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Author: Bhairavi Shankar Publisher: ISBN: Category : Languages : en Pages : 388
Book Description
Hyperve locity collisions of asteroids onto planetary bodies have catastrophic effects on the target rocks through the process of shock metamorphism. The resulting features, impact craters, are circular depressions with a sharp rim surrounded by an ejecta blanket of variably shocked rocks. With increasing impact energy, the inner crater cavity can preserve complex morphologies including terraced walls, central uplifts, and melted rocks. The lack of erosion due to the absence of water or an atmosphere makes the Moon the perfect target to study impact crater processes, in particular the distribution of highly shocked materials within impact craters of different sizes. This study focuses on the characterization and distribution of highly shocked impact melt deposits using multispectral satellite datasets around three complex craters on the farside of the Moon. The study sites have varying morphologies of central uplifts on the crater floor: 1) the 81 km Olcott crater has a cluster of peak hills; 2) Kovalevskaya crater i s a 113 km diameter complex crater with a central peak; and 3) Schrödinger basin has a central peak ring. Models propose that the collapse of crater walls and central uplifts during the final stages of crater formation determine where much of the melt rich rocks are eventually emplaced. The results of th is study indicate that for increasing crater sizes, the volume of melt - rich rocks generated also increases - at rates greater than model estimates. Impact melt deposits are emplaced beyond the crater rims at each of the sites and preserve a range of morphologies, including melt veneers, melt sheet, and ponded deposits. The regional and local topography, together with crater modification processes greatly affect where the impact melts are finally emplaced. The compositional analyses of the farside crust, using multispectral reflectance spectroscopy in the UV-VIS-NIR range, indicates that there is increasing evidence of highly mafic compositions (i.e., rocks rich in high-Ca pyroxene, olivine, spinel) intercalate d with in the original crustal highlands (rocks rich in plagioclase feldspar, and low-Ca pyroxenes) on the lunar farside, proving that the lunar farside is a far more geologically complicated terrain than originally assumed.
Author: Bhairavi Shankar Publisher: ISBN: Category : Languages : en Pages : 388
Book Description
Hyperve locity collisions of asteroids onto planetary bodies have catastrophic effects on the target rocks through the process of shock metamorphism. The resulting features, impact craters, are circular depressions with a sharp rim surrounded by an ejecta blanket of variably shocked rocks. With increasing impact energy, the inner crater cavity can preserve complex morphologies including terraced walls, central uplifts, and melted rocks. The lack of erosion due to the absence of water or an atmosphere makes the Moon the perfect target to study impact crater processes, in particular the distribution of highly shocked materials within impact craters of different sizes. This study focuses on the characterization and distribution of highly shocked impact melt deposits using multispectral satellite datasets around three complex craters on the farside of the Moon. The study sites have varying morphologies of central uplifts on the crater floor: 1) the 81 km Olcott crater has a cluster of peak hills; 2) Kovalevskaya crater i s a 113 km diameter complex crater with a central peak; and 3) Schrödinger basin has a central peak ring. Models propose that the collapse of crater walls and central uplifts during the final stages of crater formation determine where much of the melt rich rocks are eventually emplaced. The results of th is study indicate that for increasing crater sizes, the volume of melt - rich rocks generated also increases - at rates greater than model estimates. Impact melt deposits are emplaced beyond the crater rims at each of the sites and preserve a range of morphologies, including melt veneers, melt sheet, and ponded deposits. The regional and local topography, together with crater modification processes greatly affect where the impact melts are finally emplaced. The compositional analyses of the farside crust, using multispectral reflectance spectroscopy in the UV-VIS-NIR range, indicates that there is increasing evidence of highly mafic compositions (i.e., rocks rich in high-Ca pyroxene, olivine, spinel) intercalate d with in the original crustal highlands (rocks rich in plagioclase feldspar, and low-Ca pyroxenes) on the lunar farside, proving that the lunar farside is a far more geologically complicated terrain than originally assumed.
