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Geology topics

M. H. Carr

Publications and source records attributed to M. H. Carr.

At least 73 records · Page 4Linked to original sources
USGS1976

Preliminary results from the Viking orbiter imaging experiment

During its first 30 orbits around Mars, the Viking orbiter took approximately 1000 photographic frames of the surface of Mars with resolutions that ranged from 100 meters to a little more than 1 kilometer. Most were of potential landing sites in Chryse Planitia and Cydonia and near Capri Chasma. Contiguous high-resolution coverage in these areas has led to an increased understanding of surface processes, particularly cratering, fluvial, and mass-wasting phenomena. Most of the surfaces examined appear relatively old, channel features abound, and a variety of features suggestive of permafrost have been identified. The ejecta patterns around large craters imply that fluid flow of ejecta occurred after ballistic deposition. Variable features in the photographed area appear to have changed little since observed 5 years ago from Mariner 9. A variety of atmospheric phenomena were observed, including diffuse morning hazes, both stationary and moving discrete white clouds, and wave clouds covering extensive areas.

Science↗
USGS1974

The regolith at the Apollo 15 site and its stratigraphic implications

Regolith samples from the Apollo 15 landing site are described in terms of two major fractions, a homogeneous glass fraction and a non-homogeneous glass fraction. The proportions of different components in the homogeneous glass fraction were determined directly by chemical analyses of individual particles. They are mainly green glass, a mare-like glass, and different types of Fra Mauro and Highland type glasses. The proportions of various components in the remainder of each of the soils were determined indirectly by finding the mix of components that best fits their bulk compositions. The mixing model suggests that the Apennine Front consists mainly of rocks of low-K Fra Mauro basalt composition. These may overlie rocks with the composition of anorthositic gabbro. Green glass, which occurs widely throughout the site is believed to be derived from a green glass layer which darkens upland surfaces and lies beneath the local mare surface.

Geochimica et Cosmochimica Acta↗
USGS1974

The role of lava erosion in the formation of lunar rilles and Martian channels

Lava tubes and channels develop around active sources of low viscosity lava. The channels normally form without erosion; however, sustained flow can result in the incision of a lava channel and simulation of fluvial erosion features. Lava erosion by means of thermal incision was modelled by computer, erosion rates calculated, and these compared with rates observed terrestrially. Lunar sinuous rilles are examined in light of the proposed lava erosion. The mechanism explains many features of lunar rilles that were heretofore puzzling and implies erosion rates comparable to terrestrial rates. Many Mars channels also appear to form by the action of lava; however, the larger, more spectacular Mars channels do not appear to have been formed by the same process.

Icarus↗
USGS1974

North polar region of Mars: Imaging results from Viking 2

During October 1976, the Viking 2 orbiter acquired approximately 700 high-resolution images of the north polar region of Mars. These images confirm the existence at the north pole of extensive layered deposits largely covered over with deposits of perennial ice. An unconformity within the layered deposits suggests a complex history of climate change during their time of deposition. A pole-girdling accumulation of dunes composed of very dark materials is revealed for the first time by the Viking cameras. The entire region is devoid of fresh impact craters. Rapid rates of erosion or deposition are implied. A scenario for polar geological evolution, involving two types of climate change, is proposed.

Science↗
USGS1973

Stratigraphic studies: Part A: basalt stratigraphy of southern Mare Serenitatis

Mare Serenitatis has long been noted for its conspicuous dark border (fig. 29-1). The Apollo 17 metric photographs traverse this border in southern Mare Serenitatis and show clearly superposition relationships among the mare and mare-related stratigraphic units. These photographs, together with full-Moon photographs, albedo measurements, and color information (table 29-I), provide the basis for a revised stratigraphic framework for these presumedly basaltic rocks (figs. 29-2 and 29-3). In contrast to most previous studies, we conclude that the darker units are older than lighter ones. Similar conclusions have been reached by Bryan and Adams (part C of sec. 30) and Boyce and Dial (part C of this section). The relatively light-colored central part of Mare Serenitatis is thought to represent the youngest basalt in the region; a very dark unit that includes the Apollo 17 landing site is one of the oldest.

