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Occator crater on Ceres' limb

Occator crater on Ceres' limb
Occator crater on Ceres' limb Dawn took this picture on Oct. 16 in its fifth mapping orbit at an altitude of 920 miles (1,480 kilometers). The most salient feature is Occator Crater at upper left, with its famous and intriguing bright regions, composed of reflective salt (principally sodium carbonate) left on the ground when briny water sublimated. We have seen other appealing views of Ceres’ limb, but those were opportunistic, showing whatever landscape happened to be in view when Dawn was rotating to point its main antenna at Earth. In this case, however, mission controllers instructed Dawn to turn to photograph Occator when they knew it would be near the limb. This was part of the observing campaign explained last month. This perspective of Occator is different from the others we have presented in past Dawn Journals, most recently in July. Dawn was northeast of Occator Crater when it took this picture, so it was looking southwest. As a result, the grouping of secondary bright regions is to the left of the primary bright feature, and we are looking over the sizable crater on Occator’s north rim. A bright region on a planet is known as a facula, and the International Astronomical Union approved names for the faculae in Occator last week, just in time for this Dawn Journal. The central one, the brightest and largest on Ceres, is Cerealia Facula, and the others are collectively now known as Vinalia Faculae. (Cerealia was a Roman festival to honor Ceres. Vinalia was a Roman wine festival held twice a year. Here is the naming convention for features on Ceres.) You can see them more clearly in the photo presented in July and the pictures shown in March. Occator is on this map at 20°N, 239°E. Full image (with different picture adjustments) and caption. NASA / JPL-Caltech / UCLA / MPS / DLR / IDA