Host: The Japanese Society for Planetary Sciences: Local Organizing Committee for 2006 Fall Meeting
About 200 Venusian channels have been classified into 6 types. Sinuous rilles and canali are both composed of a single main conduit with meandering. Sinuous rilles are typically from several 10s to a hundred and several 10s of km long and show narrowing with downstream distance. Canali are from several 100s to several 1000s of km long and have characteristics similar to terrestrial rivers such as cut-off meanders and point-bars. First, we reconstructed cross-sectional topography of 10 sinuous rilles and Baltis Vallis, a 6800-km long canali-type channel, from the brightness of Magellan SAR images. The groove-like morphology as well as the paucity of levee structures indicates that both sinuous rilles and Baltis Vallis are erosional in origin. Second, we examined depth distributions along the channels on the basis of the cross-sectional profiles. The depth of sinuous rilles decreases with increasing distance. The decreasing trend of depth consistent with numerical results of thermal erosional models indicates thermal erosion. In contrast, the undulations in depth distribution along the Baltis Vallis can be explained by mechanical erosion. Difference in formational process between Baltis Vallis and sinuous rilles is considered to reflect the diversity of igneous activity on Venus.
