After a suspense-packed, seven-hour descent, the European Space Agency's Philae lander made an unprecedented touchdown on the surface of a comet Wednesday — marking the high point of a $1.3 billion, 10-year mission.
Cheers erupted as the confirming signals were received at from the European Space Operations Center in Darmstadt, Germany, at 11:03 a.m. ET. The signals took 28 minutes to travel at the speed of light over the 317 million miles (510 million kilometers) between Comet 67P/Churyumov-Gerasimenko and Earth.
"It is sitting on the surface," reported Stefan Ulamec, Philae lander manager at the DLR German Aerospace Center. "Philae is talking to us — we are on the comet."
Philae was released for its descent seven hours earlier by ESA's car-sized Rosetta spacecraft, which has been keeping pace with the comet since August. The boxy lander, which is about the size of a washing machine, made its way to the comet's surface at a leisurely walking pace — roughly 2 mph (1 meter per second).
At the end of the trip, a cold-gas thruster system was supposed to be fired to hold the lander steady and keep it from bouncing off the surface, while harpoons were shot into the comet to secure it in place. But mission managers said readings from the lander suggested that the system was not properly activated.
"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," Ulamec said in an ESA blog posting before the landing. "We'll need some luck not to land on a boulder or a steep slope."
A wave of applause swept through the VIP audience in Darmstadt as Ulamec announced that the harpoons were indeed deployed.