نتایج جستجو برای: impact crater
تعداد نتایج: 763604 فیلتر نتایج به سال:
Introduction: The highly successful Voyager [1,2] and Cassini [3] imaging experiments revealed high quality imaging data that allows for a reasonably good analysis of the crater distributions on the Saturnian satellites [4,5,6]. The observed crater distributions appear to conflict with theoretical crater distributions that are derived from observed projectile populations [6,7]. In order to comp...
Introduction: Previous surveys have been conducted of the Venusian and lunar impact crater populations in an effort to empirically determine the onset angle of various oblique impact forms. Those surveys showed a general consistency with predictions from small-scale experiments [1,2,3]. That previous work also showed that in the presence of a dense atmosphere the onset angle increases for vario...
Numerous martian impact craters have been heavily modified by processes restricted to the crater interior. A common expression of this modification is the presence of extensive fractures arranged in a concentric plan and typically forming moats that engulf the old crater wall. Although similar styles of modification occur on the moon, martian floor-fractured craters display a greater diversity ...
The Bedout High, located on the northwestern continental margin of Australia, has emerged as a prime candidate for an end-Permian impact structure. Seismic imaging, gravity data, and the identification of melt rocks and impact breccias from drill cores located on top of Bedout are consistent with the presence of a buried impact crater. The impact breccias contain nearly pure silica glass (SiO2)...
Lacustrine sediments from the 24 km diameter Boltysh impact structure record the rapid formation of an intra-crater lake. Stable isotope compositions and organic maturity parameters from the lake sediments deposited post-impact show that they were heated by underlying impactites. This heating is attributed to the establishment of an impactgenerated hydrothermal system. Estimates of the duration...
The rover Opportunity has investigated the rim of Endeavour Crater, a large ancient impact crater on Mars. Basaltic breccias produced by the impact form the rim deposits, with stratigraphy similar to that observed at similar-sized craters on Earth. Highly localized zinc enrichments in some breccia materials suggest hydrothermal alteration of rim deposits. Gypsum-rich veins cut sedimentary rocks...
Hydrothermal systems have previously been reported in ancient Noachian and Hesperian-aged craters on Mars using CRISM but not in Amazonian-aged impact craters. However, the nakhlite meteorites do provide evidence of Amazonian hydrothermal activity. This study uses CRISM data of 144 impact craters of ≥7 km diameter and 14 smaller craters (3–7 km diameter) within terrain mapped as Amazonian to se...
Fluvial features present around impact craters on Mars can offer insight into the ancient martian climate and its relationship to the impact cratering process. The widespread spatial and temporal distribution of surface ice on Mars suggests that the interaction between impact cratering and surface ice could have been a relatively frequent occurrence. We explore the thermal and melting effects o...
Introduction: The Lonar crater, India [1] is believed to have formed entirely on basaltic target rock (Deccan Trap, 65 Ma) and is therefore comparable to impact craters formed on other planetary surfaces with basaltic crusts. The genesis of Lonar crater has recently become complicated because isotopic studies on some impact-melt looking glasses found on the surface or in talus occurring mostly ...
Crater chains, presumably formed by weak asteroids or comets stretched apart by planetary tides, have been tentatively identiied on both the Earth and Moon. By modeling tidal disruption by the Earth and Moon of \rubble-pile" bodies, we nd that the Earth disrupts enough objects over the last 3.8 billion years to account for one or two lunar crater chains, but that the reciprocal production rate ...
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