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Due to the vast distances involved and the time delays in receiving data, confirmation of the landing reached Earth about 11:00 a.m. EST.

“We are sitting on the surface,” ESA official Stephan Ulamec said after receiving a signal from the Rosetta lander.

“Philae is talking to us. First thing he told us was the harpoons have been fired, rewound and the landing gear has been moved inside … We are there, it’s done it’s job. We are on the comet.”

Philae was supposed to drift down to the comet and latch on using harpoons and ice screws. ESA announced hours before the release that a third component — an active descent system that uses thrust to prevent the craft from bouncing off the surface of the low-gravity comet — could not be activated. It wasn’t clear how big of a setback that was.

“We’ll need some luck not to land on a boulder or a steep slope,” Ulamec said.

During the descent, scientists were powerless to do anything but watch, because the vast distance to Earth — 500-million kilometres — makes it impossible to send instructions in real time. It takes more than 28 minutes for a command to reach Rosetta.

About two hours after the separation from Rosetta was confirmed, scientists re-established contact with the lander.

“Now we can follow it on its descent,” said Paolo Ferri, head of mission operations at ESA.

Rosetta, which was launched in 2004, had to slingshot three times around Earth and once around Mars before it could work up enough speed to chase down the comet, which it reached in August. Rosetta and the comet have been travelling in tandem since then.