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All sourcesNASA NTRSDOE OSTI
NASA NTRS2006

Moessbauer Mineralogical Evidence for Aqueous Processes at Gusev Crater and Meridiani Planum

The Moessbauer spectrometers on the MER rovers have measured the relative abundances of iron with respect to both oxidation state and iron-bearing phase at Gusev Crater (Spirit rover) and Meridiani Planum (Opportunity rover). The assemblage of phases indicates aqueous alteration processes at both landing sites. Although the rock and soil of the Gusev Crater plains are dominated by Fe(2+) in olivine-bearing basalt (approx.Fo60), a Fe(3+)-rich component (nanophase ferric oxide, np-Ox) has significant abundance in surface soils (13-28% of total Fe) and in the surface coatings (rinds) of certain rocks (39%) but not in rock interiors exposed by grinding (5-6%). The mode of occurrence of np-Ox implies that it is the product of oxidative alteration of Fe(2+) silicate and oxide phases in the presence of H2O. The ubiquitous presence of sulfur in soil and in rock coatings, as determined by the MER-A APXS instrument, suggests that the alteration occurred under acid-sulfate conditions, so that both hydrolytic and sulfatic reactions are viable. A possible source for the weathering agents is volcanic emanations rich in H2O and SO2. Generally, rocks in the Columbia Hills are significantly more altered than those in the Gusev plains, with a higher proportion of Fe(3+) oxide phases compared to Fe(2+) silicate phases. This mineralogical dichotomy implies a difference in the timing, rate, duration, and/or mechanism of alteration for basaltic material in the Gusev plains compared to basaltic material in the Columbia Hills. It is possible, for example, that the basaltic material in the Columbia Hills underwent aqueous alteration in a paleoclimate that favored nearly complete alteration and that the basaltic material of the Gusev plains will not achieve the degree of alteration exhibited by the Columbia Hills under current martian surface conditions.

Morris, R. V.↗
NASA NTRSDate not supplied

The geologic evolution of Imdr Regio: a possible active hot spot on Venus

Imdr Regio is a large igneous rise that extends approximately from 35ºS-50ºS and 195ºE-225ºE between the plains of Helen, Nsomeka and Wawalag Planitiae. Imdr Regio was classified as a volcano-dominated igneous rise with a minimum-maximum diameter of 1200-1400 km and a swell height of 1.6 km. The major volcanic feature in Imdr Regio is Idunn Mons (46.5ºS/214.5ºE), a large volcano. Studies using the 1 mm (derived) surface emissivity from the Venus Express mission of the volcanic flows surrounding Idunn Mons suggest that high emissivity values in the volcano flanks are related to relatively unweathered basaltic rock and therefore indicative of a recent or even ongoing volcanic activity in Idunn Mons. Building on this previous work, here we present the first preliminary geologic map of Imdr Regio, characterize the different types of volcanism besides Idunn Mons, and their relationship with the rift and other regional structures, and discuss its geologic evolution.

I. López↗
NASA NTRSDate not supplied

Imdr Regio: The Geology of A Possible Active Hot Spot on Venus and A Target for Future Exploration By the ESA Envision Mission.

With Venus being the focus of future new missions like ESA’s EnVision, we need to look for target sites for future investigations on Venus. The different instruments will help to study the planet in a unprecedented detail. In particular, the VenSAR instrument will map the 20% of the surface of Venus at a resolution of 5 to 10 meters/pixel, so it gets crucial to select what areas of Venus deserve to be targeted for such a high-resolution mapping. We propose here Imdr Regio as a good candidate location for combined high resolution SAR mapping and for study with the rest of the mission instruments (e.g., Subsurface Radar Sounder). Imdr Regio is a large topographic rise that extends approximately from 35ºS-50ºS and 195ºE-225ºE between the volcanic plains of Helen, Nsomeka and Wawalag Planitiae. Imdr Regio was classified as a volcano-dominated topographic rise with a minimum-maximum diameter of 1200-1400 km and a swell height of 1.6 km. The southeast of Imdr Regio is dominated by Idunn Mons (46.5ºS/214.5ºE). Studies using the 1 µm (derived) surface emissivity from the Venus Express mission of the volcanic flows surrounding Idunn Mons suggest that high emissivity values in the volcano flanks are related to relatively unweathered basaltic rock and therefore indicative of a recent or even ongoing volcanic activity. We have carried out geologic mapping in the area to constrain volcanic and tectonic structures, and the geologic history of the large topographic rise. This geologic mapping reveals that different styles of volcanism are present across Imdr Regio and that this volcanic activity takes place in all the hot spot in close relation with the formation of a rift throughout all time represented by in the area. The first stages on the evolution of this large volcano are characterized by the formation of a radial fracture system and contemporaneous large sheet flows. These large sheet flows are locally difficult to distinguish from regional plains and are also deformed by regional N-trending wrinkle ridges. After this initial phase, multiple overlapping digitate flow units form the flanks and summit of the volcano and are contemporaneous with NW-SE trending fractures and graben of Olapa Chasma, a rift system that cross the topographic rise. To the northwest another large volcano also presents a system of radial fractures but lacks clear large sheet flows. Numerous pit chains are associated to fractures and graben, suggesting that transport of magma under the surface is important. The geologic history based on the mapping suggests that activity in Imdr Regio started with the emplacement of a plume/diapir in the southeast, which resulted in the formation of a radial dyke system and the emplacement of large sheet flows in Idunn Mons. The presence of other large volcanoes to the northwest suggests the presence of another magmatic source (plume or diapir). After this initial stage, volcanism continues in Idunn Mons and activity in the topographic rise is strongly related to the formation of Olapa Chasma. Rift-related volcanic flows postdate these other volcanoes and are contemporaneous with the late activity in Idunn Mons. Monogenetic volcanism is present in the rift and in all the units that are in the area.

