BERLIN, Nov. 15 (Xinhua/Sun) -- Comet lander Philae fell asleep on Saturday morning after sending back all acquired scientific data before its batteries exhausted, confirmed the European Space Agency (ESA) in operations center in Darmstadt Germany, hailing the lander as delivering "incredible scientific success."

The lander, started a comet chasing 10 years ago, separated from its mother ship Rosetta on Wednesday, and descent to its target Comet 67P/Churyumov-Gerasimenko, some 500 million kilometers away from the earth.

It took nearly seven hours for Philae to touchdown the comet whose gravity was only 1/100,000 of that on the earth. The lander thus made a history as the first man-made probe on a comet.

Different from other comets, Comet 67P doesn't have a shape of a potato. Instead, it looks like a rubber duck, on the head of which Philae was planned to touchdown. To prevent it from bouncing, scientists equipped the lander with three ice screws, two harpoons, as well as a cold gas thruster to ensure it anchored on the comet surface.

The ten-year-old design, however, did not become reality. The thruster was found unable to be activated before Philae's departure, harpoons also failed to be fired into the surface when Philae touched the comet.

The lander bounced twice on the head of the "rubber duck" with an initial jump of 2 hours and rested somewhere which was not yet determined.

Pictures sent back by Philae showed that the lander was rested in a shadow of a cliff, which blocked the essential sunlight that was needed for Philae to continue operation after its main battery exhausted.

The lander communicated with controllers for the last time for nearly 2 hours last night. It accepted a command to rotate itself for 35 degrees in order to expose larger solar panels to the weak sunlight. During the last hours, Philae sent back all the acquired scientific data before it lost contacts with the earth at 0036 GMT, ESA confirmed.

The agency said further contacts would not be possible unless Philae's solar panels received sufficient sunlight to generate enough power to wake it up.

Despite the tough situation, the agency said, Philae deployed all the instruments on board, including a drill which took samples from a depth of 25 centimeters. Now, scientists are analyzing the data to confirm whether all the experiments were completed.

"I'm feeling a bit tired, did you get all my data? I might take a nap ..." Philae "tweeted" and fell silent shortly after.

"This machine performed magnificently under tough conditions, and we can be fully proud of the incredible scientific success Philae has delivered," said Stephan Ulamec, Philae Lander Manager.

Scientists believe that discovering comets could help to reveal secrets of our solar system as they keep ancient information back to the time when the solar system was formed, and might even be the origin of water and lives on the earth.

"This is a big step for human civilization," said Jean-Jacques Dordain, Director General of the ESA. "Our ambitious Rosetta mission has secured a place in the history books."