The European Space Agency's Rosetta probe made its historic rendezvous with a comet on Wednesday after a 10-year, 4 billion-mile journey.
"We're at the comet! Yeah!" spacecraft operations manager Sylvain Lodiot yelled when confirmation of the crucial engine burn was received at ESA's Mission Control in Darmstadt, Germany.
Rosetta thus became the first spacecraft to hang out with a comet. Earlier missions, including ESA's Giotto as well as NASA's Deep Impact and Stardust, have had comet encounters but didn't stick around.
"After 10 years, five months and four days traveling towards our destination, looping around the sun five times and clocking up 6.4 billion kilometers, we are delighted to announce finally, 'We are here,'" ESA's director general, Jean-Jacques Dordain, said in a statement. "Europe's Rosetta is now the first spacecraft in history to rendezvous with a comet, a major highlight in exploring our origins. Discoveries can start."
The car-sized Rosetta probe was launched in 2004, and woke up from hibernation in January for its final approach to Comet 67P/Churyumov-Gerasimenko, a 2.5-mile-wide (4-kilometer-wide) conglomeration of ice and dust that's been compared to a rubber ducky.
Rosetta's orbit is an odd duck as well. Technically speaking, it's not so much an "orbit" as a triangular course that keeps up with the comet. The maneuvers will give ESA's mission managers a chance to determine the dynamics for a true orbit and up-close observations that should continue through the end of 2015.
Right now, Rosetta is in a holding pattern about 60 miles (100 kilometers) from Churyumov-Gerasimenko, but eventually it's expected to close in to an altitude of 12 to 20 miles (20 to 30 kilometers).
In November, Rosetta is scheduled to send out a piggyback probe, named Philae, to descend to the comet's surface. Based on temperature readings made by Rosetta's instruments, scientists already have surmised that the comet has a porous, dusty crust with ice beneath. The surface is strewn with boulders the size of houses, and Churyumenko-Gerasimov's icy cliffs rise as high as 500 feet (150 meters).
ESA's science team will have to choose a suitable spot for Philae to drill into the surface, extract and analyze samples, and send pictures and data back to Earth. Meanwhile, the main Rosetta spacecraft will "escort" the comet as it makes its swing around the sun and heads back out toward Jupiter.
"Rosetta is the sexiest space mission that's ever been," Matt Taylor, the $1.75 billion (€1.3 billion) mission's project scientist, declared during Wednesday's webcast.
On the way to Churyumov-Gerasimenko, Rosetta made a series of flybys of Earth and Mars, and observed two asteroids called Steins and Lutetia. During the coming months, it will employ its OSIRIS camera as well as a spectrometer called VIRTIS, a miniature radio telescope called MIRO and other scientific instruments.
Rosetta gets its name from the Rosetta Stone, which archaeologists used in the 1800s to decipher the meaning of Egyptian hieroglyphs. In a similar way, astronomers plan to use the data from Rosetta to figure out the chemistry of comets, which are thought to preserve the primordial stuff of the solar system and potentially contain the building blocks of life.
Philae's name comes from an island in the River Nile where an obelisk was found with inscriptions that contributed to deciphering Egypt's ancient writing.