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Discovery of heavy negative ions in Titan's ionosphere
Lewis, G. R.; Coates, A. J.; Sittler, E. C. +3 more
Titan's ionosphere contains a rich positive ion population including organic molecules. Here, using CAPS electron spectrometer data from sixteen Titan encounters, we reveal the existence of negative ions. These ions, with densities up to ~100 cm-3, are in mass groups of 10-30, 30-50, 50-80, 80-110, 110-200 and 200+ amu/charge. During on…
Pressurized oceans and the eruption of liquid water on Europa and Enceladus
Manga, M.; Wang, C. -Y.
It is difficult for liquid water to erupt onto the surface of icy satellites, such as Europa and Enceladus, because liquid water is more dense than ice. If the ice shell thickens, the volume expansion of ice upon freezing increases pressure in the subsurface ocean. The excess pressure is determined by a balance between compression of ocean water a…
A Saturnian longitude system based on a variable kilometric radiation period
Gurnett, D. A.; Kurth, W. S.; Averkamp, T. F. +2 more
This paper describes a longitude system for Saturn which is locked to the period of Saturn kilometric radiation. Because the apparent radio emission period varies with time, the period used in the system is allowed to vary. The resulting system results in the 'diurnal' peak of the radio emission occurring when the subsolar longitude is 100°, as wa…
Strong rapid dipolarizations in Saturn's magnetotail: In situ evidence of reconnection
Russell, C. T.; Dougherty, M. K.; Jackman, C. M. +3 more
The oppositely directed magnetic field in the kronian magnetic tail is expected eventually to reconnect across the current sheet, allowing plasma to escape in an anti-solar direction down the tail. This reconnection process accelerates ions and electrons both toward and away from the planet, allowing the magnetotail to relax to a more dipolar conf…
Titan's young surface: Initial impact crater survey by Cassini RADAR and model comparison
Lorenz, R. D.; Anderson, Y. Z.; Lunine, J. I. +9 more
Cassini's Radar instrument has mapped over 10% of Titan's surface through the T18 flyby in August 2006 and has detected remarkably few impact craters. Three impact craters have been conclusively identified and named, and a handful of unconfirmed candidate impact structures are documented. These results indicate that the overall crater density is a…
Ring current at Saturn: Energetic particle pressure in Saturn's equatorial magnetosphere measured with Cassini/MIMI
Krupp, N.; Krimigis, S. M.; Mitchell, D. G. +5 more
The Magnetospheric Imaging Instrument (MIMI) on the Cassini spacecraft provides measurements of the energetic ion population within the magnetosphere of Saturn. Energetic ion directional intensities, energy spectra and ion composition, are measured by the Charge Energy Mass Spectrometer (CHEMS) over the range ~3 to 236 keV per charge and by the Lo…
Ionospheric electrons in Titan's tail: Plasma structure during the Cassini T9 encounter
Coates, A. J.; Hartle, R. E.; Sittler, E. C. +6 more
We present results from the CAPS electron spectrometer obtained during the downstream flyby of Titan on 26 December 2005, which occurred during a period of enhanced plasma pressure inside the magnetosphere. The electron data show an unusual split signature with two principal intervals of interest outside the nominal corotation wake. Interval 1 sho…
Convection in Enceladus' ice shell: Conditions for initiation
McKinnon, William B.; Barr, Amy C.
Observations of Enceladus by the Cassini spacecraft indicate that this tiny Saturnian moon is geologically active, with plumes of water vapor and ice particles erupting from its southern polar region. This activity suggests that tidal dissipation has become spatially localized, perhaps due to a compositional, rheological, and/or thermal anomaly in…
Role of photoionization in the formation of complex organic molecules in Titan's upper atmosphere
Imanaka, Hiroshi; Smith, Mark A.
Recent observations by the Cassini Orbiter suggest that complex organic chemistry occurs in the upper atmosphere of Titan. To understand the role of EUV-VUV light in the complex organic chemistry of Titan's upper atmosphere, we investigate the formation of gaseous species from a N2/CH4 gas mixture as a function of irradiation…
Mass of Saturn's magnetodisc: Cassini observations
André, N.; Coates, A. J.; Russell, C. T. +5 more
Saturn's ring current was observed by Pioneer 11 and the two Voyager spacecraft to extend 8-16 R S in the equatorial plane and appeared to be driven by stress balance with the centrifugal force. We present Cassini observations that show thin current sheets on the dawn flank of Saturn's magnetosphere, symptomatic of the formation of a …