Engineering topics

Murray, J. B.

Publications and source records attributed to Murray, J. B..

5 records

NASA NTRS1993

Discharge rates in Ma'adim Vallis, Mars

A digital elevation model (DEM) of a small part of the Martian channel Ma'adim Vallis was produced using the Frankot and Chellappa shape-from-shading algorithm. Software developed by the Dept. of Photogrammetry and Surveying at University College London uses this technique to extract slope information from the grey levels of image pixels. This technique was applied to a Viking Orbiter image of part of Ma'adim Vallis, and measurements of the channel depth and bed-slope of a channel incised into the floor of Ma'adim Vallis were made. These results were used to calculate order of magnitude estimates for discharge rates through the channel. The maximum values calculated are three orders of magnitude less than those for N. Kasei Vallis and are similar to values cited for the Missoula floods. However, when more realistic values of the water depth are used, discharge rates comparable with those for the Mississippi River result.

Thornhill, G. D.↗

NASA NTRS1992

Topography of Apollinaris Patera and Ma'adim Vallis

Digital elevation models of the northern part of Ma'adim Vallis (603a41 607m/pix, 639a91 721m/pix), and Apollinaris Patera (603a42 612m/pix, 639a92 717m/pix), covering the area between 180 degrees to 190 degrees long and -2 degrees to -20 degrees lat. were obtained using a method described here. The results for the Ma'adim Vallis area show broad agreement with the United States Geological Survey (USGS) topographic map of the area with a channel depth of 1 to 2 km. A detailed study of the variations in the channel depth along its course and calculations of its discharge rate from channel cross section and slope are currently being undertaken. Results for Apollinaris Patera have been obtained, although the absolute heights relative to the Mars datum are not well constrained. However, the relative heights are sufficient for some analysis. Again, the topographic map is in reasonable agreement with the USGS map of the area, although there are significant differences.

Thornhill, G. D.↗

NASA NTRS1977

Some Martian Volcanic Features as Viewed from the Viking Orbiters

A summary is presented of the results of some new observations on Martian volcanic features made from the Viking orbiters. Most of these observations are concerned with the Tharsis and Alba regions. The youth, size, and style of the volcanic features in these areas render them particularly susceptible to analysis. Excellent coverage was also acquired of Apollinaris Patera. It has many features of the Tharsis shields, with a cliff around its circumference and a large central caldera. Olympus Mons and its vicinity are examined, taking into account the shield of Olympus Mons, mass movement features along the basal scarp, the basal plains, the relative ages of Olympus Mons and the basal plains, and grooved terrain.

Carr, M. H.↗

NASA NTRS1975

Some comparisons of impact craters on Mercury and the moon

Although the general morphologies of fresh mercurian and lunar craters are remarkably similar, comparisons of ejecta deposits, interior structures, and changes in morphology with size reveal important differences between the two populations of craters. The differences are attributable to the different gravity fields in which the craters were formed and have significant implications for the interpretation of cratering processes and their effects on all planetary bodies.

Gault, D. E.↗

NASA NTRS1972

Circularity of Martian craters.

A modified method of calculating crater circularity based on the average deviation of crater radius from mean radius is presented and used to calculate circularity of Martian craters. Calculation of the circularity indices of over 200 Martian craters yields values similar to circularity indices of terrestrial meteorite craters and different from indices of terrestrial calderas.

Oberbeck, V. R.↗