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Organic molecules in saturnian E-ring particles. Probing subsurface oceans of Enceladus?

Published online by Cambridge University Press:  01 February 2008

Frank Postberg
Affiliation:
MPI für Kernphysik, Heidelberg, Germany email: Frank.Postberg@mpi-hd.mpg.de
S. Kempf
Affiliation:
MPI für Kernphysik, Heidelberg, Germany and Institut für Geophysik und extraterrestrische Physik Universität Braunschweig, Germany
R. Srama
Affiliation:
MPI für Kernphysik, Heidelberg, Germany
E. Grün
Affiliation:
MPI für Kernphysik, Heidelberg, Germany
J. K. Hillier
Affiliation:
Planetary and Space Science Research Institute, The Open University, Milton Keynes, U. K.
S. F. Green
Affiliation:
Planetary and Space Science Research Institute, The Open University, Milton Keynes, U. K.
N. McBride
Affiliation:
Planetary and Space Science Research Institute, The Open University, Milton Keynes, U. K.
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Abstract

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The population of Saturn's outermost tenuous E-ring is dominated by tiny water ice particles, some of which contain organic or mineral impurities. Active cryo-volcanism on the moon Enceladus, embedded in the E-ring, has been known to be a major source of particles replenishing the ring since late 2005. Therefore, particles in the vicinity of Enceladus provide crucial information about the dynamic and chemical processes occurring far below the moon's icy surface.

We present a compositional analysis of thousands of impact ionisation mass spectra of Saturn's E-ring particles, with sizes predominantly below 1 μm, detected by the Cosmic Dust Analyser onboard the Cassini spacecraft. Our findings imply that organic compounds are a significant component of icy particles ejected by Enceladus plumes. Our in situ measurements are supported by detections of other Cassini instruments. They hint at a dynamic interaction of a hot rocky core with liquid water below the icy surface, where the organic molecules are generated. Further insights are expected from two close Enceladus flybys to be performed by Cassini in 2008. Then, for the first time, we will obtain spectra of freshly ejected particles at the traversals through the cryo-volcanic plumes.

Type
Contributed Papers
Copyright
Copyright © International Astronomical Union 2008