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Carr, M. H.

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

At least 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS1985

Io: Generation of Silicate Magma by Shear Melting at the Base of a Basaltic Lithosphere

Tidal theory and observational evidence indicates that about 1 w/sq. m. of energy is released at the surface of Io. In order to place limits on how much tidal energy can be dissipated within a rigid lithosphere, depth-temperature profiles were calculated for different lithosphere thickness assuming that the tidal energy was dissipated uniformly throughout the lithosphere. Thus a thick lithosphere implies that a significant fraction of the tidal energy is dissipated below the depth where solidus temperatures are reached. One possibility is that Io has a crust consisting of a low melting temperature fraction such as basalt, overlying a mantle of a high melting temperature fraction such as peridotite. Thus, if the lithosphere of Io is thicker than 30 km, as appears probable, then high rates of silicate volcanism are implied and a significant fraction of the tidal energy must be dissipated by viscous deformation rather than rigid flexure.

Carr, M. H.↗
NASA NTRS1984

The structure of the Ionian lithosphere

Exploratory work on the structure of the Ionian lithosphere is reported. The approach is to examine temperature profiles within the lithosphere that result from different distributions of sulfur and silicates and different conductive heat fluxes, then compare such profiles with observations in the expectation that only a limited set of the profiles are possible. In this preliminary work some rather simplistic assumptions were taken and the report should be viewed more as a demonstration of a method rather than a presentation of results.

Carr, M. H.↗
NASA NTRS1984

Freezing of Martian streams under climatic conditions

The valley networks of Mars are widely believed to have formed at a time when climatic conditions on the planet were significantly different from those that currently prevail. This view arises from the following observations: (1) the valleys form integrated branching networks which suggests fluid drainage, and water is the most plausible fluid, (2) the present atmosphere contains only minute amounts of water, (3) the networks appear to be more akin to terrestrial valleys that are eroded by streams of modest discharges than features that form by catastrophic floods, and (4) small streams of water will rapidly freeze under present climatic conditions. Climatic conditions at the time of formation of the valleys are studied based on the assumption that they were cut by running water.

Carr, M. H.↗
NASA NTRS1983

Stability of streams and lakes on Mars

The freezing of small Martian streams is modelled for a variety of climatic conditions, on the supposition that the Martian atmosphere may have been considerably thicker in the past, at the time of the formation of the valley networks. This model examines the energy balance at the upper and lower surfaces of ice on streams, in order to determine the rate at which ice thickens with time. Results indicate that freezing rates are not strongly dependent on atmospheric pressure, and, under windy conditions, dependence on atmospheric pressure is even weaker. It is noted that the main problem in valley formation is in initiating the flow. Groundwater seepage alone is inadequate, due to the difficulty of groundwater system replenishment.

Carr, M. H.↗
NASA NTRS1983

The geology of the terrestrial planets

Knowledge regarding the geology of the terrestrial planets has increased considerably during the last four years. The present investigation provides a brief summary of work during these years on the geology of Mercury, Venus, moon, and Mars. Following the Mariner 10 encounter with Mercury in 1974, the geologic history of the planet was broadly outlined by Strom (1979). McCauley et al. (1981) recognized several facies of ejecta around Caloris. Hostetler and Drake (1980) showed that unless Mercury received more than 60-70 percent of its thermal energy from tidal interactions, it must have undergone early, almost global melting. Knowledge of the Venusian surface has increased substantially over the last few years both through improvement of earth-based observations and in connection with the Pioneer Venus mission. A topographic map of Venus is presented. Attention is also given to the composition and character of lunar highlands, the evolution of different maria, photographs obtained of almost the entire planet Mars, and Martian craters and volcanism.

Carr, M. H.↗
NASA NTRS1981

Martian channels and valleys - Their characteristics, distribution, and age

The distribution and ages of Martian channels and valleys, which are generally believed to have been cut by running water, are examined with particular emphasis on the small branching networks referred to as runoff channels or valley networks. Valleys at latitudes from 65 deg S to 65 deg N were surveyed on Viking images at resolutions between 125 and 300 m. Almost all of the valleys are found in the old cratered terrain, in areas characterized by high elevations, low albedos and low violet/red ratios. The networks are deduced to have formed early in the history of the planet, with a formation rate declining rapidly shortly after the decline of the cratering rate 3.9 billion years ago. Two types of outflow channels are distinguished: unconfined, in which broad swaths of terrain are scoured, and confined, in which flow is restricted to discrete channels. Both types start at local sources, and have formed episodically throughout Martian history. Fretted channels, found mainly in two latitude belts characterized by relatively rapid erosion along escarpments, are explained by the lateral enlargement of other channels by mass wasting.

Carr, M. H.↗
NASA NTRS1980

Stability of sulfur slopes on Io

The mechanical properties of elemental sulfur are such that the upper crust of Io cannot be primarily sulfur. For heat flows in the range 100-1000 ergs/sq cm sec sulfur becomes ductile within several hundred meters of the surface and would prevent the formation of calderas with depths greater than this. However, the one caldera for which precise depth data are available is 2 km deep, and this value may be typical. A study of the mechanical equilibrium of simple slopes shows that the depth to the zone of rapid ductile flow strongly controls the maximum heights for sulfur slopes. Sulfur scarps with heights greater than 1 km will fail for all heat flows greater than 180 ergs/sq cm sec and slope angles greater than 22.5 deg. The observed relief on Io is inconsistent with that anticipated for a predominantly sulfur crust. However, a silicate crust with several percent sulfur included satisfies both the mechanical constraints and the observed presence of sulfur on Io.