Author: Mitali Chandnani Publisher: ISBN: Category : Lunar basins Languages : en Pages : 426
Book Description
The transition from simple to complex crater morphology in impact craters with increase in crater size has been modelled and observed in planetary bodies across the Solar System. The transition diameter depends upon the strength and gravity of the planetary body. On the Moon, this transition takes place over a diameter range of several kilometers. This range spans a diversity of crater morphologies including simple, transitional and complex craters. The diameter range of 15 20 km falls within the lunar simple-to-complex transition. All other impactor properties held constant, the 15-20 km range corresponds to a factor of three in the magnitude of impact kinetic energy. I conducted detailed geologic investigation of 244 well-preserved craters in this diameter range to elucidate the root causes of morphological variations. I used panchromatic data for observing crater and surface morphology, Digital Elevation Models (DEMs) for evaluating crater morphometry and topographic variation of pre-impact terrain, near-infrared (NIR) bands for determining the composition of crater cavity and surrounding terrain, thermal infrared bands for examining rock abundance, and Synthetic Aperture Radar (SAR) data for detecting impact melt deposits. The results of my investigation indicate that the morphological differences are primarily governed by target properties. Simple craters are confined to the highlands, and the mare are more abundant in complex craters. The mare are composed of solidified basaltic lava flows interlayered with regolith. The layering creates vertical strength heterogeneities that drive the destabilization of the transient cavity and its collapse, causing the transition to complex craters at smaller diameters in the mare. The non-layered highlands are more vertically homogeneous in strength and therefore favor simple crater formation. Eight atypically deep simple craters were identified in the highlands near the mare highlands boundaries, the most porous terrains on the lunar surface. After detailed examination of these craters in comparison to their normal-depth counterparts, I conclude that part of the energy from impact on porous target was spent in target compaction. The higher the porosity of the target, the deeper the crater and greater its volume, due to increased compaction. That only some of the craters in the high porosity terrains are deep suggests that those craters are on locally extreme-high porosity patches. However, an unusual impactor property, such as a high velocity impact, a high density impactor, or a near-vertical impact may also be a contributor. The simple craters in the highlands were observed to be located on flat or gradually sloping surfaces or degraded rims and terraces of pre-existing craters. Most craters with localized slumps superpose sharp topographic breaks such as well-developed rims and terraces of pre-existing craters. However, the topographic settings of 35% of the craters with localized slumps appeared to be similar to that of the simple craters. More detailed topographic study of the pre-impact terrains of these two morphologies revealed that the pre-impact terrains of 35% of the craters with localized slumps are gradually sloping or have subtle topographic breaks. Both sharp and subtle breaks are characterized with similar sloping directions as the adjacent craters’ walls, which led to over steepening of the transient cavity walls around this part of the rim and their collapse, thereby causing the accumulation of localized slumped material. Several simple craters were also identified to have formed on pre-impact topographic breaks. However, the simple craters’ walls that superpose these breaks were observed to be sloping in directions opposite to that of the breaks. So the ejecta around these walls was deposited along the break slopes, and thus syn-impact mass wasting occurred external (and not internal) to the crater cavity.
Author: G. R. Osinski Publisher: John Wiley & Sons ISBN: 140519829X Category : Science Languages : en Pages : 362
Book Description
Impact cratering is arguably the most ubiquitous geological process in the Solar System. It has played an important role in Earth’s history, shaping the geological landscape, affecting the evolution of life, and generating economic resources. However, it was only in the latter half of the 20th century that the importance of impact cratering as a geological process was recognized and only during the past couple of decades that the study of meteorite impact structures has moved into the mainstream. This book seeks to fill a critical gap in the literature by providing an overview text covering broad aspects of the impact cratering process and aimed at graduate students, professionals and researchers alike. It introduces readers to the threat and nature of impactors, the impact cratering process, the products, and the effects – both destructive and beneficial. A series of chapters on the various techniques used to study impact craters provide a foundation for anyone studying impact craters for the first time.
