Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “geologic model”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 955 records · Page 53
All sourcesNASA NTRSDOE OSTI
NASA NTRS1972

Thermal evolution of the moon.

The thermal history and current state of the lunar interior are investigated using constraints imposed by recent geological and physical data. Theoretical temperature models are computed taking into account different initial conditions, heat sources, differentiation and simulated convection. To account for the early formation of the lunar highlands, the time duration of magmatism and present-day temperatures estimated from lunar electrical conductivity profiles, it is necessary to restrict initial temperatures and abundances of radioactive elements. Successful models require that the outer half of the moon initially heated to melting temperatures, probably due to rapid accretion. Differentiation of radioactive heat sources toward the lunar surface occurred during the first 1.6 billion years. Temperatures in the outer 500 km are currently low, while the deep interior (radius less than 700 to 1000 km) is warmer than 1000 C, and is of primordial material.

Toksoz, M. N.↗
NASA NTRS1974

Solar luminosity variations and the climate of Mars

Attempts to resolve the solar neutrino flux problem have led to suggestions of large scale oscillations in the solar luminosity on a geological time scale. A simple climatological model of Mars indicates that its climate may be much more sensitive to luminosity changes than the earth's because of strong positive feedback mechanisms at work on Mars. Mariner-9 photographs of Mars show an abundance of large sinuous channels that point to an epoch of higher atmospheric pressures and abundant liquid water. Such an epoch could have been the result of large-scale, solar luminosity variations. However, our climatological model suggests that other less controversial mechanisms, such as obliquity or polar albedo changes, also could have led to such an epoch. As more becomes known about Mars, it may prove possible to formulate a history of Martian climate. By discovering effects that cannot be due to other mechanisms one may be able to form a chronology of solar luminosity variations to compare with data from the earth.

Toon, O. B.↗
NASA NTRS1979

Origin of Valles Marineris

The purpose of the paper is to propose an origin of Valles Marineris and contiguous features such as Noctis Labyrinthus, chaotic terrain, and the large channels of Mars. These are found to: (1) be continuous to each other, (2) have gradual transition between the morphologies, (3) be related by tectonic fracturing, and associated with features of possible magmatic origin. A model is presented in which the geological process is a magmatic process, and after initial uplift and fracturing, Valles Marineris, Noctis Labyrinthus and some chaotic terrain were produced by subsidence caused by lava withdrawal.

Schonfeld, E.↗
NASA NTRS1987

Morphologic contrasts between Nirgal and Auqakuh Valles, Mars: Evidence of different crustal properties

Photoclinometric measurements were made of sidewall slopes in Nirgal and Auqakuh Valles and these results were interpreted in terms of the geologic setting and a simple geomorphic model to provide insights into the physical properties of crustal materials in these areas. Nirgal was interpreted to be a runoff channel and Auqakuh to be a fretted channel. Geomorphologic arguments for the sapping origin of Nirgal and Auqakuh Valles were presented. The morphologies of the channels, however, differ greatly: the tributaries of Nirgal end abruptly in theater-headed canyons, whereas the heads of tributaries of Auqakuh shallow gradually. The plateau surface surrounding both channels appears to be covered by smooth materials, presumably lava flows; they are continuous and uneroded in the Nirgal area, but at Auqakuh they are largely eroded and several layers are exposed that total about 200 m in thickness. For Nirgal Valles, the measurements show that sidewalls in the ralatively shallow upper reaches of the channel have average slopes near 30 degrees and, in the lower reaches, sidewall slopes exceed 50 degrees. Auqakuh, on the other hand, has maximum sidewall slopes of 14 degrees and an approximate maximum depth of 1000 m. Faint, horizontal layering in portions of the lower reaches of Nirgal may indicate inhomogeneity in either composition or topography.

