Paper No. 6
Presentation Time: 3:00 PM
SINUOUS RILLES IN HESPERIA PLANUM, MARS: WATER, LAVA, OR SOMETHING ELSE?
Hesperia Planum, Mars, contains sinuous rilles. These rilles are typically <100 m wide along their length, tens to hundreds of kilometers long, and have no obvious sources or sinks. They are affected by wrinkle ridge topography, indicating that the rilles post-date wrinkle ridge formation. Therefore, the rilles are among the youngest endogenic features in Hesperia Planum, and their origin reveals important information about Mars’ recent past. Although it is widely accepted that Hesperia Planum is composed of fluid basaltic lava flows, the origin of its sinuous rilles may not be volcanic. One such rille is located in the center of an elongate lobate deposit; this deposit appears to be associated with, rather than cross-cut by, the rille. The nature of this deposit is unclear. Another rille appears to be genetically associated with Reull Vallis. The Hesperia Planum rilles are filled with younger (probably aeolian) deposits, although the observed slopes on the visible portions of the rille walls suggest a rectangular or u-shaped (rather than v-shaped) cross-section.
To constrain the origin of the Hesperia Planum rilles, we are comparing their morphometry with lunar volcanic sinuous rilles. Lunar sinuous rilles formed by flowing lava, although the precise roles played by erosional, constructional, and tectonic processes continue to be debated. It is likely that the morphologic diversity of lunar sinuous rilles reflects a similar diversity in their origin and evolution. Here, we present our preliminary results. Using available data from the Lunar Reconnaissance Orbiter, and focusing our initial studies on rilles near Aristarchus plateau, we compare parameters that can be measured both on the Moon and on Hesperia Planum: length, width, gradient of the surrounding plains, sinuousity, and radius of curvature for individual meanders. For comparison, we will obtain similar measurements for martian channels and gullies that have a purported fluvial origin.