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At least 343 records · Page 19
All sourcesNASA NTRSDOE OSTI
NASA NTRS1975

Tektites - Volcanic ejecta from the moon

The possibility is considered that tektites are lunar volcanic ejecta, and lunar regions are examined from which tektites could be ejected with the necessary velocities and trajectories to reach the earth. The examined regions include areas around the Lunar Transient Phenomena sites near Censorinus, Messier, Messier A, and Taruntius, the area of Mare Foecunditatis near Secchi X, areas near Cauchy and Capella, and the eastern part of Mare Tranquillitatis. Evidence of acidic volcanic activity in these regions is described in detail, including possible calderas, mudflows, and endogenous domes. It is suggested that the moon is still gently degassing and that more violent eruptions of material may still occur on rare occasions. Remotely-sensed evidence of recent lunar internal activity is noted.

Cameron, W. S.↗
NASA NTRS1975

The effect of volcanic activity on climate

Radiative transfer calculations of the global energy balance were performed to estimate the change in mean surface temperature that results from the addition of volcanic aerosols to the stratosphere. Results of the calculations are consistent with stratospheric warming observed in the last few months following the eruption of Mt. Agung and the average surface temperature decrease found for the two year period following major volcanic explosions.

Pollack, J. B.↗
NASA NTRS1976

Volcanic explosions and climatic change - A theoretical assessment

A theoretical assessment is presented of the influence of volcanic activity on the climate. The methodology of radiative transfer calculations is described and the sources of the adopted parameters are considered. The dependence of various quantities of interest is plotted as a function of the change in the optical depth of the stratosphere at a reference wavelength. An investigation is conducted concerning the increase in optical depth produced by volcanic explosions. An estimate is obtained regarding the magnitude of the mean surface temperature change resulting from the added aerosols.

Pollack, J. B.↗
NASA NTRS1976

Additional evidence of Mercurian volcanism

Evidence concerned with (1) the character and distribution of terrain surrounding fresh basins; (2) albedo, color, and temporal differences between a basin rim and smooth plains on its floor; and (3) the stratigraphic relations and local distribution of smooth plains in the hilly and lineated terrain are cited as additional evidence for an internal origin of much of the Mercurian smooth plains. Although the question of Mercurian volcanism should be kept open, this evidence together with that presented in an earlier paper suggests that volcanism occurred on Mercury early in its history.

Trask, N. J.↗
NASA NTRS1976

The duration of volcanism in Mare Serenitatis

The crystallization ages of a suite of Apollo 17 basalts from four different stations have been measured using the Ar-39 to Ar-40 stepwise heating technique. The rocks analyzed include all principal petrographic types found at Apollo 17 landing site. A correlation between the ages and the petrographic type exists; plagioclase-poikilitic ilmenite basalts are youngest and olivine porphyritic ilmenite basalts are the oldest. The duration of volcanism in Mare Serenitatis is about 200 million years, the same as observed for Mare Imbrium, and less than observed for Mare Tranquillitatis, 400 million years. A relationship between duration of volcanism and gravity anomalies is noted. The cosmic ray exposure ages (in millions of years) for various locations range as: station 4, 58-315; station 5, 85-440; station 6, 110; station 8, 90-160.

Schaeffer, O. 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 NTRS1978

Imbrian-age highland volcanism on the moon - The Gruithuisen and Mairan domes

The Gruithuisen and Mairan domes on the moon represent morphologically and spectrally distinct nonmare extrusive volcanic features of Imbrian age. The composition, morphology, and age relationships of the domes indicate that nonmare extrusive volcanism in the northern Procellarum region of the moon continued until about 3.3 x 10 to the 9th to 3.6 x 10 to the 9th years ago and was partially contemporaneous with the emplacement of the main sequence of mare deposits.

Head, J. W., III↗
NASA NTRS1977

Lunar farside tectonics and volcanism

The reported study is primarily concerned with the identification and mapping of structural and volcanic features on the lunar farside. The study represents a continuation and extension of a similar investigation made of the nearside of the moon by Scott et al. (1975). Mapping reveals that tectonic structures on the moon's farside are comparatively scarce and such less prominently developed than those on the nearside. Rilles and mare-type ridges that form major linear and basin concentric systems on the nearside are nearly absent on the farside as are large normal faults like Rupes Recta and Rupes Cauchy. The azimuth orientations of five types of geologic structures were measured, including lineaments, crater chains, terra ridges, faults and linear rilles, and straight segments of crater rims. Mare basalts are concentrated in low regions, especially in a large southern basin which is also the site of relatively numerous volcanic constructs as well as geochemical and magnetic anomalies.

Scott, D. H.↗
NASA NTRS1978

Volcanism and soil mercury on Mars - Consequences for terrestrial microorganisms

An earth-Mars depletion formula proposed by Anders and Owen for volatiles is used to calculate a range of putative Hg levels for Martian volcanic soils based upon analyzed samples from Hawaii. The range is about 50-150 microgram per kg. When applied either in conventional or special media (e.g., basalt powder), these levels of Hg are effective inhibitors of the growth of earth microorganisms. Taken together with other hostile chemical and physical factors, volcanic toxicants would appear to provide a further deterrent to the accidental establishment of terrestrial microbiota on Mars.

