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Arthur L. Dial

Publications and source records attributed to Arthur L. Dial.

4 recordsLinked to original sources
USGS1975

A summary of relative ages of lunar nearside and farside plains

This report contains a summary of the moon-wide distribution of relative ages of lunar plains units determined with Apollo and Lunar Orbiter photographs. Relative ages are expressed as the largest diameter of craters (D L , meters) in a mappable unit that are eroded to a slope of 1 ° by the net accumulated flux of small impacts. New data show that the technique used here generally requires a sample area less than 2,000 km 2 for satisfactory results. Additionally, the measurement of relative age (D L ) using this technique is unaffected by resolutions of about 0.15 D L or smaller. Results obtained indicate there are two types of plains: 1) light plains and 2) mare plains. The light plains units have two separate and distinct ages (D L ≃ 550 m and D ≃ 1100 m). The range in ages for each of these units is so small that each could represent two separate synchronous lunar events. The maria were deposited in three major stages after the emplacement of the light plains units. The oldest mare units ( > 3.7 b.y. old) are in Mare Tranquillitatis, Mare Vaporum, southeastern Mare Imbrium, the dark ring around Mare Serenitatis and a thin band from the crater Reinhold to Sinus Medii. Young mare volcanism ( < 2.5 b.y. old) occurred in western Mare Serenitatis, southwestern Mare Imbrium and Oceanus Procellarum. All other mare areas investigated are of intermediate age.

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USGS1974

Viking rover studies

Intensive study of Mariner 9 data has resulted in an understanding--although far from complete--of the geologic processes affecting the Martian surface and of its history of development. The results are briefly summarized in the following section. The second section consists of geologic studies of four widely separated areas on Mars (figure 1) selected to provide as wide a variety of environments as possible. For each area a detailed geologic map of a high resolution Mariner 9 B-frame was made and several exemplary traverses were plotted to show how the various geologic units might be visited, sampled, and analyzed. In each area 5 to 10 geologic units appear to be accessible. A substantial fraction of each area is covered by loess-like or dune-like units or channel deposits. That is, there are extensive deposits of transported debris that may be strongly sorted by sedimentational processes. However a variety of indigenous rocks are also present in each of the areas selected. Volcanic rocks of several types and impact debris occur locally. These are masked to varying degrees by the transported debris. Two additional capabilities are necessary beyond those available for Viking '75. The first is a decrease in the size of the landing ellipse so the spacecraft can be put down close to a desirable landing point. The second is a mobility system to allow exploration in the vicinity of the landing point in order to sample the various units locally present more effectively.

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