The planets: Mysteries surrounding the ‘butterscotch’ planet’s equator


Saturn, the second largest planet in the Solar System, is easily spotted because of the brightness of the rings around its equator. Two companion papers in this week’s Nature report on features of its atmosphere, one using data collected by the Cassini mission and the other from over two decades of ground-based observations.

The equatorial stratospheres of Earth and Jupiter oscillate more or less periodically on timescales of about two and four years, respectively. By analysing infrared observations from the Cassini probe, Thierry Fouchet and colleagues discovered that Saturn has an equatorial oscillation like Earth's and Jupiter's, as well as a mid-latitude subsidence that may be associated with the equatorial motion. Glenn Orton and co-workers’ ground-based observations of Saturn's stratospheric emission reveal a similar oscillation.

The period of the oscillation is approximately 15 terrestrial years, which is roughly half of Saturn's year, suggesting the influence of seasonal forcing —rather like the Earth's semi-annual oscillation.

CONTACT

Glenn Orton (Jet Propulsion Laboratory, Pasadena, CA, USA) Author paper [3]
Tel: +1 818 354 2460; E-mail: Glenn.Orton@jpl.nasa.gov

Thierry Fouchet (Observatoire de Paris, Meudon, France) Author paper [4]
Tel: +33 1 45 07 71 11; E-mail: Thierry.Fouchet@obspm.fr

Timothy Dowling (University of Louisville, KY, USA) N&V author
Tel: +1 502 852 3927; E-mail: dowling@louisville.ed