Publications

Comparison of radar backscatter coefficients (σ°, in dB), calculated by using the empirical model of Oh et al. [1992], to σ° extracted from AIRSAR data of four geologic units at Pisgah shows that the model predicts measured σ°vv and σ°hv to within ±3 dB. The model predicts higher σ°hh than those observed. For smooth surfaces (rms height=s, s

Compilation of a simplified geologic/geomorphic map onto digital terrain models of the Valles Marineris permitted an evaluation of elevations in the vicinity of the troughs and the calculation of depth of troughs below surrounding plateaus, thickness of deposits inside the troughs, volumes of void spaces above geologic/geomorphic units, and volumes of deposits. The central troughs north...

Recently Brown et al. (1991) showed that Triton's internal heat source could amount to 5–20% of the absorbed insolation on Triton, thus significantly affecting volatile transport and atmospheric pressure. Subsequently, Kirk and Brown (1991a) used simple analytical models of the effect of internal heat on the distribution of volatiles on Triton's surface, confirming the speculation of...

Velocity measurements were made for two time intervals on the Smith Glacier ice tongue (1973–88 and 1988–90) and three on the Dotson Ice Shelf (1972–88, 1973–88 and 1988–90). The Smith Glacier ice tongue velocities for the two intervals are similar near the grounding line but show a progressive increase toward the terminus in the late 1980s. The Dotson Ice Shelf velocities remained...

The surface of Gaspra can be divided into several facets separated by ridges. Superimposed on the facets and ridges are two populations of craters. Type 1 craters are crisply defined and constitute a production function of impact origin. Type 2 craters are mostly irregular shallow depressions and probably of various origins. Some of the type 2 craters may have formed by impact and be...

Venusian canali, outflow channels, and associated volcanic deposits resemble fluvial landforms more than they resemble volcanic features on Earth and Mars. Some canali have meandering habits and features indicative of channel migration that are very similar to meandering river channels and flood plains on Earth, venusian outflow channels closely resemble water-carved outflow channels on...

Galileo images of Gaspra make it possible for the first time to determine a main-belt asteroid's photometric properties accurately by providing surface-resolved coverage over a wide range of incidence and emission angles and by extending the phase angle coverage to phases not observable from Earth. We combine Earth-based telescopic photometry over phase angles 2° ≤ α ≤ 25° with Galileo...

Copernican‐age craters are among the most conspicuous features seen on the far side and western limb of the Moon in the Galileo multispectral images acquired in December 1990. Among the new morphologic observations of far‐side craters are bright rays, continuous ejecta deposits, and dark rings associated with probable impact‐melt veneers. These observations suggest that the mapped age...

The Thwaites Glacier/iceberg tongue complex has been a significant feature of the Antarctic coastline for at least 50 years. In 1986, major changes began to occur in this area. Fast ice melted and several icebergs calved from the base of the iceberg tongue and the terminus of Thwaites Glacier. The iceberg tongue rotated to an east-west orientation and drifted westward. Between 1986 and...

We measured the velocities of six glacier tongues and a few tongues within ice shelves distributed around the Antarctic coastline by determining the displacement of crevasse patterns seen on sequential Landsat images. The velocities range from less than 0.2 km a−1 for East Antarctic ice-shelf tongues to more than 2.5 km a−1 for the Thwaites Glacier Tongue. All glacier tongues show...

The differences of radar data from more familiar photographic images, coupled with the unique geologic characteristics of Venus's surface, can make interpretation of the standard Magellan data products difficult for both planetary scientists and nonspecialists. We describe a set of digital processing techniques for transforming individual remote‐sensing datasets in order to make the...

Magellan has revealed an ensemble of impact craters on Venus that is unique in many important ways. We have compiled a data base describing the 842 craters on 89% of Venus' surface mapped through orbit 2578. (The craters range in diameter from 1.5 to 280 km.) We have studied the distribution, size‐density, morphology, geology, and associated surface properties of these craters both in...