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NASA NTRS1984

Valles Marineris layered deposits: Implications of origin

Layered deposits within Valles Marineris and its associated system of canyons have been considered to consist of two different rock types: (1) thick, competent, cliff-forming, light and dark bedded material in canyon walls, and (2) relatively thin, alternating series of light and dark layered material, both horizontal and inclined, that form rounded hills and large flat-topped mesas rising above the canyon floors. The dissimilarity in appearance between canyon wall and floor materials, as well as their contrasting patterns of erosion, have been considered strong evidence that their modes of origin were different.

Scott, D. H.↗
NASA NTRS1986

A preliminary report on a possible stromatolite find from the Elephant Moraine, Antarctica: A potential directional indicator for ice movement

During the 1983 to 1984 Antarctic Search for Meteorites field season, numerous specimens of a shiny black rock were collected from among the glacial debris at the Elephant Moraine. From a distance these black rocks gave the appearance of meteorites, but upon closer inspection, distinct layering and radial crystal growth patterns became clearly visible. Laboratory investigations showed that these unusual specimens are primarily composed of carbonate minerals. Petrographically, microscopic examination of twelve randomly collected specimens revealed a variety in the habits of the carbonates, but the overall trend tends to be one of radiating acicular crystals that have the appearance of a pseudo-cellular structure reminiscent of stromatolites. It is not possible at this time to specifically identify this possible stromatolite material or its source locality.

Sipiera, P. P.↗
NASA NTRS1986

Composition of the Cayley Formation at Apollo 16 as inferred from impact melt splashes

Abundances of major and trace elements and magnetic properties of 50 impact melt splashes (IMSs) from the Apollo 16 landing site are analzyed to determine the composition of their meteoritic component. MgO-Sc and Ca-Sc variation diagrams and least-squares mixing models are utilized to analyze the IMS, soil, and rock data. Consideration is given to progenitor lithologies of the IMS, the number of impact events represented by the IMS, and the heterogeneity of impact melts from single events. It is observed that the IMSs are composed of either a mixture of anorthosite and low-Sc impact melt rocks or anorthositic norite. It is determined that the surface Cayley layer is composed of TiO2, MgO, Sc, and La concentrations of 0.69, and 7.1 wt pct and 10.5 and 21.2 microg/g, respectively and 0.38 and 5.9 wt pct and 6.1 and 11.8 microg/g, respectively, for the subsurface Cayley layer. The Descartes Formation composition is estimated as TiO2, MgO, Sc, and La concentrations of 0.25, and 3.5 wt pct and 7.7 and 2.2 microg/g, respectively.

Morris, Richard V.↗
NASA NTRS2004

Evidence for Possible Exposed Water Ice Deposits in Martian Low Latitude Chasms and Chaos

A light-toned interior layer deposit (ILD) on the floor of the deep martian depression Juventae Chasma is found to have a relatively high thermal inertia approx. 500 J m(exp -2) s(exp -1/2) K(exp -1). This could imply rock, but is also similar to the average value of thermal inertia found for north polar layered deposits. Furthermore, ILD-B is found to exhibit a bluff and terrace structure . A terrace structure arises naturally in model simulations of the sublimation of large ice deposits. Such a staircase terrain, of course, is a further characteristic of north polar layered terrain. Morphological similarity, thermal inertia in the range of thermal inertias of the north polar cap layered terrain, and relatively high albedo lead us to propose that the ILD-B may consist of residual water ice partially covered by, and perhaps mixed with, varying amounts of dust or sand. Other ILDs (A-C) are also found in Juventae Chasma. While these ILDs lack the close morphological resemblance to the north polar cap, they share many other common features and appear to be part of the same formation. Similar ILDs are found in chaotic terrain elsewhere in the martian tropics. This leads us to propose that water ice may exist in the martian tropics today and may be implicit in the formation of chaotic terrain.

Leovy, C.↗
NASA NTRS1982

Anomalies within the system - Rochechouart target rock meteorite

Contaminated impact crater formations are pertinent to the study of meteoritic contamination at the Cretaceous-Tertiary boundary and other Ir-enriched layers. Target mixing considerations and volumetric estimates of Rochechouart breccias are presently combined with the geochemistry of both major and siderophile trace elements, to evaluate how the chemistry of the preserved target rock-projectile mixture evolved since deposition. Over 99 percent of the mass of extraterrestrial Ir and Os in preserved formations at Rochechouart is located in suevite-like breccias and impact melts. Hydrothermal alteration and/or weathering are the most likely processes to explain both major and trace element redistribution in Rochechouart formations.

