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At least 73 records · Page 4

Preliminary geologic terrain map of Mercury

A geologic terrain map of Mercury has been constructed by use of the photogeologic methods employed for the moon and Mars. The oldest and most widespread unit, intercrater plains, forms nearly level to rolling surfaces on which are superposed numerous secondary impact craters. This unit may represent a very old surface that predates the last heavy bombardment of the inner planets. The effects of this bombardment are recorded in a second widespread unit, heavily cratered terrain, consisting of closely spaced craters and basins from 30 km to several hundred kilometers in diameter. Units formed by excavation of the 1300-km-diameter Caloris basin are widespread on one hemisphere of the planet. The development of the Caloris basin was followed relatively quickly by emplacement of widespread plains materials, most of which are probably volcanic.

Trask, N. J.↗

Impact-induced fractionation in the lunar highlands

A synthesis of the relevant data concerning lunar highland polymict breccias from the fields of petrography, chemistry, photogeology, and impact studies compels the prediction that the breccias should have homogeneous matrices from rock to rock within regions of the highlands of limited size where impact mixing has been efficient and extensive. But the matrices of returned breccias, even from one landing site, display a wide range in composition. This incompatibility between prediction and observation is a paradox that may be resolved by a process that acts after impact mixing to cause a differentiation of the breccia compositions. Partial melting of the local surficial material, and separation of melt and residue in ejecta and/or fall-back blankets, is compatible with the reviewed data and may resolve the paradox.

Warner, J. L.↗

Exploration for fossil and nuclear fuels from orbital altitudes

Studies of LANDSAT and Skylab-EREP data have defined both the advantages and limitations of space platforms as a new 'tool' in mineral exploration. One LANDSAT investigation in the Anadarko Basin of Oklahoma has demonstrated a correlation between several types of anomalies recognized in the imagery and the locations of known oil and gas fields. In addition to supporting several LANDSAT follow-on investigations in petroleum exploration, NASA has approved a broad in-house study at Goddard Space Flight Center designed to verify the general applicability of the initial Anadarko Basin results. Using both conventional photogeologic methods and special computer processing, imagery taken over oil-producing areas is being subjected to detailed analysis in search of definitive recognition criteria.

Short, N. M.↗

Geologic and mineral and water resources investigations in western Colorado using ERTS-1 data

The author has identified the following significant results. Most of the geologic information in ERTS-1 imagery can be extracted from bulk processed black and white transparencies by a skilled interpreter using standard photogeologic techniques. In central and western Colorado, the detectability of lithologic contacts on ERTS-1 imagery is closely related to the time of year the imagery was acquired. Geologic structures are the most readily extractable type of geologic information contained in ERTS images. Major tectonic features and associated minor structures can be rapidly mapped, allowing the geologic setting of a large region to be quickly accessed. Trends of geologic structures in younger sedimentary appear to strongly parallel linear trends in older metamorphic and igneous basement terrain. Linears and color anomalies mapped from ERTS imagery are closely related to loci of known mineralization in the Colorado mineral belt.

Knepper, D. H.↗

LANDSAT image studies as applied to petroleum exploration in Kenya

The Chevron-Kenya oil license, acquired in 1972, covers an area at the north end of the Lamu Embayment. Immediately after acquisition, a photogeologic study of the area was made followed by a short field inspection. An interpretation of LANDSAT-1 images as a separate attempt to improve geological knowledge was completed. The method used in the image study, the multispectral characteristics of rock units and terrain, and the observed anomalous features as seen in the LANDSAT imagery are described. It was found that the study helped to define the relationship of the Lamu Embayment and its internal structure with surrounding regional features, such as the East Africa rifting, the Rudolf Trough, the Bur Acaba structural ridge, and the Ogaden Basin.

Miller, J. B.↗

A search for sulfide-bearing areas using LANDSAT-1 data and digital image-processing techniques

Two experiments were conducted using LANDSAT-1 multispectral scanner data to identify ground features that are indicators of sulfide-bearing rock. A nearby known sulfide deposit was used as a control. In the first experiment, false-color composites were examined visually to locate possible favorable areas; in the second, favorable areas were classified by digital-computer processing. The results of the experiment show that outcrops of hydrothermally altered and mineralized rock can be identified from LANDSAT-1 data under favorable conditions. The empirical method of digital-computer classification of the multispectral scanner data was relatively unrefined and rapid. The five mineralized prospecting sites identified are in locations that the geologist would not have selected as favorable on the basis of geologic knowledge or photogeologic interpretation at the time of the investigation.