Siegel, B. Z.↗
NASA NTRS1979

Evidence for explosive volcanic density currents on certain Martian volcanoes

The morphologies of certain of the smaller Martian volcanoes are discussed as possible results of explosive volcanic density currents. An examination of newly-photographed flank and caldera features of the Martian volcanoes Ceraunius Tholus, Uranius Tholus, Uranius Patera and Hecates Tholus, including steep slope angles, Krakatoa-type caldera morphologies, erosional features (radial channels and anastamosing gullies) and constructional features (blanketed flanks and possible lava deltas) reveals their similarity to terrestrial cones and composite volcanoes such as Barcena Volcano. Crater age data from the surface of Martian domes and shields indicates that such explosive activity occurred more frequently early in Martian geologic history, consistent with the view that the volcanic density currents were base surges rather than nuees ardentes, with the melting of permafrost supplying the water required in base surge generation.

Reimers, C. E.↗
NASA NTRS1979

Volcanic eruption plumes on Io

Preliminary analyses of the eight volcanic eruption plumes detected on Io by Voyager 1 are presented. Plumes were observed on the bright and dark limbs of the satellite corresponding to half of the surface and range from 10,000 to 75 km in width and 280 to 70 km in height. Most plumes were observed to be umbrella-shaped, however one consists of a very diffuse cloud lacking columnar fountain characteristics. Plume sources are characterized by a dark central area, surrounded by a bright ring, which in turn is surrounded by a broad, diffuse region; the presence of similar markings in regions not observed at the limb indicates additional volcanic activity on Io. No changes were detected in the sizes or intensities of the eruptions over the 6.5-day viewing period, however a change in the appearance of a region near one plume suggests a short-lived eruption between observations. Seven of the eight plumes are located within 30 deg of the equator, implying that equatorial surfaces are generally younger than those in the polar regions.

Strom, R. G.↗
NASA NTRS1979

Evidence for early volcanism in mare Smythii

The major geologic units in and around the Smythii basin are reflected in the Al2O3 and MgO values obtained using improved orbital X-ray fluorescence data from Apollo 15. One of these units is a high albedo plains-forming unit that has Al2O3 and MgO concentrations different from those of similar plains-forming units located in the terra west of Smythii and south of Crisium and also different from those of adjacent terra and mare materials. The chemical composition of the plainsforming unit suggests a volcanic origin; the inferred Al2O3 and MgO-rich nature of this presumed early volcanic material is supported by the fact that even the later, low albedo, lightly cratered mare fill in Mare Smythii has a high MgO value, and its Al2O3 concentration is higher than that of similar basaltic material in other maria.

Conca, J.↗
NASA NTRS1979

Basaltic volcanism - The importance of planet size

The volumetrically abundant basalts on the earth, its moon, and the eucrite parent planet all have chemical compositions that are controlled to a large extent by dry, low-pressure, crystal-liquid equilibria. Since this generalization is valid for these three planetary bodies, we infer that it may also apply to the other unsampled terrestrial planets. Other characteristics of basaltic volcanism show variations which appear to be related to planet size: the eruption temperatures, degrees of fractionation, and chemical variety of basalts and the endurance of basaltic volcanism all increase with planet size. Although the processes responsible for chemical differences between basalt suites are known, no simple systematization of the chemical differences between basalts from planet to planet has emerged.

Walker, D.↗
NASA NTRS1979

Formation and deposition of volcanic sulfate aerosols on Mars

The paper considers the formation and deposition of volcanic sulfate aerosols on Mars. The rate limiting step in sulfate aerosol formation on Mars is the gas phase oxidation of SO2 by chemical reactions with O, OH, and HO2; submicron aerosol particles would circuit Mars and then be removed from the atmosphere by gravitational forces, globally dispersed, and deposited over a range of equatorial and mid-latitudes. Volcanic sulfate aerosols on Mars consist of liquid droplets and slurries containing sulfuric acid; aerosol deposition on a global or hemispheric scale could account for the similar concentrations of sulfur within surficial soils at the two Viking lander sites.

Settle, M.↗
NASA NTRS1980

Time analysis of volcanic activity on Io by means of plasma observations

A model of Io volcanism in which the probability of activity obeys a binomial distribution is presented. Observed values of the electron density obtained over a 3-year period by ground-based spectroscopy are fitted to such a distribution. The best fit is found for a total number of 15 volcanoes with a probability of individual activity at any time of 0.143. The Pioneer 10 ultraviolet observations are reinterpreted as emissions of sulfur and oxygen ions and are found to be consistent with a plasma much less dense than that observed by the Voyager spacecraft. Late 1978 and the first half of 1979 are shown to be periods of anomalous volcanicity. Rapid variations in electron density are related to enhanced radial diffusion.

Mekler, Y.↗
NASA NTRS1982

An investigation into the utilization of HCMM thermal data for the discrimination of volcanic and Eolian geological units

The nature of the HCMM data set and the general geologic application of thermal inertia imaging using HCMM data were studied. The CCT's of five sites of interest were obtained and displayed. The upgrading of the image display system was investigated. Fragment/block size distributions in various terrain types wre characterized with emphasis on volcanic terrain. The SEASAT L-band radar images of volcanic landforms at Newberry Volcano, Oregon, were analyzed and compared to imagery from LANDSAT band 7.

Head, J. W., III↗