image: The green line provides an approximate trace of the magnetic field lines connecting Saturn's ionosphere with Enceladus and its south polar plume of gas and icy grains. The inset shows the electron beam viewed by CAPS-ELS during Cassini's encounter with Enceladus on Oct. 31, 2008. The centering of the electron beam on the position of the magnetic field (asterix) indicates that the electrons are flowing parallel to the local magnetic field. view more
Credit: Geraint Jones, UCL
Data from NASA's Cassini spacecraft have revealed that Enceladus, one of Saturn's diminutive moons, is linked to Saturn by powerful electrical currents - beams of electrons that flow back and forth between the planet and moon. The finding is part of a paper published in Nature today.
CAPS, one of the instruments on board Cassini which made the electron beam discovery, includes a electron sensor called CAPS-ELS – led by UCL (University College London).
Since Cassini's arrival at Saturn in 2004 it has passed 500km-wide Enceladus 14 times, gradually discovering more of its secrets on each visit. Research has found that jets of gas and icy grains emanate from the south pole of Enceladus, which become electrically charged and form an ionosphere. The motion of Enceladus and its ionosphere through the magnetic bubble that surrounds Saturn acts like a dynamo, setting up the newly-discovered current system.
Scientists already knew that the giant planet Jupiter is linked to three of its moons by charged current systems set up by the satellites orbiting inside its giant magnetic bubble, the magnetosphere, and that these current systems form glowing spots in the planet's upper atmosphere. The latest discovery at Enceladus shows that similar processes take place at the Saturnian system too.
The detection of the beams was made by the Cassini Plasma Spectrometer's electron spectrometer, CAPS-ELS, the design and building of which was led at UCL's Mullard Space Science Laboratory. UCL co-authors of the Nature paper, Dr Geraint Jones and Professor Andrew Coates, are delighted with this new finding.
Dr Jones said: "Onboard Cassini, only CAPS-ELS has the capability of directly detecting the electron beams at the energies they're seen; this finding marks a great leap forward in our understanding of what exactly is going on at mysterious Enceladus."
Lead co-investigator of CAPS-ELS, Professor Coates, added: "This now looks like a universal process – Jupiter's moon Io is the most volcanic object in the solar system, and produces a bright spot in Jupiter's aurora. Now, we see the same thing at Saturn – the variable and majestic water-rich Enceladus plumes, probably driven by cryovolcanism, cause electron beams which create a significant spot in Saturn's aurora too."
The Nature paper in which the discovery is reported is co-led by Dr Wayne Pryor of Central Arizona College and Dr Abigail Rymer of the Johns Hopkins University Applied Physics Laboratory. The work also reports the presence of an ultraviolet auroral spot in Saturn's upper atmosphere, and of energetic ions flowing towards Enceladus: discoveries made using other Cassini instruments.
Cassini-related work at UCL-MSSL is supported by the UK Space Agency, the Science and Technology Facilities Council, and the European Space Agency. Geraint Jones is supported by a STFC Advanced Fellowship.
Notes for Editors
1. For more information or to interview Dr Geraint Jones or Professor Andrew Coates, please contact Clare Ryan in the UCL Media Relations Office on tel: +44 (0)20 3108 3846, mobile: +44 07747 565 056, out of hours +44 (0)7917 271 364, e-mail: clare.ryan@ucl.ac.uk.
2. 'The Enceladus Auroral Footprint at Saturn' is published in the April 21st issue of Nature. For copies of the paper please contact UCL Media Relations.
3. The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency, and the Italian Space Agency. NASA's Jet Propulsion Laboratory, Pasadena, Calif., 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. For information about Cassini, please contact the JPL Media Relations Office on tel: +1 818 354 5011. More information is also available at http://www.nasa.gov/cassini and http://saturn.jpl.nasa.gov.
4. Cassini-related work at UCL-MSSL is supported by the UK Space Agency, the Science and Technology Facilities Council, and the European Space Agency. Geraint Jones is supported by a STFC Advanced Fellowship. www.stfc.ac.uk
About UCL (University College London)
Founded in 1826, UCL was the first English university established after Oxford and Cambridge, the first to admit students regardless of race, class, religion or gender, and the first to provide systematic teaching of law, architecture and medicine. UCL is among the world's top universities, as reflected by performance in a range of international rankings and tables. Alumni include Marie Stopes, Jonathan Dimbleby, Lord Woolf, Alexander Graham Bell, and members of the band Coldplay. UCL currently has over 13,000 undergraduate and 9,000 postgraduate students. Its annual income is over £700 million. www.ucl.ac.uk
UCL Mullard Space Science Laboratory
The UCL Mullard Space Science Laboratory delivers a cutting-edge science programme, underpinned by a capability in space science instrumentation, systems engineering and project management. Its staff are committed to a broad outreach programme and are very happy to receive enquiries from the public and fellow space science professionals alike. http://www.mssl.ucl.ac.uk/
Journal
Nature