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Geology topics

H. Masursky

Publications and source records attributed to H. Masursky.

34 records · Page 2Linked to original sources
USGS1979

The Galilean satellites and Jupiter: Voyager 2 imaging science results

Voyager 2, during its encounter with the Jupiter system, provided images that both complement and supplement in important ways the Voyager 1 images. While many changes have been observed in Jupiter's visual appearance, few, yet significant, changes have been detected in the principal atmospheric currents. Jupiter's ring system is strongly forward scattering at visual wavelengths and consists of a narrow annulus of highest particle density, within which is a broader region in which the density is lower. On Io, changes are observed in eruptive activity, plume structure, and surface albedo patterns. Europa's surface retains little or no record of intense meteorite bombardment, but does reveal a complex and, as yet, little-understood system of overlapping bright and dark linear features. Ganymede is found to have at least one unit of heavily cratered terrain on a surface that otherwise suggests widespread tectonism. Except for two large ringed basins, Callisto's entire surface is heavily cratered.

Science↗
USGS1977

Voyager imaging experiment

The overall objective of this experiment is exploratory reconnaissance of Jupiter, Saturn, their satellites, and Saturn's rings. Such reconnaissance, at resolutions and phase angles unobtainable from Earth, can be expected to provide much new data relevant to the atmospheric and/or surface properties of these bodies. The experiment also has the following specific objectives: Observe and characterize the global circulation of the atmospheres of Jupiter and Saturn; Determine the horizontal and vertical structure of the visible clouds and establish their relationship to the belted appearance and dynamical properties of the planetary atmospheres; Determine the vertical structure of high, optically-thin, scattering layers on Jupiter and Saturn; Determine the nature of anomalous features such as the Great Red Spot, South Equatorial Belt disturbances, etc.; Characterize the nature of the colored material in the clouds of Jupiter and Saturn, and identify the nature and sources of chromophores on Io and Titan; Perform comparative geologic studies of many satellites at less than 15-km resolution; Map and characterize the geologic structure of several satellites at high resolution (???1 km); Investigate the existence and nature of atmospheres on the satellites; Determine the mass, size, and shape of many of the satellites by direct measurement; Determine the direction of the spin axes and periods of rotation of several satellites, and establish coordinate systems for the larger satellites; Map the radial distribution of material in Saturn's rings at high resolution; Determine the optical scattering properties of the primaries, rings, and satellites at several wavelengths and phase angles; Search for novel physical phenomena, e.g., phenomena associated with the Io flux tube, meteors, aurorae, lightning, or satellite shadows. ?? 1977 D. Reidel Publishing Company.

Space Science Reviews↗
USGS1977

10. The surface and interior of venus

Present ideas about the surface and interior of Venus are based on data obtained from (1) Earth-based radio and radar: temperature, rotation, shape, and topography; (2) fly-by and orbiting spacecraft: gravity and magnetic fields; and (3) landers: winds, local structure, gamma radiation. Surface features, including large basins, crater-like depressions, and a linear valley, have been recognized from recent ground-based radar images. Pictures of the surface acquired by the USSR's Venera 9 and 10 show abundant boulders and apparent wind erosion. On the Pioneer Venus 1978 Orbiter mission, the radar mapper experiment will determine surface heights, dielectric constant values and small-scale slope values along the sub-orbital track between 50??S and 75??N. This experiment will also estimate the global shape and provide coarse radar images (40-80 km identification resolution) of part of the surface. Gravity data will be obtained by radio tracking. Maps combining radar altimetry with spacecraft and ground-based images will be made. A fluxgate magnetometer will measure the magnetic fields around Venus. The radar and gravity data will provide clues to the level of crustal differentiation and tectonic activity. The magnetometer will determine the field variations accurately. Data from the combined experiments may constrain the dynamo mechanism; if so, a deeper understanding of both Venus and Earth will be gained. ?? 1977 D. Reidel Publishing Company.

Space Science Reviews↗
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↗
USGS1976

The Viking landing sites: Selection and certification

During the past several years the Viking project developed plans to use Viking orbiter instruments and Earth-based radar to certify the suitability of the landing sites selected as the safest and most scientifically rewarding using Mariner 9 data. During June and July 1976, the Earth-based radar and orbital spacecraft observations of some of the prime and backup sites were completed. The results of these combined observations indicated that the Viking 1 prime landing area in the Chryse region of Mars is geologically varied and possibly more hazardous than expected, and was not certifiable as a site for the Viking 1 landing. Consequently, the site certification effort had to be drastically modified and lengthened to search for a site that might be safe enough to attempt to land. The selected site considered at 47.5°W, 22.4°N represented a compromise between desirable characteristics observed with visual images and those inferred from Earth-based radar. It lies in the Chryse region about 900 kilometers northwest of the original site. Viking 1 landed successfully at this site on 20 July 1976.

