3,676 research outputs found
Geologic history of Martian regolith breccia Northwest Africa 7034: Evidence for hydrothermal activity and lithologic diversity in the Martian crust
The timing and mode of deposition for Martian regolith breccia Northwest Africa (NWA) 7034 were determined by combining petrography, shape analysis, and thermochronology. NWA 7034 is composed of igneous, impact, and brecciated clasts within a thermally annealed submicron matrix of pulverized crustal rocks and devitrified impact/volcanic glass. The brecciated clasts are likely lithified portions of Martian regolith with some evidence of past hydrothermal activity. Represented lithologies are primarily ancient crustal materials with crystallization ages as old as 4.4 Ga. One ancient zircon was hosted by an alkali-rich basalt clast, confirming that alkalic volcanism occurred on Mars very early. NWA 7034 is composed of fragmented particles that do not exhibit evidence of having undergone bed load transport by wind or water. The clast size distribution is similar to terrestrial pyroclastic deposits. We infer that the clasts were deposited by atmospheric rainout subsequent to a pyroclastic eruption(s) and/or impact event(s), although the ancient ages of igneous components favor mobilization by impact(s). Despite ancient components, the breccia has undergone a single pervasive thermal event at 500–800°C, evident by groundmass texture and concordance of ~1.5 Ga dates for bulk rock K-Ar, U-Pb in apatite, and U-Pb in metamict zircons. The 1.5 Ga age is likely a thermal event that coincides with rainout/breccia lithification. We infer that the episodic process of regolith lithification dominated sedimentary processes during the Amazonian Epoch. The absence of pre-Amazonian high-temperature metamorphic events recorded in ancient zircons indicates source domains of static southern highland crust punctuated by episodic impact modification
Spectral and thermal mapping of desert surface sediments for agricultural development
A combination of multispectral, thermal and microwave data obtained from space and supported by ground measurements are used to investigate the surface sediment characteristics of a desert plain area in Egypt (El-Gallaba Plain, NW of Aswan). This plain once hosted an ancestral river system that is nowadays largely covered by aeolian and gravelly sands, and thus, only detectible with radar and thermal images. The methodology consists of extracting thermo-physical and textural parameters to guide and improve supervised spectral classification results. The results show that surface mineralogy (obtained from spectral information) correlates strongly with surface emissivity, whereas grain size and surface roughness strongly correlates with apparent thermal inertia. Furthermore, several broad strips of thermal cooling-anomalies are arranged in a linear fashion and diagonally crossing the alluvial basin. The sediments within these strips show very different textural, thermo-physical and compositional characteristics with respect to the surrounding areas suggesting that they were deposited under different depositional environments such as structurally controlled linear basins. These tectonic depressions were confirmed by ground penetrating radar and could be promising areas for groundwater accumulation and exploration enabling agricultural development in the El-Gallaba Plain of the Western Desert in Egypt
Benthic habitat mapping in the Olympic Coast National Marine Sanctuary: Classification of side scan sonar data from survey HMPR-108-2002-01: Version I
In September 2002, side scan sonar was used to image a portion of the sea floor in the northern OCNMS and was mosaiced at 1-meter pixel resolution using 100 kHz data
collected at 300-meter range scale. Video from a remotely-operated vehicle (ROV), bathymetry data, sedimentary samples, and sonar mapping have been integrated to
describe geological and biological aspects of habitat and polygon features have been created and attributed with a hierarchical deep-water marine benthic classification
scheme (Greene et al. 1999). The data can be used with geographic information system (GIS) software for display, query, and analysis. Textural analysis of the sonar images
provided a relatively automated method for delineating substrate into three broad classes representing soft, mixed sediment, and hard bottom. Microhabitat and presence of
certain biologic attributes were also populated into the polygon features, but strictly limited to areas where video groundtruthing occurred. Further groundtruthing work in
specific areas would improve confidence in the classified habitat map. (PDF contains 22 pages.
