Spacecraft to asteroid belt set to fly Sunday

The mission aims to learn more about two large asteroids.

By ASSOCIATED PRESS
Published July 6, 2007

CAPE CANAVERAL - NASA this weekend is set to launch a spacecraft that will journey to the asteroid belt that lies between Mars and Jupiter, a mission that involves a rendezvous with two of the solar system's largest asteroids.

Weather permitting, Dawn is set to blast off Sunday afternoon from Cape Canaveral on a Delta 2 rocket. Seeking clues about the birth of the solar system, the Dawn spacecraft will first encounter Vesta, the smaller of the two bodies, four years from now. In 2015, it will meet up with Ceres, which carries the status of both asteroid and, like Pluto, dwarf planet.

"We're trying to go back in time as well as to go out there in space, " said planetary scientist Christopher Russell of the University of California, Los Angeles, who is heading up the mission.

The launch caps a tumultuous effort in which the $344-million mission was killed last year because of cost overruns and technical problems.

Ultimately, though, the Jet Propulsion Laboratory in Pasadena, which manages the spacecraft, appealed to NASA Administrator Michael Griffin and got the project revived.

Adding to the drama, Ceres briefly flirted with planethood during last summer's scientific debate about whether Pluto is a planet. Both Pluto and Ceres were finally classified dwarf planets.

Vesta and Ceres are believed to have evolved in different parts of the solar system more than 4.5 billion years ago around the same time as the formation of the rocky planets including Mercury, Venus, Earth and Mars. Scientists believe the asteroids' growth was stunted by Jupiter's gravitational pull and never had the chance to become full-fledged planets.

When Dawn reaches each asteroid, first Vesta in 2011, it will orbit each body, photographing the surface and studying the asteroid's interior makeup, density and magnetism. Pictures and data will be sent back to Earth.

Dawn will be powered by ion propulsion instead of conventional rocket fuel, making it more fuel efficient.

[Last modified July 5, 2007, 22:25:05]