Clow, G. D.↗
NASA NTRS1980

Volcanic features of Hawaii. A basis for comparison with Mars

Despite the difference in size Martian and Hawaiian volcanoes have numerous characteristics in common. Specific features such as lava channels, collapsed lava tubes, levees and flow fronts, all very common in Hawaii, are also abundant on the flanks of some of the Martian volcanoes. Striking differences also exist, such as the apparent lack of radial rift zones on some Martian volcanoes and the paucity of cinder and spatter cones. Some of the best photographs of Martian and Hawaiian volcanic features are presented. Descriptive legends are provided for each picture. An overview of the geological processes and structures depicted is included.

Carr, M. H.↗
NASA NTRS1980

Viking orbiter views of Mars

Images acquired by the Viking orbiters, beginning in 1976 are presented. The pictures represent only a small fraction of the many thousands taken, and were chosen to illustrate the diverse geology of Mars and its atmospheric phenomena. Specific topics discussed include the Viking mission and its objectives, a brief comparison of Earth and Mars, and surface features of Mars including the great equatorial canyons, channels, volcanic and deformational features, and craters. Martian moons, surface processes, polar regions, and the Martian atmosphere are also covered.

Carr, M. H.↗
NASA NTRS1979

Volcanic features of Io

The various volcanic landforms observed on Io by Voyager 1 are described and compared with similar features on earth. Ionian calderas, observed to cover 5% of the surface, are generally found to be of low relief, similar to certain terrestrial calderas. Flow patterns observed include dark, linear markings with lobate margins resembling terrestrial lava flows, bright lobate markings originating at calderas, and a bright flow feature surrounding the calderas. Positive relief features associated with volcanic structures include pancake-like constructions similar to low volcanic cones, sheet-like structures, rugged mountains, and a type of surface upheaval. Bright and dark diffuse markings have also been found. The implications of the high rates of volcanic activity and the apparent abundance of sulfur on Io for the type of volcanism observed are discussed, and it is concluded that while there are strong arguments for sulfur flows on the surface of Io, silicate volcanism of the type observed on earth may also occur.

Carr, M. H.↗
NASA NTRS1979

Formation of Martian flood features by release of water from confined aquifers

It is proposed that the rapid release of water under great pressure from deeply buried aquifers is responsible for the formation of the Martian channels suggestive of catastrophic flooding (outflow channels). Fine channels in the Martian surface suggest the presence of surface water early in the history of the planet, which would have entered the ground water system through the porous near-surface rocks. Subsequent global cooling would have trapped the ground water under a thick permafrost layer and formed a system of confined aquifers. High pore pressures within the aquifers are considered to have triggered the breakout of water from the aquifers at rates of from 10 to the 5th to 10 to the 7th cu m/sec, which would be prevented from reentering the ground water system by the layer of permafrost. Outflow from the aquifer is also considered to have caused the undermining of adjacent areas and the collapse of the surface to form areas of chaos, often associated with channels.

Carr, M. H.↗
NASA NTRS1979

The Jupiter system through the eyes of Voyager 1

The cameras aboard Voyager 1 have provided a closeup view of the Jupiter system, revealing heretofore unknown characteristics and phenomena associated with the planet's atmosphere and the surfaces of its five major satellites. On Jupiter itself, atmospheric motions - the interaction of cloud systems - display complex vorticity. On its dark side, lightening and auroras are observed. A ring was discovered surrounding Jupiter. The satellite surfaces display dramatic differences including extensive active volcanism on Io, complex tectonism on Ganymede and possibly Europa, and flattened remnants of enormous impact features on Callisto.

Smith, B. A.↗
NASA NTRS1977

Some Martian Volcanic Features as Viewed from the Viking Orbiters

A summary is presented of the results of some new observations on Martian volcanic features made from the Viking orbiters. Most of these observations are concerned with the Tharsis and Alba regions. The youth, size, and style of the volcanic features in these areas render them particularly susceptible to analysis. Excellent coverage was also acquired of Apollinaris Patera. It has many features of the Tharsis shields, with a cliff around its circumference and a large central caldera. Olympus Mons and its vicinity are examined, taking into account the shield of Olympus Mons, mass movement features along the basal scarp, the basal plains, the relative ages of Olympus Mons and the basal plains, and grooved terrain.

Carr, M. H.↗
NASA NTRS1977

Geology of Chryse Planitia

Chryse Planitia, the site of the first successful landing on Mars by Viking 1, is an asymmetrical basin, centered at 45 deg W and 24 deg N, about 2000 km northeast of Valles Marineris. High-resolution Viking orbiter images show Chryse Planitia to be much more complex than had been suspected from Mariner 9 images. On the basis of a study of the Viking pictures it is concluded that the geological history of Chryse Planitia involves a complex sequence of impact cratering, mantling by extensive deposits of unknown origin, redistribution of mantling and crater materials by erosion and deposition with concurrent eruptions of flood-type basalts, and aeolian activity.

Greeley, R.↗
NASA NTRS1976

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 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.

Cutts, J. A.↗
NASA NTRS1976

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.

Carr, M. H.↗
NASA NTRS1976

A geological basis for the exploration of the planets: Introduction

The geological aspects of solar-system exploration were considered by first showing how geologic data are related to space science in general, and, second, by discussing the approach used in planetary geology. The origin, evolution, and distribution of matter condensed in the form of planets, satellites, comets, and asteroids were studied. Terrestrial planets, comets, and asteroids, and the solid satellites of the outer planets are discussed. Jupiter and Saturn, in particular, have satellites of prime importance. Geophysics, geochemistry, geodesy, cartography, and other disciplines concerned with the solid planets were all included.

Greeley, R.↗