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Dial, A. L., Jr.

Publications and source records attributed to Dial, A. L., Jr..

7 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1988

Search for Mars lander/rover/sample-return sites: A status review

Ten Mars sites were studied in the USA for four years. The sites are the Chasma Boreale (North Pole), Planum Australe (South Pole), Olympus Rupes, Mangala Valles, Memnonia Sulci, Candor Chasma, Kasel Valles, Nilosyrtis Mensae, Elysium Montes, and Apollinaris Patera. Seven sites are being studied by the USSR; their prime sites are located at the east mouth of Kasel Valles and near Uranius Patera. Thirteen geological maps of the first six USA sites are compiled and in review. Maps of the Mangala East and West sites at 1:1/2 million scale and a 1:2 million scale map show evidence of three episodes of small-channel formation interspersed with episodes of volcanism and tectonism that span the period from 3.5 to 0.6 b.y. ago. The tectonic and geological history of Mars, both ancient and modern, can be elucidated by sampling volcanic and fluvial geologic units at equatorial sites and layered deposits at polar sites. The evidence appears clear for multiple episodes of fluvial channeling, including some that are quite recent; this evidence contrasts with the theses of Baker and Partridge (1986) and many others that all channels are ancient. Verification of this hypothesis by Mars Observer will be an important step forward in the perception of the history of Mars.

Masursky, Harold↗
NASA NTRS1987

Martian terrains

Terrain studies of candidate landing sites for a future rover/sample-return mission to Mars are being conducted to evaluate the geologic and trafficability aspects of each site. An optimum site should have geologic units of widely diverse ages and chemical compositions occurring in close enough proximity and in smooth enough terrain so that a roving vehicle of limited traverse ability (+ or - 100 km) could collect representative samples. In FY 1986, geologic maps were compiled at 1:500,000 and 1:2 million scales of the Mangala Valles, Kasei Valles, Chasma Boreale (north polar), and Planum Australe (south polar) areas, and a study was begun of the topography and surface roughness characteristics of the Mangala Valles site. Geologic mapping has been greatly facilitated by specially enhanced, high-resolution Viking photographs, which clarify stratigraphic relations of units unrecognized earlier. Photoclinometric profiles of topographic features provide width and depth measurements of four classes of channels, the thickness of some volcanic units, and the throw on some faults. Estimates of the surface roughness of units are calculated using a newly developed USGS computer program and using measurements derived from Earth-based radar.

Masursky, Harold↗
NASA NTRS1987

Geology of six possible Martian landing sites

Thirteen detailed maps of the first six (of ten) possible sites for a future Lander/Rover/Sample-return mission to Mars are either nearing completion or in review. Basic mosaic of all sites were available at 1:2 million scale. In addition to preparing new base maps, special enhancements were generated for computer mosaics and individual images that delineate the geologic units more clearly. Photoclinometric profiles that allowed measurement of the thicknesses of geologic units, the depth of channels, and the throw on faults were prepared. Crater counts were made for each geologic unit.

Masursky, Harold↗
NASA NTRS1978

Lava flow materials in the Tharsis region of Mars

Lava-flow materials in the Tharsis region of Mars were studied from moderate-resolution (100-280 m/pixel) Viking Orbiter imagery. Individual eruptive sequences were recognized primarily by stratigraphic relations, density of superimposed impact craters, flow morphology, flow trend, and variations in surface albedo. Nine detailed maps of lava flows based on delineation of flow scarps were compiled for a total area of 7.25 million sq km. Two thirds of this area was covered by mappable flows representing at least 14 distinct eruptive sequences. Assuming a rate of crater production twice that of the moon, the observed range of superimposed crater densities (90 to 3200 craters at least 1 km in diameter per sq km) indicates an age range of 100 m.y. to several billion years for these flows. The youngest lavas are associated with flood lavas filling the depression surrounding the Olympus Mons shield. Flow thicknesses range from less than 5 meters to 20 meters on steeper shield slopes (0.5 to 4.5 deg) and from 20 to 65 meters on relatively flat (less than 0.5 deg slope) terrain.

Schaber, G. G.↗
NASA NTRS1975

Relative ages of flow units in Mare Imbrium and Sinus Iridum

A method for determining relative ages from low-resolution Lunar Orbiter photographs of lunar plains has been developed and applied to Mare Imbrium and Sinus Iridum. The method is an extension of previous ones and uses the shapes of craters and a small-impact erosion model to estimate the net accumulated impact flux. The net impact flux that has accumulated on a surface of uniform age is a measure of relative age of that surface and can be estimated by the largest diameters of craters that have been degraded by the net impact flux. Frequency distributions or relative ages indicate that there are four major units present in Mare Imbrium and Sinus Iridum. The older mare units are generally found along the edge of the basin and the younger units in the center. A similar distribution of ages of units in Mare Serenitatis shows the two basins have had similar filling histories. Filling histories for other circular basins may be similar to these two.

Boyce, J. M.↗
NASA NTRS1973

Relative ages of some near-side Mare units based on Apollo 17 metric photographs

Relative flux ages were determined for 110 areas on parts of Serenitatis, Vaporum, and Imbrium, using Apollo 17 metric photographs. The crater-morphology technique for determining relative ages is described. It is concluded that these maria formed over an interval of 1.5 billion years, extending from 3.7 to 2.2 billion years ago.

Boyce, J. M.↗