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Weaker solar wind from the polar coronal holes and the whole Sun
McComas, D. J.; Goldstein, B. E.; Schwadron, N. A. +4 more
Observations of solar wind from both large polar coronal holes (PCHs) during Ulysses' third orbit showed that the fast solar wind was slightly slower, significantly less dense, cooler, and had less mass and momentum flux than during the previous solar minimum (first) orbit. In addition, while much more variable, measurements in the slower, in-ecli…
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…
Decrease in heliospheric magnetic flux in this solar minimum: Recent Ulysses magnetic field observations
Smith, Edward J.; Balogh, Andre
The Ulysses spacecraft has traveled from the solar equator at 1.3 and 5.3 AU to above the polar caps at 2.2 AU three times during the last 17 years and has provided measurements of the solar-heliospheric magnetic field. The open magnetic flux, i.e., the radial component, BR, multiplied by the square of the radial distance, r, is indepen…
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…
Compositional stratigraphy of clay-bearing layered deposits at Mawrth Vallis, Mars
Mustard, J. F.; Wray, J. J.; Ehlmann, B. L. +2 more
Phyllosilicates have previously been detected in layered outcrops in and around the Martian outflow channel Mawrth Vallis. CRISM spectra of these outcrops exhibit features diagnostic of kaolinite, montmorillonite, and Fe/Mg-rich smectites, along with crystalline ferric oxide minerals such as hematite. These minerals occur in distinct stratigraphic…
Variable winds on Venus mapped in three dimensions
Baines, K. H.; Hueso, R.; Sánchez-Lavega, A. +9 more
We present zonal and meridional wind measurements at three altitude levels within the cloud layers of Venus from cloud tracking using images taken with the VIRTIS instrument on board Venus Express. At low latitudes, zonal winds in the Southern hemisphere are nearly constant with latitude with westward velocities of 105 ms-1 at cloud-top…
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…
A comet-like escape of ionospheric plasma from Mars
Barabash, S.; Lundin, R.; Holmström, M. +4 more
New measurements of the ion escape from Mars display a mantle of low-energy ionospheric ions swept from the dayside over the terminator, expanding into the tail in a comet-like fashion. The finding is based on data obtained with new energy settings for the ASPERA-3 ion mass analyzer (IMA), enabling us to also measure cold ionospheric ions. By incl…
Characteristic size and shape of the mirror mode structures in the solar wind at 0.72 AU
Russell, C. T.; Zhang, T. L.; Glassmeier, K. -H. +10 more
We investigate the structure of mirror modes in the solar wind at 0.72 AU using Venus Express magnetic field measurements. The mirror mode structure is identified as the presence of magnetic depression or magnetic ``holes'' in the solar wind with little or no directional change across them. We determine the characteristic size and shape of these s…
Solar forcing and planetary ion escape from Mars
Fedorov, A.; Barabash, S.; Lundin, R. +4 more
The variability of planetary ion escape from Mars is studied using data from the Ion Mass Analyzer, IMA, on Mars Express (MEX). 42 orbits were selected during 17 months for different solar wind conditions, focusing on the low energy (~30 - 800 eV) heavy ion (e.g. O+, O2 + and CO2 +) outflow. A…