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An infrared camera aboard NASA's Cassini spacecraft has discovered a unique aurora lighting up Saturn’s polar cap. The mysterious new aurora is unlike any other known in our solar system.

"We’ve never seen an aurora like this elsewhere," said Tom Stallard, an RCUK Academic Fellow working with Cassini data at the University of Leicester. Stallard is lead author of a paper released today (13th November) in the journal Nature. "It’s not just a ring of aurorae like those we’ve seen at Jupiter or Earth. This one covers an enormous area across the pole. Our current ideas on what forms Saturn’s aurorae predict that this region should be empty, so finding such a bright one here is a fantastic surprise."

Aurorae are caused when charged particles stream along the magnetic field of a planet and into its atmosphere. On Earth these charged particles come from the solar wind – a stream of particles that emanates from the Sun.

Jupiter's main auroral ring, caused by interactions internal to Jupiter's magnetic environment, is constant in size. Saturn's main aurora, which is caused by the solar wind, changes size dramatically as the wind varies. The newly observed aurora at Saturn, however, doesn’t fit into either category.

"Saturn's unique auroral features are telling us there is something special and unforeseen about this planet's magnetosphere and the way it interacts with the solar wind and the planet's atmosphere," said Nick Achilleos, Cassini scientist on the Cassini magnetometer team at the University College London. "Trying to explain its origin will no doubt lead us to physics which uniquely operates in the environment of Saturn."

The new infrared aurora appears in a region hidden from NASA’s Hubble Space Telescope, which has provided views of Saturn’s ultraviolet aurora. Cassini observed it when the spacecraft flew near Saturn’s polar region. In infrared light, the aurora sometimes fills the region from around 82 degrees north all the way over the pole. This new aurora is also constantly changing, even disappearing within a 45 minute-period.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The UK researchers have been funded by the Science and Technology Facilities Council (STFC) and Research Councils UK (RCUK).

Notes for editors

Images

The new pictures are available online at: http://www.nasa.gov/cassini

Contact

Julia Short

STFC Press Office

Tel: +44 (0)1793 442 012

Mob: + 44 (0)777 0276 721

Tom Stallard

University of Leicester

Tel: +44 (0)116 252 3589

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 visual and infrared mapping spectrometer team is based at the University of Arizona, Tucson.

The research is drawn from data collected by NASA’s InfraRed Telescope Facility. Saturn’s main aurora has been studied using the NASA/ESA Hubble Space Telescope.

Nature Paper

Paper title: Complex structure within Saturn’s infrared aurora

Authors: Tom Stallard1, Steve Miller2, Makenzie Lystrup2, Nicholas Achilleos2, Emma J. Bunce1, Christopher S. Arridge3, Michele K. Dougherty4, Stan W. H. Cowley1, Sarah V. Badman1, Dean L. Talboys1, Robert H. Brown5, Kevin H. Baines6, Bonnie J. Buratti6, Roger N. Clark7, Christophe Sotin6, Phil D. Nicholson8 & Pierre Drossart9

1 Department of Physics and Astronomy, University of Leicester, Leicester LE1 7RH, UK.

2 Atmospheric Physics Laboratory, Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, UK.

3 Department of Space and Climate Physics, Mullard Space Science Laboratory, University College London, Holmbury St Mary, Dorking, Surrey RH5 6NT, UK.

4 Space and Atmospheric Physics Group, Department of Physics, Imperial College of Science, Technology and Medicine, South Kensington Campus, London SW7 2AZ, UK.

5 Lunar and Planetary Laboratory and Steward Observatory, University of Arizona, Tucson, Arizona 85721-0092, USA.

6 Jet Propulsion Laboratory, California Institute of Technology, M/S 183-601, 4800 Oak Grove Drive, Pasadena, California 91109-8099, USA.

7 US Geological Survey, Denver, Colorado 80225, USA.

8 Cornell University, Astronomy Department, Ithaca, New York 14853, USA.

9 Observatoire de Paris, Meudon 92195, France.

About STFC

The Science and Technology Facilities Council is an independent, non-departmental public body of the Department for Innovation, Universities and Skills (DIUS).

We were formed as a new Research Council on 1 April 2007 through a merger of the Council for the Central Laboratory of the Research Councils (CCLRC) and the Particle Physics and Astronomy Research Council (PPARC) and the transfer of responsibility for nuclear physics from the Engineering and Physical Sciences Research Council (EPSRC). We are one of seven national research councils in the UK.

STFC is a science-driven organisation. We make it possible for a broad range of scientists to do the highest quality research tackling some of the most fundamental scientific questions.

We do this by:

• funding researchers in universities directly through grants particularly in astronomy, particle physics, space science and nuclear physics.

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