Study of Landsat imagery prompted Cannon (1) to suggest that Sithylemenkat Lake in central Alaska occupies a meteorite impact crater. In support of his thesis, he cites physiographic, structural, geochemical, and aeromagnetic evidence from various published sources. We believe, on the basis of our previous work in the area (2-4), that Cannon has largely misinterpreted these published data, whic...

available online at http://meteoritics.org 1137 © Meteoritical Society, 2003. Printed in USA. Geology and geochemistry of shallow drill cores from the Bosumtwi impact structure, Ghana Daniel BOAMAH† and Christian KOEBERL* Department of Geological Sciences, University of Vienna, Althanstrasse 14, A-1090 Vienna, Austria †Present address: Ghana Geological Survey Department, P.O. Box M80, Accra, Gh...

Currently about 170 impact craters are known on Earth; about one third of those structures are not exposed on the surface and can only be studied by geophysics or drilling. The impact origin of geological structures can only be confirmed by petrographic and geochemical studies; thus, it is of crucial importance to obtain samples of subsurface structures. In addition, structures that have surfac...

Radar imaging results for Mercury’s non-polar regions are presented. The dual-polarization, delay-Doppler images were obtained from several years of observations with the upgraded Arecibo S-band (λ12.6-cm) radar telescope. The images are dominated by radar-bright features associated with fresh impact craters. As was found from earlier Goldstone-VLA and pre-upgrade Arecibo imaging, three of the ...

Morphologies and size-frequency distributions of impact craters on Mercury imaged during MESSENGER's first flyby elucidate the planet's geological history. Plains interior to the Caloris basin displaying color and albedo contrasts have comparable crater densities and therefore similar ages. Smooth plains exterior to Caloris exhibit a crater density approximately 40% less than on interior plains...

Introduction: Modeling of hydrothermal alteration has progressed greatly in recent years. One of the next challenges for modeling is to explain the observations of elemental transport observed in terrestrial impact craters. We present data from our work that illustrates some of the evidence for impact craters of different sizes. For the large, 180-200 km diameter, Chicxulub impact crater, data ...

About 35 km from São Paulo, near Colônia, there is a conspicuous ring feature, 3.64 km in diameter, centered at 23 o 52'S, 46 o 42'20"W, within Precambrian crystalline basement rocks, and defined by a hilly circular outer rim up to 125m higher than an inner alluvial plain presently occupied by a swamp. The crater is filled with organic-rich clayey sediments of Quaternary age. Seismic survey ind...

Introduction: Cavities of secondary calcite and veins of secondary anhydrite and quartz in the Yuca-tan-6 borehole drilled into the Chicxulub structure suggested the impact generated a hydrothermal system [1, 2]. Based on work at other craters, mostly Siljan and Puchezh-Katunki [3, 4], we estimate this system could be several kilometers deep in the center of the crater and may extend to the rim...

Peak-ring basins are important in understanding the formation of large impact basins on planetary bodies; however, debate still exists as to how peak rings form. Using altimetry and image data from the MESSENGER and LRO spacecraft in orbit around Mercury and the Moon, respectively, we measured the morphometric properties of impact structures in the transition from complex craters with central p...

[1] The ages of large impact craters on the Moon can be estimated by measuring the size-frequency distribution of smaller craters superimposed on their ejecta, but applying this method to individual craters under 3 km in diameter remains difficult due to their limited areal extent. The ejecta blankets of fresh lunar impact craters are expressed as halos of optical and radar bright material that...