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Cassini Observes the Active South Pole of Enceladus
Burns, J. A.; Neukum, G.; Wagner, R. +22 more
Cassini has identified a geologically active province at the south pole of Saturn's moon Enceladus. In images acquired by the Imaging Science Subsystem (ISS), this region is circumscribed by a chain of folded ridges and troughs at ~55°S latitude. The terrain southward of this boundary is distinguished by its albedo and color contrasts, elevated te…
Cassini Ion and Neutral Mass Spectrometer: Enceladus Plume Composition and Structure
Ip, Wing-Huen; McNutt, Ralph L.; Waite, J. Hunter +11 more
The Cassini spacecraft passed within 168.2 kilometers of the surface above the southern hemisphere at 19:55:22 universal time coordinated on 14 July 2005 during its closest approach to Enceladus. Before and after this time, a substantial atmospheric plume and coma were observed, detectable in the Ion and Neutral Mass Spectrometer (INMS) data set o…
Cassini Encounters Enceladus: Background and the Discovery of a South Polar Hot Spot
Buratti, B. J.; Hendrix, A. R.; Spencer, J. R. +7 more
The Cassini spacecraft completed three close flybys of Saturn's enigmatic moon Enceladus between February and July 2005. On the third and closest flyby, on 14 July 2005, multiple Cassini instruments detected evidence for ongoing endogenic activity in a region centered on Enceladus' south pole. The polar region is the source of a plume of gas and d…
Enceladus' Water Vapor Plume
West, R.; Pryor, W.; Stewart, A. I. F. +5 more
The Cassini spacecraft flew close to Saturn's small moon Enceladus three times in 2005. Cassini's UltraViolet Imaging Spectrograph observed stellar occultations on two flybys and confirmed the existence, composition, and regionally confined nature of a water vapor plume in the south polar region of Enceladus. This plume provides an adequate amount…
Episodic outgassing as the origin of atmospheric methane on Titan
Sotin, Christophe; Lunine, Jonathan I.; Tobie, Gabriel
Saturn's largest satellite, Titan, has a massive nitrogen atmosphere containing up to 5 per cent methane near its surface. Photochemistry in the stratosphere would remove the present-day atmospheric methane in a few tens of millions of years. Before the Cassini-Huygens mission arrived at Saturn, widespread liquid methane or mixed hydrocarbon seas …
The Sand Seas of Titan: Cassini RADAR Observations of Longitudinal Dunes
Lorenz, R. D.; Stiles, B.; Kelleher, K. +37 more
The most recent Cassini RADAR images of Titan show widespread regions (up to 1500 kilometers by 200 kilometers) of near-parallel radar-dark linear features that appear to be seas of longitudinal dunes similar to those seen in the Namib desert on Earth. The Ku-band (2.17-centimeter wavelength) images show ~100-meter ridges consistent with duneforms…
Identification of a Dynamic Atmosphere at Enceladus with the Cassini Magnetometer
Russell, C. T.; Dougherty, M. K.; Khurana, K. K. +4 more
The Cassini magnetometer has detected the interaction of the magnetospheric plasma of Saturn with an atmospheric plume at the icy moon Enceladus. This unanticipated finding, made on a distant flyby, was subsequently confirmed during two follow-on flybys, one very close to Enceladus. The magnetometer data are consistent with local outgassing activi…
Cassini Dust Measurements at Enceladus and Implications for the Origin of the E Ring
Schmidt, Jürgen; Sremčević, Miodrag; Albers, Nicole +13 more
During Cassini's close flyby of Enceladus on 14 July 2005, the High Rate Detector of the Cosmic Dust Analyzer registered micron-sized dust particles enveloping this satellite. The dust impact rate peaked about 1 minute before the closest approach of the spacecraft to the moon. This asymmetric signature is consistent with a locally enhanced dust pr…
The Gravity Field of the Saturnian System from Satellite Observations and Spacecraft Tracking Data
Jacobson, R. A.; Owen, W. M., Jr.; Mackenzie, R. A. +11 more
We present values for the masses of Saturn and its major satellites, the zonal harmonics in the spherical harmonic expansion of Saturn's gravitational potential, and the orientation of the pole of Saturn. We determined these values using an extensive data set: satellite astrometry from Earth-based observatories and the Hubble Space Telescope; Eart…
Titan's methane cycle
Atreya, Sushil K.; Ferri, Francesca; Niemann, Hasso B. +5 more
Methane is key to sustaining Titan's thick nitrogen atmosphere. However, methane is destroyed and converted to heavier hydrocarbons irreversibly on a relatively short timescale of approximately 10-100 million years. Without the warming provided by CH 4-generated hydrocarbon hazes in the stratosphere and the pressure induced opacity in t…