Impact craters

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-... 

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)...

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). 

Some asteroids are marked by grooves, and all are pockmarked by impact craters of varying sizes. One crater on Mathilde (Fig. 11.1) is so large that it is difficult to envision how the asteroid survived the impact. The surfaces of all these bodies are covered by fine-grained regoliths and by boulders of various sizes. 

Collisions among asteroids are commonplace, and impact craters occur on all asteroid surfaces (Fig. 11.1) (Chapman, 2002). Cratering rates within the main asteroid belt are a... 

The bulk chemical composition of the dust, obtained by averaging the compositions of particles in numerous tracks (Fig. 12.11a) and impact crater residues (Fig. 12.11b), is chondritic for iron, silicon, titanium, chromium, manganese, nickel, germanium, and selenium, within the 2o confidence level (Flynn el al., 2006). Copper, zinc, and gallium are... 

A gross subdivision of the Moon s surface is based on albedo. The bright regions are the highlands, which are clearly ancient because of their high densities of impact craters. The dark regions are younger maria, basaltic lavas that flooded the impact basins on the nearside of the Moon. Mare basalts are exposed over 17% of the lunar surface and probably comprise only 1% of the crustal volume. 

Heat and impact volcanic and impact crater. Defects produced by natural radiation are annealed by heating event. Rocks, clay and lithic tools heated by ancient man or by geothermal events such as volcanic eruptions18 are objects of ESR dating and will be so in future planetary survey. 

Si02 Igneous Rocks, Fault Gauge, Impact Craters and Sediment. -... 

Defects in Crushed Si02 and Those of Quartz in Meteorite Impact Crater. 

Studies of the impact crater were investigated using signals of sands at the crater. ESR spectrum in shocked quartz from western rim of Wolfe Creek meteorite crater Australia, showed Ef centres in normal quartz sand at 0.001 mW. The same crater sample showed signals of peroxy centres at g = 2.0074 and an intense new ones ascribed to CCE" in SiOj at 5 mW, where E centre is saturated. 

Kenneth and Steve Shoulders report an experiment in which a previously deuteron-loaded palladium cathode was subjected to the impact of a charge cluster [22]. Where the charge cluster impacted the deuteron-loaded palladium a visually-evident, explosive-like reaction occurs (Fig. 8). The palladium cathode was then subjected to an X-ray analysis of the impact crater (see chart in Fig. 8). Typically, the X-ray analysis shows a considerable number of elements not seen when scanning the nearby palladium surface. Such elements as oxygen, calcium, silicon, and magnesium are detected in the exploded region where a charge cluster impacted the palladium. 

Buseck PR, Schwartz SE (2004) Tropospheric aerosols. In Holland HD, Turekian KK (eds) Treatise on geochemistry, Vol. 4, The atmosphere [Keeling RF (ed)] Elsevier, Amsterdam, pp 91-142 Cabrol NA, Wynn-Williams DD, Crawford DA, Grin EA (2001) Recent aqueous environments in Martian impact craters an astrobiological perspective. Icarus 154 98-112... 

The early stage erosion surface of material SiC-C resulting from SiC erosion at 90° impact is shown in Fig. 20.9. A few isolated pits similar to those shown in Fig. 20.9(a), marked by arrows, were found in these regions. Interestingly, detailed examination revealed that damage features associated with individual impact sites were quite different. In the impact crater marked... 

Bloch, M. R., Fechtig, H., Gentner, W., Neukum, G., Schneider, E. (1971) Meteorite impact craters, crater simulations, and the meteoroid flux in the early solar system. Proc. Second Lunar Science Conf., 3, 2639-52. 

Melosh H. J. (1989) Impact Cratering, Oxford University Press, NY. 

Ancient solid surfaces throughout the solar system are covered in impact craters (e.g., the Moon, Mercury, Mars, Callisto). Most of the planets have large axial tilts with respect to their orbits. Earth possesses a large companion with a mass 1% that of the planet itself. 

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