MARTIAN CHAOS: EVIDENCE OF SLOPE RETREAT WITHIN THE LARGEST KNOWN CHANNEL SYSTEM

Martian chaotic terrain -- in particular, those terrains that fall within the Ganges, Capri, and Eos chasmata -- is characterized primarily by fractured mesa-like features, spur-ridged knobs, densely populated knobby fields, and fairly indeterminable small knobs and cone-like structures.

The chaotic terrain within the Chryse outflow channels may be a source for the original erosion processes that carved the notable channel systems. Chaotic terrain may be a primary feature of collapse due to subsurface volatile sapping, phreatovolcanism, volatile release with glacial interaction, or as features associated with catastrophic floods analogous to those that carved the Channeled Scablands. However, recent data from the Mars Global Surveyor and Mars Odyssey offers new insight into chaotic terrain as secondary features of slope retreat and collapse following the initial formation of Valles Marineris and the Chryse outflow channels.

Using ESRI GIS programs, I processed data from the high-resolution thermal inertia information generated by THEMIS, from narrow angle visible light images produced by the Mars Orbiter Camera, and from elevation data collected by the Mars Orbiter Laser Altimeter. I was able to digitize the entire region of Valles Marineris and the Chryse outflow channels and withdraw exceptionally accurate physical characteristics from the morphologic features that comprise the previously unattainable chaotic terrain: desiccated mesas, spur-ridged knobs, the smaller knobs that dominate knobby fields, the far less robust cone-like structures, as well as regional slumping and alluvial fan-like elements. Digitization of this terrain included basal area, thickness, slope, aspect, and orientation data for each individual feature, and I classified the features according to the data. Additionally, I was able to process volumes of particular chasmata and create a preliminary estimate of the total amount of sediment loss from individual canyons. Along with numerical and statistical data, I was able to generate several maps and three-dimensional models of voids that dwarf the Grand Canyon.