Volumetric Analysis of the Reull Vallis Fluvial System in the Eastern Hellas Region of Mars: Investigations into the Contributions of Water

Eileen Capitoli, University of Pennsylvania

Presented to the Faculties of the University of Pennsylvania in Partial Fulfillment of the Requirements for the Degree of Master of Science in Applied Geosciences, 2008.

Abstract

In this study I make volume estimates of the different parts of the Reull Vallis fluvial system in order to determine the contributions of water to this system. Reull Vallis is an outflow channel located east of Hellas Basin in the Hesperia Planum and Promethei Terra regions of Mars. Reull Vallis consists of several parts. Its source area (segment 1) is believed to have provided the water for the main canyon (segments 2 and 3). Teviot Vallis is an additional source area that enlarged segment 3 downstream. In between segments 1 and 2 is a large topographic depression called the Morpheos Basin. This basin is believed to have stored the effluents of segment 1 until it breached its run and carved segment 2. The extent of the basin is defined by the 650 m contour level. Due to the Morpheos Basin being much larger in volume than segments 1 and 2, I chose to measure the Morpheos Basin at lower contour levels, in addition to the 650 m contour level, suggesting only the western side of the basin may have been filled with water. I conducted my measurements using the Mars Orbiter Laser Altimeter (MOLA) 64 pixels/degree Digital Elevation Model (DEM) with the IDL-based (Interactive Data Language) module GRIDVIEW. My results support segment 1 as being the sole source area for segment 2 and that the Morpheos Basin was likely filled to one of the lower contour levels. My results also show that segment 3 is significantly greater than its source areas (segment 2 and Teviot Vallis). Several possible factors may explain this; (1) A possible second release of water from Teviot Vallis, (2) The presence of a pre-existing aquifer in the area around segment 3, (3) The drastic slope increase in the lower part of segment 2 may have increased eroding power of the water as it approached segment 3, (4) Sediment buildup on the floors of the source channels could be underestimating their volumes, (5) A blocked connection between Reull Vallis and Harmakhis Vallis may have resulted in backcutting of segment 3.