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Analysis of Neptune’s 2017 Bright Equatorial Storm

Molter, Edward and de Pater, Imke and Luszcz-Cook, Statia and Hueso, Ricardo and Tollefson, Joshua and Alvarez, Carlos and Sánchez-Lavega, Agustín and Wong, Michael H. and Hsu, Andrew I. and Sromovsky, Lawrence A. and Fry, Patrick M. and Delcroix, Marc and Campbell, Randy and de Kleer, Katherine and Gates, Elinor and Lynam, Paul David and Ammons, S. Mark and Coy, Brandon Park and Duchêne, Gaspard and Gonzales, Erica J. and Hirsch, Lea and Magnier, Eugene A. and Ragland, Sam and Rich, R. Michael and Wang, Feige (2019) Analysis of Neptune’s 2017 Bright Equatorial Storm. Icarus, 321 . pp. 324-345. ISSN 0019-1035. doi:10.1016/j.icarus.2018.11.018.

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We report the discovery of a large ( ∼ 8500 km diameter) infrared-bright storm at Neptune’s equator in June 2017. We tracked the storm over a period of 7 months with high-cadence infrared snapshot imaging, carried out on 14 nights at the 10 m Keck II telescope and 17 nights at the Shane 120 inch reflector at Lick Observatory. The cloud feature was larger and more persistent than any equatorial clouds seen before on Neptune, remaining intermittently active from at least 10 June to 31 December 2017. Our Keck and Lick observations were augmented by very high-cadence images from the amateur community, which permitted the determination of accurate drift rates for the cloud feature. Its zonal drift speed was variable from 10 June to at least 25 July, but remained a constant 237.4 ± 0.2 m s^(−1) from 30 September until at least 15 November. The pressure of the cloud top was determined from radiative transfer calculations to be 0.3-0.6 bar; this value remained constant over the course of the observations. Multiple cloud break-up events, in which a bright cloud band wrapped around Neptune’s equator, were observed over the course of our observations. No “dark spot” vortices were seen near the equator in HST imaging on 6 and 7 October. The size and pressure of the storm are consistent with moist convection or a planetary-scale wave as the energy source of convective upwelling, but more modeling is required to determine the driver of this equatorial disturbance as well as the triggers for and dynamics of the observed cloud break-up events.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Molter, Edward0000-0003-3799-9033
de Pater, Imke0000-0002-4278-3168
Hueso, Ricardo0000-0003-0169-123X
Sánchez-Lavega, Agustín0000-0001-7355-1522
Wong, Michael H.0000-0003-2804-5086
Hsu, Andrew I.0000-0002-6190-9336
Sromovsky, Lawrence A.0000-0001-5480-8580
Fry, Patrick M.0000-0002-7367-6541
Delcroix, Marc0000-0002-9828-7390
Campbell, Randy0000-0002-3289-5203
de Kleer, Katherine0000-0002-9068-3428
Gates, Elinor0000-0002-3739-0423
Ammons, S. Mark0000-0001-5172-7902
Hirsch, Lea0000-0001-8058-7443
Magnier, Eugene A.0000-0002-7965-2815
Rich, R. Michael0000-0003-0427-8387
Wang, Feige0000-0002-0210-7499
Additional Information:© 2018 Published by Elsevier Inc. Received 2 July 2018, Revised 5 November 2018, Accepted 19 November 2018, Available online 28 November 2018. Some of the data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Maunakea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain. Partial support for this work was also provided by the Keck Visiting Scholar Program at W.M. Keck Observatory. Portions of this research are based on observations made with the NASA/ESA Hubble Space Telescope, (OPAL program GO14756) obtained from the data archive at the Space Telescope Science Institute. STScI is operated by the Association of Universities for Research in Astronomy, Inc. under NASA contract NAS 5–26555. Research at Lick Observatory is partially supported by a generous gift from Google. This work has been supported in part by the National Science Foundation, NSF Grant AST-1615004 to UC Berkeley. R. H. and A.S-L. were supported by the Spanish MINECO project AYA2015-65041-P with FEDER, UE support and Grupos Gobierno Vasco IT-765-13. Portions of this work were performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. We thank the referees, Amy Simon and one anonymous person, for their insightful comments, which substantially improved the manuscript. We thank Conor McPartland as well as all of the Keck Observing Assistants for executing our volunteer observing program during their observing time at Keck Observatory. We thank Geoff Chen, Ian Crossfield, Donald Gavel, and Robert de Rosa for executing our volunteer observing program during their observing time at Lick Observatory.
Group:Astronomy Department
Funding AgencyGrant Number
W. M. Keck FoundationUNSPECIFIED
NASANAS 5-26555
Ministerio de Economía, Industria y Competitividad (MINECO)AYA2015-65041-P
Grupos Gobierno VascoIT-765-13
Department of Energy (DOE)DE-AC52-07NA27344
Record Number:CaltechAUTHORS:20181128-090728975
Persistent URL:
Official Citation:Edward Molter, Imke de Pater, Statia Luszcz-Cook, Ricardo Hueso, Joshua Tollefson, Carlos Alvarez, Agustín Sánchez-Lavega, Michael H. Wong, Andrew I. Hsu, Lawrence A. Sromovsky, Patrick M. Fry, Marc Delcroix, Randy Campbell, Katherine de Kleer, Elinor Gates, Paul David Lynam, S. Mark Ammons, Brandon Park Coy, Gaspard Duchene, Erica J. Gonzales, Lea Hirsch, Eugene A. Magnier, Sam Ragland, R. Michael Rich, Feige Wang, Analysis of Neptune’s 2017 bright equatorial storm, Icarus, Volume 321, 2019, Pages 324-345, ISSN 0019-1035, (
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:91268
Deposited By: Tony Diaz
Deposited On:28 Nov 2018 17:24
Last Modified:16 Nov 2021 03:39

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