Those bright spots on micro-planet (or macro-asteroid) Ceres are not giving up their secrets easily.
The latest image release from NASA’s Dawn mission is the closest view yet of the crater floor that houses them, and ‘everything’ has just become more complicated as a result.
For those space watchers who like to predict what they will prove to be, the latest image features a very fresh, steep crater wall on the right. It rises around 1600 metres above the floor, and with two notable exceptions, the base of that partly shaded cliff shows very little debris from its slopes.
But above the start of the presumably newer wall at about the 1.45 clock position, there is a jumbled field of slumped debris that looks as if it might be the oldest part of the Occator crater’s rim. Moving around the rest of the rim there are similar but less degraded examples of wall or cliff front collapses.
Before considering the very complex bright deposits of material there are some previously undetected North-South oriented fissures or fracture lines on the crater floor and in places, smooth plain like areas covered in pimples of material that might be the residue of earlier white spots that have faded under exposure to sunlight and the loss of any volatile ices or salts they might have contained.
On the white spots, or collections of spots as seen at this closer range, there appears to be a gradation of reflectivity with what may be faded spots adjacent to or partly covered by newer brighter spots.
The white spots themselves seem to be very flat with only subtle hints of areas of more depth. The view seems to confirm the widely held interpretation of the spots as having been caused by material that has through some mechanism leaked or been extruded onto the crater surface from below.
But what that material might be remains unresolved. There are very tiny white spots apparent in this closer view scattered across the surface of Ceres that had not been seen before.
Immediately to the left of the brightest concentration of white material there is a sharp black dot that at first looks like a speck of black dirt on the image. Under magnification it looks like a steep narrow tube like pit, with the black coming from a shadow while there is a paler sunlit view of the opposing side, consistent with the play of sunlight and shadow across the rest of the frame.
The NASA media release with links to additional information can be found here.
Ceres is the largest object in the main asteroid belt between the orbits of Mars and Jupiter and has a diameter of about 950 kilometres.