Search Publications
Hydrocarbon lakes on Titan: Distribution and interaction with a porous regolith
Callahan, P.; Gim, Y.; Stofan, E. +11 more
Synthetic Aperture Radar (SAR) images of Titan's north polar region reveal quasi-circular to complex features which are interpreted to be liquid hydrocarbon lakes. We investigate methane transport in Titan's hydrologic cycle using the global distribution of lake features. As of May 2007, the SAR data set covers ~22% of the surface and indicates mu…
Titan's inventory of organic surface materials
Kirk, Randolph L.; Lorenz, Ralph D.; Janssen, Michael A. +13 more
Cassini RADAR observations now permit an initial assessment of the inventory of two classes, presumed to be organic, of Titan surface materials: polar lake liquids and equatorial dune sands. Several hundred lakes or seas have been observed, of which dozens are each estimated to contain more hydrocarbon liquid than the entire known oil and gas rese…
Energetic ion precipitation at Titan
Krimigis, S. M.; Waite, J. H.; Cravens, T. E. +3 more
Energetic protons and oxygen ions have been observed in Saturn's outer magnetosphere and can precipitate into Titan's atmosphere where they deposit energy, ionize, and drive ionospheric chemistry. Ion production rates caused by this precipitation are calculated using fluxes of incident 27 keV to 4 MeV protons measured by the Cassini MIMI instrumen…
Evidence for temporal variability of Enceladus' gas jets: Modeling of Cassini observations
Dougherty, Michele K.; Saur, Joachim; Simon, Sven +5 more
Time variability of Enceladus' gas plume is deduced from a joint investigation of Cassini spacecraft magnetic field data obtained during the first three flybys E0, E1 and E2 and neutral density measurements during the E2 flyby with a model that describes Enceladus' plasma interaction with individual jets. We infer a total plume content of ~7 × 10<…
Enceladus: An estimate of heat flux and lithospheric thickness from flexurally supported topography
Neukum, Gerhard; Thomas, Peter C.; Hussmann, Hauke +4 more
We have identified flexural uplift along a rift zone of the Harran Sulci, Enceladus, using Cassini images and stereo-derived topography. On the assumption that the upraised topography is related to a flexed elastic plate, shape modeling yields an effective lithospheric thickness of 0.3 km and, combined with the strength envelope, a mechanical lith…
ENA periodicities at Saturn
Krimigis, S. M.; Mitchell, D. G.; Paranicas, C. +2 more
The Magnetospheric Imaging Instrument (MIMI) on the Cassini spacecraft has observed energetic neutral atoms (ENA) at Saturn for three years from 2004 to 2007. The 20-50 keV hydrogen and 64-144 keV oxygen neutrals were examined for periodic behavior by projecting their images onto a plane perpendicular to Saturn's equatorial plane and summing the e…
Discovery of a transient radiation belt at Saturn
Krupp, N.; Jones, G. H.; Roussos, E. +7 more
Radiation belts have been detected in situ at five planets. Only at Earth however has any variability in their intensity been heretofore observed, in indirect response to solar eruptions and high altitude nuclear explosions. The Cassini spacecraft's MIMI/LEMMS instrument has now detected systematic radiation belt variability elsewhere. We report t…
Large-scale structure of Saturn's E-ring
Morfill, Gregor E.; Horányi, Mihály; Juhász, Antal
Geysers on the recently discovered, geologically active south-polar region of the moon Enceladus are now recognized as the dominant source of material in Saturn's E ring. The ring was traditionally thought to span the region between 3 to 8 R S , where R S is the radius of Saturn. However, new in situ dust measurements indi…
Cassini detection of water-group pick-up ions in the Enceladus torus
Thomsen, M. F.; Wilson, R. J.; Tokar, R. L. +8 more
This study reports direct detection by the Cassini plasma spectrometer of freshly-produced water-group pick-up ions within the proposed Enceladus torus, a radially narrow toroidal region surrounding Saturn that contains a high density of water-group neutrals. This torus is produced by the icy plumes observed near the south pole of Enceladus. The i…
Periodic tilting of Saturn's plasma sheet
Krimigis, S. M.; Mitchell, D. G.; Roelof, E. C. +2 more
From the vantage of the dawn sector, the INCA instrument on Cassini imaged neutral hydrogen atoms (20-50 keV) emitted from the center of the Saturn's plasma sheet for five days during late 2004. Points along the center of the plasma sheet were found from contoured images projected onto the noon-midnight plane; points within 20 RS of Sat…