Last month, NASA chose the Dawn mission, which will take nine years to visit two primordial asteroids, for detailed study as a candidate for the agencys Discovery Missions Program.

The spacecraft will be using the most futuristic propulsion system available today -- solar-electric propulsion -- validated over the last two and one-half years on NASAs Deep Space 1.

Targeting the Asteroid Belt between Mars and Jupiter, Dawn will first orbit Vesta, a dry rock thought to be the source of many meteorites that have impacted Earth, and then Ceres, considered a water-rich asteroid that likely does not have a metallic core, unlike Vesta.

Dawn gives us something to compare meteorites to for a better understanding of where they came from and how they evolved.

Launching in July, 2005, the spacecraft is scheduled to arrive at Vesta in 2008, orbiting for nine months before moving on to Ceres in 2013 for a nine-month orbit ending in 2014.

"What appealed to NASA reviewers was that we are comparing two very different asteroids with each other," said principal investigator Christopher Russell, a professor of geophysics and space physics at the University of California at Los Angeles and the person who conceived the mission. "Ive never gotten such glowing reviews from a NASA panel before -- they found our science really compelling."

The mission goal is to understand conditions during the solar system's earliest epoch by investigating two protoplanets that have remained intact since their formation just 10 million years after the start of our solar system approximately 4.5 billion years ago.

"Dawn will help us to understand the planetary formation process that was interrupted in the Asteroid Belt when Jupiter was formed," explained co-investigator Mark Sykes, an associate astronomer at the University of Arizonas Stewart Observatory.