University of Oulu

Hsu, H., Schmidt, J., Kempf, S., Postberg, F., Moragas-Klostermeyer, G., Seiß, M., Hoffmann, H., Burton, M., Ye, S., Kurth, W., Horányi, M., Khawaja, N., Spahn, F., Schirdewahn, D., O’Donoghue, J., Moore, L., Cuzzi, J., Jones, G., Srama, R. (2018) In situ collection of dust grains falling from Saturn’s rings into its atmosphere. Science, 362 (6410), eaat3185. doi:10.1126/science.aat3185

In situ collection of dust grains falling from Saturn’s rings into its atmosphere

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Author: Hsu, Hsiang-Wen1; Schmidt, Jürgen2; Kempf, Sascha1;
Organizations: 1Laboratory for Atmospheric and Space Physics, University of Colorado Boulder, USA
2Astronomy Research Unit, University of Oulu, Finland
3Institut für Geowissenschaften, Universität Heidelberg, Germany
4Institut für geologische Wissenschaften, Freie Universität Berlin, Germany
5Institut für Raumfahrtsysteme, Universität Stuttgart, Germany
6Institut für Physik und Astronomie, Universität Potsdam, Germany
7Jet Propulsion Laboratory, USA
8Department of Physics and Astronomy, University of Iowa, USA
9NASA Goddard Space Flight Center, USA
10Center for Space Physics, Boston University, USA
11NASA Ames Research Center, USA
12Mullard Space Science Laboratory, University College London, UK
13The Centre for Planetary Sciences, University College London/Birkbeck, UK
14Center for Astrophysics, Space Physics, and Engineering Research, Baylor University, USA
Format: article
Version: accepted version
Access: open
Online Access: PDF Full Text (PDF, 1.9 MB)
Persistent link:
Language: English
Published: American Association for the Advancement of Science (AAAS), 2018
Publish Date: 2018-10-15


Saturn’s main rings are composed of >95% water ice, and the nature of the remaining few percent has remained unclear. The Cassini spacecraft’s traversals between Saturn and its innermost D ring allowed its cosmic dust analyzer (CDA) to collect material released from the main rings and to characterize the ring material infall into Saturn. We report the direct in situ detection of material from Saturn’s dense rings by the CDA impact mass spectrometer. Most detected grains are a few tens of nanometers in size and dynamically associated with the previously inferred “ring rain.” Silicate and water-ice grains were identified, in proportions that vary with latitude. Silicate grains constitute up to 30% of infalling grains, a higher percentage than the bulk silicate content of the rings.

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Series: Science
ISSN: 0036-8075
ISSN-E: 1095-9203
ISSN-L: 0036-8075
Volume: 362
Issue: 6410
Article number: eaat3185
DOI: 10.1126/science.aat3185
Type of Publication: A1 Journal article – refereed
Field of Science: 115 Astronomy and space science
Funding: We acknowledge the support from NASA, ESA, and the Cassini project. This work is partially supported by the NASA/ROSES-2015 NNX16AI35G Cassini Data Analysis and Participating Scientist program, the Deutsches Zentrum f¨ur Luft- und Raumfahrt (OH 1401) and the Deutsche Forschungsgemeinschaft (Sp384/33-1, Ho5720/1-1). J.S. acknowledges support by the Academy of Finland. F.P. was supported by German Research Foundation (DFG) projects PO 1015/2-1, /3-1. F.P. and N.K. were supported by DFG project PO 1015/4-1 and ERC Consolidator Grant 724908–Habitat-OASIS. G.H.J. is grateful to the UK Science and Technology Facilities Council for partial support.
Academy of Finland Grant Number: 298571
Detailed Information: 298571 (Academy of Finland Funding decision)
Dataset Reference: The CDA and HRD data presented are available in the Planetary Data System at: and, respectively. The numerical simulation code (in IDL) for modeling the grain dynamics is available at
Copyright information: © 2018 The Authors. This is the author’s version of the work. It is posted here by permission of the AAAS for personal use, not for redistribution. The definitive version was published in Science on Vol. 362, Issue 6410, eaat3185, 05 Oct 2018,