Free Astronomy Magazine July-August 2015

PLANETOLOGY P lane projection map of Ceres, created with im- ages taken by the Dawn spacecraft in March, before entering into or- bit. The colouring has been enhanced to highlight the differences be- tween neighbour- ing structures and provide clues on the physical-chem- ical properties of the surface mate- rials. Right, image of a heavily cra- tered region of Ceres’ northern hemisphere, taken on 6 June at the beginning of the second mapping phase of the dwarf planet. [NASA/JPL- Caltech/UCLA/MPS/ DLR/IDA] long descent to a lower orbit, from where it will undertake a more detailed mapping of the dwarf planet. While the spacecraft was changing its or- bit, Russell and colleagues examined the latest and more detailed images of the mysterious couple of bright spots, which now appeared to be made up of many smaller spots, gathered into two groups. The good image resolution (1.3 km/pixel) allowed Dawn’s team to better discern the shape and size of the crater housing the spots, and to doubt the possible cryovolca- nic origin. On 3 June, Dawn reached the new orbit – altitude 4,400 km, orbital pe- riod 3 days, from where it restarted map- ping the surface, but with a resolution which was never before obtained, all with the aim of revealing the geological history of the dwarf planet to tell if it is still active in some way. If there is still some residual geological activity, it could be related to the rock and ice mantle, supposedly shroud- ing the rocky/metal core lying at its centre. When it was about halfway towards the new orbit, on 23 April, Dawn took a series