Schmidt, R. G.↗

Geologic and mineral and water resources investigations in western Colorado, using Skylab EREP data

The author has identified the following significant results. Skylab photographs are superior to ERTS images for photogeologic interpretation, primarily because of improved resolution. Lithologic contacts can be detected consistently better on Skylab S190A photos than on ERTS images. Color photos are best; red and green band photos are somewhat better than color-infrared photos; infrared band photos are worst. All major geologic structures can be recognized on Skylab imagery. Large folds, even those with very gentle flexures, can be mapped accurately and with confidence. Bedding attitudes of only a few degrees are recognized; vertical exaggeration factor is about 2.5X. Mineral deposits in central Colorado may be indicated on Skylab photos by lineaments and color anomalies, but positive identification of these features is not possible. S190A stereo color photography is adequate for defining drainage divides that in turn define the boundaries and distribution of ground water recharge and discharge areas within a basin.

Lee, K.↗

Geologic setting of Boulder 1, Station 2, Apollo 17 landing site

Boulder 1 at Station 2 is one of three boulders sampled by Apollo 17 at the base of the South Massif, which rises 2.3 km above the floor of a linear valley interpreted as a graben formed by deformation related to the southern Serenitatis impact. The boulders probably rolled from the upper part of the massif after emplacement of the light mantle. The massif exposures are suggested to represent the upper part of thick ejecta deposited by the southern Serenitatis impact near the rim of the transient cavity. The ring structure of the southern Serenitatis basin and the radial grabens that give the massifs definition were imposed on this ejecta at a slightly later stage in the basin-forming process. There is no clear-cut compositional, textural, or photogeological evidence that Imbrium ejecta was collected at the Apollo 17 site.

Wolfe, E. W.↗

Surficial geology of Mars: A study in support of a penetrator mission to Mars

Physiographic and surficial cover information were combined into unified surficial geology maps (30 quadrangles and 1 synoptic map). The surface of Mars is heterogeneous and is modified by wind, water, volcanism, tectonism, mass wasting and other processes. Surficial mapping identifies areas modified by these processes on a regional basis. Viking I mission results indicate that, at least in the landing site area, the surficial mapping based on Mariner data is fairly accurate. This area was mapped as a lightly cratered plain with thin or discontinuous eolian sediment. Analysis of lander images indicates that this interpretation is very close to actual surface conditions. These initial results do not imply that all surficial units are mapped correctly, but they do increase confidence in estimates based on photogeologic interpretations of orbital pictures.

Spudis, P.↗

Geologic evolution of the terrestrial planets

The paper presents a geologic comparison of the terrestrial planets Mercury, Venus, Earth, the Moon and Mars, in the light of the recent photogeologic and other evidence gathered by satellites, and discusses the relationships between their regional terrain types, ages, and planetary evolution. The importance of the two fundamental processes, impact cratering and volcanism, which had formed these planets are stressed and the factors making the earth unique, such as high planetary evolution index (PEI), dynamic geological agents and the plate tectonics, are pointed out. The igneous processes which dominate earth and once existed on the others are outlined together with the planetary elevations of the earth which has a bimodal distribution, the moon which has a unimodal Gaussian distribution and Mars with a distribution intermediate between the earth and moon. Questions are raised concerning the existence of a minimum planetary mass below which mantle convection will not cause lithospheric rifting, and as to whether each planet follows a separate path of evolution depending on its physical properties and position within the solar system.

Head, J. W.↗

Basis for interpretation regarding the ages of the Serenitatis, Imbrium and Orientale events

One of the most important objectives of lunar study is to relate the lunar sample data to important lunar events. This paper utilizes as the basis of interpretation consideration of the following: (1) photogeologic data, (2) the choice of a cratering model, (3) estimates of temperature of impact ejecta and shock-induced heating, (4) petrologic data of lunar breccias and their thermal and shock history, and (5) meaningful age measurements. Both the author's interpretations and alternative views are discussed. The age of the Serenitatis event is not yet known. The interpreted age of the Imbrium event is between 3.90 and 3.84 Ga. The age of the Orientale event is 3.84 Ga.

Chao, E. C. T.↗

Lunar Science Conference, 7th, Houston, Tex., March 15-19, 1976, Proceedings. Volume 1 - Regolith studies. Volume 2 - Petrogenetic studies of mare and highland rocks. Volume 3 - The moon and other bodies

Attention is given to lunar core studies (multi-core, deep drill, and drive tube), surface soil studies (petrography and geochemistry, light and volatile element studies, and agglutinate related studies), and surfaces process studies. Also considered are mare basalts, with emphasis on mineralogy and petrology, chemical and isotopic studies, and constraints and models of basalt evolution, along with breccia and highland samples with attention given to geochronology, boulders and consortium studies and the formation of highland samples. Remote sensing and photogeology of the moon, crustal bombardment, physical properties of the moon, and comparative planetology are also discussed.

