Search Publications
The Interaction of the Atmosphere of Enceladus with Saturn's Plasma
Gurnett, D. A.; Lewis, G. R.; Coates, A. J. +10 more
During the 14 July 2005 encounter of Cassini with Enceladus, the Cassini Plasma Spectrometer measured strong deflections in the corotating ion flow, commencing at least 27 Enceladus radii (27 × 252.1 kilometers) from Enceladus. The Cassini Radio and Plasma Wave Science instrument inferred little plasma density increase near Enceladus. These data a…
Evidence for a Polar Ethane Cloud on Titan
Baines, K. H.; Jaumann, R.; Clark, R. +11 more
Spectra from Cassini's Visual and Infrared Mapping Spectrometer reveal the presence of a vast tropospheric cloud on Titan at latitudes 51° to 68° north and all longitudes observed (10° to 190° west). The derived characteristics indicate that this cloud is composed of ethane and forms as a result of stratospheric subsidence and the particularly coo…
A Clathrate Reservoir Hypothesis for Enceladus' South Polar Plume
Spencer, John R.; Kieffer, Susan W.; Lu, Xinli +3 more
We hypothesize that active tectonic processes in the south polar terrain of Enceladus, the 500-kilometer-diameter moon of Saturn, are creating fractures that cause degassing of a clathrate reservoir to produce the plume documented by the instruments on the Cassini spacecraft. Advection of gas and ice transports energy, supplied at depth as latent …
Explaining the Color Distributions of Globular Cluster Systems in Elliptical Galaxies
Yoon, Suk-Jin; Lee, Young-Wook; Yi, Sukyoung Ken
The colors of globular clusters in most large elliptical galaxies are bimodal. This is generally taken as evidence for the presence of two cluster subpopulations that have different geneses. However, here we find that, because of the nonlinear nature of the metallicity-to-color transformation, a coeval group of old clusters with a unimodal metalli…
A Long-Period, Violently Variable X-ray Source in a Young Supernova Remnant
Caraveo, P. A.; Bignami, G. F.; Tiengo, A. +2 more
Observations with the Newton X-ray Multimirror Mission satellite show a strong periodic modulation at 6.67 +/- 0.03 hours of the x-ray source at the center of the 2000-year-old supernova remnant RCW 103. No fast pulsations are visible. If genetically tied to the supernova remnant, the source could either be an x-ray binary, composed of a compact o…
Plasma Acceleration Above Martian Magnetic Anomalies
Coates, A. J.; Kallio, E.; Fedorov, A. +20 more
Auroras are caused by accelerated charged particles precipitating along magnetic field lines into a planetary atmosphere, the auroral brightness being roughly proportional to the precipitating particle energy flux. The Analyzer of Space Plasma and Energetic Atoms experiment on the Mars Express spacecraft has made a detailed study of acceleration p…
The Second Ring-Moon System of Uranus: Discovery and Dynamics
Showalter, Mark R.; Lissauer, Jack J.
Deep exposures of Uranus taken with the Hubble Space Telescope reveal two small moons and two faint rings. All of them orbit outside of Uranus's previously known (main) ring system but are interior to the large, classical moons. The outer new moon, U XXVI Mab, orbits at roughly twice the radius of the main rings and shares its orbit with a dust ri…
Probing the Faintest Stars in a Globular Star Cluster
Anderson, Jay; Rich, R. Michael; Stetson, Peter B. +10 more
NGC 6397 is the second closest globular star cluster to the Sun. Using 5 days of time on the Hubble Space Telescope, we have constructed an ultradeep color-magnitude diagram for this cluster. We see a clear truncation in each of its two major stellar sequences. Faint red main-sequence stars run out well above our observational limit and near to th…
Saturn's Spokes: Lost and Found
Porco, C. C.; Horányi, M.; Mitchell, C. J. +1 more
The spokes are intermittently appearing radial markings in Saturn's B ring that are believed to form when micrometer-sized dust particles are levitated above the ring by electrostatic forces. First observed by the Voyagers, the spokes disappeared from October 1998 until September 2005, when the Cassini spacecraft saw them reappear. The trajectorie…
Enceladus' Varying Imprint on the Magnetosphere of Saturn
Krupp, N.; Woch, J.; Dougherty, M. K. +6 more
The bombardment of Saturn's moon Enceladus by >20-kiloelectron volt magnetospheric particles causes particle flux depletions in regions magnetically connected to its orbit. Irrespective of magnetospheric activity, proton depletions are persistent, whereas electron depletions are quickly erased by magnetospheric processes. Observations of these …