Search Publications
Co-registration of laser altimeter tracks with digital terrain models and applications in planetary science
Oberst, J.; Gläser, P.; Haase, I. +1 more
We have derived algorithms and techniques to precisely co-register laser altimeter profiles with gridded Digital Terrain Models (DTMs), typically derived from stereo images. The algorithm consists of an initial grid search followed by a least-squares matching and yields the translation parameters at sub-pixel level needed to align the DTM and the …
Mars surface phase function constrained by orbital observations
Vincendon, Mathieu
The bidirectional photometric properties of the surface of Mars describe how remote measurements of surface reflectance can be linked to hemispherical albedo used for energy balance calculations. A simple Lambert's law is frequently assumed for global data processing, even though several local studies have revealed the complexity of Mars surface p…
Scaling relationships and concavity of small valley networks on Mars
Fassett, Caleb I.; Penido, Julita C.; Som, Sanjoy M.
Valley networks are widely interpreted as the preserved erosional record of water flowing across the martian surface. The manner in which valley morphometric properties scale with drainage area has been widely examined on Earth. Earlier studies assessing these properties on Mars have suggested that martian valleys are morphometrically distinct fro…
The origin of Phobos grooves from ejecta launched from impact craters on Mars: Tests of the hypothesis
Head, James W.; Ramsley, Kenneth R.
The surface of the martian moon Phobos is characterized by parallel and intersecting grooves that bear resemblance to secondary crater chains observed on planetary surfaces. Murray (2011) has hypothesized that the main groove-forming process on Phobos is the intersection of Phobos with ejecta from primary impact events on Mars to produce chains of…
Composition of Titan's upper atmosphere from Cassini UVIS EUV stellar occultations
Zhang, X.; Shemansky, D. E.; Yung, Y. L. +1 more
Identifying seasonal and spatial variability in Titan's atmospheric structure is a key factor in improving theoretical models of atmospheric loss and understanding the physical processes that control the loss rate. In this work, the extreme ultraviolet (EUV) stellar occultation lightcurves from the Cassini Ultraviolet Imaging Spectrograph (UVIS) e…
Morphotectonic features on Titan and their possible origin
Coustenis, Athena; Solomonidou, Anezina; Bampasidis, Georgios +5 more
Spectro-imaging and radar measurements by the Cassini-Huygens mission suggest that some of the Saturnian satellites may be geologically active and could support tectonic processes. In particular Titan, Saturn's largest moon, possesses a complex and dynamic geology as witnessed by its varied surface morphology resulting from aeolian, fluvial, and p…
The Hohmann-Parker effect measured by the Mars Science Laboratory on the transfer from Earth to Mars: Consequences and opportunities
Frahm, R. A.; Wimmer-Schweingruber, R. F.; Christian, E. R. +33 more
We show that a spacecraft launched from Earth towards Mars following a Hohmann minimum energy transfer trajectory has a strong tendency to remain well-connected magnetically to Earth, in the early phase of the transfer, or to Mars in the late phase, via the Parker spiral magnetic field. On the return trip, the spacecraft would remain reasonably we…
Redistribution of lunar polar water to mid-latitudes and its role in forming an OH veneer
Delory, G. T.; Halekas, J. S.; Farrell, W. M. +4 more
We suggest that energization processes like ion sputtering and impact vaporization can eject/release polar water molecules residing within cold trapped regions with sufficient velocity to allow their redistribution to mid-latitudes. We consider the possibility that these polar-ejected molecules can contribution to the water/OH veneer observed as a…
Modeling the seasonal variability of the plasma environment in Saturn's magnetosphere between main rings and Mimas
Johnson, R. E.; Elrod, M. K.; Tseng, W. -L.
The detection of O2+ and O+ ions over Saturn's main rings by the Cassini INMS and CAPS instruments at Saturn orbit insertion (SOI) in 2004 confirmed the existence of the ring atmosphere and ionosphere. The source mechanism was suggested to be primarily photolytic decomposition of water ice producing neutral O2…
Variability in ionospheric total electron content at Mars
Withers, Paul; Kofman, Wlodek; Mendillo, Michael +3 more
The Mars Express (MEX) mission includes a multi-purpose radio instrument called the Mars Advanced Radar for Subsurface and Ionospheric Sounding (MARSIS). When used in its ionospheric-penetrating subsurface sounder (SS) radar mode, a by-product of the MARSIS observations is the ray-path-integral of electron densities, called the total electron cont…