I. López↗
NASA NTRS1993

Paleomagnetism and Tectonic Interpretations of the Taos Plateau Volcanic Field, Rio Grande Rift, New Mexico

The tectonic response of the Taos Plateau volcanic field in the southern San Luis basin to the late stage extensional environment of the Rio Grande rift was investigated using paleomagnetic techniques. Sixty-two sites (533 samples) of Pliocene volcanic units were collected covering four major rock types with ages of 4.7 to 1.8 Ma. Twenty-two of these sites were from stratigraphic sections of the lower, middle and upper Servilleta Basalt collected in the Rio Grande gorge at two locations 19 km apart. Flows from the lower and middle members in the southern gorge record reversed polarities, while those in Garapata Canyon are normal with an excursion event in the middle of the sequence. The uppermost flows of the upper member at both sites display normal directions. Although these sections correlate chemically, they seem to represent different magnetic time periods during the Gilbert Reversed-Polarity Chiron. Alternating field demagnetization, aided by principal component analysis, yields 55 sites with stable directions representing both normal and reversed polarities, and five sites indicating transitional fields. Mean direction of the normal and inverted reversed sites is I=49.3 deg. and D=356.7 deg. (alpha(sub 95)=3.6 deg). Angular dispersion of the virtual geomagnetic poles is 16.3 deg, which is consistent with paleosecular variation model G, fit to data from the past 5 m.y. Comparison with the expected direction indicates no azimuthal rotation of the Taos Plateau volcanic field; inclination flattening for the southern part of the plateau is 8.3 deg +/- 5.3 deg. Previous paleomagnelic data indicate 10 deg- 15 deg counterclockwise rotation of die Espanola block to the south over the past 5 m.y. The data suggest the Taos Plateau volcanic field, showing no rotation and some flattening in the south and east, has acted as a stable buttress and has been downwarped by overriding of the southeastern end of the plateau by the Picuris Mountains, which make up the northern corner of the counterclockwise rotating Espanola block.

Brown, Laurie L.↗
NASA NTRS2006

Laboratory Simulated Acid-Sulfate Weathering of Basaltic Materials: Implications for Formation of Sulfates at Meridiani Planum and Gusev Crater, Mars

Acid-sulfate weathering of basaltic materials is a candidate formation process for the sulfate-rich outcrops and rocks at the MER rover Opportunity and Spirit landing sites. To determine the style of acid-sulfate weathering on Mars, we weathered basaltic materials (olivine-rich glassy basaltic sand and plagioclase feldspar-rich basaltic tephra) in the laboratory under different oxidative, acid-sulfate conditions and characterized the alteration products. We investigated alteration by (1) sulfuric-acid vapor (acid fog), (2) three-step hydrothermal leaching treatment approximating an open system and (3) single-step hydrothermal batch treatment approximating a "closed system." In acid fog experiments, Al, Fe, and Ca sulfates and amorphous silica formed from plagioclase-rich tephra, and Mg and Ca sulfates and amorphous silica formed from the olivine-rich sands. In three-step leaching experiments, only amorphous Si formed from the plagioclase-rich basaltic tephra, and jarosite, Mg and Ca sulfates and amorphous silica formed from olivine-rich basaltic sand. Amorphous silica formed under single-step experiments for both starting materials. Based upon our experiments, jarosite formation in Meridiani outcrop is potential evidence for an open system acid-sulfate weathering regime. Waters rich in sulfuric acid percolated through basaltic sediment, dissolving basaltic phases (e.g., olivine) and forming jarosite, other sulfates, and iron oxides. Aqueous alteration of outcrops and rocks on the West Spur of the Columbia Hills may have occurred when vapors rich in SO2 from volcanic sources reacted with basaltic materials. Soluble ions from the host rock (e.g., olivine) reacted with S to form Ca-, Mg-, and other sulfates along with iron oxides and oxyhydroxides.

