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Pluto’s Haze Abundance and Size Distribution from Limb Scatter Observations by MVIC

Kutsop, N. W. and Hayes, A. G. and Buratti, B. J. and Corlies, P. M. and Ennico, K. and Fan, S. and Gladstone, R. and Helfenstein, P. and Hofgartner, J. D. and Hicks, M. and Lemmon, M. and Lunine, J. I. and Moore, J. and Olkin, C. B. and Parker, A. H. and Stern, S. A. and Weaver, H. A. and Young, L. A. (2021) Pluto’s Haze Abundance and Size Distribution from Limb Scatter Observations by MVIC. Planetary Science Journal, 2 (3). Art. No. 91. ISSN 2632-3338. doi:10.3847/psj/abdcaf. https://resolver.caltech.edu/CaltechAUTHORS:20210513-133955936

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Abstract

The New Horizons spacecraft observed Pluto and Charon at solar-phase angles between 16° and 169°. In this work, we use the Multispectral Visible Imaging Camera (MVIC) observations to construct multiwavelength phase curves of Pluto's atmosphere, using the limb scatter technique. Observational artifacts and biases were removed using Charon as a representative airless body. The size and distribution of the haze particles were constrained using a Titan fractal aggregate phase function. We find that monodispersed and log-normal populations cannot simultaneously describe the observed steep forward scattering, indicative of wavelength-scale particles, and the non-negligible backscattering indicative of particles much smaller than the wavelength. Instead, we find it necessary to use bimodal or power-law distributions, especially below ~200 km, to properly describe the MVIC observations. Above 200 km, where the atmosphere is isotropically scattering, a monodisperse, log-normal, or a bimodal/power law approximating a monodispersed population is able to fit the phase curves well. As compared to the results of previously published articles, we find that Pluto's atmosphere must contain haze particle number densities an order of magnitude greater for small (~10 nm) and large (~1 μm) radii, and relatively fewer intermediate sizes (~100 nm). These conclusions support a lower aggregate aerosol growth rate than that found by Gao et al., indicating a higher charge-to-radius ratio, upwards of 60e⁻ μm⁻¹. In order to generate large particles with a lower growth rate, the atmosphere must also have a lower sedimentation velocity (<~0.01 m s⁻¹ at 200 km), which is possible with a fractal dimension of less than 2.


Item Type:Article
Related URLs:
URLURL TypeDescription
https://doi.org/10.3847/psj/abdcafDOIArticle
ORCID:
AuthorORCID
Kutsop, N. W.0000-0001-7188-9044
Hayes, A. G.0000-0001-6397-2630
Buratti, B. J.0000-0002-5901-4875
Corlies, P. M.0000-0002-6417-9316
Ennico, K.0000-0002-8847-8492
Fan, S.0000-0002-3041-4680
Gladstone, R.0000-0003-0060-072X
Helfenstein, P.0000-0003-4870-1300
Hofgartner, J. D.0000-0002-6517-3864
Lemmon, M.0000-0002-4504-5136
Lunine, J. I.0000-0003-2279-4131
Olkin, C. B.0000-0002-5846-716X
Parker, A. H.0000-0002-6722-0994
Stern, S. A.0000-0001-5018-7537
Weaver, H. A.0000-0003-0951-7762
Young, L. A.0000-0003-3434-8024
Additional Information:© 2021. 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 2020 July 28; revised 2021 January 11; accepted 2021 January 11; published 2021 May 7.
Funders:
Funding AgencyGrant Number
NASA Earth and Space Science Fellowship80NSSC18K1319
Subject Keywords:Pluto; Planetary atmospheres; Atmospheric composition; Planetary science; Phase angle; Radiative transfer equation
Issue or Number:3
Classification Code:Unified Astronomy Thesaurus concepts: Pluto (1267); Planetary atmospheres (1244); Atmospheric composition (2120); Planetary science (1255); Phase angle (1217); Radiative transfer equation (1336)
DOI:10.3847/psj/abdcaf
Record Number:CaltechAUTHORS:20210513-133955936
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20210513-133955936
Official Citation:N. W. Kutsop et al 2021 Planet. Sci. J. 2 91
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:109119
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:13 May 2021 21:01
Last Modified:13 May 2021 21:01

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