We have sound! The stream of data from Philae, the Rosetta mission's little lander currently hibernating on comet 67, now includes the "thump" it made while touching down. The two-second recording is more scientifically interesting than you might think.
The sound comes from sensors embedded in Philae's three legs as part of SESAME, the Surface Electric Sounding and Acoustic Monitoring Experiment. Because its harpoons didn't fire, Philae actually ended up bouncing twice and landing three times. Today, the German Aerospace Center, which is responsible for SESAME, released a recording of that first bounce.
The crunch of Philae making contact isn't just some novelty. It can be analysed for clues about the comet's surface. "The Philae lander came into contact with a soft layer several centimetres thick. Then, just milliseconds later, the feet encountered a hard, perhaps icy layer on 67P/Churyumov-Gerasimenko," explained German Aerospace Center researcher Klaus Seidensticker, who is responsible for SESAME. That fits with what other instruments on Philae have found; a hammer actually broke while trying to crack the comet's icy surface. It's hard out there on Comet 67P. [German Aerospace Center]
Top image: Illustration of Philae landing. ESA