After becoming the first spacecraft to enter orbit around an object in the main asteroid belt between Mars and Jupiter in July 2011, NASA’s Dawn spacecraft has spent the last year mapping the giant asteroid Vesta. The spacecraft has now bid adieu to Vesta and is on its way to the dwarf planet Ceres to continue its mission to help shed light on the evolution of our solar system.
Communications sent via NASA’s Deep Space Network confirmed Dawn’s departure from Vesta at about 11:26 p.m. US PDT on Tuesday, September 4. Launched on September 27, 2007, it took the spacecraft almost four years to reach its first port of call, but the second leg of its journey is set to be a bit quicker with Dawn expected to arrive at Ceres early in 2015.
Dawn’s departure from Vesta was far from dramatic. It gently spiraled out of the giant asteroid's orbit propelled by what Marc Rayman, Dawn's chief engineer and mission director, called “a blue-green pillar of xenon ions” emitted from the ion propulsion system that generates thrust by using electricity to ionize xenon.
While in orbit around Vesta, Dawn’s close up views revealed the giant asteroid in unprecedented detail. It found that Vesta had completely melted in the past, with its layered body forming around an iron core. It also revealed that Vesta had survived two colossal impacts in the last two billion years resulting in scarring in its southern hemisphere.
"We went to Vesta to fill in the blanks of our knowledge about the early history of our solar system," said Christopher Russell, Dawn's principal investigator. "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."
In around two and a half years, we can hope that Dawn will start to reveal just as much about Ceres. In the meantime, NASA has put together a video celebrating Dawn’s “greatest hits” from its time spent orbiting Vesta. Check it out below.