In 2015, Dawn will rise over the dwarf planet Ceres. Not sunrise—this Dawn is a NASA spacecraft.

Since 2011, the craft has investigated the asteroid Vesta. In so doing, Dawn became the first probe to orbit an object in the asteroid belt between Mars and Jupiter. And a big object at that—Vesta is one of the largest asteroids out there.

On September 5th Dawn shoved off in pursuit of another first, and an even bigger target. In early 2015 it will arrive at Ceres, the largest object in the asteroid belt and one of the solar system’s so-called dwarf planets.

No spacecraft has ever gotten an up-close look at a dwarf planet. But Dawn will spend several months in orbit around Ceres, and should test the theory that the mysterious world harbors a substantial amount of water ice beneath its crust.

Dawn uses a superefficient ion-propulsion engine. Ion engines deliver a tiny amount of thrust but sustain it to gradually accelerate a craft to high speeds. So the cruise to Ceres will take awhile, but it requires very little fuel, thus enabling one craft to accomplish two interplanetary firsts.

—John Matson

[The above text is a transcript of this podcast.]