Sept. 27, 2007 — NASA's Dawn spacecraft rocketed away Thursday toward an unprecedented double encounter in the asteroid belt. Scientists hope the mission sheds light on the early solar system by exploring the two largest bodies in the belt between Mars and Jupiter: an asteroid named Vesta and a dwarf planet the size of Texas named Ceres.
Dawn's mission is the world's first attempt to journey to a celestial body and orbit it, then travel to another and circle it as well. Ion-propulsion engines, once confined to science fiction, are making it possible.
"To me, this feels like the first real interplanetary spaceship," said Marc Rayman, chief engineer. "This is the first time we've really had the capability to go someplace, stop, take a detailed look, spend our time there and then leave."
The 3 billion-mile trip began a little after sunrise. The Delta II rocket thundered through a clear blue sky and headed southeast above the thick clouds over the horizon. A harvest moon was faintly visible in the west.
"Dawn, you're on your way. Good luck," Launch Control said once Dawn separated from its third rocket stage an hour later, right on cue. Already, the spacecraft was 4,000 miles from Earth.
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Dawn won't reach Vesta, its first stop, until 2011, and Ceres, its second and last stop, until 2015.
Scientists chose the two targets not only because of their size but because they are so different from one another.
