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Spacecraft sticks the landing — on a comet

An image taken from the Philae lander during its descent to the comet.
An image taken from the Philae lander during its descent to the comet.ESA/AP

In a technological feat that gives scientists their first opportunity to dig into a remnant of the early solar system, the European Space Agency’s Rosetta mission successfully placed a small spacecraft on the surface of a speeding comet Wednesday.

With this achievement, a comet is no longer a mysterious and sometimes frightening spray of light across the night sky but another member of the solar system to be explored, like the moon and Mars. The technology of landing on a comet, with its wisps of gravity, could be applied to future efforts to mine asteroids.

The agency’s director general, Jean-Jacques Dordain, described the touchdown on Comet 67P/Churyumov-Gerasimenko, a 2.5-mile-wide ball of rock, ice, and dust moving faster than 40,000 miles per hour, as “a big step for human civilization.”


“Our ambitious Rosetta mission has secured another place in the history books,” Dordain said at a news conference. “Not only is it the first to rendezvous with and orbit a comet, but it is now also the first to deliver a probe to a comet’s surface.”

For scientists, one of the key mysteries that Rosetta will explore is whether Earth’s oceans are filled with melted comets. Because the rocky bits that came together to form the planet were dry, water has to have come from somewhere else. One possibility is that comets slamming into the Earth early on seeded it with water.

News of the touchdown of the 220-pound lander, named Philae, arrived at the mission control center in Darmstadt, Germany, at 11:03 a.m. Eastern time. Cheers erupted.

“We’re there, and Philae is talking to us,” said Stephan Ulamec, the manager for the lander. “We are on the comet.”

With that news, a procession of officials from nations and organizations, including NASA, that had collaborated on the $1.75 billion mission reveled in the accomplishment, capping a 10-year, 4-billion-mile trip.


“How audacious!” said James L. Green, the director of NASA’s planetary sciences division. “How exciting! How unbelievable to be able to dare to land on a comet.”

Within the hour, though, a worrisome caveat came to light.

“It’s not only complicated to land there,” Ulamec said in a later news conference. “It’s also, as it appears, very complicated to understand what has happened.”

Two harpoons that should have fired into the comet did not, and the lander may not be secured to the surface. Ulamec said fluctuations in the radio link and the generation of power by the solar panels suggested that Philae might have bounced off the surface before settling down again.

“Maybe today we didn’t just land once, we even landed twice,” Ulamec said.

As expected, the Rosetta orbiter moved out of the line of sight of Philae, breaking radio communications.

The orbiter is to re-establish the radio link in the next day, and mission managers hope then to better understand the stability of Philae’s footing.

Nonetheless, the lander and its 10 instruments have begun 64 hours of scientific operations before its batteries drain. Solar panels will recharge the batteries, allowing intermittent operations over the coming months, about an hour every two days.

The landing culminated a tense day as Rosetta maneuvered to the correct position to let Philae go. Moments of celebration were interspersed with long, quiet stretches of waiting.

The operation proceeded despite a few small glitches and one potential showstopper problem: failure of a thruster that was to fire after touchdown to press the lander against the comet’s surface. A pin was supposed to break a wax seal on the gas tank, but repeated attempts did not succeed.


Without the thruster, the washing machine-size Philae would have to rely on ice screws on its landing legs and the harpoons to anchor it to the comet. The thruster, which was to shoot a stream of nitrogen gas, was intended to counteract not just the possibility of Philae bouncing off the surface but also the upward kick from the firing of the harpoons.

Mission managers decided to proceed because there was no way to repair it.