NASA's Dawn spacecraft remains on track to become the first probe to orbit and study two distant solar system locations.
Indeed, Dawn is currently slated to leave the giant asteroid Vesta on September 4th when the spacecraft kicks off its two-and-a-half-year journey to the dwarf planet Ceres.
As you may recall, Dawn began its 3-billion-mile (5-billion kilometer) odyssey to explore the two most massive objects in the main asteroid belt way back in 2007. The spacecraft - which arrived at Vesta in July 2011 - is scheduled to reach Ceres in early 2015.
To make its escape from Vesta, the spacecraft will spiral away as gently as it arrived, using a special, hyper-efficient system called ion propulsion. Dawn's ion propulsion system uses electricity to ionize xenon to generate thrust. Although the 12-inch-wide ion thrusters provide less power than conventional engines, it can maintain thrust for months at a time.
"Thrust is engaged, and we are now climbing away from Vesta atop a blue-green pillar of xenon ions," said Marc Rayman, Dawn's chief engineer and mission director, at NASA's Jet Propulsion Laboratory, Pasadena, Calif. "We are feeling somewhat wistful about concluding a fantastically productive and exciting exploration of Vesta, but now have our sights set on dwarf planet Ceres."
According to Rayman, Dawn's orbit provided close-up views of Vesta, revealing unprecedented detail about the giant asteroid. For example, scientists learned that Vesta completely melted in the past, essentially forming a layered body with an iron core.
The spacecraft also detected scarring from titanic collisions Vesta suffered in its southern hemisphere, surviving not one, but two colossal impacts in the last two billion years.
"Without Dawn, [we] would not have known about the dramatic troughs sculpted around Vesta, which are ripples from the two south polar impacts. [Remember], we went to Vesta to fill in the blanks of our knowledge about the early history of our solar system," explained Christopher Russell, Dawn's principal investigator, based at the University of California Los Angeles (UCLA).
"Dawn has filled in those pages, and more, revealing to us how special Vesta is as a survivor from the earliest days of the solar system. We can now say with certainty that Vesta resembles a small planet more closely than a typical asteroid."