Golden, D. C.↗
NASA NTRS1973

Applicability of ERTS-1 to Montana geology

The author has identified the following significant results. Geologic maps of four test sites were compiled at 1/250,000. Band 7 prints enlarged to 1/500,000 scale are the best for the purpose, and negative prints provide a valuable supplement. More than 100 mapped lineaments represent most of the major faults of the area and a large number of suspected faults, including many of northeast trend. Under ideal conditions dip slopes may be recognized, laccoliths outlined, and axial traces drawn for narrow, plunging folds. Use of ERTS-1 imagery will greatly facilitate construction of a needed tectonic map of Montana. From ERTS-1 imagery alone, it was possible to identify up-turned undivided Paleozoic and Mesozoic strata and to map the boundaries of mountain glaciation, intermontane basins, a volcanic field, and an area of granitic rocks. It was also possible to outline clay pans associated with bentonite. However, widespread recognition of gross rock types will be difficult.

Weidman, R. M.↗
NASA NTRS1985

The coming revolution in planetology

Current ideas about the moon appear to be mistaken on two fundamental points. First, at least within certain large classes of lunar craters, internal origin (i.e., some form of volcanism) predominates over impact; this result raises questions about the reality of the 'era of violent bombardment'. Second, the origin of tektites by meteoritic impact on the earth cannot be reconciled with physical principles and is to be abandoned. The only viable alternative is origin by lunar volcanism, which implies the following: continuance of (rare) explosive lunar volcanism to the present time; existence of silicic lunar volcanism and of small patches of silicic rock at the lunar surface; a body of rock in the lunar interior, probably at great depth, which is closely similar to the earth's mantle and which contains billions of tons of volatiles, probably including hydrogen; and origin of the moon from the earth after the formation of the earth's core.

Okeefe, J. A.↗
NASA NTRS1986

Nebular chemistry and theories of lunar origin

The cosmic history of planetary matter is traced from nucleosynthesis through accretion in an attempt to understand the origin of the moon. It is noted that nebular processes must be considered in any theory of lunar origin and that planetary differentiation and volcanism determine the final character of lunar rocks. The moon's unique blend of nebular components suggests that the earth and moon accreted from the same mix of components as the proto-moon orbited the proto-earth, with the earth winning and the moon progressively losing, its solar complement of the components.

Larimer, John W.↗
NASA NTRS1992

Twenty-Third Lunar and Planetary Science Conference

Presented here is a collection of papers from the Twenty-Third Lunar and Planetary Science Conference that were chosen for having the greatest potential interest for the general reading public. The presentations avoid jargon and unnecessarily complex terms. Topics covered include electron microscopy studies of a circumstellar rock, the fractal analysis of lava flows, volcanic activity on Venus, the isotopic signature of recent solar wind nitrogen, and the implications of impact crater distribution on Venus.

Source record↗
NASA NTRS1998

Terrestrial Biomarkers for Early Life on Earth as Analogs for Possible Martian Life Forms: Examples of Minerally Replaced Bacteria and Biofilms From the 3.5 - 3.3-Ga Barberton Greenstone Belt, South Africa

The search for extraterrestrial life and especially martian life hinges on a variety of methods used to identify vestiges of what we could recognize as life, including chemical signatures, morphological fossils, and biogenic precipitates. Although the possibility of extant life on Mars (subsurface) is being considered, most exploration efforts may be directed toward the search for fossil life. Geomorphological evidence points to a warmer and wetter Mars early on in its history, a scenario that encourages comparison with the early Earth. For this reason, study of the early terrestrial life forms and environment in which they lived may provide clues as to how to search for extinct martian life. As a contribution to the early Archean database of terrestrial microfossils, we present new data on morphological fossils from the 3.5-3.3-Ga Barberton greenstone belt (BGB), South Africa. This study underlines the variety of fossil types already present in some of the oldest, best-preserved terrestrial sediments, ranging from minerally replaced bacteria and bacteria molds of vaRious morphologies (coccoid, coccobacillus, bacillus) to minerally replaced biofilm. Biofilm or extracellular polymeric substance (EPS) is produced by bacteria and appears to be more readily fossilisable than bacteria themselves. The BGB fossils occur in shallow water to subaerial sediments interbedded with volcanic lavas, the whole being deposited on oceanic crust. Penecontemporaneous silicification of sediments and volcanics resulted in the chertification of the rocks, which were later subjected to low-grade metamorphism (lower greenschist).

