A large impact crater beneath Hiawatha Glacier in northwest Greenland

We report the discovery of a large impact crater beneath Hiawatha Glacier in northwest Greenland. From airborne radar surveys, we identify a 31-kilometer-wide, circular bedrock depression beneath up to a kilometer of ice. This depression has an elevated rim that cross-cuts tributary subglacial channels and a subdued central uplift that appears to be actively eroding. From ground investigations of the deglaciated foreland, we identify overprinted structures within Precambrian bedrock along the ice margin that strike tangent to the subglacial rim. Glaciofluvial sediment from the largest river draining the crater contains shocked quartz and other impact-related grains. Geochemical analysis of this sediment indicates that the impactor was a fractionated iron asteroid, which must have been more than a kilometer wide to produce the identified crater. Radiostratigraphy of the ice in the crater shows that the Holocene ice is continuous and conformable, but all deeper and older ice appears to be debris rich or heavily disturbed. The age of this impact crater is presently unknown, but from our geological and geophysical evidence, we conclude that it is unlikely to predate the Pleistocene inception of the Greenland Ice Sheet.

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Large impact crater histories of Mars: The effect of different model crater age techniques

Icarus ◽

10.1016/j.icarus.2013.03.019 ◽

2013 ◽

Vol 225 (1) ◽

pp. 173-184 ◽

Cited By ~ 54

Author(s):

Stuart J. Robbins ◽

Brian M. Hynek ◽

Robert J. Lillis ◽

William F. Bottke

Keyword(s):

Impact Crater ◽

Large Impact

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Gravitationally induced stresses around a large impact crater

International Journal of Rock Mechanics and Mining Sciences & Geomechanics Abstracts ◽

10.1016/0148-9062(74)90622-6 ◽

1974 ◽

Vol 11 (11) ◽

pp. A232

Author(s):

B. Dent

Keyword(s):

Impact Crater ◽

Large Impact ◽

Induced Stresses

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Fluctuation of recent large impact craters rate on Mars from automatic crater detection

10.5194/egusphere-egu2020-5003 ◽

2020 ◽

Author(s):

Anthony Lagain ◽

Misha Kreslavsky ◽

Gretchen Benedix ◽

David Baratoux ◽

Phil Bland ◽

...

Keyword(s):

Impact Crater ◽

Impact Craters ◽

Asteroid Belt ◽

Large Impact ◽

The Moon ◽

Crater Detection ◽

Impact Flux ◽

Ejecta Blanket ◽

The Impact ◽

Latitudinal Band

Knowledge of collision rates through time and space is essential because meteoritic impact crater counting is the only way to determine the ages of surface geological units and processes on the solid bodies of our Solar System. All chronology models assume a constant size distribution of impactors and an exponential decay of the impact flux between 4 Ga and 2.5 Ga before the present followed by a constant rate over the last 2.5 Ga. These two assumptions are challenged by recent evidence for an increase of the impact flux on the Moon and the Earth and probably on Mars associated with a decoupling between the flux of small and large impactors over the last billion years. Here, using the results of an automatic crater detection algorithm, we investigate the evolution of the rate of formation of large impact craters (Dc &#8805; 20km) on Mars and thus infer the evolution of the flux of large impactors (Di > 5km) from the size-frequency distribution of small craters superposed to the ejecta blankets of large ones.The dating of large impact craters on Mars is limited by several factors such as the degradation of ejecta blankets and the retention rate of small craters superposed to their ejecta. We therefore focused on craters &#8805;20km in diameter exhibiting an ejecta blanket according to the crater database and located on a latitudinal band between &#177;35&#176;. We then selected those whom their ejecta are not affected by volcanic/tectonic processes or by the formation of another large nearby impact crater. The final set includes 590 impact craters.If one can argue the impact flux cannot be fully recorded for the last 4Ga due to resurfacing processes erasing progressively the ejecta blanket and large craters themselves, Hesperian and Noachian terrains within the 35&#176; latitudinal band should nevertheless have retained all D&#8805;20km craters over a portion of the Amazonian period. The CSFD of craters younger than 600Ma (113 craters) superposed to these terrains is consistent with the 600Ma isochron, supporting the fact that the entire population of craters &#8805;20km formed over the last 600 million years on this portion of the Martian surface has been counted completely. We therefore focused on the analysis of the impact rate evolution over this range of time from this crater sub-sample.The formation of large impact craters is not homogeneously distributed over the time range investigated here. Our data suggest an inconsistency between the flux used to date each crater and the rate inferred from these datings, thus implying that the small and large body impact fluxes are decoupled from one another. We note also sharp peaks centered around 480, 280 and 100Ma. Preliminary statistical test show that 280Ma peak is marginally significant whereas the two others are too small to be statistically significant. This pattern would be consistent with other independent arguments for increased rate with similar intensity and timing on the Moon and Mars for which the causes are probably collisions and potentially formation of asteroid families within the main asteroid belt.

