HR: 1340h
AN: P23B-0192    [Abstracts]
TI: Stratigraphy of Ganges Mensa, Mars
AU: * Beyer, R A
EM: rbeyer@arc.nasa.gov
AF: NASA Ames Research Center, MS 245-3, Moffett Field, CA 94035 United States
AB: The slopes and surfaces of Ganges Mensa display a variety of morphologies which indicate that units of variable lithology constitute the stratigraphic stack of the mensa as observed by previous studies. Excellent coverage by the MOC, MOLA, and THEMIS instruments allows correlation between those data sets in order to make improved distinctions between morphologic units. Meter-scale images and detailed elevation data about the extent of these units and their boundaries allows for a better understanding of their associations with one another, and their relation to Ganges Mensa as a whole. This study identifies several thick units (several hundred meters) of erosionally resistant layered materials (some identified by previous studies based on lower-resolution data) and associated land-forms suggestive of a volcanic origin. One of these units is at the highest elevations on the mensa and appears to have acted as a resistant cap. There is evidence that it was once more areally extensive, however the unit which underlies it is more erodible and has been undermining the cap unit causing it to shrink. This morphologic evidence strengthens the hypothesis that Ganges Mensa formed in a fashion similar to terrestrial tuyas. In fact, the presence of these resistant layered units at different elevations within the stack may be markers of different water/ice levels through time, as they are in terrestrial tuyas. However, the true discriminator for the tuya origin hypothesis is the composition of the very thick (some up to 1 km), friable, finely layered units which compose the majority of Ganges Mensa. The tuya origin hypothesis requires that they be hyaloclastites, which has been difficult to discern from orbit. Unfortunately, the unit morphologies do not particularly eliminate any of the other origin hypotheses for Ganges Mensa, but these observations do have implications for them.
DE: 5460 Physical properties of materials
DE: 5464 Remote sensing
DE: 5480 Volcanism (6063, 8148, 8450)
SC: Planetary Sciences [P]
MN: Fall Meeting 2005