Cross-sectional and longitudinal profiles of valleys and channels in Xanthe Terra on Mars

摘要

On the basis of Mars Orbiter Laser Altimeter data and Viking Orbiter and Mars Global Surveyor images, cross-sectional and longitudinal profiles of channels and valleys were analyzed in Xanthe Terra on Mars. Concave and convex longitudinal profiles were observed at Bahram and Tyras Valles, respectively, while no general trend was visible at other valleys. The longitudinal profiles also showed signs of knickpoints and some short reaches with increasing elevation in the flow direction. The cross-sectional profiles of Tyras Valles show more V-shaped of upper and U-shaped of lower reaches, but the great variety of profiles of other channels suggests a complex relationship with the regional lithology/topography. Also at Tyras Valles the longitudinal profiles could be divided into upper and lower sections that probably formed at different periods under different conditions. The largest observed valleys contain small, previously unnoticed inner channels. There is no correlation between the shape of cross-sectional profiles and the direction of curvature of the valley's long axis (left/right or straight), as is found in riverbeds on the Earth, suggesting that the analyzed depressions are probably valleys and not dry riverbeds, but substantial wind-blown sedimentary infill could have modified their shape too.