On February 14 NASA's Stardust spacecraft had a close encounter with the comet Temple 1. For the first time in history, we got to visit a comet two times—a strange opportunity that allowed scientist to see how these space objects change.
The first pass was made by Deep Impact—on its way to Hartley 2, back in 2005—which launched a probe to hit the comet's surface and study the materials ejected from its core. Now, Stardust has been able to photograph the results and, as an added bonus, has sent back the noise of the comet.
Scientists have described it as the sound of flak against World War II bombers. In reality, the flak is just dust particles and rocks hitting the spacecraft's protective shield. [ NASA Jet Propulsion Laboratory California Institute of Technology]