Merrill, R. B.↗

Cosmic ray exposure ages of Apollo 17 samples and the age of Tycho

Cosmic ray exposure data for Apollo 17 samples and quantitative photogeologic data are presented which support the hypothesis that the Central Cluster unit and the Bright Mantle at the Apollo 17 landing site are related to impact of ejecta from the crater Tycho, lying about 2000 km to the southwest. The exposure ages point to a site-wide event 96 m.y ago, which included emplacement of the Bright Mantle and Central Cluster units.

Arvidson, R.↗

The exposure history of the Apollo 16 site: An assessment based on methane and hydrolysable carbon

Nineteen soils from eight stations at the Apollo 16 landing site have been analyzed for methane and hydrolysable carbon. These results, in conjunction with published data from photogeology, bulk chemistry, rare gases, primordial and cosmogenic radionuclides, and agglutinate abundances have been interpreted in terms of differing contributions from three components-North and South Ray Crater ejecta and Cayley Plains material.

Pillinger, C. T.↗

Abstracts for the Planetary Geology Field Conference on Aeolian Processes

The Planetary Geology Field Conference on Aeolian Processes was organized at the request of the Planetary Geology Program office of the National Aeronautics and Space Administration to bring together geologists working on aeolian problems on earth and planetologists concerned with similar problems on the planets. Abstracts of papers presented at the conference are arranged herein by alphabetical order of the senior author. Papers fall into three broad categories: (1) Viking Orbiter and Viking Lander results on aeolian processes and/or landforms on Mars, (2) laboratory results on studies of aeolian processes, and (3) photogeology and field studies of aeolian processes on Earth.

Greeley, R.↗

Remote sensing exploration for metallic mineral resources in central Baja California

Remote sensor data (primarily LANDSAT) was analyzed by photogeologic and computer-assisted enhancement techniques to evaluate the metallic mineral potential of Baja California. Overlays were prepared at 1:1,000,000 and 1:500,000 and included known geologic relationships and mineral occurrences, lineament, drainage and structural patterns, tonal anomalies, and enhancement results. Computer-assisted enhancement and classification of the test sites was performed using the IMAGE 100 system to identify subtle tonal anomalies thought related to mineralization using known sites as analysis guides. Mineral potential maps of Baja California were generated from these analyses and the ten highest priority targets visited. Preliminary assay results (atomic absorption analysis) for the samples recovered showed moderate to high geochemical anomalies for Copper (10 of 12 samples), Zinc (3 of 12 samples) and Lead (4 of 12 samples).

Baker, R. N.↗

Rayed craters on the moon and Mercury

Systems of bright rays are exhibited by many fresh craters on the moon and Mercury. Diameter/density distributions suggest that lunar-rayed craters represent the Class 1 craters, and that Mercurian rayed craters represent post-Caloris craters. Photogeological analyses of lunar imagery indicate that the ray systems are composed of finely divided material from the primary crater along with locally derived ejecta from secondary and tertiary craters. The primary ray material probably occurs in moderately thick (0.1-1 meter) deposits. The rate of darkening may depend more on the thickness of the ray material than on the rates of various darkening processes. Darkening rate may also be a function of crater size. It is observed that rays of craters more than 1 b.y. old remain bright, whereas those older than Class 1 generally fade to imperceptibility.

Allen, C. C.↗

Cosmic-ray exposure history at Taurus-Littrow

Recent surface history at Taurus-Littrow is dominated by emplacement of the Central Cluster and Bright Mantle morphological units, both believed to have resulted from arrival of ejecta from a large primary crater, probably Tycho. This paper reports new noble gas data for eight Apollo 17 rocks. Kr-81 - Kr cosmic ray exposure ages for these rocks affirm the observation of a pronounced grouping of ages, reinforcing the photogeologic evidence for the site-wide nature of the Central Cluster event. The consequences of post-cratering shielding changes are considered and it is concluded that the differences can reasonably be attributed to these changes, particularly because of the greater likelihood of rollover and impact fragmentation of the relatively smaller rocks from which most age data have been obtained. These considerations also lead to a more refined age estimate of 109 plus or minus 4 m.y. for Central Cluster, the Bright Mantle, and Tycho.

Drozd, R. J.↗