Search Publications
Heavy negative ions in Titan's ionosphere: Altitude and latitude dependence
Lewis, G. R.; Coates, A. J.; Jones, G. H. +4 more
One of the unexpected results of the Cassini mission was the discovery of negative ions at altitudes between 950 and 1400 km in Titan's ionosphere with masses up to 10,000 amu/q [Coates, A.J., Crary, F.J., Lewis, G.R., Young, D.T., Waite Jr., J.H., Sittler Jr., E.C., 2007. Discovery of heavy negative ions in Titan's ionosphere. Geophys. Res. Lett.…
Saturn's north polar cyclone and hexagon at depth revealed by Cassini/VIMS
Nicholson, Philip D.; Fletcher, Leigh N.; Baines, Kevin H. +6 more
A high-speed cyclonic vortex centered on the north pole of Saturn has been revealed by the visual-infrared mapping spectrometer (VIMS) onboard the Cassini-Huygens Orbiter, thus showing that the tropospheres of both poles of Saturn are occupied by cyclonic vortices with winds exceeding 135 m/s. High-spatial-resolution (~200 km per pixel) images acq…
Plasma in Saturn's nightside magnetosphere and the implications for global circulation
Coates, A. J.; Dougherty, M. K.; Thomsen, M. F. +8 more
We present a bulk ion flow map from the nightside, equatorial region of Saturn's magnetosphere derived from the Cassini CAPS ion mass spectrometer data. The map clearly demonstrates the dominance of corotation flow over radial flow and suggests that the flux tubes sampled are still closed and attached to the planet up to distances of 50 RS
Pingos on Earth and Mars
Burr, Devon M.; Tanaka, Kenneth L.; Yoshikawa, Kenji
Pingos are massive ice-cored mounds that develop through pressurized groundwater flow mechanisms. Pingos and their collapsed forms are found in periglacial and paleoperiglacial terrains on Earth, and have been hypothesized for a wide variety of locations on Mars. This literature review of pingos on Earth and Mars first summarizes the morphology of…
Sedimentary deposits in Xanthe Terra: Implications for the ancient climate on Mars
Jaumann, R.; Scholten, F.; Neukum, G. +7 more
A variety of sedimentary deposits is observed in Xanthe Terra, Mars, including Gilbert-type deltas, fan deltas dominated by resedimentation processes, and alluvial fans. Sediments were provided through deeply incised valleys, which were probably incised by both runoff and groundwater sapping. Mass balances based on High-Resolution Stereo Camera (H…
Automatic detection of sub-km craters in high resolution planetary images
Stepinski, Tomasz F.; Urbach, Erik R.
Impact craters are among the most studied geomorphic planetary features because they yield information about the past geological processes and provide a tool for measuring relative ages of observed geologic formations. Surveying impact craters is an important task which traditionally has been achieved by means of visual inspection of images. The s…
Isotopic evolution of the major constituents of Titan's atmosphere based on Cassini data
Mousis, Olivier; Mandt, Kathleen E.; Waite, J. Hunter +5 more
Using Cassini ion neutral mass spectrometer stable isotope observations, we have developed a comprehensive method for modeling the time-evolution of the stable isotopic ratios in Titan's major constituents, N 2, CH 4 and H 2. Our model provides constraints on the initial 14N/ 15N ratio in N
On the amount of heavy molecular ions in Titan's ionosphere
Gurnett, D. A.; Coates, A. J.; Garnier, P. +16 more
We present observational evidence that the ionosphere of Titan below an altitude of 1150 km is a significant source of heavy (>100 amu) molecular organic species. This study is based on measurements by five instruments (RPWS/LP, RPWS/E, INMS, CAPS/ELS, CAPS/IBS) onboard the Cassini spacecraft during three flybys (T17, T18, T32) of Titan. The io…
Heavy ion formation in Titan's ionosphere: Magnetospheric introduction of free oxygen and a source of Titan's aerosols?
Coates, A. J.; Johnson, R. E.; Hartle, R. E. +4 more
Discovery by Cassini's plasma instrument of heavy positive and negative ions within Titan's upper atmosphere and ionosphere has advanced our understanding of ion neutral chemistry within Titan's upper atmosphere, primarily composed of molecular nitrogen, with ~2.5% methane. The external energy flux transforms Titan's upper atmosphere and ionospher…
The distribution of atomic hydrogen and oxygen in the magnetosphere of Saturn
Melin, Henrik; Shemansky, Don E.; Liu, Xianming
The intensity of H Ly α1216A˚ ( 2P- 1S) and OI 1304A˚ ( 2p33s3S-2p4P) is mapped in the magnetosphere of Saturn using the ultraviolet imaging spectrograph (UVIS) [Esposito, L.W., Barth, C.A., Colwell, J.E., Lawrence, G.M., McClintock, W.E., Stewart, A.I.F., Keller, H.U., Korth, A., Lauche, H., …