Lambert, P.↗
NASA NTRS1985

The parental magma for some rocks from the Norite 1 subzone of the Stillwater Complex - A lunar analog study

Single samples from three successive homogeneous but contrasting layers (anorthosite, anorthositic norite, and norite) in the Stillwater Complex Norite 1 subzone were subjected to detailed petrographic and major and trace element chemical analyses. The petrography and the element chemistry of the three layers are found to be generally consistent with formation from a common magma, although a simple model of liquidus phases and trapped magma is not quite consistent with petrography and chemistry. Changes of oxidation level from layer to layer are indicated by both iron in plagioclase and by the distribution coefficient for Eu required for compatibility with a common parent. Such oxidation changes can explain qualitatively the Mg/Fe variation otherwise attributed to trapped liquid. The data demonstrate that for individual lunar highlands igneous rocks, a general picture of the parent magma can be derived, but detailed petrochemical comparisons using a simple trapped liquid model might deny a common parentage for two samples when such in fact existed.

Ryder, G.↗
NASA NTRSDate not supplied

Making Thin Sections from National Treasures: A Little Moon Rock Goes a Long Way

NASA’s Johnson Space Center curates the Apollo sample collection through their facilities in Houston, TX. It is a dual-purpose facility, intended both to store and preserve the precious samples, as well as to make them available for ongoing scientific study and public examination. The facilities consist of multiple vaults and lab spaces, including the Apollo Thin Section Lab. Although it is a part of the Curation facilities, this lab is intended to process specific lunar rock and dust samples into what are called “thin sections”. A thin section is a microscope slide with a very thin, highly polished slice of rock material mounted on it. These are used not only for microscope viewing, but also for a range of other sophisticated scientific instruments to map and measure fine details of the rock’s physical and chemical composition and structure. The process of making a thin section requires great care and patience and is an art in itself; each one is unique, and each sample can behave very differently while going through the same basic procedures. In general, it begins by taking a small chip of rock from a much larger sample. The rock fragment is placed within a small mold and liquid epoxy is poured over it and allowed to harden, producing what is called a “potted butt” (Figure 1). This is to stabilize the rock so that it won’t fragment or crumble during polishing, and to fill any cracks or voids within the rock. Once hardened, the epoxy on the bottom is carefully ground away to expose the rock surface within, which is then polished to a 1-micron finish. A thin new layer of fresh epoxy is then applied to the polished surface and used to mount it to a silica slide. Once the mounting epoxy has hardened, the potted butt is cut off less than one millimeter above the slide using a low-speed circular saw. This thin layer of sample material attached to the slide undergoes further grinding and polishing, typically bringing the sample thickness down to about 35 microns – roughly one third of the thickness of a human hair. The remaining potted butt is saved for future scientific investigations and can be re-polished and used again until all the rock material within it is used up. A single thin section can be reused countless times by numerous different researchers. In addition, thin sections are often exquisitely beautiful (Figure 2) and in some cases, lunar thin sections are used as public display samples, such as at the Smithsonian Air and Space Museum in Washington, DC. The production of thin sections allows an immense variety of research to be conducted on a tiny amount of rock or mineral material, allowing the bulk of the Apollo collection to stay pristine and unaltered, and thus, remain available for next generation of lunar scientists to further our insight into the Moon’s geological diversity, and to bring valuable new insights to our understanding of the origin of the Earth-Moon system.

J J Kent↗
NASA NTRS2001

Potential MER Landing Site in Melas Chasma

We have selected one area in Valles Marineris as a potential landing site for the Mars Exploration Rover (MER) mission. After 30 years of analyses, the formation of the Valles Marineris system of troughs and its associated deposits still remains an enigma. Understanding all aspects of the Valles Marineris would significantly contribute to deciphering the internal and external history of Mars. A landing site within Melas Chasma could provide insight into both the formation of Valles Marineris and the composition and origin of the interior layered deposits (ILDs). The ILDs have been proposed as: (1) sedimentary deposits formed in lakes mass wasted material from the walls; (3) remnants of the wall rock; (4) carbonate deposits; (5) aeolian deposits; and (6) volcanic. More recently, Malin and Edgett suggest that the fine-scale, rhythmic layering seen in the interior deposits, as well as other layered deposits in craters, supports a sedimentary origin. Because an understanding of the formation of Valles Marineris and its interior deposits is so important to deciphering the history of Mars, we have proposed a landing site for the MER mission on an exposure of interior deposits in western Melas Chasma. Either MER-A and MER-B could land at this same location.

