False colour map. Ignore the crater shadows and stretching near the poles.
But the changes beyond 55 degress north and south are real.

Full scale

Bright spot details (compressed light intensity range, the bright spots are a lot brighter than the background. With this photo I’m beginning to understand the bright spots. It looks like and enormously bright spot was uncovered in the centre by an impact large enough to form the crater, and the other eleven spots are where the ejected bright material crashed back to ground.

Full scale

More from http://dawnblog.jpl.nasa.gov/

Status:
All systems functioning normally. In spiral descent to lower altitude.

November 5, 2015 – Dawn Descending on Course and on Schedule. As Dawn spirals to lower orbits, its average altitude today is about 1000 kilometers. Each week, controllers update the complex flight plan for ion thrusting, so Dawn will pause thrusting this afternoon, turn to point its main antenna to Earth to receive its new instructions, and resume thrusting tonight. Nov 6 the spacecraft will reach to below 966 kilometers. It is aiming for a close-in orbit of 380 kilometers.

> It looks like and enormously bright spot was uncovered in the centre by an impact large enough to form the crater, and the other eleven spots are where the ejected bright material crashed back to ground.

But that looks a pretty ancient crater. You’d think bright material would have been overlain with the normal darker dust by now.

Bubblecar said:

> It looks like and enormously bright spot was uncovered in the centre by an impact large enough to form the crater, and the other eleven spots are where the ejected bright material crashed back to ground.

But that looks a pretty ancient crater. You’d think bright material would have been overlain with the normal darker dust by now.

Aha!

Thanks Bubblecar, hadn’t thought of that. Looking now at the crater in maximum resolution. Not only does it lie on top of the crater to its north, it also has not one single (OK perhaps one) small or tiny crater within its boundaries. That makes it quite recent.

Even more telling, for a distance of about one diameter outside the crater wall in all directions there are very few small craters. It could be that ejecta from the impact that formed the crater blanketed (lightly) all the area outside, and fairly recently.

So let’s do a crater count:
Location, Relative Area (arbitrary units), Number of craters, Crater density
Inside the crater rim, 250, 1, Crater density 0.004
Outside but near crater, 275, 66, Crater density 0.24
Away from crater to north (same image linked above), 25, 148, Crater density 5.9

The low crater density in and near Occator crater strongly suggests that it is very young indeed.

>The low crater density in and near Occator crater strongly suggests that it is very young indeed.

Well if by very young, you mean a few million years at least.

So accepting your hypothesis for the sake of argument, what do you think the bright stuff is moll?

Bubblecar said:

>The low crater density in and near Occator crater strongly suggests that it is very young indeed.

Well if by very young, you mean a few million years at least.

So accepting your hypothesis for the sake of argument, what do you think the bright stuff is moll?

Hmm, let’s see. 0.004 / 5.9 * 4.6 billion years = 32 million as a very rough approximation.

I still haven’t seen a scientific article on what the bright stuff is. I haven’t even seen a calculation of its albedo since before Dawn went into orbit. Vesta is made almost totally of rock. Ceres on the other hand seems to be made mostly of ice. So water-ice seems the most likely candidate.

This paper dates from Nov 2015. From abstract:

“Dawn discovered several extremely bright spots on Ceres, the most prominent of which is located inside the Occator crater that is at least 4-5 times brighter than the average Ceres. Interestingly, these bright spots are located in relatively young craters that are at the longitudes corresponding to the maximum water vapor observed by the Herschel Space Observatory, suggesting possible correlation with water sublimation on Ceres. We used the multi-color imaging data collected by the Dawn Framing Camera to analyze the global photometric properties of Ceres and the bright spots, especially those located inside the Occator crater. Our objectives are to determine the albedo and other light scattering properties of the bright spots on Ceres in the visible wavelengths, in order to characterize their physical properties and find clues about their composition and possible formation mechanisms and the correlation with water sublimation. The overall geometric albedo of Ceres’ global surface is 0.09-0.10, consistent with previous studies. The Hapke roughness parameter is about 20°, close to many other asteroids, rather than 44° as reported earlier. Correspondingly, the phase function of Ceres is less backscattering than previously modeled. In contrast, the geometric albedo of the bright spots inside the Occator crater is 0.4-0.5, and the single scattering albedo is 0.7-0.8.”

I don’t think I have access to the full article, but I’ll check.