Search Publications
Transient surface liquid in Titan's polar regions from Cassini
Lorenz, R. D.; Wye, L. C.; Zebker, H. A. +12 more
Cassini RADAR images of Titan's south polar region acquired during southern summer contain lake features which disappear between observations. These features show a tenfold increases in backscatter cross-section between images acquired one year apart, which is inconsistent with common scattering models without invoking temporal variability. The mo…
The haze and methane distributions on Neptune from HST-STIS spectroscopy
Karkoschka, Erich; Tomasko, Martin G.
We analyzed a data cube of Neptune acquired with the Hubble STIS spectrograph on August 3, 2003. The data covered the full afternoon hemisphere at 0.1 arcsec spatial resolution between 300 and 1000 nm wavelength at 1 nm resolution. Navigation was accurate to 0.004 arcsec and 0.05 nm. We constrained the vertical aerosol structure with radiative tra…
Redefinition of the crater-density and absolute-age boundaries for the chronostratigraphic system of Mars
Werner, S. C.; Tanaka, K. L.
For the boundaries of each chronostratigraphic epoch on Mars, we present systematically derived crater-size frequencies based on crater counts of geologic referent surfaces and three proposed "standard" crater size-frequency production distributions as defined by (a) a simple -2 power law, (b) Neukum and Ivanov, (c) Hartmann. In turn, these crater…
Heavy ion escape from Mars, influence from solar wind conditions and crustal magnetic fields
Barabash, Stas; Lundin, Rickard; Nilsson, Hans +5 more
We have used more than 4 years of Mars Express ion data to estimate the escape of heavy ions ( O+,O2+ and CO2+) from Mars. To take the limited field of view of the instrument into account, the data has been binned into spatial bins and angular bins to create average distribution functions for different positions in the near Mars space. …
Plasma, plumes and rings: Saturn system dynamics as recorded in global color patterns on its midsize icy satellites
Johnson, Robert E.; Hamilton, Douglas P.; McKinnon, William B. +4 more
New global maps of the five inner midsize icy saturnian satellites, Mimas, Enceladus, Tethys, Dione, and Rhea, have been constructed in three colors (UV, Green and near-IR) at resolutions of 1 km/pixel. The maps reveal prominent global patterns common to several of these satellites but also three major color features unique to specific satellites …
Energy deposition and primary chemical products in Titan’s upper atmosphere
Lewis, G. R.; Coates, A. J.; Galand, M. +4 more
Cassini results indicate that solar photons dominate energy deposition in Titan's upper atmosphere. These dissociate and ionize nitrogen and methane and drive the subsequent complex organic chemistry. The improved constraints on the atmospheric composition from Cassini measurements demand greater precision in the photochemical modeling. Therefore,…
The mesosphere and lower thermosphere of Titan revealed by Cassini/UVIS stellar occultations
Sandel, B. R.; West, R. A.; Yelle, R. V. +5 more
Stellar occultations observed by the Cassini/UVIS instrument provide unique data that probe the mesosphere and lower thermosphere of Titan at altitudes between 400 and 1400 km. This region is a site of complex photochemistry that forms hydrocarbon and nitrile species, and plays a crucial role in the formation of the organic hazes observed in the s…
Organic sedimentary deposits in Titan's dry lakebeds: Probable evaporite
Nicholson, Philip D.; Sotin, Christophe; Barnes, Jason W. +14 more
We report the discovery of organic sedimentary deposits at the bottom of dry lakebeds near Titan's north pole in observations from the Cassini Visual and Infrared Mapping Spectrometer (VIMS). We show evidence that the deposits are evaporitic, making Titan just the third known planetary body with evaporitic processes after Earth and Mars, and is th…
Methane on Uranus: The case for a compact CH 4 cloud layer at low latitudes and a severe CH 4 depletion at high-latitudes based on re-analysis of Voyager occultation measurements and STIS spectroscopy
Sromovsky, L. A.; Fry, P. M.; Kim, J. H.
Lindal et al. (Lindal, G.F., Lyons, J.R., Sweetnam, D.N., Eshleman, V.R., Hinson, D.P. [1987]. J. Geophys. Res. 92 (11), 14987-15001) presented a range of temperature and methane profiles for Uranus that were consistent with 1986 Voyager radio occultation measurements of refractivity versus altitude. A localized refractivity slope variation near 1…
Saturn's zonal wind profile in 2004-2009 from Cassini ISS images and its long-term variability
Hueso, R.; Sánchez-Lavega, A.; García-Melendo, E. +1 more
Five years of Cassini Imaging Science Subsystem images, from 2004 to 2009, are analyzed in this work to retrieve global zonal wind profiles of Saturn's northern and southern hemispheres in the methane absorbing bands at 890 and 727 nm and in their respective adjacent continuum wavelengths of 939 and 752 nm. A complete view of Saturn's global circu…