Weitz, C. M.↗
NASA NTRS1978

Research on lunar materials

Abstracts of 14 research reports relating to investigations of lunar samples are presented. The principal topics covered include: (1) optical properties of surface and core samples; (2) chemical composition of the surface layers of lunar grains: Auger electron spectroscopy of lunar soil and ground rock samples; (3) high frequency electrical properties of lunar soil and rock samples and their relevance for the interpretation of lunar radar observations; (4) the electrostatic dust transport process; (5) secondary electron emission characteristics of lunar soil samples and their relevance to the dust transportation process; (6) grain size distribution in surface soil and core samples; and (7) the optical and chemical effects of simulated solar wind (2keV proton and a particle radiation) on lunar material.

Gold, T.↗
NASA NTRS1980

Lunar rock surfaces as detectors of solar processes

Lunar rock surfaces exposed at or just below the lunar surface are considered as detectors of the solar wind, solar flares and solar-derived magnetic fields through their interactions with galactic cosmic rays. The degradation of the solar detector capabilities of lunar surface rocks by meteoroid impact erosion, accreta deposition, loose dust, and sputtering, amorphous layer formation and accelerated diffusion due to solar particles and illumination is discussed, and it is noted that the complex interactions of factors affecting the outer micron of exposed surface material has so far prevented the development of a satisfactory model for a particle detector on the submicron scale. Methods for the determination of surface exposure ages based on the accumulation of light solar wind noble gases, Fe and Mg, impact craters, solar flare tracks, and cosmogenic Kr isotopes are examined, and the systematic variations in the ages determined by the various clocks are discussed. It is concluded that a means of obtaining satisfactory quantitative rate or flux data has not yet been established.

Hartung, J. B.↗
NASA NTRS1985

Fault type predictions from stress distributions on planetary surfaces - Importance of fault initiation depth

The prediction of fault type on planetary surfaces from model stresses calculated at depth is discussed. These fault-type predictions yield different faults than those predicted using the surface criteria commonly employed in geophysical models. For elastic-plate flexure models of mascon loading on the moon, stresses calculated at the surface predict the occurrence of strike-slip faulting at the radial distance where grabens are found. Normal faults bounding lunar grabens and thrust faults responsible for wrinkle ridges are analyzed. It is found that the former initiate at the mechanical discontinuity that separates the breccia of the megaregolith from in situ fractured rock and that the latter initiate at the mechanical discontinuity between basalt layers and the underlying basin floor. The difference between elastic constants for the outer few kilometers of brecciated megaregolith and the underlying lunar lithosphere are evaluated. Superposing nonisotropic stresses resulting from the weight of overburden to the depth of the relevant mechanical discontinuity yield stresses that predict wrinkle ridges in the basin centers and grabens outside the basin margin, and eliminate the predicted zone of strike-slip faults.

Golombek, M. P.↗
NASA NTRS1988

Deep seismic reflection profiling and continental growth curves

The results of deep seismic reflection profiling is discussed which shows that the lower crust is prominently layered, in many continental areas, regardless of the age of the surface rocks. The seismic Moho is commonly shallower than the petrological Moho, leading to the question of the nature and origin of this prominent reflector in the deep crust. The lower crust is much less well defined in Phanerozoic and Proterozoic accreted terranes, suggesting possible differences in types of lower crusts.

Klemperer, Simon L.↗
NASA NTRS1991

Adhesion and abrasion of surface materials in the Venusian aeolian environment

In laboratory simulations of the Venusian environment, rock and mineral 'target' surfaces struck by aeolian particles develop a thin layer of accretionary material derived from the particles' attrition debris. Accretion may be (in part) a manifestation of 'cold welding', a process well known in engineering, where bonding occurs between metals at a tribological interface. Accretion on geological materials was found to occur at all Venusian surface temperatures and for all types of materials tested. First-order variations in the amount deposited by particles are related to relative attrition susceptibilities. Second-order variations relate to properties of the particle-target interface. Variations in accretion volume are apparently independent of mineral chemistry and are only weakly dependent on crystallography. The results suggest that accretion should be a fairly universal phenomenon in areas of Venus subject to aeolian activity.

Marshall, John R.↗
NASA NTRS1992

Venus: Geochemical conclusions from the Magellan data

Though the Magellan mission was not designed to collect geochemical or petrological information, it has done so nonetheless. Since the time of the Pioneer Venus mission it has been known that high-altitude (greater than 2.5-5 km) mountainous areas on Venus exhibit anomalously low radiothermal emissivity (e less than 0.6). Magellan has greatly refined and extended these observations. The low emissivity requires surface material in the uplands to have a mineralogical composition that gives it a high bulk dielectric constant, greater than 20. The dielectric constant of dry terrestrial volcanic rocks seldom exceeds 7. The high-dielectric character of high-altitude surface material cannot be a primary property of the local volcanic rock, because there is no reason why rock having the required special mineralogy would erupt only at high altitudes. Therefore it is a secondary property; the primary Venus rock has reacted with the atmosphere to form a mineralogically different surface layer, and the secondary minerals formed are controlled by the ambient temperature, which decreases with altitude on Venus. A further investigation of venusian mineralogy is presented.

