Europe's spacecraft Rosetta releases comet lander

European spacecraft Rosetta released probe Philae to make the first-ever comet landing on Comet 67P/Churyumov-Gerasimenko on Wednesday, despite a problem onboard the lander, European Space Operations Centre (ESOC) confirmed in Darmstadt, Germany.

Rosetta released Philae at 9:35 (0835 GMT) at a point 22.5 kilometers above the comet's center, the ESOC said in a statement.

"Philae is alone, it's on its own now," said Stephan Ulamec, Philae Lander Manager at the German Aerospace Center (DLR), a member of a consortium which led the European Space Agency mission.

Rosetta, carrying Philae, has chased Comet 67P/Churyumov-Gerasimenko for over 10 years since being launched on March 2004, and traveled for about 7 billion kilometers, passing the Earth, Mars and two asteroids on its way.

Philae would fly for another 7 hours after the separation before it touched down at a site named "Agilkia" on the "head" of the duck-shaped comet, said ESOC.

Checks over last night, however, found that a thruster system onboard Philae that would prevent it from rebounding could not be activated at the moment of touchdown.

As designed, landing gear would absorb the forces of the landing while ice screws in each of Philae's feet and a harpoon system would lock the lander to the comet surface. A cold gas thruster on top of the lander would push the lander onto the surface to ensure that the lander was anchored there.

"The cold gas thruster on top of the lander does not appear to be working so we will have to rely fully on the harpoons at touchdown," Philae Lander Manager Ulamecat said.

"We'll need some luck not to land on a boulder or a steep slope," he said.

Signals confirming the landing was expected to be received in a one-hour window centered on 18:02 (1702 GMT), about half an hour later than the actual action as the comet was about 500 million kilometers far from the earth.

If succeeded, it would be the first human-made object landed, instead of colliding as NASA Deep Impact probe did in 2005, on a comet in history.

Pictures of the comet surface would be taken by the seven cameras around Philae once it landed. Scientists hope to study the comet's make-up with the help of the 10 scientific instruments on board and to watch its evolution as it approaches the sun.

Earlier, a variety of molecules, including water, carbon monoxide, carbon dioxide, methane, and a few nitrogen or sulphur species have been detected by scientific instruments on Rosetta.