The New Horizons mission to Pluto might get all the attention, but 2015 had plenty of other amazing space mission firsts — and lasts, as scientists said good-bye to two orbiters.
Dawn
The Dawn probe arrived at Ceres March 6, becoming the first spacecraft to orbit a dwarf planet (take that, Pluto!) (SN: 4/4/15, p. 9). Dawn quickly started mapping its new home. Bright patches sitting within craters (SN Online: 9/10/15), which at first glance looked like exposed ice, are probably salt deposits. The craters themselves are also puzzlingly scattered unevenly across the surface (SN: 9/5/15, p. 8).