An evaluation of the suitability of ERTS data for the purposes of petroleum exploration
There are no author-identified significant results in this report
Fluids mobilization in Arabia Terra, Mars: depth of pressurized reservoir from mounds self-similar clustering
Arabia Terra is a region of Mars where signs of past-water occurrence are
recorded in several landforms. Broad and local scale geomorphological,
compositional and hydrological analyses point towards pervasive fluid
circulation through time. In this work we focus on mound fields located in the
interior of three casters larger than 40 km (Firsoff, Kotido and unnamed crater
20 km to the east) and showing strong morphological and textural resemblance to
terrestrial mud volcanoes and spring-related features. We infer that these
landforms likely testify the presence of a pressurized fluid reservoir at depth
and past fluid upwelling. We have performed morphometric analyses to
characterize the mound morphologies and consequently retrieve an accurate
automated mapping of the mounds within the craters for spatial distribution and
fractal clustering analysis. The outcome of the fractal clustering yields
information about the possible extent of the percolating fracture network at
depth below the craters. We have been able to constrain the depth of the
pressurized fluid reservoir between ~2.5 and 3.2 km of depth and hence, we
propose that mounds and mounds alignments are most likely associated to the
presence of fissure ridges and fluid outflow. Their process of formation is
genetically linked to the formation of large intra-crater bulges previously
interpreted as large scale spring deposits. The overburden removal caused by
the impact crater formation is the inferred triggering mechanism for fluid
pressurization and upwelling, that through time led to the formation of the
intra-crater bulges and, after compaction and sealing, to the widespread mound
fields in their surroundings
Autoencoding the Retrieval Relevance of Medical Images
Content-based image retrieval (CBIR) of medical images is a crucial task that
can contribute to a more reliable diagnosis if applied to big data. Recent
advances in feature extraction and classification have enormously improved CBIR
results for digital images. However, considering the increasing accessibility
of big data in medical imaging, we are still in need of reducing both memory
requirements and computational expenses of image retrieval systems. This work
proposes to exclude the features of image blocks that exhibit a low encoding
error when learned by a autoencoder (). We examine the
histogram of autoendcoding errors of image blocks for each image class to
facilitate the decision which image regions, or roughly what percentage of an
image perhaps, shall be declared relevant for the retrieval task. This leads to
reduction of feature dimensionality and speeds up the retrieval process. To
validate the proposed scheme, we employ local binary patterns (LBP) and support
vector machines (SVM) which are both well-established approaches in CBIR
research community. As well, we use IRMA dataset with 14,410 x-ray images as
test data. The results show that the dimensionality of annotated feature
vectors can be reduced by up to 50% resulting in speedups greater than 27% at
expense of less than 1% decrease in the accuracy of retrieval when validating
the precision and recall of the top 20 hits.Comment: To appear in proceedings of The 5th International Conference on Image
Processing Theory, Tools and Applications (IPTA'15), Nov 10-13, 2015,
Orleans, Franc
Evaluation of the suitability of Skylab data for the purpose of petroleum exploration
There are no author-identified significant results in this report
Sediment transport inferred by submarine bedforms
By means of bathymetric and side scan sonar records, the net circulation of sediments caused by tidal currents and waves in the outer Principal Channel of Bahía Blanca Estuary is inferred. On the northern coast of the studied area there are two harbours, Belgrano and Rosales, which are simultaneously affected by internal and external hydrosedimentological processes. Through this study, present and potential negative interactions between human activities and natural processes within the studied area are demonstrated.A través del análisis de registros batimétricos y de sonar de barrido lateral se infiere la circulación neta de sedimentos causada por olas y mareas en el sector externo del Canal Principal del estuario de Bahía Blanca. Sobre la costa norte del área de estudio se encuentran dos puertos, Puerto Belgrano y Puerto Rosales, los cuales son simultáneamente afectados por procesos hidrosedimentológicos internos y externos al estuario. Por medio de este estudio se evidencian las interacciones negativas, presentes y futuras, entre las actividades humanas y los procesos naturales.Fil: Cuadrado, Diana Graciela. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto Argentino de Oceanografía. Universidad Nacional del Sur. Instituto Argentino de Oceanografía; ArgentinaFil: Gomez, Eduardo Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto Argentino de Oceanografía. Universidad Nacional del Sur. Instituto Argentino de Oceanografía; ArgentinaFil: Ginsberg, Silvia Susana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto Argentino de Oceanografía. Universidad Nacional del Sur. Instituto Argentino de Oceanografía; Argentin
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