work. Peer reviewer reports are available.
Funding AgencyGrant Number
NASA Hubble FellowshipHST-HF2-51456.001-A
Subject Keywords:Asteroids, comets and Kuiper belt; Atmospheric chemistry; Atmospheric dynamics
PubMed Central ID:PMC8752795
Record Number:CaltechAUTHORS:20220111-721365800
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Official Citation:Fan, S., Gao, P., Zhang, X. et al. A bimodal distribution of haze in Pluto’s atmosphere. Nat Commun 13, 240 (2022).
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:112830
Deposited By: Tony Diaz
Deposited On:11 Jan 2022 21:45
Last Modified:03 May 2022 19:17

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