Westall, F.↗
NASA NTRS2014

Single Piezo-Actuator Rotary-Hammering (SPaRH) Drill

A Single Piezo-Actuator Rotary-Hammering (SPaRH) Drill includes a horn actuator having high power piezoelectric materials and a flexure pre-stress to increase the actuators effectiveness. The drill is a low mass, low power, compact coring drill measuring 20-cm high by 7-cm diameter and having a total weight of 2 kg including drive electronics. Using an average power of 50-Watts, the drill basalt is expected to cut basalt at a rate of 0.2 cm/min down to depth of 10-cm and create cuttings and an intact core. The drill is expected to operate under different environments including Martian ambient (6 Torr and down to -50 degree C), and liquid nitrogen temperatures (77 K) and low pressure (<<1 Torr) to simulate lunar polar and Europa conditions. Materials expected to be sampled include Kaolinite, Saddleback Basalt, Limestone, Volcanic Breccia, Siltstone, ice, permafrost and layered rocks with different hardness.

Sherrit, Stewart↗
NASA NTRS1993

Paleomagnetism and Tectonic Interpretations of the Taos Plateau Volcanic Field, Rio Grande Rift, New Mexico

The tectonic response of the Taos Plateau volcanic field in the southern San Luis basin to the late stage extensional environment of the Rio Grande rift was investigated using paleomagnetic techniques. Sixty-two sites (533 samples) of Pliocene volcanic units were collected covering four major rock types with ages of 4.7 to 1.8 Ma. Twenty-two of these sites were from stratigraphic sections of the lower, middle and upper Servilleta Basalt collected in the Rio Grande gorge at two locations 19 km apart. Flows from the lower and middle members in the southern gorge record reversed polarities while those in Garapata Canyon are normal with an excursion event in the middle of the sequence. The uppermost flows of the upper member at both sites display normal directions. Although these sections correlate chemically, they seem to represent different magnetic time periods during the Gilbert Reversed-Polarity Chron...

Matthew P. Golombek↗
DOE OSTI2021

Trace element geochemistry of coarse-grained angrites from Northwest Africa: Implications for their petrogenesis on the angrite parent body

The angrites are a class of achondrites that encompass a wide range of igneous textures from quenched, volcanic, and subvolcanic stones to slowly cooled, plutonic rocks. The compositions of the various geochemical reservoirs generating this variety of rocks have not been investigated fully because historically the numbers and masses of angrites available for study have been quite small. However, the rapid increase in meteorites from Northwest Africa (NWA) has enabled a renewed opportunity for such an investigation. In particular, three samples, NWA 2999, 4590, and 4801, have provided a new window into our understanding of the origin and petrogenesis of the coarse-grained (plutonic) angrites. We report here the trace element abundances in individual mineral grains of pyroxene, plagioclase, olivine/kirschsteinite, and phosphate and in the whole-rock samples. We utilize these data to constrain the petrogenetic history of each of these samples on the angrite parent body (e.g., parental melt compositions and oxygen fugacity conditions) and assess genetic relationships to previously investigated angrites. The trace element abundances in each of the three coarse-grained angrites studied here indicate a unique history for each. The observed trace element abundances and patterns in NWA 2999 show similarities with previously studied fine-grained, volcanic angrites and potentially indicate a common geochemical source reservoir, even though NWA 2999 is temporally distinct from the volcanic angrites. In contrast, NWA 4590 has trace element characteristics analogous to other coarse-grained angrites (e.g., Lewis Cliff [LEW] 86010), suggesting that these samples originated from geochemically similar source reservoirs. The third angrite, NWA 4801, exhibits geochemical characteristics most similar to the plutonic, coarse-grained angrites, but also appears to have some affinities in its trace element characteristics to the volcanic, fine-grained angrites. This suggests that NWA 4801 may represent a petrogenetic link between two distinct geochemical reservoirs on the angrite parent body. In aggregate, the trace element distributions in these three plutonic angrites suggest that while they may have originated up to several million years after the fine-grained angrites, they sampled a range of source reservoirs on the angrite parent body. Here, some of these source reservoirs were likely similar to those of the fine-grained angrites, but others had distinct geochemical characteristics.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1979

