[meteorite-list] Cassini Sees Collisions of Moonlets on Saturn's Ring

[Ron Baalke]

Science and Technology Facilities Council
Swindon, U.K.

Contacts

Julia Maddock
STFC Press Office
Tel: +44 (0)1793 442 094

Prof Carl Murray
Queen Mary, University of London
Tel: +44 (0)20 7882 5456

Dr Sebastien Charnoz
Universite Paris 7 / CEA Saclay
Tel : +33 1 69 086 130
Fax: +33 1 69 086 577

5 June 2008

Cassini sees collisions of moonlets on Saturn's ring

A team of scientists led from the UK has discovered that the rapid changes
in Saturn's F ring can be attributed to small moonlets causing
perturbations. Their results are reported in Nature (5th June 2008).

Saturn's F ring has long been of interest to scientists as its features
change on timescales from hours to years and it is probably the only
location in the solar system where large scale collisions happen on a daily
basis. Understanding these processes helps scientists understand the early
stages of planet formation.

Prof Carl Murray of Queen Mary, University of London and member of the
Cassini Imaging Team led the analysis. He says: "Saturns F ring is perhaps
the most unusual and dynamic ring in the solar system; it has multiple
structures with features changing on a variety of timescales from hours to
years."

The team used images gathered by the NASA-ESA Cassini Huygens mission.
Images snapped by Cassini in 2006 and 2007 show the formation and evolution
of a series of structures (called "jets" in the paper) that are the result
of collisions between small nearby moonlets and the core of the F ring.

A ~5km object discovered by Cassini in 2004 (called S/2004 S 6) is the best
candidate to explain some of the largest jets seen in the images.

Prof Murray adds, "Previous research has noted the features in the F ring
and concluded that either another moon of radius about 100km must be present
and scattering the particles in the ring, or a much smaller moonlet was
colliding with its constituent particles. We can now say that the moonlet is
the most likely explanation and even confirm the identity of one culprit."

The F ring and all the nearby objects are being continually perturbed by
encounters with the shepherding moon Prometheus and this allows the
gravitational signature of the embedded objects to be detected, even when
the objects themselves cannot be seen.

Dr Sebastien Charnoz of Universite Paris 7 / CEA Saclay is a co-author on
the paper. He says, "Large scale collisions happen in Saturns F ring almost
daily -- making it a unique place to study. We can now say that these
collisions are responsible for the changing features we observe there."

The Cassini images also show new features (called "fans") which result from
the gravitational effect of small (~1km) satellites orbiting close to the F
ring core.

Prof Keith Mason, STFC Chief Executive Officer, which funds UK involvement
in Cassini-Huygens said, "This incredibly successful mission has taught us a
great deal about the solar system and the processes at work in it.
Understanding how small objects move within the dust rings around Saturn
gives an insight into the processes that drive planetary formation, where
the proto-planet collects material in its orbit through a dust plane and
carves out similar grooves and tracks."

Notes for Editors

Paper title:
"The determination of the structure of Saturn's F ring by nearby moonlets"
Carl D. Murray, Kevin Beurle, Nicholas J. Cooper, Michael W. Evans, Gareth
A. Williams & Sebastien Charnoz

Images

* Saturn's F-Ring. Credit: NASA/JPL/Space Science Institute
  http://www.scitech.ac.uk/resources/image/CassFRing.jpg (173KB)

Further images showing Saturn's F ring are available below:

http://saturn.jpl.nasa.gov/multimedia/images/image-details.cfm?imageID=3055
http://saturn.jpl.nasa.gov/multimedia/images/image-details.cfm?imageID=3052
http://saturn.jpl.nasa.gov/multimedia/images/image-details.cfm?imageID=2933
http://saturn.jpl.nasa.gov/multimedia/images/image-details.cfm?imageID=2850
http://saturn.jpl.nasa.gov/multimedia/images/image-details.cfm?imageID=2648
http://saturn.jpl.nasa.gov/multimedia/images/image-details.cfm?imageID=2560
http://saturn.jpl.nasa.gov/multimedia/images/image-details.cfm?imageID=2463
http://saturn.jpl.nasa.gov/multimedia/images/image-details.cfm?imageID=2335
http://saturn.jpl.nasa.gov/multimedia/images/image-details.cfm?imageID=2330
http://saturn.jpl.nasa.gov/multimedia/images/image-details.cfm?imageID=1700

Cassini-Huygens mission

The Cassini-Huygens mission is a cooperative project of NASA, the European
Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a
division of the California Institute of Technology in Pasadena, manages the
Cassini-Huygens mission for NASA's Science Mission Directorate, Washington.
The Cassini orbiter was designed, developed and assembled at JPL.

For more information on the Cassini-Huygens mission, visit the NASA website,
     http://www.nasa.gov/cassini/

About STFC,
     http://www.scitech.ac.uk/about/introduction.aspx