DARMSTADT, Germany — Hundreds of millions of miles from Earth, a European spacecraft made history Wednesday by successfully landing on the icy, dusty surface of a speeding comet — an audacious cosmic first designed to answer big questions about the origin of the universe.
Paolo Ferri, head of mission operations for the European Space Agency, said the landing on the comet named 67P/Churyumov-Gerasimenko appeared to have been almost perfectly on target.
"Everyone cried," he said.
The European Space Agency celebrated the cosmic achievement after sweating through a tense seven-hour countdown that began when the Philae lander dropped from the agency's Rosetta space probe as both it and the comet hurtled through space at 41,000 mph (66,000 kph).
ESA controllers clapped and embraced at mission control in Darmstadt as they got confirmation that the unmanned Rosetta space had successfully released the 220-pound (100-kilogram), washing machine-sized Philae lander.
During the descent, scientists were powerless to do anything but watch, because the vast distance to Earth — 500 million kilometers (311 million miles) — made it impossible to send instructions in real time.
Finally, at 1603 GMT (11:03 a.m. EST), the agency received a signal from Philae after it touched down on the comet's icy surface.
"We definitely confirm that the lander is on the surface," said flight director Andrea Accomazzo.
While further checks are needed to ascertain the state of the lander, the fact that it is resting on the surface of the comet is already a huge success, the highlight of a decade-long mission to study comets and learn more about the origins of these celestial bodies.
Scientists have likened the trillion or so comets in our solar system to time capsules that are virtually unchanged since the earliest moments of the universe.
"By studying one in enormous detail, we can hope to unlock the puzzle of all of the others," said Mark McCaughrean, a senior scientific adviser to the mission.
Philae was supposed to have drifted down to the comet and latched on using harpoons and ice screws. Ferri said thrusters meant to push the lander down failed to deploy, and there appeared to have been a problem with the harpoons as well that is now being investigated. But he added that Philae seemed to be stable on the surface of the comet.
Scientists also noted a problem with the signal from the lander, which they are now trying to fix. In the meantime, all the data that Philae collects is safely being stored for later transmission, Ferri said.
The head of the European Space Agency underlined Europe's pride in having achieved a unique first ahead of its U.S. counterpart NASA.
"We are the first to have done that, and that will stay forever," said ESA director-general Jean-Jacques Dordain.
Rosetta and Philae now plan to accompany the comet as it races past the sun and becomes increasingly active in the rising temperatures. Using 21 different instruments, the twin spacecraft will collect data that scientists hope will help explain the origins and evolution of celestial bodies, and maybe even life on Earth.
"The science starts the minute we get down to the ground," McCaughrean said.
The landing Wednesday capped a 6.4 billion-kilometer (4 billion-mile) journey that began a decade ago. 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 traveling in tandem ever since.
The mission will also give researchers the opportunity to test the theory that comets brought organic matter and water to Earth billions of years ago, said Klim Churyumov, one of the two astronomers who discovered the comet in 1969.
Philae's instruments include devices to measure light, electrical magnetism and heat. The lander will also drill below the surface of the comet to extract a sample that will be analyzed onboard and it will provide plenty of images of a world no human has ever seen close up.
The lander's batteries are expected to last just 64 hours. But that should be enough for scientists to gather a huge wealth of data. In addition, the lander has a solar panel that should be able to provide an hour's worth of battery life each day.
The real question is how Philae will cope with the comet's activity. As 67P approaches the sun, the amount of matter it releases will greatly increase, posing a potential risk to the lander and even Rosetta.
As the comet reaches perihelion, the closes point to the sun, the rising temperature could also damage Philae. But the lander should remain stuck to the comet forever, even after its systems have shut down.
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Geir Moulson in Berlin contributed to this report.