Impact cratering

Chabai, A. J., Influence of Gravitational Fields and Atmospheric Pressures on Scaling of Explosion Craters, Impact and Explosion Cratering, (pp. 1191-214), Pergamon Press, New York, 1977. 

The dollar amount is the statistic that makes this void in educational management a deep crater impacting day-to-day operations (Figures 35.3 and 35.4). Falls accounted for 11,241,952 in loss from 2005 through 2009. Overexertion injuries, which we identified as mainly back strains among teachers, amounted to 10,338,849 in lost revenue. The total cost for this same period equaled 33,913,211.00. Although this was cost paid by the carrier of the insurance, in this case the Kentucky School Board Association, the cost is then passed along to districts in the form of an increased premium (Isaacs, 2010). 

Fairen et ah, 2009 [124] conclude from data from the Mars Exploration Rover (Guseev Crater, impact occurred 2 Gyr BP) that minor amounts of shallow acidic liquid water have been present on the surface of Mars at local scales during the Amazonian Period. They investigated jarosite deposits. Jarosite is a basic hydrous sulfate of potassium and iron with a chemical formula of KFe3 (OH)6(804)2. 

Stishovite. Stishovite was first prepared (68) ia the laboratory ia 1961 at 1200—1400°C and pressures >16 GPa (158,000 atm). It was subsequentiy discovered, along with natural coesite, ia the Ari2ona meteor crater. It has been suggested that these minerals are geological iadicators of meteorite impact stmctures. Stishovite (p = 4.35 g/cm ) is the densest known phase of silica. The stmcture, space group P42/nmn is similar to that of... 

The sizes and shapes of impact craters are easily measured at leisure after the impact event. The particles of a debris cloud can present more of a problem, however, because of the difficulty of recovering the particles without damaging them during the recovery process. Attempts at soft recovery have been numerous and of varying degress of success. Occasionally, it has been desir-... 

Ahrens, T.J., and O Keefe, J.D. (1977), Equation of State and Impact-Induced Shock-Wave Attenuation on the Moon, in Impact and Explosion Cratering (edited by Roddy D.J. et al.), Pergamon Press, New York, pp. 639-656. 

McQueen, R.G., Marsh, S.P., Taylor, J.W., Fritz, J.N., and Crater, W.J. (1970), The Equation of State of Solids from Shock Wave Studies, in High-Velocity Impact Phenomena (edited by Kinslow, R.), Academic Press, San Diego, pp. 249-419. 

The emphasis of the present work is science and technology in the laboratory. The natural shock-compression laboratory of meteoritic impact should not be overlooked. In these environments unique solid state materials have been synthesized for the first time. Perhaps the most common features of our Earth, Moon, and other planets and moons are the craters produced by such high velocity impacts [67C01, 87A03]. 

When particle impacts with a solid surface, the atoms of the surface layer undergo crystal lattice deformation, and then form an atom pileup on the outlet of the impacted region. With the increase of the collision time, more craters present on the solid surface, and amorphous transition of silicon and a few crystal grains can be found in the subsurface. 

Fig. 8.36 Leyt Spectrum of the soil close to the crater rim where Opportunity entered and exited the crater. The basaltic soil is unusually high in hematite (but no indication of significant contribution Irom hematitic spherules). Middle rover tracks. Right 750 m diameter (. 75 m deep) eroded impact crater Victoria Crater, formed in sulfate-rich sedimentary rocks. Image acquired by the Mars Reconnaissance Orbiter High-Resolution Science Experiment camera (Hirise). The red line is the drive path of Opportunity exploring the crater. (Courtesy NASA, JPL, ASU, Cornell University)...

This planet, the nearest to the sun, has almost no atmosphere its surface is covered with craters. During the formation of Mercury, planetesimals were able to impact the planet s surface without any resistance. Thus, the lack of erosion processes (due to... 

Figure 1.6 Impact frustration (a) the Chicxulub crater, seen as a three-dimensional gravity map, thought to be responsible for the extinction of the dinosaurs (b) the cratered surface of the Moon. (Reproduced from photos by courtesy of NASA)...

Only with silica was the nature of the surface groups studied as extensively as with carbon. Silica, like carbon, has several polymorphs. Apart from the amorphous state, it is known to exist in numerous crystalline modifications. The most important forms are quartz, tridymite, and cristobalite. Each of these can occur in a low-temperature form and in a high-temperature form of somewhat higher symmetry. Tridymite is only stable if small amounts of alkali ions are present in the lattice 159). Ar. Weiss and Al. Weiss 160) discovered an unstable fibrous modification with the SiSj structure. Recently, a few high-pressure modifications have been synthesized keatite 161), coesite 162), and stishovite 16S). The high-pressure forms have been found in nature in impact craters of meteorites, e.g., in the Arizona crater or in the Ries near Nbrdlingen (Bavaria). 

Stishovite is the most dense phase of silica. Its density is 4.35 g/cm. It has a rutde-type crystal structure in which the sdicon atom is octahedrally surrounded by six oxygen atoms. Four Si—O bonds are 1.76A and two 1.8lA. Stishovite has been prepared similarly to coesite but at temperatures between 1,200 to 1,400°C and a pressure above 150,000 atm. Both the coesite and stishovite are found in nature in certain meteorite craters resulting from meteorite impacts. 

Hypervelocity Impact Dependence of Crater Dimensions on Impact Velocity. Craters in copper and lead, produced by hypervelocity impact, were measured and the dimensions correlated with impact vel. The results indicate that craters scale with ca the 1.7 power of vel, in agreement with computer physics results based upon hydrodynamic calculations... 

KL) Anon, "Military Explosives", TM 9-1300-214/TO 11A-1-34 (1967). Chapter 5. Properties and Tests of High Explosives Sensitivity to Frictional Impact (pp 5 1 to 5-3) Sensitivity to Friction (5 3 to 5-6) Sensitivity to Frictional Impact (5-6) Sensitivity to Heat and Spark, which includes Explosion Temperature Test (5-6 to 5-9) Sensitivity to Initiation (5-9) Stability Tests, which include 75° International Test, 100° Heat Test, Vacuum Stability Test and Potassium Iodide—Starch Test (5 9 to 5-15) Brisance Tests which include Sand Test, Plate Dent Test and Fragmentation Test (5 15 to 5-18 and Fig 5 13 on p 5-19) Initiating Value (5-18 5-20) Sympathetic Detonation (5-20 to 5-21) Power which includes Heat of Explosion Test, Ballistic Pendulum Test and Trauzl Lead Block Test (5-21. to 5-24) Blast Effect (5-24 to 5-27) Cratering Effect (5-28 5 29) and Munroe-Neumann Effect (5-29 to 5 35)... 

Absolute time measurements using radioactive isotopes are presently limited to samples that can be carefully processed and analyzed in the laboratory. Estimates of the relative times of formation of various geologic units on other planets can be gained from spacecraft imagery, by crater counting. The older a surface is, the longer it has been exposed to meteorite impacts and thus the higher the density of craters on that surface. However, very old surfaces can become saturated with craters, when every new crater effectively obliterates an older one. 

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