NASA's Ion-Drive Asteroid Hunter Lifts Off

Nearly enveloped by the smoke after ignition, the Delta II rocket carrying NASA's Dawn spacecraft . i i

hide captionNearly enveloped by the smoke after ignition, the Delta II rocket carrying NASA's Dawn spacecraft rises from the smoke and fire on the launch pad.

NASA
Nearly enveloped by the smoke after ignition, the Delta II rocket carrying NASA's Dawn spacecraft .

Nearly enveloped by the smoke after ignition, the Delta II rocket carrying NASA's Dawn spacecraft rises from the smoke and fire on the launch pad.

NASA

NASA's Dawn spacecraft, equipped with revolutionary ion engines and destined for a 2011 rendezvous with the asteroid belt, blasted off Thursday from Cape Canaveral, Fla.

Scientists hope the mission will shed 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, both thought to date from 4 1/2 billion years ago.

Dawn ion engines, a technology once confined to science fiction, will make possible the mission of firsts, which includes traveling to a celestial body and orbiting it, then journeying to another and orbited it as well.

"To me, this feels like the first real interplanetary spaceship," said Marc Rayman, chief engineer of the Dawn Project. "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."

A Four-Year Journey

The 3 billion-mile trip began a little after sunrise Thursday. 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.

Dawn won't reach Vesta, its first stop, until 2011, and Ceres, its second and last stop, until 2015.

Two Stops, Two Different Destinations

Scientists chose the two targets not only because of their size but because they are so different from one another.

Vesta, an asteroid about the length of Arizona and not quite spherical, is dry and rocky, and appears to have a surface of frozen lava. It's where many of the meteorites found on Earth came from.

Ceres, upgraded to a dwarf planet just last year, is nearly spherical, icy and may have frost-covered poles.

Spacecraft have flown by asteroids before — albeit much smaller — and even orbited and landed on them, and more asteroid missions are on the horizon. But none has attempted to orbit two on the same mission, until Dawn.

"While these other asteroid missions are, I think, very exciting, I hope one doesn't confuse the kind of asteroids that Dawn is going to with the near-Earth asteroids and these other small bodies," said Rayman, who is based at Jet Propulsion Laboratory in Pasadena, Calif. "I think many people think of asteroids as kind of little chips of rock. But the places that Dawn is going to really are more like worlds."

Dawn has cameras, an infrared spectrometer and a gamma ray and neutron detector to probe the surfaces of Vesta and Ceres from orbit. It also has solar wings that measure nearly 65 feet from tip to tip, to generate power as it ventures farther from the sun.

From NPR reports and The Associated Press

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