Mackinnon, David J.↗
NASA NTRS1989

Kinematics at the Intersection of the Garlock and Death Valley Fault Zones, California: Integration of TM Data and Field Studies

Kinematic relationships at the intersection of the southern Death Valley and Garlock fault zones were examined to identify and delineate the eastern structural boundary between the Mojave and the Basin and Range geologic terrains, and to construct a model for the evolution of this boundary through time. In order to accomplish this, satellite imagery was combined with field investigations to study six areas in the vicinity of the intersection, or possible extensions, of the fault zones. The information gathered from these areas allows the test of various hypotheses that were proposed to explain the interaction between the Death Valley and Garlock fault zones.

Verosub, Kenneth L.↗
NASA NTRS1991

Geology and structure of Beta Regio, Venus - Results from Arecibo radar imaging

Arecibo radar images of a portion of the equatorial region of Venus provide the first high resolution (1.5- to 2.0-km) synoptic coverage of Beta Regio. Within this area, tessera, a complex deformed terrain, is identified as a major geologic unit with the largest region corresponding to a plateau on the east flank of the highland. Three models are proposed to explain the origin and evolution of Beta Regio and are identified as Mantle Plume/Passive Crust, Mantle Plume/Active Crust, and Mantle Plume/Crustal Spreading. The Mantle Plume/Passive Crust model appears to be the most consistent with the geology in this region and suggests that a plume disrupts a preexisting region of tessera.

Senske, D. A.↗
NASA NTRS1993

Workshop on the Martian Northern Plains: Sedimentological, Periglacial, and Paleoclimatic Evolution

Papers that have been accepted for presentation at the Workshop on the Martian Northern Plains: Sedimentological, Periglacial, and Paleoclimatic Evolution, on 12-14 Aug. 1993 in Fairbanks, Alaska are included. Topics covered include: hydrological consequences of ponded water on Mars; morphological and morphometric studies of impact craters in the Northern Plains of Mars; a wet-geology and cold-climate Mars model: punctuation of a slow dynamics approach to equilibrium; the distribution of ground ice on Mars; and stratigraphy of the Martian Northern Plains.

Kargel, Jeffrey S.↗
NASA NTRS1988

The role of extraterrestrial phenomena in extinction

In the several years since the Alvarez report of anomalously high iridium concentrations at the Cretaceous-Tertiary boundary, evidence for the involvement of meteorite impacts in biological extinction has increased dramatically. Much more research will be needed, however, before meteorite impact is established as a general causal factor in extinction. Of ever greater long-term interest is the possibility that other extraterrestrial forces have had important influences on the evolution of life. To recognize the effects of such forces, it will be necessary to coordinate the research of astronomy and paleontology so that testable predictions can be formulated. It is possible that known, systematic changes in the Solar System or Galaxy have had effects on global biology and that these effects have been preserved in the paleontological record.

Non-NASA Center↗
NASA NTRS1988

The cryptoendolithic microbial environment in the Ross Desert of Antarctica: mathematical models of the thermal regime

Microbial activity in the Antarctic cryptoendolithic habitat is regulated primarily by temperature. Previous field studies have provided some information on the thermal regime in this habitat, but this type of information is limited by the remoteness of the site and the harsh climatic conditions. Therefore, a mathematical model of the endolithic thermal regime was constructed to augment the field data. This model enabled the parameters affecting the horizontal and altitudinal distribution of the community to be examined. The model predicts that colonization should be possible on surfaces with zenith angle less than 15 degrees. At greater zenith angles, colonization should be restricted to surfaces with azimuth angles less than 135 degrees or greater than 225 degrees. The upper elevational limit of the community should be less than 2,500 m. The thermal regime probably does not influence the zonation of the community within a rock.

Non-NASA Center↗
NASA NTRS1991

A kill curve for Phanerozoic marine species

A kill curve for Phanerozoic species is developed from an analysis of the stratigraphic ranges of 17,621 genera, as compiled by Sepkoski. The kill curve shows that a typical species' risk of extinction varies greatly, with most time intervals being characterized by very low risk. The mean extinction rate of 0.25/m.y. is thus a mixture of long periods of negligible extinction and occasional pulses of much higher rate. Because the kill curve is merely a description of the fossil record, it does not speak directly to the causes of extinction. The kill curve may be useful, however, to li inverted question markmit choices of extinction mechanisms.

