Ted A. Maxwell

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At 8 to 15 kilometers wide, Ma'adim Vallis is one of the largest valleys in the martian highlands. Although a groundwater source was previously suggested, the channel originates at a spillway in the divide of a approximately 3,000,000-square-kilometer closed drainage basin. The interior morphology of this source basin, including likely shoreline features(More)
[1] Ma’adim Vallis, one of the largest valleys in the Martian highlands, appears to have originated by catastrophic overflow of a large paleolake located south of the valley heads. Ma’adim Vallis debouched to Gusev crater, 900 km to the north, the landing site for the Spirit Mars Exploration Rover. Support for the paleolake overflow hypothesis comes from(More)
[1] Ground-penetrating radar (GPR) helps to constrain the origin of relict and largely buried fluvial channels in the Bir Kiseiba region of southern Egypt. Our results indicate that the trunk channel to a tributary system identified in Shuttle Imaging Radar data is incised 10–12 m into bedrock, was southwest draining in its final configuration and laterally(More)
Landsat images of the Selima sand sheet in southwestern Egypt display alternating light and dark chevron-shaped patterns that occur downwind from low scarps and major dune fields. Images acquired between 1972 and 1988 indicate that these features move as discrete bedforms at a rate of up to 500 meters per year. Extremely long-wavelength (130 to 1200(More)
From the southwestern border of Egypt to the Nile Valley, the surficial deposits of the Western Desert record the effects of changing climate on landscape evolution. Since the first geologic mapping of this desert by the Geological Survey of Egypt in the 1960's. improvements in techniques and recognition of the archaeological importance of the region have(More)
Introduction: Most studies of martian erosion have focused on crater statistics, aeolian landforms and deposits, and valley network morphology. Previous workers have noted that the martian crater population is deficient in craters less than ~30 km in diameter, presumably due to erosion [1], and that ancient martian craters were subjected to different(More)
SEDIMENTARY DEPOSIT. R. P. Irwin III, T. R. Watters, A. D. Howard, T. A. Maxwell, and R. A. Craddock, Center for Earth and Planetary Studies, National Air and Space Museum, Smithsonian Institution, 4 St. and Independence Ave. SW, Washington DC 20560-0315, Irwinr@nasm.si.edu, twatters@nasm.si.edu, tmaxwell@nasm.si.edu, craddock@nasm.si.edu. Dept.(More)
Introduction: Many previous regionalto globalscale studies have identified features that may be attributable to paleolakes on early Mars [e.g., 1–8]. The most suggestive landforms include outlet valleys from basins with undissected floors [e.g., 6] (leaving a residual basin on the crater floor); positive-relief deposits with a frontal scarp at the end of(More)
Overview: Some workers have proposed that large Martian basins contained extensive water bodies in the past, and have hypothesized that an ancient ocean extended over much or all of the northern lowland plains. With considerable depths over large areas, these water bodies would have represented massive surficial loads. The irregular form of some Martian(More)