HR: 0800h
AN: P21A-0133    [Abstracts]
TI: The Origin of the Columbia Hills
AU: * Rice, J W
EM: jrice@asu.edu
AF: Department of Geological Sciences Arizona State University, PO Box 876305, Tempe, AZ 85287 United States
AB: The Columbia Hills form a rugged ridge complex comprised of 7 peaks spanning some 3.5 km in length and reaching a maximum height of 106 m (Husband Hill) above the plains of Spirit's landing site. As of this writing Spirit has been exploring the Columbia Hills for over 440 sols (since sol 156 on June 11, 2004). Thus far the origin of the Columbia Hills has remained elusive despite detailed analysis of numerous rock and soil targets, including outcrops. The chemical differences among the 6 distinct rock classes attest to the lithologic diversity and geologic complexity of the Hills. Origin of the Columbia Hills Several hypothesis have been put forth to explain the origin of the Columbia Hills: Old eroded partially buried impact crater rim(s), central peak, residual intracrater fill material, volcanic construct, wrinkle ridge, delta and or combinations of the above. Observations that support various aspects of these multiple hypotheses will be discussed. Numerous buried craters are observed on the floor of Gusev lending credence to the idea that the Columbia Hills are the remains of an ancient impact crater rim or possibly a central peak. Morphologic evidence of the rim of Thira crater and the Columbia Hills appears to support this hypothesis. The Aeolis region contains numerous craters that contain layered materials in the absence of any major fluvial systems. This could imply that the Columbia Hills are the remnants of a formerly extensive unit(s). Gusev contains many hills scattered across its floor such as Grissom, White, Chaffee and numerous other buttes and mesas that may be remnants of a former extensive intracrater deposit. Another possibility is that the Columbia Hills are composed of volcanic materials (cinder cones and associated ash and lava flows) derived either locally or from Apollinaris Patera located 300 km to the north. Several depressions are located in the Columbia Hills. These features could be calderas but are most likely impact craters. The most obvious large depressions have diameters that range from 350 to 820 m. Terra Nova: The Inner Basin and the Promised Land Newly acquired Pancam imagery, from the summit, allows for the unobstructed viewing of numerous interesting landforms on McCool Hill (ledges/terraces) the Inner Basin (Home Plate, buttes, ridges and dunes) and Promised Land located to the south of Husband Hill. Images from the surface and orbit shows a series of 4 to 5 ledges or terraces located on the both the south facing flanks of Husband Hill and north facing flanks of McCool Hill. Home Plate is a circular feature forming a raised platform up to 80 m across. This feature is surrounded by a series of buttes. Home Plate appears to be the floor of a heavily eroded crater and the buttes are crater rim remnants. The material capping the buttes appears to be the same material making up Home Plate. The Promised Land is a region of ridges and hills that contain some of the highest thermal inertia values of the Columbia Hills region. Plans are currently being made for the detailed exploration of these regions and landforms.
DE: 6225 Mars
SC: Planetary Sciences [P]
MN: Fall Meeting 2005