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uni'wissen 02-2013_ENG

High-speed film sequences show how a crater is formed: In a laboratory experiment, a small meteorite knocks a cone-shaped cloud of fragments out of the rock. Photos: Fraunhofer EMI Ernst Mach Institute (EMI) plays a key role in the network: Geologists and geophysicists work to- gether with engineers and physicists to under- stand precisely what happens when meteorites collide with the Earth – in the cellar and on a small scale. Hot Iron and Wet Stone A two-stage light-gas accelerator in the cellar of the EMI in Freiburg accelerates metal balls to the speed of a meteorite. In a room with a length of approximately 20 meters, the researchers let pieces of real meteorites fly at blocks of stone from the side. The balls are shaped from the Ar- gentinian meteorite Campo del Cielo into 2.5 mil- limeter-large projectiles. They produce craters measuring roughly five to ten centimeters in sandstone, quartzite, or tuff. The stone blocks are cubes with an edge length of 20 centimeters, representing the Earth’s surface in miniature. In the town of Efringen-Kirchen near Lörrach, the EMI also has a larger accelerator capable of fir- ing balls with a diameter of up to 1.2 centimeters at one cubic meter-large blocks. The research- ers also use a simpler testing facility located at the Institute of Earth and Environmental Scienc- es of the University of Freiburg, at which a small meteorite gun fires at colorful layers of sand- stone – this time from above. The researchers use the two-stage light-gas accel- erator at the Ernst Mach Institute of the Fraunhofer Association (A) to shoot iron balls made from the meteorite Campo del Cielo (B) at blocks of stone (C). A miniature crater is formed. Photos: Fraunhofer EMI “We’re something of a global impact crater taskforce” B C A 5