NASA Discipline Number 52-40↗
NASA NTRS1992

Modelling the Phanerozoic carbon cycle and climate: constraints from the 87Sr/86Sr isotopic ratio of seawater

A numerical model describing the coupled evolution of the biogeochemical cycles of carbon, sulfur, calcium, magnesium, phosphorus, and strontium has been developed to describe the long-term changes of atmospheric carbon dioxide and climate during the Phanerozoic. The emphasis is on the effects of coupling the cycles of carbon and strontium. Various interpretations of the observed Phanerozoic history of the seawater 87Sr/86Sr ratio are investigated with the model. More specifically, the abilities of continental weathering, volcanism, and surface lithology in generating that signal are tested and compared. It is suggested that the observed fluctuations are mostly due to a changing weatherability over time. It is shown that such a conclusion is very important for the modelling of the carbon cycle. Indeed, it implies that the conventional belief that the evolution of atmospheric carbon dioxide and climate on a long time scale is governed by the balance between the volcanic input of CO2 and the rate of silicate weathering is not true. Rather carbon exchanges between the mantle and the exogenic system are likely to have played a key role too. Further, the increase of the global weathering rates with increasing surface temperature and/or atmospheric CO2 pressure usually postulated in long-term carbon cycle and climate modelling is also inconsistent with the new model. Other factors appear to have modulated the weatherability of the continents through time, such as mountain building and the existence of glaciers and ice sheets. Based on these observations, a history of atmospheric carbon dioxide and climate during Phanerozoic time, consistent with the strontium isotopic data, is reconstructed with the model and is shown to be compatible with paleoclimatic indicators, such as the timing of glaciation and the estimates of Cretaceous paleotemperatures.

NASA Discipline Number 52-30↗
NASA NTRS1992

Large-body impact and extinction in the Phanerozoic

The kill curve for Phanerozoic marine species is used to investigate large-body impact as a cause of species extinction. Current estimates of Phanerozoic impact rates are combined with the kill curve to produce an impact-kill curve, which predicts extinction levels from crater diameter, on the working assumption that impacts are responsible for all "pulsed" extinctions. By definition, pulsed extinction includes the approximately 60% of Phanerozoic extinctions that occurred in short-lived events having extinction rates greater than 5%. The resulting impact-kill curve is credible, thus justifying more thorough testing of the impact-extinction hypothesis. Such testing is possible but requires an exhaustive analysis of radiometric dating of Phanerozoic impact events.

Non-NASA Center↗
NASA NTRS2007

Applications and Results of MODIS Lunar Observations

Both Terra and Aqua MODIS have been making periodic lunar observations since their launch in December 1999 and May 2002, respectively. The primary objective of the MODIS lunar observations is to monitor on-orbit response changes for the reflective solar bands (RSB) and to track long-term radiometric calibration stability. The Moon is an extremely stable surface reflectance reference and, together with the lunar radiometric model developed recently by the US Geological Survey (USGS), the applications of lunar observations for Earth remote sensing missions have been greatly enhanced and expanded. In particular, calibration inter-comparisons among sensors on different platforms and operated in different time frames have been enabled in the VIS/NIR/SWIR spectral regions. In this paper, we discuss various applications of MODIS lunar observations, such as monitoring the RSB radiometric stability and calibration consistency between the two sensors, evaluating the calibration differences among detectors within the same spectral band, and tracking the on-orbit changes of band-to-band registration (BBR). Other applications designed for the thermal emissive bands (TEB) and special sensor characterization purposes are also illustrated. Results from multi-year Terra and Aqua MODIS lunar observations demonstrate clearly that the two sensors have been calibrated consistently to within 1% for most RSB compared to the 2% radiometric calibration requirement. In addition the spatial characterization results derived from lunar observations are in good agreement with those derived from the instrument's on-board calibrator. The applications and results of MODIS lunar observations presented in this paper provide useful references for other sensors that also make use of lunar surface observations.

