Monday, February 20, 2012

Impactites Rock Our World at the NOVA Center

Falling stars, more commonly known as meteors, are constantly striking the Earth’s atmosphere. The fragments of cosmic debris robust enough to survive the fiery Earth’s atmosphere and strike the planet’s surface are referred to as meteorites. If a meteorite is large enough to form astroblemes (giant craters), the catastrophic impact will transform the terrestrial surface materials into metamorphic rock by means of extreme heat, pressure, and shock waves. The initial collision of the meteorite melts the rock, sand, or earth it impacts and splashes it around like boiling taffy. Simultaneously, contact parts of the meteorite melt, mix, and cool with the earth, resulting in the formation of impactites. Impactites, shown below, vary in size from microscopic to as large as walnuts. 
So why are impactites so important?  Meteorites, which are predominantly made of iron, rust and decompose over time. Impactites such as melt glasses, breccias, and shatter cones live on as remnants of the impact events. Even after the meteor and giant craters themselves vanish, impactites leave traces of the original meteorite and cataclysmic occurrences. Studying these unique rocks provides evidence of our planet’s brutal history and the momentuous events Earth has endured.
The meteorite and impactites we scanned at the Nondestructive Analysis Center are fragments of the Canyon Diablo in Arizona. The original meteorite presumably struck Arizona approximately 50,000 years ago. The meteorite and impactites were discovered around the outer edge of the crater. The meteorite is composed of 90% iron and 7% nickel with minor amounts of cobalt, copper, chromium, platinum, gallium, palladium, and gold.


The Large Chamber SEM at WKU Nova Center previously collected images of the impactites shown above. An elemental analysis on the impactites, soon to be carried out using energy dispersive spectroscopy (EDS), should reveal a mixture of elements present in the meteorite as well as earthly substances. Initial images reveal interesting designs like the Widmanstätten patterns in the microstructure. The impactites, although different textures, both appear uniform in color signifying an even mixture of components during the liquid transformation of the earth and meteorite.

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