Thursday marked the official end of the primary mission of NASA's Dawn spacecraft. Dawn demonstrated the potential of ion engines in the exploration of the Solar System, as it was able to rendezvous with and enter orbit around two different asteroids, Vesta and Ceres. Scientifically, its findings have changed what we thought we knew about some of the bodies of the asteroid belt.
Dawn isn't going to shut down now that its mission is over, as it's in reasonable working order and still observing Ceres. But there's a hint that NASA has bigger plans for the spacecraft.
Yesterday, the Jet Propulsion Lab (which operates Dawn) put up and then removed what it calls a "Dawn Journal" entry. The entry described the future plans for Dawn, and they don't involve staying in orbit around Ceres. Instead, the craft's ion engines will be used to gradually nudge it away from Ceres. The low-power, high-efficiency engines will take until the end of the year to get the spacecraft free of the dwarf planet's gravitational pull.