The European Space Agency's unmanned Rosetta probe successfully landed on the surface of comet 67P/Churyumov-Gerasimenko today, capping its final seven-hour journey with a historic rendezvous with the fast-moving lump of dust and ice. Philae's audacious landing attempt is the climax of a decade-long mission to study the 2.5-mile-wide comet, which is traveling at 41,000mph. It's also the end of a 4-billion-mile journey on which Rosetta carried Philae piggyback. Checks are still ongoing, but Philae is alive. "We definitely confirmed that the lander is on the surface," said an ebullient ESA official on the agency's live stream.
"It's on its own now," said Stephan Ulamec, Philae's lander manager, when the lander cut loose earlier today. ESA announced early today that the 220-pound lander's active descent system, which uses thrust to prevent the craft from bouncing off the comet's surface, could not be activated. Instead, the agency relied on ice screws and a harpoon system to secure the lander. Mission control workers clapped and embraced as the lander's separation was confirmed. "Philae has gone—it's on its path down to the comet," Andrea Accomazzo, Rosetta's flight director, said. "We are all glad that it worked flawlessly in the past minutes." (Read more Rosetta stories.)