Landing on a comet: Spacecraft Rosetta attempts the impossible today

A historic attempt to land a spacecraft on a comet was set in motion Wednesday by scientists at the European Space Agency, despite a last-minute problem with the landing system. It is also the end of a 6.4 billion-kilometer journey on which Rosetta carried its sidekick lander Philae piggyback to reach the comet. ESA announced early Wednesday that the lander’s active descent system, which uses thrust to prevent the craft from bouncing off the comet’s surface, could not be activated. The European Space Agency says that even if the landing doesn’t succeed, the 1.3 billion euro mission launched in 2004 won’t be a failure.