NASA is shooting marbles at 16,000 mph to simulate meteoroid impacts with the lunar surface:
“We measure the flash so we can figure out how much of the kinetic energy goes into light,” he explained. “Once we know this luminous efficiency, as we call it, we can apply it to real meteoroids when they strike the Moon.” High-speed cameras and a photometer (light meter) record the results.The Ames Vertical Gun Range was built in the 1960s to support Project Apollo, America’s first human missions to the lunar surface. The Ames gun can fire a variety of shapes and materials, even clusters of particles, at speeds from 0.5 to 7 km/s. The target chamber usually is pumped down to a vacuum, and can be partially refilled to simulate atmospheres on other worlds or comets.
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Cooke’s experiments are being run in two rounds. The first set of 12 shots in October 2006 fired Pyrex glass balls into dust made from pumice, a volcanic rock, at up to 7 km/s. Follow-up experiments will use JSC-1a lunar simulant, one of the “true fakes” developed from terrestrial ingredients to mimic the qualities of moon soil.Knowing the speed and mass of the projectile will let Cooke to scale the flash and estimate the energies of the softball-size meteoroids that hit the Moon at up to 72 km/s, more than six times the speed of the Ames gun. But luminous efficiency is just part of the question. A lot of the impact energy goes into shattering and melting the projectile — the main reason for using glass rather than metal — and then spraying debris everywhere.