Using a computer simulation, scientists from the University of Stanford in California have managed to visualize what happens to the Earth's crust after a meteorite impact. The findings, published in Nature Materials, were used to predict how minerals would mutate under the extreme conditions produced by such an event.
The researchers wanted to recreate the first nanosecond – a billionth of a second – of impact. The computer model simulates half a million molecules of silica and what happens when they are put under the intense pressure and temperature brought about by impact-induced shockwaves. Silicas are minerals made of silicon and oxygen, the two most abundant elements in the Earth's crust. Silicas constitute 90% of the rocks found on the planet’s surface.
The study uses the conditions created by the Barringer meteor crater impactor. The Barringer Crater in Arizona (pictured) is probably one of the most famous meteor craters in the world. It was created 50,000 years ago when a nickel-iron meteorite 50 meters (160 feet) in diameter hit the Earth at a speed between 12.8 and 20 kilometers per second (8-12.4 miles per second). The crater that it formed is 1,200 meters (3,900 feet) in diameter and 170 meters (560 feet) deep. The impact energy is estimated around 10 megatons (around 500 times the energy released by the Nagasaki atomic bomb explosion).
In the team’s simulation, the impacted ground experienced shockwaves traveling at speeds over 7 kilometers per second (4 miles per second), which led to temperatures rising to 3,000 degrees Celsius (5,400 degrees Fahrenheit) and pressure reaching half a million atmospheres.
According to the study, within the first 10 trillionths of a second the shockwaves forced the silica molecules to form an incredibly dense structure that in the first nanosecond crystallizes into a rare mineral. The mineral, called stishovite, is chemically akin to quartz, but it can only be formed through a powerful metamorphic event that changes how silicon and oxygen are bound together in the silica molecule.
This result is in agreement with the geological findings in Arizona. Stishovite is found in abundance in shocked rocks around the Barringer crater. The development of these kinds of simulation is important in materials science as they help predict how materials transform under stressful conditions.