CERES: THE ASTRONOMERS' VIEW

Dawn’s visit to Ceres has given us thrilling close-up views that show it to be a fascinating world that will keep geologists occupied for years to come. Before Dawn’s visit, two centuries of astronomical observations painted Ceres in ever-finer strokes. To the astronomers of the early 19^th century it was a full-fledged planet (von Zach, 1802), though by the start of the 20^th century it and its fellow asteroidal travelers were considered more of a footnote in the solar system (Metcalf , 1912). Indeed, it took nearly 100 years to establish that Ceres was the largest body in the asteroid belt rather than the intrinsically brighter Vesta (Barnard, 1895). Over the last forty years, improved data in a number of areas has led to a better understanding of Ceres, accelerating in the last decade as Dawn’s visit has drawn closer.

I will review astronomical observations of Ceres, particularly interpretations of its surface composition (Rivkin et al. 2012), surface features (Li et al. 2006, Carry et al. 2008), and interior structure (Thomas et al. 2005, McCord and Sotin 2005) and touch on the important future observations that will still remain to be made after Dawn’s observations end.