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Science. 2018 Oct 5;362(6410). pii: eaat3185. doi: 10.1126/science.aat3185.

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

Author information

1
Laboratory for Atmospheric and Space Physics, University of Colorado-Boulder, Boulder, CO, USA. sean.hsu@lasp.colorado.edu.
2
Astronomy Research Unit, University of Oulu, Oulu, Finland.
3
Laboratory for Atmospheric and Space Physics, University of Colorado-Boulder, Boulder, CO, USA.
4
Institut für Geowissenschaften, Universität Heidelberg, Heidelberg, Germany.
5
Institut für Geologische Wissenschaften, Freie Universität Berlin, Berlin, Germany.
6
Institut für Raumfahrtsysteme, Universität Stuttgart, Stuttgart, Germany.
7
Institut für Physik und Astronomie, Universität Potsdam, Potsdam, Germany.
8
Jet Propulsion Laboratory, Pasadena, CA, USA.
9
Department of Physics and Astronomy, University of Iowa, Iowa City, IA, USA.
10
NASA Goddard Space Flight Center, Greenbelt, MD, USA.
11
Center for Space Physics, Boston University, Boston, MA, USA.
12
NASA Ames Research Center, Moffett Field, CA, USA.
13
Mullard Space Science Laboratory, University College London, Holmbury St. Mary, Dorking, UK.
14
The Centre for Planetary Sciences at University College London/Birkbeck, London, UK.
15
Center for Astrophysics, Space Physics, and Engineering Research, Baylor University, Waco, TX, USA.

Abstract

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.

PMID:
30287635
DOI:
10.1126/science.aat3185

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