Search Publications
Saturn's F ring as seen by Cassini UVIS: Kinematics and statistics
Colwell, Joshua E.; Esposito, Larry W.; Sremčević, Miodrag +1 more
We present a new orbital model of Saturn's F ring core based on 93 occultations by the Cassini Ultraviolet Imaging Spectrograph (UVIS) and the Voyager radio and stellar occultations. We demonstrate that the core, despite its intrinsic variability, is well-described as an inclined, freely precessing ellipse. We find that post-fit residuals with a r…
Illumination conditions at the Asteroid 4 Vesta: Implications for the presence of water ice
Stubbs, Timothy J.; Wang, Yongli
The mean illumination conditions and surface temperatures over one orbital period are calculated for the Asteroid 4 Vesta using a coarse digital elevation model produced from Hubble Space Telescope images. Even with the anticipated effects of finer-scale topography taken into account, it is unlikely that any significant permanently shadowed region…
Classification of F ring features observed in Cassini UVIS occultations
Esposito, Larry W.; Sremčević, Miodrag; Meinke, Bonnie K. +1 more
The Cassini Ultraviolet Imaging Spectrograph (UVIS) has detected 27 statistically significant features in 101 occultations by Saturn’s F ring since July 2004. This work nearly doubles the number of features reported by Esposito et al. (Esposito, L.W. et al. [2008]. Icarus 194, 278-289). As the number of statistically significant features has grown…
Adhesion and collisional release of particles in dense planetary rings
Schmidt, Jürgen; Spahn, Frank; Bodrova, Anna +1 more
We propose a simple theoretical model for aggregative and fragmentative collisions in Saturn’s dense rings. In this model the ring matter consists of a bimodal size distribution: large (meter sized) boulders and a population of smaller particles (tens of centimeters down to dust). The small particles can adhesively stick to the boulders and can be…
Thermospheric/mesospheric temperatures on Venus: Results from ground-based high-resolution spectroscopy of CO 2 in 1990/1991 and comparison to results from 2009 and between other techniques
Mahieux, Arnaud; Sonnabend, Guido; Sornig, Manuela +8 more
We report temperatures in Venus' upper mesosphere/lower thermosphere, deduced from reanalyzing very high resolution infrared spectroscopy of CO 2 emission lines acquired in 1990 and 1991. Kinetic temperatures at ∼110 km altitude (0.15 Pa) are derived from the Doppler width of fully-resolved single line profiles measured near 10.4 µ…
Searching for evidence of hydrothermal activity at Apollinaris Mons, Mars
Markiewicz, Wojciech J.; Heggy, Essam; Marzo, Giuseppe A. +5 more
A multidisciplinary approach involving various remote sensing instruments is used to investigate Apollinaris Mons, a prominent volcano on Mars, as well as the surrounding plains for signs of prolonged hydrologic and volcanic, and possibly hydrothermal activity. The main findings include (1) evidence from laser altimetry indicating the large thickn…
Direct wind measurements from November 2007 in Venus' upper atmosphere using ground-based heterodyne spectroscopy of CO 2 at 10 µm wavelength
Sornig, M.; Sonnabend, G.; Kroetz, P. +2 more
Between November 23 and 28, 2007, the Cologne Tuneable Heterodyne Infrared Spectrometer THIS was installed at the McMath-Pierce Solar Telescope (Kitt Peak, Arizona, USA) to determine zonal wind velocities and to estimate the subsolar-to-antisolar flow. We investigate dynamics in the upper atmosphere of Venus by measuring the Doppler shift of fully…
Mimas' far-UV albedo: Spatial variations
Johnson, Robert E.; Buratti, Bonnie J.; Hendrix, Amanda R. +7 more
We present Cassini Ultraviolet Imaging Spectrograph (UVIS) observations of Mimas at far-ultraviolet wavelengths (170-190 nm) which show an interesting albedo gradient across the anti-saturnian hemisphere. We discuss the photometric behavior of Mimas in the far-UV and review the important exogenic processes and their expected effects, relevant over…
Venusian middle-atmospheric dynamics in the presence of a strong planetary-scale 5.5-day wave
Yamamoto, Masaru; Takahashi, Masaaki
The middle atmospheric dynamics on Venus are investigated using a middle atmosphere general circulation model. The magnitude of the superrotation is sensitive to the amplitude of the planetary-scale waves. In particular, the critical level absorptions of the forced planetary-scale waves might contribute to the maintenance of the superrotation near…
The brightening of Saturn's F ring
Nicholson, Philip D.; Hedman, Matthew M.; Showalter, Mark R. +5 more
Image photometry reveals that the F ring is approximately twice as bright during the Cassini tour as it was during the Voyager flybys of 1980 and 1981. It is also three times as wide and has a higher integrated optical depth. We have performed photometric measurements of more than 4800 images of Saturn's F ring taken over a 5-year period with Cass…