STEVE INSKEEP, HOST:
Scientists are celebrating after receiving a signal from a spacecraft on a very long journey. The Rosetta is traveling through the heavens to study a comet in more detail than ever before. As NPR's Rob Stein reports, the Rosetta spacecraft's call home meant the robot onboard had successfully awakened itself from a long hibernation, and is now on course to achieve its historic mission.
ROB STEIN, BYLINE: The European Space Agency launched Rosetta nearly 10 years ago. The 6,400-ton unmanned spacecraft's goal was ambitious: To orbit and study a comet as it hurtles through space. One of the mission's directors, Gerhard Schwehm, says scientists think that could provide exciting clues to how Earth and other planets formed, and even possibly how life began.
GERHARD SCHWEHM: Comets are the messengers that bring material that we had at the beginning of the evolution of the planetary system.
STEIN: But Rosetta had to take a long, circuitous journey to catch up to the comet. The trip would take Rosetta around the sun almost four times, through the asteroid belt twice, and skittering close to Mars once and the Earth three times. To preserve power, Rosetta was placed into hibernation in 2011. Finally, on Monday, Rosetta was programmed to wake itself up and call home. Scientists around the world waited anxiously for Rosetta's signal. Tension mounted when the window opened to receive the transmission and there was nothing, just silence. But finally, the signal arrived, and a celebration erupted at mission control in Germany.
STEIN: Rosetta now continues its journey to rendezvous with the comet in August. Rosetta will even hopefully do something never been tried before: drop a small probe to land on the comet in November to drill into the surface. French scientist Jean-Pierre Bibring says that should yield a wealth of data.
JEAN-PIERRE BIBRING: We've been to comets far away. We know what a comet is. We never landed. And we are absolutely convinced that when we do that, then the entire reality of a comet will finally be revealed.
STEIN: And that will hopefully reveal many of the secrets comets carry with them as they journey through space. Rob Stein, NPR News. Transcript provided by NPR, Copyright NPR.