Science↗
USGS1976

Search for the Viking 2 landing site

The search for the landing site of Viking 2 was more extensive than the search for the Viking 1 site. Seven times as much area (4.5 million square kilometers) was examined as for Viking 1. Cydonia (B1) and Capri (C1) sites were examined with the Viking 1 orbiter. The B latitude band (40° to 50°N) was selected before the final midcourse maneuver of Viking 2 because of its high scientific interest (that is, high atmospheric water content, surface temperature, possible near-surface permafrost, and a different geological domain). The Viking 1 orbiter continued photographing the Cydonia (B1) site to search for an area large and smooth enough on which to land (three-sigma ellipse; 100 by 260 kilometers); such an area was not found. The second spacecraft photographed and made infrared measurements in large areas in Arcadia (B2) and Utopia Planitia (B3). Both areas are highly textured, mottled cratered plains with abundant impact craters like Cydonia (B1), but smaller sectors in each area are partially mantled by wind-formed deposits. The thermal inertia, from which the grain size of surface material can be computed, and atmospheric water content were determined from the infrared observations. A region in Utopia Planitia, west of the crater Mie, was selected: the landing took place successfully on 3 September 1976 at 3:58:20 p.m. Pacific Daylight Time, earth received time.

Science↗
USGS1975

The new Martian nomenclature of the international Astronomical Union

A new nomenclature for Martian regions and topographic features uncovered by Mariner 9, as officially adopted by the International Astronomical Union, is described. About 180 craters, generally of diameters >100 km, have been named, as well as 13 classes of topographic features designated catena, chasma, dorsum, fossa, labyrinthus, mensa, mons, patera, planitia, planum, tholus, vallis, and vastitas. In addition seven craters and the Kepler Dorsum are named on Phobos, and two craters on Deimos. Coordinates and maps of each named features are displayed.

Icarus↗
USGS1974

A comparison of infrared, radar, and geologic mapping of lunar craters

Between 1000 and 2000 infrared (eclipse) and radar anomalies have been mapped on the nearside hemisphere of the Moon. A study of 52 of these anomalies indicates that most are related to impact craters and that the nature of the infrared and radar responses is compatible with a previously developed geologic model of crater aging processes. The youngest craters are pronounced thermal and radar anomalies; that is, they have enhanced eclipse temperatures and are strong radar scatterers. With increasing crater age, the associated thermal and radar responses become progressively less noticeable until they assume values for the average lunar surface. The last type of anomaly to disappear is radar enhancement at longer wavelengths. A few craters, however, have infrared and radar behaviors not predicted by the aging model. One previously unknown feature - a field strewn with centimeter-sized rock fragments - has been identified by this technique of comparing maps at the infrared, radar, and visual wavelengths.

The Moon↗
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↗
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↗
USGS1970

Television experiment for Mariner Mars 1971

The Television Experiment objectives are to provide imaging data which will complement previously gathered data and extend our knowledge of Mars. The two types of investigations will be fixed-feature (for mapping) and variable-feature (for surface and atmospheric changes). Two cameras with a factor-of-ten difference in resolution will be used on each spacecraft for medium- and high-resolution imagery. Mapping of 70% of the planet's surface will be provided by medium-resolution imagery. Spot coverage of about 5% of the surface will be possible with the high-resolution imagery. The experiment's 5 Principal Investigators and 21 Co-Investigators are organized into a team. Scientific disciplines and technical task groups have been formed to provide the formulation of experiment requirements for mission planning and instrument development. It is expected that the team concept will continue through the operational and reporting phases of the Mariner Mars 1971 Project.

Icarus↗
USGS1968

Chapter IX: Lunar theory and processes

Whereas the previous Surveyor missions were undertaken to examine mare surfaces as potential landing areas for the Apollo Program, the primary objective of the Surveyor VII mission, based on purely scientific motivations, was to explore a contrasting highland region and, specifically, to determine the chemistry of the highland material for comparison with the Surveyor V and VI chemical analyses at the mare sites. Site selection was limited to some extent by Surveyor operational constraints, but primarily by the requirements of 10-m-resolution photographs from the Lunar Orbiter Program for landing site certification. None of the nine sites studied in detail appeared capable of providing an unambiguous answer to the highland chemistry. The final selection of a site to the north of Tycho was based on the belief that the youthful character of the structure implied a minimum of contamination to the surface layers by foreign material via meteoritic processes. Moreover, the selection of a site near the rim of a major lunar crater promised insight into the “microscale” properties of a structure that represents the dominant morphologic feature on the moon.

Book chapter↗
USGS1967

Chapter 8: Lunar theory and processes

Significant new information has been provided by Surveyor III's successful landing and operation on the lunar surface; some of the most significant and interesting events are presented here. Pending completion of data reduction and more detailed analysis of the information available from the Surveyor mission, only limited interpretive discussion is included.

Book chapter↗
USGS1967

Chapter VIII: Lunar theory and processes

Much valuable new information has been provided by Surveyor III ; some of the most significant and interesting events are presented here. Only a limited interpretive discussion is included at this time, pending completion of data reduction and more detailed analysis of information available from the Surveyor mission.

Book chapter↗