The Philae spacecraft has this afternoon successfully landed on comet 67P/Churyumov-Gerasimenko.
The historic attempt to land a spacecraft on a comet was earlier set in motion by scientists at the European Space Agency, despite a last-minute problem with the landing system.
A milestone was crossed shortly after 11am when European Space Agency (ESA) controllers received a radio signal from the descending lander relayed from Rosetta.
It is the climax of a decade-long mission to study a four-kilometre (2.5-mile) wide lump of dust and ice known as 67P/Churyumov-Gerasimenko.
It is also the end of a 6.4 billion-kilometre (four billion-mile) journey during which Rosetta carried its sidekick lander Philae piggyback to reach the comet.
The ESA earlier said the 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.
The washing machine-sized craft was scheduled to separate from Rosetta at 0835 GMT and drift down to the comet.
During the descent, scientists were powerless to do anything but watch, because the vast distance to Earth - 500 million kilometres (311 million miles) - made it impossible to send instructions in real time.
The plan is that Rosetta and Philae will accompany the comet as it hurtles towards the Sun and becomes increasingly active as it heats up. Using 21 different instruments they will collect data that scientists hope will help explain the origins of comets and other celestial bodies.
Two Irish companies are involved in the mission.
Space Technology Ireland Ltd (Stil), led by scientist Prof Susan McKenna-Lawlor, developed the hardware supporting communications between the orbiter and lander.
Captec developed the software for the communications interface between the orbiter and the lander.
PA