T. Duxbury

Global Mineralogical and Aqueous Mars History Derived from OMEGA/Mars Express Data

Global mineralogical mapping of Mars by the Observatoire pour la Mineralogie, lEau, les Glaces et lActivité (OMEGA) instrument on the European Space Agencys Mars Express spacecraft provides new information on Mars geological and climatic history. Phyllosilicates formed by aqueous alteration very early in the planets history (the “phyllocian” era) are found in the oldest terrains; sulfates were formed in a second era (the “theiikian” era) in an acidic environment. Beginning about 3.5 billion years ago, the last era (the “siderikian”) is dominated by the formation of anhydrous ferric oxides in a slow superficial weathering, without liquid water playing a major role across the planet.

Perennial water ice identified in the south polar cap of Mars.

The inventory of water and carbon dioxide reservoirs on Mars are important clues for understanding the geological, climatic and potentially exobiological evolution of the planet. From the early mapping observation of the permanent ice caps on the martian poles, the northern cap was believed to be mainly composed of water ice, whereas the southern cap was thought to be constituted of carbon dioxide ice. However, recent missions (NASA missions Mars Global Surveyor and Odyssey) have revealed surface structures, altimetry profiles, underlying buried hydrogen, and temperatures of the south polar regions that are thermodynamically consistent with a mixture of surface water ice and carbon dioxide. Here we present the first direct identification and mapping of both carbon dioxide and water ice in the martian high southern latitudes, at a resolution of 2u2009km, during the local summer, when the extent of the polar ice is at its minimum. We observe that this south polar cap contains perennial water ice in extended areas: as a small admixture to carbon dioxide in the bright regions; associated with dust, without carbon dioxide, at the edges of this bright cap; and, unexpectedly, in large areas tens of kilometres away from the bright cap.

Spirit rover localization and topographic mapping at the landing site of Gusev crater, Mars

[1]xa0By sol 440, the Spirit rover has traversed a distance of 3.76 km (actual distance traveled instead of odometry). Localization of the lander and the rover along the traverse has been successfully performed at the Gusev crater landing site. We localized the lander in the Gusev crater using two-way Doppler radio positioning and cartographic triangulations through landmarks visible in both orbital and ground images. Additional high-resolution orbital images were used to verify the determined lander position. Visual odometry and bundle adjustment technologies were applied to compensate for wheel slippage, azimuthal angle drift, and other navigation errors (which were as large as 10.5% in the Husband Hill area). We generated topographic products, including 72 ortho maps and three-dimensional (3-D) digital terrain models, 11 horizontal and vertical traverse profiles, and one 3-D crater model (up to sol 440). Also discussed in this paper are uses of the data for science operations planning, geological traverse surveys, surveys of wind-related features, and other science applications.

Astrometric observations of Phobos and Deimos with the SRC on Mars Express

Observations of Phobos and Deimos, carried out by the SRC (Super Resolution Channel) on the Mars Express spacecraft between May 2004-April 2005, were used to determine the center-of-figure positions of the two Satellites with accuracies of 0.5-5 km (Phobos) and 1.0 km (Deimos). We find that the Phobos and Deimos orbit predictions from NASA-JPL (Jet Propulsion Laboratory) and ESA-ESOC (European Space Operation Center) differ substantially among each other and also do not agree with the actually observed positions of the satellites. Hence, our new astrometric data may motivate new efforts for Phobos and Deimos orbit modeling.

Phobos: Spectrophotometry between 0.3 and 0.6 μm and IR-radiometry

A 0.3–0.6 (μm UV-visible spectrophotometer and a 5–50 μm radiometer in the KRFM experiment on Phobos 2 measured two groundtracks in the equatorial region of Phobos. Preliminary results indicate that three surface units can be recognized on the basis of differing UV-visible spectral reflectance properties. One of the units is most comparable spectrally to optically darkened mafic material, and a second is comparable either to anhydrous carbonaceous chondrite or to blackened mafic material. Spectral properties of the third unit do not resemble those of known meteorite types. Brightness temperatures measured by the radiometer are consistent with a typlcal surface thermal inertia of 1-3 x 10^(-3) cal/(cm^2) deg S^(1/2), as suggested by previous investigations, implying a lunar-like regolith texture. At least one area of possibly higher thermal inertia has been tentatively identified, where a large degraded crater is crossed by several grooves. These results indicate significant lateral heterogeneity in the optical and textural properties of Phoboss surface.

Photogrammetric analysis of clementine multi-look angle images obtained near mare orientale

Abstract A local point network and a DTM (Digital Terrain Model) are derived from Clementine UVVIS multi-look angle images that were obtained on April 30, 1994, covering a small region of the Lunar Orientale Basin (19.5°S to 15°S and 84.5°W to 86.0°W). The nominal camera pointing and spacecraft trajectory data were photogrammetrically adjusted, a procedure which was found to improve estimates of the coordinates of 41 control points significantly to an internally consistent accuracy of 30 m in the horizontal and 50 m in the height direction. The terrain model correlates well with features identified in the image data, two craters, volcanic constructs, and the dark lavafilled Lacus Veris, located in a topographic depression. The terrain model indicates a steep 2000 m drop in elevation within a range of only 6–8 km towards the center of Orientale Further studies of the lunar topography in this particular region using Clementine stereo data seem well warranted and feasible.