Europe's audacious bid to put a robot on the surface of a comet is under way.
At 08:35 GMT, the Rosetta satellite released its Philae lander towards Comet 67P/Churyumov-Gerasimenko, a large mass of ice and dust some 510 million km from Earth.
The descent should take seven hours, with a signal confirming touchdown received at Earth at around 16:00 GMT.
Success would be a first for space exploration - no mission has previously made a soft landing on a comet.
Rosetta spacecraft comet landing – live coverage Click Me