Book chapter↗
USGS1972

Preliminary mariner 9 report on the geology of Mars

Mariner 9 pictures indicate that the surface of Mars has been shaped by impact, volcanic, tectonic, erosional and depositional activity. The moonlike cratered terrain, identified as the dominant surface unit from the Mariner 6 and 7 flyby data, has proven to be less typical of Mars than previously believed, although extensive in the mid- and high-latitude regions of the southern hemisphere. Martian craters are highly modified but their size-frequency distribution and morphology suggest that most were formed by impact. Circular basins encompassed by rugged terrain and filled with smooth plains material are recognized. These structures, like the craters, are more modified than corresponding features on the Moon and they exercise a less dominant influence on the regional geology. Smooth plains with few visible craters fill the large basins and the floors of larger craters; they also occupy large parts of the northern hemisphere where the plains lap against higher landforms. The middle northern latitudes of Mars from 90 to 150† longitude contain at least four large shield volcanoes each of which is about twice as massive as the largest on Earth. Steep-sided domes with summit craters and large, fresh-appearing volcanic craters with smooth rims are also present in this region. Multiple flow structures, ridges with lobate flanks, chain craters, and sinuous rilles occur in all regions, suggesting widespread volcanism. Evidence for tectonic activity postdating formation of the cratered terrain and some of the plains units is abundant in the equatorial area from 0 to 120° longitude.Some regions exhibit a complex semiradial array of graben that suggest doming and stretching of the surface. Others contain intensity faulted terrain with broader, deeper graben separated by a complex mosaic of flat-topped blocks. An east-west-trending canyon system about 100–200 km wide and about 2500 km long extends through the Coprates-Eos region. The canyons have gullied walls indicative of extensive headward erosion since their initial formation. Regionally depressed areas called chaotic terrain consist of intricately broken and jumbled blocks and appear to result from breaking up and slumping of older geologic units. Compressional features have not been identified in any of the pictures analyzed to data. Plumose light and dark surface markings can be explained by eolian transport. Mariner 9 has thus revealed that Mars is a complex planet with its own distinctive geologic history and that it is less primitive than the Moon.

Icarus↗
USGS1972

Imaging experiment: The Viking Mars orbiter

The general objectives of the Imaging Experiment on the Viking Orbiter are to aid the selection of Viking Lander sites, to map and monitor the chosen sites during lander operations, to aid in the selection of future landing sites, and to extend our knowledge of the planet. The imaging system consists of two identical vidicon cameras each attached to a 1026 mm T/8 telescope giving approximately 1° square field of view. From an altitude of 1500 km the picture elements will be approximately 24m apart. The vidicon is coupled with an image intensifier which provides increased sensitivity and permits electronic shuttering and image motion compensation. A vidicon readout time of 2.24 sec enables pictures to be taken in rapid sequence for contiguous coverage at high resolution. The camera differs from those previously flown to Mars by providing contiguous coverage at high resolution on a single orbital pass, by having sufficient sensitivity to use narrow band color filters at maximum resolution, and by having response in the ultraviolet. These capabilities will be utelized to supplement lander observations and to extend our knowledge particularly of volcanic, erosional, and atmospheric phenomena on Mars.

Icarus↗
USGS1972

Mariner 9 television reconnaissance of Mars and its satellites: Preliminary results

At orbit insertion on 14 November 1971 the Martian surface was largely obscured by a dust haze with an extinction optical depth that ranged from near unity in the south polar region to probably greater than 2 over most of the planet. The only features clearly visible were the south polar cap, one dark, spot in Nix Olympica, and three dark spots in the Tharsis region. During the third week the atmosphere began to clear and surface visibility improved, but contrasts remained a fraction of their normal value. Each of the dark spots that apparently protrude through most of the dust-filled atmosphere has a crater or crater complex in its center. The craters are rimless and have featureless floors that, in the crater complexes, are at different levels. The largest crater within the southernmost spot is approximately 100 kilometers wide. The craters apparently were formed by subsidence and resemble terrestrial calderas. The south polar cap has a regular margin, suggesting very flat topography. Two craters outside the cap have frost on their floors; an apparent crater rim within the cap is frost free, indicating preferential loss of frost from elevated ground. If this is so then the curvilinear streaks, which were frost covered in 1969 and are now clear of frost, may be low-relief ridges. Closeup pictures of Phobos and Deimos show that Phobos is about 25 ±5 by 21 ±1 kilometers and Deimos is about 13.5 ± 2 by 12.0 ±0.5 kilometers. Both have irregular shapes and are highly cratered, with some craters showing raised rims. The satellites are dark objects with geometric albedos of 0.05.

Science↗
USGS1972

Orbital-science investigation: Part H: sketch map of the region around the candidate Littrow Apollo landing sites

The photograph in figure 25-59 and the corresponding map (fig. 25-60) show the geology of part of the lunar surface just east of the Littrow rilles at the eastern edge of Mare Serenitatis. The most striking feature of the region is the extremely low albedo of the area mapped as Eld in the western half of the map. The low albedo is believed to be caused by a thin layer of pyroclastic volcanic material at the surface. Another notable feature is the fresh-appearing ridges that cross the mare and the adjacent terra. The fine-braided texture of these ridges contrasts markedly with the rounded, subdued topography more common to such features, an indication that the ridges here may be unusually young. Also evident is a well-exposed succession of marelike plains units, which probably represent different stages in the filling of the Serenitatis basin. Several sets of rilles are present; most are roughly tangential to the basin and terminate against the different plains units according to the relative ages. In the northwest corner of the map is a relatively fresh volcanic crater chain (Cch) from which material appears to have been ejected over the surrounding terrain, forming rays of volcanic ejecta. The area thus includes an unusually wide variety of lunar features.

