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Global Mineralogical and Aqueous Mars History Derived from OMEGA/Mars Express Data
Drossart, Pierre; Korablev, Oleg; Forget, F. +43 more
Global mineralogical mapping of Mars by the Observatoire pour la Mineralogie, l'Eau, les Glaces et l'Activité (OMEGA) instrument on the European Space Agency's Mars Express spacecraft provides new information on Mars' geological and climatic history. Phyllosilicates formed by aqueous alteration very early in the planet's history (the ``phyllocian'…
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…
Formation of Glaciers on Mars by Atmospheric Precipitation at High Obliquity
Forget, F.; Montmessin, F.; Head, J. W. +2 more
Surface conditions on Mars are currently cold and dry, with water ice unstable on the surface except near the poles. However, geologically recent glacierlike landforms have been identified in the tropics and the midlatitudes of Mars. The ice has been proposed to originate from either a subsurface reservoir or the atmosphere. We present high-resolu…
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…
Massive-Star Supernovae as Major Dust Factories
Gordon, Karl D.; Kennicutt, Robert C.; Panagia, Nino +15 more
We present late-time optical and mid-infrared observations of the Type II supernova 2003gd in the galaxy NGC 628. Mid-infrared excesses consistent with cooling dust in the ejecta are observed 499 to 678 days after outburst and are accompanied by increasing optical extinction and growing asymmetries in the emission-line profiles. Radiative-transfer…