Search Publications
The timing of martian valley network activity: Constraints from buffered crater counting
Head, James W.; Fassett, Caleb I.
Valley networks, concentrations of dendritic channels that often suggest widespread pluvial and fluvial activity, have been cited as indicators that the climate of Mars differed significantly in the past from the present hyperarid cold desert conditions. Some researchers suggest that the change in climate was abrupt, while others favor a much more…
Valley network-fed, open-basin lakes on Mars: Distribution and implications for Noachian surface and subsurface hydrology
Head, James W.; Fassett, Caleb I.
A new catalog of 210 open-basin lakes (lakes with outlet valleys) fed by valley networks shows that they are widely distributed in the Noachian uplands of Mars. In order for an outlet valley to form, water must have ponded in the basin to at least the level of the outlet. We use this relationship and the present topography to directly estimate the…
Tidal heating and the long-term stability of a subsurface ocean on Enceladus
Nimmo, Francis; Roberts, James H.
Tidal dissipation has been suggested as the heat source for the south polar thermal anomaly on Enceladus. We find that under present-day conditions and assuming Maxwellian behavior, tidal dissipation is negligible in the silicate core. Dissipation may be significant in the ice shell if the shell is decoupled from the silicate core by a subsurface …
Dunes on Titan observed by Cassini Radar
Lorenz, R. D.; Callahan, P.; Lunine, J. I. +13 more
Thousands of longitudinal dunes have recently been discovered by the Titan Radar Mapper on the surface of Titan. These are found mainly within ±30° of the equator in optically-, near-infrared-, and radar-dark regions, indicating a strong proportion of organics, and cover well over 5% of Titan's surface. Their longitudinal duneform, interactions wi…
North polar region of Mars: Advances in stratigraphy, structure, and erosional modification
Herkenhoff, Kenneth E.; Tanaka, Kenneth L.; Skinner, James A. +5 more
We have remapped the geology of the north polar plateau on Mars, Planum Boreum, and the surrounding plains of Vastitas Borealis using altimetry and image data along with thematic maps resulting from observations made by the Mars Global Surveyor, Mars Odyssey, Mars Express, and Mars Reconnaissance Orbiter spacecraft. New and revised geographic and …
Compositional mapping of Saturn's satellite Dione with Cassini VIMS and implications of dark material in the Saturn system
Nicholson, Philip D.; Baines, Kevin H.; Buratti, Bonnie J. +9 more
Cassini VIMS has obtained spatially resolved imaging spectroscopy data on numerous satellites of Saturn. A very close fly-by of Dione provided key information for solving the riddle of the origin of the dark material in the Saturn system. The Dione VIMS data show a pattern of bombardment of fine, sub-0.5-µm diameter particles impacting the s…
Titan's middle-atmospheric temperatures and dynamics observed by the Cassini Composite Infrared Spectrometer
Nixon, Conor A.; Achterberg, Richard K.; Flasar, F. Michael +2 more
The Composite Infrared Radiometer-Spectrometer (CIRS) instrument, on the NASA Cassini Saturn orbiter, has been acquiring thermal emission spectra from the atmosphere of Titan since orbit insertion in 2004. Observation sequences for measuring stratospheric temperatures have been obtained using both a nadir mapping mode and a limb viewing mode. The …
Spectral and geological study of the sulfate-rich region of West Candor Chasma, Mars
Gendrin, Aline; Mangold, Nicolas; Bibring, Jean-Pierre +7 more
Sulfates have been discovered by the OMEGA spectrometer in different locations of the planet Mars. They are strongly correlated to light toned layered deposits in the equatorial regions. West Candor Chasma is the canyon with the thickest stack of layers and one with the largest area covered by sulfates. A detailed study coupling mineralogy derived…
Observation of the hydrogen corona with SPICAM on Mars Express
Leblanc, F.; Bertaux, J. L.; Quémerais, E. +1 more
A series of seven dedicated Lyman- α observations of exospheric atomic hydrogen in the martian corona were performed in March 2005 with the ultraviolet spectrometer SPICAM on board Mars Express. Two types of observations are analyzed, observations at high illumination (for a solar zenith angle SZA equal to 30°) and observations at low illumination…
Spectroscopy, morphometry, and photoclinometry of Titan's dunefields from Cassini/VIMS
Sotin, Christophe; Barnes, Jason W.; Rodriguez, Sebastien +10 more
Fine-resolution (500 m/pixel) Cassini Visual and Infrared Mapping Spectrometer (VIMS) T20 observations of Titan resolve that moon's sand dunes. The spectral variability in some dune regions shows that there are sand-free interdune areas, wherein VIMS spectra reveal the exposed dune substrate. The interdunes from T20 are, variously, materials that …