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Cassini ISS observation of Saturn’s String of Pearls

Sayanagi, Kunio M. and Dyudina, Ulyana A. and Ewald, Shawn P. and Muro, Gabriel D. and Ingersoll, Andrew P. (2014) Cassini ISS observation of Saturn’s String of Pearls. Icarus, 229 . pp. 170-180. ISSN 0019-1035. doi:10.1016/j.icarus.2013.10.032.

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We present the dynamics of the String of Pearls (SoPs) feature observed by the Cassini spacecraft’s Imaging Science Subsystem (ISS) camera between 2007 and 2010. The SoPs was originally discovered in the 5 μm images captured by Cassini VIMS instrument, where it appeared as a chain of infrared-bright spots (Momary, T.W., et al. [2006]. The Zoology of Saturn: The Bizarre Features Unveiled by the 5 Micron Eyes of Cassini/VIMS. AAS/Division for Planetary Sciences Meeting Abstracts 38, 499). Using ISS images of Saturn, we found a chain of 23–26 dark spots at 33.2°N planetocentric latitude with characteristics that are consistent with those of SoPs. Our measurements imply that the feature propagated at −2.26 ± 0.02° day^−1 in longitude (−22.27 ± 0.2 m s^−1, negative values denote westward) during the observed period that spans three Earth years. Our measurements imply that the SoPs is a chain of cyclones, which we infer from the motion of clouds on the periphery of the individual pearls. We tracked the motion of 26 pearls for 6 months in 2008 and noted a few pearls appearing and disappearing, all near the east–west termini of the SoPs feature. During this period, a few of the pearls, varying between 6 and 10, harbored a small circular cloud at the center, which we call the central peaks. In general, a group of vortices with the same sign of vorticity tend to merge; however, our measurements did not detect merger of pearls. The interest in the feature was heightened when the latest planet-encircling storm erupted from the SoPs on December 5, 2010 (Sayanagi, K.M., Dyudina, U.A., Ewald, S.P., Fischer, G., Ingersoll, A.P., Kurth, W.S., Muro, G.D., Porco, C.C., West, R.A. [2013]. Icarus 223, 460–478). The storm severely disrupted the region; the SoPs was last seen on December 24, 2010 in the turbulent wake of the storm, and has not reappeared as of August 2013.

Item Type:Article
Related URLs:
URLURL TypeDescription
Sayanagi, Kunio M.0000-0001-8729-0992
Ewald, Shawn P.0000-0002-1567-9154
Ingersoll, Andrew P.0000-0002-2035-9198
Additional Information:© 2013 Elsevier Inc. Received 12 July 2013; Revised 25 October 2013; accepted 28 October 2013; available online 11 November 2013. We thank the two anonymous reviewers for their extremely constructive comments. Our work was supported by the Cassini- Huygens mission, a cooperative project of NASA, ESA, ASI, managed by JPL a division of the California Institute of Technology, under a contract with NASA.
Funding AgencyGrant Number
Cassini-Huygens MissionUNSPECIFIED
European Space Agency (ESA)UNSPECIFIED
Agenzia Spaziale Italiana (ASI)UNSPECIFIED
Subject Keywords:Jovian planets; Saturn, atmosphere; Atmospheres, dynamics; Meteorology; Lightning
Record Number:CaltechAUTHORS:20140228-135448783
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Official Citation:Sayanagi, K. M., Dyudina, U. A., Ewald, S. P., Muro, G. D., & Ingersoll, A. P. (2014). Cassini ISS observation of Saturn’s String of Pearls. Icarus, 229(0), 170-180. doi:
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:44071
Deposited By: Jason Perez
Deposited On:28 Feb 2014 22:11
Last Modified:10 Nov 2021 16:47

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