Wood, J. A.↗
NASA NTRS1993

Twenty-Fourth Lunar and Planetary Science Conference. Part 3: N-Z

Papers from the conference are presented, and the topics covered include the following: planetary geology, meteorites, planetary composition, meteoritic composition, planetary craters, lunar craters, meteorite craters, petrology, petrography, volcanology, planetary crusts, geochronology, geomorphism, mineralogy, lithology, planetary atmospheres, impact melts, K-T Boundary Layer, volcanoes, planetary evolution, tectonics, planetary mapping, asteroids, comets, lunar soil, lunar rocks, lunar geology, metamorphism, chemical composition, meteorite craters, planetary mantles, and space exploration.

Source record↗
NASA NTRS1994

Field guide to Cretaceous-tertiary boundary sections in northeastern Mexico

This guide was prepared for the field trip to the KT elastic sequence of northeastern Mexico, 5-8 February 1994, in conjunction with the Conference on New Developments Regarding the KT Event and Other Catastrophes in Earth History, held in Houston, Texas. The four-day excursion offers an invaluable opportunity to visit three key outcrops: Arroyo El Mimbral, La Lajilla, and El Pinon. These and other outcrops of this sequence have recently been interpreted as tsunami deposits produced by the meteorite impact event that produced the 200 to 300-km Chicxulub basin in Yucatan, and distributed ejecta around the world approximately 65 m.y. ago that today is recorded as a thin clay layer found at the K/T boundary. The impact tsunami interpretation for these rocks has not gone unchallenged, and others examining the outcrops arrive at quite different conclusions: not tsunami deposits but turbidites; not KT at all but 'upper Cretaceous.' Indeed, it is in hopes of resolving this debate through field discussion, outcrop evaluation, and sampling that led the organizers of the conference to sanction this field trip. This field guide provides participants with background information on the KT clastic sequence outcrops and is divided into two sections. The first section provides regional and logistical context for the outcrops and a description of the clastic sequence. The second section presents three representative interpretations of the outcrops by their advocates. There is clearly no way that these models can be reconciled and so two, if not all three, must be fundamentally wrong. Readers of this guide should keep in mind that many basic outcrop observations that these models are based upon remain unresolved. While great measures were taken to ensure that the information in the description section was as objective as possible, many observations are rooted in interpretations and the emphasis placed on certain observations depends to some degree upon the perspective of the author.

Keller, Gerta↗
NASA NTRS1994

Lithospheric-scale buckling and thrust structures on Mars: The Coprates rise and south Tharsis ridge belt

Detailed photogeologic mapping documents for the first time the deformation sequence of the Coprates rise. Materials of Middle Noachian through perhaps Early Hesperian age were involved in the horizontal shortening of crustal and lithospheric rocks that produced uplift and asymmetric, east-vergent folding of these layers during the Late Noachian and perhaps Early Hesperian. Previous suggestions of normal faulting as the deforming mechanism are not supported by the new mapping or by dislocation models of rise topography. The most likely mechanism for producing the Coprates rise is folding due to buckling instability and perhaps thrust faulting. An extensive ridge belt concentric to south Tharsis is defined by a newly recognized system of approximately coeval long-wavelength topogtaphic ridges and swales that include the Coprates rise. Horizontal shortening of crust and lithosphere is manifested by periodically spaced structures at two different scales: wrinkle ridges spaced tens of kilometers apart and the south Tharsis system of ridges spaced hundreds of kilometers apart. Both types of structures may be associated with early volcanotectonic activity and crustal thickening in south Tharsis. These and other large ridges indicate that lithospheric buckling and thrust faulting may have been common on early Mars.

Schultz, Richard A.↗
NASA NTRS1999

Coal Thickness Gauging Using Elastic Waves

The efforts of a mining crew can be optimized, if the thickness of the coal layers to be excavated is known before excavation. Wave propagation techniques can be used to estimate the thickness of the layer based on the contrast in the wave velocity between coal and rock beyond it. Another advantage of repeated wave measurement is that the state of the stress within the mine can be estimated. The state of the stress can be used in many safety-related decisions made during the operation of the mine. Given these two advantages, a study was carried out to determine the feasibility of the methodology. The results are presented herein.

Nazarian, Soheil↗