Volcano-ice interactions on Mars

Central volcanic eruptions beneath terrestrial glaciers have built steep-sided, flat-topped mountains composed of pillow lava, glassy tuff, capping flows, and cones of basalt. Subglacial fissure eruptions produced ridges of similar composition. In some places the products from a number of subglacial vents have combined to form widespread deposits. The morphologies of these subglacial volcanoes are distinctive enough to allow their recognition at the resolutions characteristic of Viking orbiter imagery. Analogs to terrestrial subglacial volcanoes have been identified on the northern plains and near the south polar cap of Mars. The polar feature provides probable evidence of volcanic eruptions beneath polar ice. A mixed unit of rock and ice is postulated to have overlain portions of the northern plains, with eruptions into this ground ice having produced mountains and ridges analogous to those in Iceland. Subsequent breakdown of this unit due to ice melting revealed the volcanic features. Estimated heights of these landforms indicate that the ice-rich unit once ranged from approximately 100 to 1200 m thick.

Allen, C. C.↗
NASA NTRS1974

Ultra sound absorption measurements in rock samples at low temperatures

A new technique, comparable with the reverberation method in room acoustics, is described. It allows Q-measurements at rock samples of arbitrary shape in the frequency range of 50 to 600 kHz in vacuum (.1 mtorr) and at low temperatures (+20 to -180 C). The method was developed in particular to investigate rock samples under lunar conditions. Ultrasound absorption has been measured at volcanics, breccia, gabbros, feldspar and quartz of different grain size and texture yielding the following results: evacuation raises Q mainly through lowering the humidity in the rock. In a dry compact rock, the effect of evacuation is small. With decreasing temperature, Q generally increases. Between +20 and -30 C, Q does not change much. With further decrease of temperature in many cases distinct anomalies appear, where Q becomes frequency dependent.

Herminghaus, C.↗
NASA NTRS1988

Cathodoluminescence of shocked quartz at the Cretaceous-Tertiary boundary

Empirical studies have documented an association between rock type and the cathodoluminescence color of constituent quartz grains. Quartz from extrusive igneous sources luminesces uniform pale blue. Quartz from intrusive igneous and high-grade metamorphic rocks generally luminesces darker purple-blue, whereas quartz recrystallized under low-grade metamorphic conditions luminesces reddish-brown. Quartz grains in most sandstones luminesce a heterogeneous mixture of these colors because the grains were derived from a variety of ultimate source rocks. If shocked quartz found at the Cretaceous-Tertiary (K-T) boundary is volcanic in origin, its cathodoluminescence should be predominantly pale blue. Alternatively, quartz grains derived from bolide impact upon, and ejection of, mixed igneous, metamorphic, and sedimentary rocks should luminesce a variety of colors. Grain mounts of sand collected at the K-T boundary horizon from the Clear Creek North site in the Raton Basin, Colorado were examined. Shocked quartz luminesced a variety of colors and very few grains luminesced the pale blue color that is typical of volcanic quartz. It was concluded that the shocked quartz was derived from a petrologically diverse source region without substantial volcanic contribution. Most shocked grains apparently were derived from low-grade metamorphic rocks, with a slightly smaller contribution from high-grade metamorphic and intrusive igneous rocks. Rare quartz grains with brown-luminescing rims reflect a minor addition from detrital sedimentary sources. The apparent relative abundances of intrusive (and rare extrusive) igneous, metamorphic, and sedimentary ultimate source rocks suggested by CL colors of shock-deformed quartz at the K-T boundary is consistent with a crustal/supracrustal origin for the grains.

Owen, Michael R.↗
NASA NTRS1988

Geochemistry and origin of gold mineralization in the Kolar Schist Belt

Geological, mineralogical, mineral-textural and geochemical data of the sulfide lodes in the belt indicate that the gold mineralization could be related to low temperature, low Eh and high pH rock-dominated geothermal systems set up in the submarine volcanic pile prior to amphibolite metamorphism. A relatively long-lived geothermal system produced an economic deposit, whereas short-lived ones, because of rapid burial by younger basalts throttled the geothermal system and diffused the discharge yielding low grade ore bodies. The source for gold and iron could be iron enriched tholeiites derived from source regions enriched in komatiitic melt components and komatiitic rocks derived by very low extents of melting of metasomatised mantle sources. On the other hand, the geographical restriction of the quartz-calcite lodes, their mineralogical and geochemical data and their estimated temperature of formation all seem to suggest that a major part of the hydrothermal fluids, and a significant portion of gold could have been derived from mantle derived intrusive, sanukitoid type magma sources, similar to the Champion Gneiss occurring on the eastern part of the belt. However, the possibility of some input by remobilization of a premetamorphic sulfide protore to quartz lodes cannot be ruled out completely.

Siddaiah, N. Siva↗