Cassini Confirms a Dynamic Atmosphere at Saturn's Moon Enceladus

Joint Imperial College London and PPARC news release

For further information, please contact:

Abigail Smith
Imperial College London Press Office
Tel: +44 20 7594 6701

Gill Ormrod
PPARC Press Office
Tel +44 1793 442012

Professor Michele Dougherty
Principal Investigator, Magnetometer Imperial College London
Tel: +44 20 7594 7757

Carolina Martinez
Jet Propulsion Laboratory, Pasadena, Califonia, USA
Tel: +1 (818) 354-9382

Professor Fritz Neubauer
Co-investigator, Magnetometer University of Koln
Tel: + 0049 221 02310 or 0049 2235 92274

For immediate release: Friday 29 July 2005

Cassini confirms a dynamic atmosphere at Saturn's moon Enceladus

The latest close flyby of Saturn's icy moon Enceladus by NASA's Cassini

spacecraft confirms that the moon has a significant, extended and
dynamic
atmosphere. The flyby, which took place on 14th July 2005, was
Cassini's
lowest altitude flyby of any object to date, a mere 173 kilometres (108

miles) above the surface of Enceladus.

The 500 km diameter moon Enceladus is a very bright icy moon at a
distance
of 4 Saturn radii away from Saturn. It has long been associated with
the
formation of the E ring, Saturn's outermost ring. The first two more
distant flybys of Enceladus on February 17th at an altitude of 1,167
kilometres (725 miles), and on March 9th, 500 kilometres (310 miles)
above
Enceladus' surface had shown draping or bending of the magnetic field
around the moon, revealing that Enceladus was acting as a large
obstacle
to the flow of plasma and magnetic field from Saturn by its extended
asymmetric atmosphere.

The recent close flyby confirms and extends the observations from the
two
more distant flybys which took place earlier this year. Although no
other
instruments on the Cassini spacecraft had detected evidence of this
atmosphere on the first two flybys, on the basis of the magnetometer
[MAG]
instrument observations alone a decision was made to modify the
spacecraft
trajectory for the 14th July encounter to fly much closer to the
surface
of Enceladus.

Professor Michele Dougherty from Imperial College London, who is
Principal Investigator on the Magnetometer instrument on Cassini, says:
"These
latest observations are very exciting, they confirm the existence of an

atmosphere which we predicted from the distant earlier flybys and they
will also allow us to gain a much better understanding of the processes

taking place which are producing this very exotic atmosphere".

Observations from numerous instruments now confirm what MAG was able to

see from a great distance. Not only is the magnetic field even more
strongly bent around the atmospheric obstacle connected to the moon but

the other instruments also detected the presence of the atmosphere. The

magnetic data also suggests that the atmosphere is not symmetric and
may
be arising from a comet-like jet from the southern hemisphere. Also the

spacecraft passed right through the electric current carrying region
associated with the atmospheric interaction.

-ends-

Notes to Editors

1. Saturn's rings
The rings are (in order out from the planet) D, C, B, Cassini Gap, A,
F, G
and E. The A ring has its own gap called the Encke Gap.

2. Previous PPARC release on previous two flybys:
http://www.pparc.ac.uk/nw/enceladus.asp

3. For an artist's impression of the third flyby of Enceladus see
http://www.pparc.ac.uk/nw/md/artcl/enceladus_images.asp

For images, including those from the three flybys of Enceladus, and
information on the Cassini mission visit
http://saturn.jpl.nasa.gov and http://www.nasa.gov/cassini

4. 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 mission for NASA's Science Mission Directorate,
Washington, D.C. The Cassini orbiter was designed, developed and
assembled
at JPL. The magnetometer team is based at Imperial College London,
working
with team members from the United States and Germany.

5. Consistently rated in the top three UK university institutions,
Imperial College London is a world leading science-based university
whose
reputation for excellence in teaching and research attracts students
(11,000) and staff (6,000) of the highest international quality.

Innovative research at the College explores the interface between
science,
medicine, engineering and management and delivers practical solutions
that
enhance the quality of life and the environment -- underpinned by a
dynamic enterprise culture.

Website: www.imperial.ac.uk

6. The Particle Physics and Astronomy Research Council (PPARC) is the
UK's
strategic science investment agency. It funds research, education and
public understanding in four broad areas of science -- particle
physics,
astronomy, cosmology and space science.

PPARC is government funded and provides research grants and
studentships
to scientists in British universities, gives researchers access to
world-class facilities and funds the UK membership of international
bodies
such as the European Particle Physics Laboratory, CERN, the European
Space
Agency and the European Southern Observatory. It also contributes money

for the UK telescopes overseas on La Palma, Hawaii, Australia and in
Chile, the UK Astronomy Technology Centre at the Royal Observatory,
Edinburgh and the MERLIN/VLBI National Facility.

External Sites:

* Partical Physics and Astronomy Research Coucil (PPARC)
http://www.pparc.ac.uk/
* Jet Propulsion Laboratory, California Institute of Technology
http://www.jpl.nasa.gov/