Xiong, X.↗
NASA NTRS2024

Combining Multi-Faceted Laboratory Studies of 74001-2 and Regional Remote Sensing to Address How Pyroclastic Eruptions Record and Affect the Lunar Volatile Budget

Basaltic magmatism is an efficient process for bringing volatiles from a planetary interior to its surface, with the possibility of generation of a transient lunar atmosphere as abundant volcanic materials de-gassed. However, pyroclastic deposits are locations where trapped gases may be studied [e.g., 2,3]. Volatile-rich pyroclastic deposits occur over a wide surface area of the Moon, indicating that the transport of volatiles and associated pyroclastic materials from the Moon’s mantle to the surface was a wide-spread phenomenon. Numerous studies analyzing remotely sensed data and using empirical modeling have demonstrated that various stages of pyroclastic eruptions significantly influence gas release patterns, morphology, and mineralogy of the deposit. Many observations based on mare basalts and pyroclastic deposits have identified potential histories of gas release [e.g., 2-10] and their influence on volatiles and their stable isotopes [e.g., 11-13]. The best representation of these pyroclastic deposits in the sample collection is core sample 74001-74002 that was collected during the Apollo 17 mission to the Taurus-Littrow Valley (TLV). The double drive tube penetrated a part of a regional-scale pyroclastic deposit and sampled approximately 68.1 cm of that deposit in the TLV. Remnants of this and other pyroclastic depos-its are represented throughout and beyond the TLV [e.g., 14-16]. The stratigraphy of this core has been investigated and defined by numerous studies. The CASA Moon SSERVI research team is conducting a multi-faceted analytical study of this deposit. Data generated from revisiting the stratigraphy of 74001-74002 will be used to place stable isotopes (H, B, Cl, S, Zn, Cu, Rb, Ga, Pb), Ar-Ar and U-Pb chronology, geochemistry, nanometer-scale observations of mineral surfaces, orbital observations, and experiments and modeling within a stratigraphic, eruptive, and geologic context. It is important to place these data into such a context. For example, recent S isotope measurements reported by Dottin et al. show differences within this core that may be related to either changes in source or eruptive process over the course of the eruption (vs. multiple eruptions). A fuller understanding of the stratigraphy is fundamental to resolving this interpretation. This comprehensive approach can only be achieved within the context of a program such as SSERVI. In addition, imaging produced in this project will be incorporated into a citizen scientist program to further identify many of the textural features of this double drive tube.

SSERVI↗
DOE OSTI2020

Investigation and Analysis of Dolomite Dissolution in Variable Strength Systems Relevant to the WIPP

The Waste Isolation Pilot Plant (WIPP) was opened in 1999 as a solution to the long-term disposal of the nation's nuclear defense-generated transuranic (TRU) waste. The salt beds were recommended as the ideal location because they are free from flowing fresh water, easily mined, impermeable, and geologically stable. However, for performance assessment modeling, release scenarios must be considered. The most likely release scenario was determined to be human intrusion leading to direct and/or long-term brine release (US DOE 1995, US DOE 1996, Perkins et al., 1999). The focus of this research is the Rustler formation because it is located above the WIPP and is the most transmissive layer (Perkins et al., 1999). Objective: To determine the effect of chelating ligands ( e.g. EDTA) on dissolution of dolomite in high ionic strength systems. Do brines impact dolomite dissolution and how is it affected by EDTA binding with cations? By varying the ionic strengths, different brine conditions can be simulated similar to those in and around the Culebra member and evaluate trends of dissolved Ca and Mg in the aqueous phase from the quantified data. Conclusions: <2% of dolomite dissolved over one week at pH 8.5. Greater dissolution occurred at higher ionic strength and in the presence of NaCl with approximately 0.4 vs. 0.9% of Mg removed from dolomite in 0.1 and 1.0 M Na. Further, 0.3 vs. 0.9% of Mg was removed from dolomite in 1.0 M IS CaCl{sub 2} versus NaCl. EDTA increased dissolution of dolomite at low ionic strength due to its strong complexation affinity for Ca/Mg with slightly greater removal of Ca than Mg. Significant differences were not observed at high ionic strength due to the presence of large concentrations of competing cations (Na, Ca, Mg). Slightly higher concentrations of Ca were removed from dolomite than Mg after one week, suggesting either incongruent dissolution or release through ion exchange of Ca from trace mineral impurities. Further, when EDTA was present, it may have increased Ca removal due to its greater complexation for Ca than Mg. Environmental Implications: High ionic strength brines and low ionic strength solutions with organic ligands increase dissolution of dolomite. Due to the long half-lives of radionuclides in the TRU waste, it may be important to consider the long term impact of dolomite dissolution for potential release scenarios.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2018

