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We have quantitatively assessed the resurfacing sources and styles in eighteen mapped venusian quadrangles, about 30% of the venusian surface. Each quadrangle was split into 0.5° by 0.5° boxes, which were then identified as corona materials, large volcano materials (>100 km diameter), intermediate volcano materials (10–100 km), small edifice materials (<10 km), flow materials from rifts or fractures,...
We have used the Mars Global Surveyor Mars Orbiter Camera Wide Angle (MGS MOC WA) dataset to study albedo trends on the martian northern residual cap. Six study regions were selected, the Chasma Boreale source region, three regions near the center of the cap (“fish hook” region, latitude=87°; “bottle opener” region, latitude=87°, “steep-shallow” region, latitude=85°), and two lower latitude regions...
The geology and stratigraphy of Millochau crater (21.4° S, 275° W), located in the highlands of Tyrrhena Terra, Mars, are documented through geomorphic analyses and geologic mapping. Crater size-frequency distributions and superposition relationships are used to constrain relative ages of geologic units and determine the timing and duration of the geologic processes that modified Millochau rim materials...
Wind erosion and deposition are powerful agents of surface change on Mars. Erosion is sensitive to the atmospheric density, so feedback between orbit variations and atmospheric density can enhance the sensitivity of erosion rates to orbital parameters. We use statistics derived from a 1 Gyr integration of the spin axis of Mars, coupled with runs of the NASA Ames 3-D general circulation model (GCM)...
A survey of craters in the vicinity of Newton Basin, using high-resolution images from Mars Global Surveyor and Mars Odyssey, was conducted to find and analyze examples of gullies and arcuate ridges and assess their implications for impact crater degradation processes. In the Phaethontis Quadrangle (MC-24), we identified 225 craters that contain these features. Of these, 188 had gullies on some portion...
Optical constants are estimated from near-infrared reflectance spectra of the smectite clay montmorillonite using an iterative combination of particulate scattering theory and Kramers–Kronig analysis. The final results provide wavelength dependent imaginary indices of refraction similar to previous studies, but in addition produce wavelength dependent real indices of refraction, unlike most previous...
Distinct competent layers are observed in the slopes of eastern Coprates Chasma, part of the Valles Marineris system on Mars. Our observations indicate that the stratigraphy of Coprates Chasma consists of alternating thin strong layers and thicker sequences of relatively weak layers. The strong, competent layers maintain steeper slopes and play a major role in controlling the overall shape and geomorphology...
We present near-IR spectra of solid CO 2 in H 2 O and CH 3 OH, and find they are significantly different from that of pure solid CO 2 . Peaks not present in either pure H 2 O or pure CO 2 spectra become evident when the two are mixed. First, the putative theoretically forbidden CO 2 (2ν3) overtone near 2.134 μm (4685 cm −1 ), that is...
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