Author: National Aeronautics and Space Administration (NASA) Publisher: Createspace Independent Publishing Platform ISBN: 9781722245573 Category : Languages : en Pages : 92
Book Description
Impact cratering of the earth's surface is discussed and compared with lunar craters. The basic types found on earth are either simple craters or complex impact structures and basins. Meteorite fragments and shock metamorphism provide evidence of a crater's formation by meteorite impact. Known craters on earth are ordered by location and a few principal facts are given for each crater and the general terrain in which it is located. A satellite picture of each crater and maps identifying crater locations are provided. Grieve, R. A. F. and Wood, C. A. and Garvin, J. B. and Mclaughlin, G. and Mchone, J. F., Jr. Goddard Space Flight Center; Johnson Space Center...
Author: Enrico Flamini Publisher: Springer ISBN: 3030054519 Category : Science Languages : en Pages : 691
Book Description
This comprehensive atlas explains the genesis and evolution of impact known craters on Earth, presenting a wealth of radar images from the Italian COSMO-SkyMed satellites that were acquired at the same frequency, spatial resolution, operating mode, and illumination, allowing excellent comparison of different impact structures. It also discusses in detail the processes that have hidden or erased terrestrial impact craters, and clearly explains the basic principles of remote sensing and the COSMO-SkyMed system and radar instruments. Also, the optical satellite remote sensing technique used to produce the optical images is described. The main section documents each of the exposed craters officially recognized as caused by meteoritic impact, presenting a table with the COSMO-SkyMed radar image and, where available, a Sentinel optical image and a photograph taken in situ. A short accompanying text reports the location, context, geographical coordinates, and other ancillary information to support future researches.
Author: Rogelio Daniel Acevedo Publisher: Springer ISBN: 3319130935 Category : Science Languages : en Pages : 108
Book Description
A complete and updated catalogue of impact craters and structures in South America from 2014 is presented here. Approximately eighty proven, suspected and disproven structures have been identified by several sources in this continent. All the impact sites of this large continent have been exhaustively reviewed: the proved ones, the possible ones and some very doubtful. Many sites remain without a clear geological "in situ" confirmation and some of them could be even rejected. Argentina and Brazil are leading the list containing almost everything detected. In Bolivia, Chile, Colombia, Guyana, Paraguay, Perú, Uruguay and Venezuela only a few were observed. Only Ecuador is waiting for new discoveries. So far, the largest well stated impact site is still the Araguainha structure in Brazil with its 40 kilometers in diameter. However, two possible impact structures are larger than Araguainha: Malvinas, (with 250 kilometers in diameter) and Vichada in Colombia, (50 kilometers). This study also reports the existence of some Tertiary-Quaternary glassy impactite layers: the "escorias" and "tierras cocidas" of the pampas in Argentina.
Author: Thomas Wm. Hamilton Publisher: Strategic Book Publishing & Rights Agency ISBN: 1631353535 Category : Science Languages : en Pages : 63
Book Description
Craters have been found on planets and moons throughout the solar system, caused when asteroids or meteors have collided with them. Our Earth has not escaped these impacts, and nearly 200 craters are known on Earth today. Some are easily visited, others are in locations few would ever want to get near. This book details all the known terrestrial impact craters, telling their age, size, and other details, as well as highlighting those easily visited. One has an annual “Craterfest” to attract tourists, while it is possible to swim in lakes that have filled others.
Author: Bhairavi Shankar
Author: Bhairavi Shankar
Author: Mitali Chandnani
Author: G. R. Osinski
Author: National Aeronautics and Space Administration (NASA)
Author: Enrico Flamini
Author: Rogelio Daniel Acevedo
Author: Paul W. Hodge
Author: Thomas Wm. Hamilton
Author: Tim Krüger
Author: Piero Leonardi