Crater-forming

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)...

The outline of Victoria Crater is serrated, with sharp and steep promontories separated by rounded alcoves (Fig. 8.36). The crater formed in sulfate-rich sedimentary rocks, and is surrounded by a smooth terrain that extends about one crater diameter from the rim. On the crater floor is a dune field. There are no perched ejecta blocks preserved on the smooth terrain around the crater rim, probably planed off by Aeohan abrasion. The Mossbauer mineralogy of the sedimentary rocks at the crater rim and inside the crater itself is nearly the same as at Eagle crater landing site and Endurance crater, both about 6-8 km away [335]. 

The 2001 massive ammonium nitrate explosion near Toulouse, France that led to 30 fatalities, 2500 injuries, damage to nearly a third of the city of Toulouse, and the permanent closing of the facility. Figure 1.1 shows the crater formed by the blast. 

The long diameter(a), short diameterfb) and depth (h) of the crater formed are measured, and the volume of the crater is calculated according to the following formula v = 7T abh/12... 

The relationship among equivalent depth (d/W 1/3 ) of explosive under the sand, the weight of the explosive (W) and the volume of the crater formed is shown in Fig.3.131. The location of the explosive and the representive shapes of craters are illustrated in Fig.3.130. 

Fig. 3.132 shows the relationship between the volume of the crater and the mass of the explosive. Diameters of the explosive charge are 30 mm and 50 mm, their length is 20 cm, and the tubes are composed of vinyl polychloride. There is correlation between the mass of the explosive and the volume of the crater formed. The relationship can be used to determine of... 

Under a-particle irradiation a crater forms in the foam similar to their traces in Wilson s chamber [19]. Fig. 7.3 shows the light flashes created when the foam films rupture. 

Burial deeper than this results in smaller and smaller craters until the point is reached where no crater forms. Figure 29.3 (Ref. 30) shows craters typical for various heights or depths of burial (DOB). 

In 2003, astronomers announced that data and observations indicated one particular crater might well be classified as the youngest crater thus far discovered. The crater, formed in 1953 by an asteroid impact, is the only known lunar crater to have been formed during recorded human history. New and more powerful telescopes, along with orbiting satellite photos now allow examination of the impact site and astronomers observed indications of a fresh crater in the impact zone (i.e., the area corresponding to the impact flash observed in 1953). 

The United States first tested its nuclear bomb capabilities in a desert-region of New Mexico on July 16, 1945. When the atomic bomb was detonated, a huge crater formed. The heat from the plutonium-based bomb melted the desert sands, which then solidified, forming a glassy residue. The resulting mineral (pictured here) was named trinitite after the site (named Trinity) of the test. IMAGE COPYRIGHT 2009, STEVE SHOUP. USED UNDER LICENSE FROM SHUTTERSTOCK.COM,... 

The number of craters or holes forming the honeycomb-like structure increased rapidly with the quantity of evolved hydrogen, as can be seen from Fig. 42 which shows the dependence of the number of holes or craters formed due to the attachment of hydrogen bubbles on the average current efficiency of hydrogen evolution. 

Each drop of the tamper leaves a crater which may be as much as six feet deep. Figure 3.9 shows the craters formed on a field job. At the end of tamping, these craters must be filled and then tamped, in what is called an ironing pass. The tamper used for ironing is much lighter, of course, and larger in diameter. Between passes, craters are generally filled by a bulldozer. 

The depth of crater formed at one location increases at a decreasing rate with successive drops. If crater depth is plotted vertically against number of drops plotted horizontally, the curve joining the points eventually will become asymptotic to the horizontal axis. These data can be used to determine when drops at one location become economically ineffective. 

Fig. i8.—Crater form of the potential of the field of force which binds an a-particle to the rest of the nucleus. 

The appearance of the craters obtained at low fluences varies partly from the morphologies of the craters formed at high fluences. Figure 6 shows the craters created on TM2 at fluences of 69 and 51 mj cm 2, respectively. Conical structures were observed in both cases at the bottom of the circular cra-... 

Figure 1.1. Crater formed by explosion near Toulouse, France (Reuters).

Tests. Until now, only a few tests have been performed concerning debris throw from crater-forming mechanisms, some of them being only small-scale tests. Small-scale tests for debris throw are subject to problems of scaling laws (e.g., gravity effects) and the difficulty of simulating real rock material with its joints, cracks, and fissures. 

Earth-Moon Differences. Scientists believe that the moon s surface has a large number of craters formed by the impact of meteorites. In contrast, there are relatively few meteorite craters on the Earth, even though, based simply on its size, the Earth is likely to have been hit by as many or even more meteorites than the Moon. This notable difference is attributed to the Earth s atmosphere, which bums up incoming meteorites, particularly small ones (the Moon does not have an atmosphere). Larger meteorites can pass through the Earth s atmosphere, but their impact craters may have been filled in or washed away over millions of years. Only the more recent ones, such as Meteor Crater in northern Arizona, with a diameter of 4,000 feet and a depth of 600 feet, remain easily recognizable. 

Due to repeated interaction of the laser beam with the target, structural changes occur on the surface with craters forming. Therefore, the composition and properties of the deposited material will depend on the duration of the deposition process... 

FIG. 1—Crater formed in the surface of a ductile material by an Impinging particle. 

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