The European Space Agency's lander didn't quite end up where it was supposed to after jumping around a few times after the initial touchdown. This continues to make the mission challenging - and keeps up the suspense.
The historic news keeps resounding: Philae has landed on comet 67P/ Churyumov-Gerasimenko! While this unleashed euphoria in ESA operation centers all over Europe, this was dampened a bit later.
Yes, Philae did land on the comet - three times. The micro-lab that separated from space probe Rosetta first touched ground at 5:03 pm on Wednesday, then bounced twice before it settled into its final position.
Stephan Ulamec, Philae lander manager at the German Aerospace Center (DLR), said at the ESA press conference Thursday afternoon that the lander's first bounce resulted in a 1-kilometer-high, two-hour-long jump in ultra-slow-motion due to extremely low gravity of the comet.
This "huge leap," as Ulamec called it, was followed by a second, smaller bounce of seven minutes.
Naysayers proved wrong
The reason for all this bouncing around: the harpoons that were supposed to anchor Philae to the comet upon landing didn't deploy. "They were supposed to be released when two of Philae's three legs hit the ground, but maybe the ground was too soft to trigger that mechanism," Gerhard Schwehm told DW.
Based on images delivered by Philae, the comet appears to consist of dust, debris, and rocks. Scientists described the surface as a "trampoline."
Schwehm, who is known as one of Rosetta's "fathers" among his colleagues, said that he and other ESA colleagues from Rosetta's early days were gratified when Philae touched down on the comet - because it proved the naysayers wrong.
No more talk of "silly dreams" or "science fiction ideas" - humankind actually put a lander on a comet that's moving through space at 135,000 kilometers per hour, and toward which Rosetta had to travel a cumulative distance of 6.4 billion kilometers to arrive to.
All things considered, it is astounding that Philae originally landed directly in its predetermined landing zone. After the bounces, however, the lander rests in a somewhat precarious position. Only two of its three legs are on the ground, while the third one seems to be hovering in open space. That's because Philae came to rest on a steep slope.
Researchers now have to be extra careful with operations like extracting samples, because Philae could be propelled off the comet again. Another problem with the lander's position is that it appears to be situated against and partially underneath a large ledge.
Since Philae's batteries run on solar power, it can only catch about one hour of sunlight per day, instead of the six or seven hours the scientists had originally hoped for.
In addition, Philae's partially hidden position means it can be in contact with Rosetta only for shorter time periods.
But despite its difficult position, ESA scientists and engineers emphasize that the lander appears to be in good working order.
Origins of life
Still, Philae has already managed to send pictures and started gathering information about the comet's magnetic field and the gases emanating from it. The deeper purpose behind the mission is to gain knowledge about the materials that make up the comet - and thus about Earth's earliest days.
"With this mission, we want to find out whether comets brought complex molecules to the Earth, or whether these molecules originated here," Schwehm explained. "It's supposed to answer questions like why life seems to have formed only on earth."
"And it's a glance into the beginning of our solar system," Schwehm concluded.