Book chapter↗
USGS1971

Lunar Apennine-Hadley region: Geological implications of earth-based radar and infrared measurements

Recently completed high-resolution radar maps of the moon contain information on the decimeter-scale structure of the surface. When this information is combined with eclipse thermal-enhancement data and with high-resolution Lunar Orbiter photography, the surface morphology is revealed in some detail. A geological history for certain features and subareas can be developed, which provides one possible framework for the interpretation of the findings from the Apollo 15 landing. Frequency of decimeter- and meter-size blocks in and around lunar craters, given by the remote-sensed data, supports a multilayer structure in the Palus Putredinis mare region, as well as a great age for the bordering Apennine Mountains scarp.

Science↗
USGS1971

Geologic maps of the Apennine-Hadley region of the Moon Apollo 15 pre-mission maps

This map shows the regional setting of the landing site for the Apollo 15 mission. The area lies approximately 650 km southeast of the center of the Imbrium basin, a large basalt-filled multi-ringed structure in the northwest quadrant of the Moon’s near side. Several arcuate structures surround the Imbrium basin (Hartmann and Kuiper, 1962). The most prominent of these forms the northwest-facing scarp of the Apennine Mountains that crosses the area from NNE to SSW. The scarp is a major structural boundary separating mostly basin-fill deposits to the northwest from either basin-synchronous or pre-basin deposits to the southeast. Of special interest is Rima Hadley, one of the widest and freshest appearing sinuous rilles on the Moon. It cuts through the mare surface to a maximum depth of about 400 meters and may expose in its walls a substantial section of the post-basin basalt. Rimae Fresnal and Rima Bradley are typical linear rilles older than Rima Hadley and do not cut mare materials. This area was previously mapped geologically at the 1:1,000,000-scale by Hackman (1966) from telescopic data.

IMAP↗
USGS1970

(ORB II-2 (100)) Geologic map of the Maskelyne DA region of the moon, Lunar Orbiter site II P-2, southeastern Mare Tranquillitatis including Apollo landing site l

This map shows the geology in and around potential early Apollo landing site 1 in the lunar equatorial belt. The Maskelyne DA region, at the southeastern edge of the Mare T ranquillitatis , is in the area transitional between mare and terra. Patches of typical terra material occur on northwest-trending ridges , and typical heavily cratered mare materials occurs only in the east-central part of the region. The terrain in the rest of the region, including the potential landing site, is exceptionally smooth and deficient in craters more than 50 m (meters) in diameter. A large cratered dome, possibly indicative of late-stage volcanism , o ccurs in the southern part of the region. Telescopically, the terrain over most of the region resembles that of mare areas with intermediate albedo; hence, at a scale of 1:1,000,000 the materials here were mapped as unit Ipm2 of the Procellarum Group ( Wilhelms , 1965).

IMAP↗
USGS1969

(RLC-14) Geologic map of the Alphonsus region of the moon

This 1:250,000- scale geologic map is one of a series prepared largely from photographs transmitted by Ranger IX (reproduced in a report by Jet Propulsion Lab., 1966). It depicts the geology of the crater Alphonsus (in which Ranger IX impacted) and environs. The primary objective of the mapping was to apply extant lunar mapping techniques used on relatively small scale telescopic photographs to the larger scale Ranger photographs, in preparation for extensive analysis of Lunar Orbiter photography in support of the Apollo program. An additional objective was to shed more light on the formation of Alphonsus and its associated features. The map outlines rock units that are inferred from surface features and characteristics, such as topography and albedo. Each rock unit is assigned an age and arranged in the explanation so that the youngest unit are at the top and the oldest at the bottom. The age classification is based on the early work of Shoemaker and Hackman (1962), and subsequent revisions reported by McCauley (1967) and Wilhelms (1966). Geology of the region has been mapped at a scale of 1:1,000,000 on the basis of Earth-based photographs and observations (Howard and Masursky , 1968). A more detailed, 1;50,000-scale map of part of the Alphonsus floor was prepared by McCauley (1969), who used Ranger IX photographs as his source of geologic information.

IMAP↗
USGS1969

(ORB II-13 (100)) Geologic map of the Maestlin G region of the moon, Lunar Orbiter site II P-13, Oceanus Procellarum, including Apollo landing site 5

This map shows the geology in and around potential early Apollo landing site 5 in the lunar equatorial belt. The Maestlin G region is in Oceanus Procellarum, about midway between the crater Kepler to the northeast and Flamsteed to the southwest. Terra materials occur only in the northeast corner of the region. Dark mare covers the remainder, and the entire region is crossed by rays from Kepler. The general geology of the larger Kepler region was mapped at a scale of 1:1,000,000 from telescopic photography (Hackman, 1962), and a 1:25,000 geologic map has been prepared of the landing site in the central part of the region (Titley and Trask, 1969).

IMAP↗