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New version of Eugene Shoemaker formula more suitable for calculating the impact energy of meteorites and methods for calculating the mass and volume of meteorites

10.31219/osf.io/zwgrh ◽

2020 ◽

Author(s):

Huadong Dian Zhao ◽

Weigao Li ◽

Haishan Dang ◽

Jundong Tian

Keyword(s):

Physical Process ◽

Impact Energy ◽

Impact Crater ◽

Impact Angle ◽

Large Impact ◽

The Earth ◽

History Of ◽

The Impact ◽

General Method

For an impact crater on land, scientists often need to estimate the impact energyaccording to the diameter of the impact crater. Since there is no unified formula to describe thecomplex physical process of impact, the results estimated by different scholars are quitedifferent, which makes it difficult to judge which one is more consistent with the facts. Forimpact craters in the history of the earth, which have been unable to know the impact angle, thereis an urgent need for a unified formula to obtain a more pertinent calculation result.Aftercomparing and analyzing several formulas put forward by previous scientists, we think thatEugene Shoemaker's formula in 1990 is better. We simplify and improve it in order to make itadapt to the calculation of very large impact energy, so as to avoid fallacies. At the end of thepaper, we also give a general method to estimate the mass and volume of meteorites afterobtaining the impact energy. The improved formula and method proposed in this paper can beused for reference by scholars and science lovers, and may need further research to improve it inthe future.

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Large impact crater in the Barents Sea

Geology ◽

10.1130/0091-7613(1993)021<0291:licitb>2.3.co;2 ◽

1993 ◽

Vol 21 (4) ◽

pp. 291 ◽

Cited By ~ 64

Author(s):

Steinar Thor Gudlaugsson

Keyword(s):

Impact Crater ◽

Barents Sea ◽

Large Impact ◽

The Barents Sea

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Chicxulub impact crater

AccessScience ◽

10.1036/1097-8542.129760 ◽

2017 ◽

Keyword(s):

Impact Crater ◽

Chicxulub Impact Crater ◽

Chicxulub Impact

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A Review on Load Balancing Model Using Best Partition Technique

International Journal of Advanced Research in Computer Science and Software Engineering ◽

10.23956/ijarcsse.v7i8.69 ◽

2017 ◽

Vol 7 (8) ◽

pp. 284

Author(s):

M. Chaitanya ◽

K. Durga Charan

Keyword(s):

Cloud Computing ◽

Fault Tolerance ◽

Load Balancing ◽

Load Balance ◽

Large Impact ◽

Cloud Environment ◽

Public Cloud ◽

The Public ◽

Partition Technique ◽

Textual Content

Load balancing makes cloud computing greater knowledgeable and could increase client pleasure. At reward cloud computing is among the all most systems which offer garage of expertise in very lowers charge and available all the time over the net. However, it has extra vital hassle like security, load administration and fault tolerance. Load balancing inside the cloud computing surroundings has a large impact at the presentation. The set of regulations relates the sport idea to the load balancing manner to amplify the abilties in the public cloud environment. This textual content pronounces an extended load balance mannequin for the majority cloud concentrated on the cloud segregating proposal with a swap mechanism to select specific strategies for great occasions.

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