NASA's Dawn spacecraft has concluded its survey of the asteroid Vesta and is now heading to Ceres, the largest asteroid (or smallest dwarf planet) in the solar system. As Dawn's mission director puts it, "thrust is engaged, and we are now climbing away from Vesta atop a blue-green pillar of xenon ions." Whoa.
That ion pillar comes from Dawn's DS1 xenon ion thrusters, which use electricity to accelerate xenon atoms to absurdly high speeds. Ion thrusters are far less powerful than chemical engines, but they make up for it in efficiency by generating a small amount of thrut continuously as opposed to a larger amount of thrust in a big burp like a conventional thruster. Dawn will spend less than 250 pounds of propellant for to get to Ceres from Vesta, and it'll be able to make the trip in just two and a half years.
While Vesta might be the second largest object in the asteroid belt, Ceres is far larger, at over 600 miles in diameter, qualifying it as a full-on dwarf planet as opposed to an asteroid. At the moment, this is the best view of Ceres that we've got, courtesy Hubble:
Astronomers think that Ceres probably has a rocky core with an icy surface, and there's a chance for a liquid water ocean somewhere underneath. Hubble has seen a mysterious bright spot on the surface of Ceres that nobody has been able to identify as of yet, and there's even a slim chance that there may be life out there, although if there is, Dawn isn't necessarily equipped to detect it. By 2015, the spacecraft will be sending back better pictures of Ceres than we've ever seen before, and the plan is for Dawn to spend nearly a year in orbit.
Below, watch a high-res farewell tour of Vesta made up of images from Dawn, with highlights narrated by a guy with a German accent.