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Unexpected Cooling Effect in Saturn's Upper Atmosphere
Unexpected Cooling Effect in Saturn's Upper Atmosphere
26 Jan 2007
(Source: Particle Physics and Astronomy Research Council)

UK researchers from University College London (UCL), along with colleagues from Boston University, have found that the hotter than expected temperature of Saturns upper atmosphere and that of the other giant planets is not due to the same mechanism that heats the atmosphere around the Earths Northern Lights. Reporting in Nature (25th January) the researchers findings thus rule out a long held theory.

A simple calculation to give the expected temperature of a planets upper atmosphere balances the amount of sunlight absorbed by the energy lost to the lower atmosphere. But the calculated values dont tally with the actual observations of the Gas Giants: they are consistently much hotter.

It has long been thought that the culprit behind the heating process was the ionosphere, being driven by the planets magnetic field, or magnetosphere. By using numerical models of Saturns atmosphere the researchers found that the net effects of the winds driven by polar energy inputs is not to heat the atmosphere but actually cool it.

Professor Alan Aylward, of the UCL Department of Physics & Astronomy, and an author of the study, explains: The aurora has been studied for over a hundred years, yet our discovery takes us back to first principles. We need to re-examine our basic assumptions about planetary atmospheres and what causes the observed heating.

Studying what happens on planets such as Saturn gives us an insight into what happens closer to home. Planets can lose their atmospheres as we see with Mars. Do we completely understand how this happens? Are there mechanisms heating the gas and causing it to escape that we do not yet fully understand? By studying what happens in other atmospheres we may find clues to Earths future.

The study was funded by the UK Particle Physics and Astronomy Research Council (PPARC) and Sun Microsystems Ltd and carried out using the HiPerSPACE facility at University College London. Contacts

Gill Ormrod - PPARC Press Office Tel: 01793 442012.

Professor Alan Aylward, UCL Department of Physics & Astronomy Tel: +44 (0)20 7679 2446.

Judith H Moore, UCL Media Relations Tel: +44 (0) 20 7679 7678, Mobile: +44 (0)77333 075 96. Notes to editors

The paper: An unexpected cooling effect in Saturns upper atmosphere is published in the January 25th edition of the journal Nature. C. G. A. Smith1, A. D. Aylward1, G. H. Millward1{, S. Miller1 & L. E. Moore2

1Department of Physics and Astronomy, University College London, WC1E 6BT, UK. 2Center for Space Physics, Boston University, Boston, Massachusetts 02215, USA. {Present address: Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder, Colorado 80303, USA.
PPARC is a partner in the British National Space Centre [BNSC] which coordinates the UK's civil space activities.

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Last Updated: 26 Jan 2007