Geocellular model of St. Peter Sandstone for University of Illinois at Urbana-Champaign DDU Feasibility Study

The geocellular model of the St. Peter Sandstone was constructed for the University of Illinois at Urbana-Champaign DDU feasibility study. Starting with the initial area of review (18.0 km by 18.1 km [11.2 miles by 11.3 miles]) the boundaries of the model were trimmed down to 9.7 km by 9.7 km (6 miles by 6 miles) to ensure that the model enclosed a large enough volume so that the cones of depression of both the production and injection wells would not interact with each other, while at the same time minimizing the number of cells to model to reduce computational time. The grid-cell size was set to 61.0 m by 61.0 m (200 feet by 200 feet) for 160 nodes in the X and Y directions. The top surface of the St. Peter Sandstone was provided by geologists working on the project, and the average thickness of the formation was taken from the geologic prospectus they provided. An average thickness of 68.6 m (225 feet) was used for the St. Peter Sandstone, resulting in 45 layers for the model. Petrophysical data was taken from available rotary sidewall core data (Morrow et al., 2017). As geothermal properties (thermal conductivity, specific heat capacity) are closely related to mineralogy, specifically the percentage of quartz, available mineralogical data was assembled and used with published data of geothermal values to determine these properties (Waples and Waples, 2004; Robertson, 1988). The St. Peter Sandstone was divided into facies according to similar geothermal and petrophysical properties, and distributed according to available geophysical log data and prevailing interpretations of the depositional/diagenetic history (Will et al. 2014). Petrophysical and geothermal properties were distributed through geostatistical means according to the associated distributions for each lithofacies. The formation temperature was calculated, based on data from continuous temperature geophysical log from a deep well drilled into the Precambrian basement at the nearby Illinois Basin Decatur Project (IBDP) where CO2 is currently being sequestered (Schlumberger, 2012). Salinity values used in the model were taken from regional studies of brine chemistry in the St. Peter Sandstone, including for the IBDP (e.g., Panno et al. 2018). After being reviewed by the project's geologists, the model was then passed onto the geological engineers to begin simulations of the geothermal reservoir and wellbores.

15 GEOTHERMAL ENERGY↗
DOE OSTI2018

Best Practices for Modeling and Simulation of CO 2 Storage

The purpose of this best practices manual (BPM) is to describe lessons learned and best practices for modeling and simulation of carbon dioxide (CO 2 ) geologic storage (herein “storage”) projects. Information presented here is derived from laboratory and field storage project activities conducted by the Plains CO 2 Reduction (PCOR) Partnership. Modeling and simulation collectively comprise one of four technical elements of the adaptive management approach (AMA) formalized by the PCOR Partnership for storage project development. The other technical elements are site characterization; risk assessment; and monitoring, verification, and accounting (MVA) of injected CO 2 .

54 ENVIRONMENTAL SCIENCES↗