The auroral footprint of Enceladus on Saturn

• Published in: Nature (London) Vol. 472; no. 7343; pp. 331 - 333
• Main Authors: Pryor, Wayne R., Rymer, Abigail M., Mitchell, Donald G., Hill, Thomas W., Young, David T., Saur, Joachim, Jones, Geraint H., Jacobsen, Sven, Cowley, Stan W. H., Mauk, Barry H., Coates, Andrew J., Gustin, Jacques, Grodent, Denis, Gérard, Jean-Claude, Lamy, Laurent, Nichols, Jonathan D., Krimigis, Stamatios M., Esposito, Larry W., Dougherty, Michele K., Jouchoux, Alain J., Stewart, A. Ian F., McClintock, William E., Holsclaw, Gregory M., Ajello, Joseph M., Colwell, Joshua E., Hendrix, Amanda R., Crary, Frank J., Clarke, John T., Zhou, Xiaoyan
• Format: Journal Article Web Resource
• Language: English
• Published: London Nature Publishing Group UK 01.04.2011; Nature Publishing Group
• Subjects: 639/766/33/445/846; Analysis; Astronomy; Astrophysics; Auroras; Aérospatiale, astronomie & astrophysique; Earth, ocean, space; Electrodynamics; Emissions; Enceladus; Enceladus (Satellite); Exact sciences and technology; Footprints; Humanities and Social Sciences; Ionosphere; Ionospheres; magnetospheres; Joining; Jupiter; Jupiter (planet); Jupiter satellites; letter; Moon; multidisciplinary; Observations; Physical, chemical, mathematical & earth Sciences; Physics; Physique, chimie, mathématiques & sciences de la terre; Planetary, asteroid, and satellite characteristics and properties; Planets, their satellites and rings. Asteroids; Saturn; Saturn (Planet); Science; Science (multidisciplinary); Solar system; Space science, astronomy & astrophysics; United States; Saturn planet; Aurorae; Electron beams; Enceladus; Saturn satellite; Magnetic fields; Planetary magnetospheres; Ion beams
• ISSN: 0028-0836; 1476-4687; 1476-4687
• DOI: 10.1038/nature09928

Enceladus makes its mark on Saturn Despite considerable differences between the magnetospheres of Saturn and Jupiter, cryovolcanic activity on Saturn's icy moon Enceladus was suspected to connect the moon to Saturn in a similar way to the electrodynamic coupling seen between Jupiter and its Galilean moons. This suspicion has been confirmed. Analysis of data collected during a Cassini fly-by within 55 kilometres of Enceladus in August 2008 reveals magnetic field-aligned ion and electron beam emissions from Enceladus with sufficient power to stimulate detectable aurora. Subsequent observations with the Cassini ultraviolet imaging spectrometer system detected the expected Enceladus auroral footprint in Saturn's atmosphere. Although there are substantial differences between the magnetospheres of Jupiter and Saturn, it has been suggested that cryovolcanic activity at Enceladus 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 could lead to electrodynamic coupling between Enceladus and Saturn like that which links Jupiter with Io, Europa and Ganymede. Powerful field-aligned electron beams associated with the Io–Jupiter coupling, for example, create an auroral footprint in Jupiter’s ionosphere 10 , 11 . Auroral ultraviolet emission associated with Enceladus–Saturn coupling is anticipated to be just a few tenths of a kilorayleigh (ref. 12 ), about an order of magnitude dimmer than Io’s footprint and below the observable threshold, consistent with its non-detection 13 . Here we report the detection of magnetic-field-aligned ion and electron beams (offset several moon radii downstream from Enceladus) with sufficient power to stimulate detectable aurora, and the subsequent discovery of Enceladus-associated aurora in a few per cent of the scans of the moon’s footprint. The footprint varies in emission magnitude more than can plausibly be explained by changes in magnetospheric parameters—and as such is probably indicative of variable plume activity.