I would like to propose a different conjecture about the surface of Ceres from what I proposed earlier.
It occurred to me that any ice that would have been present from the primordial surface of Ceres (from releasing steam that froze in cold space) would most likely have been blasted away from galactic cosmic-ray particles and solar energetic particles (from the solar winds). I initially thought that the rocky material on the surface of Ceres would have protected ice underneath. However, without a protective magnetosphere, a thin layer of rocky material would probably not be enough to protect ice underneath.
Consider this. Planets, asteroids and meteorites are bombarded with
Solar energetic particles [SEPs] – 10^3 eV to 10^9 eV
protons, electrons, helium ions, and high-Z [HZE] ions
Intergalactic cosmic rays – 10^5 to 10^21 eV*
“All of the natural elements in the periodic table are present in cosmic rays, in roughly the same proportion as they occur in the solar system.”
† They are going so fast that the electrons and nuclei travel separately. The mix of nuclei is about 90% hydrogen nuclei (protons), 9% are helium nuclei (alpha particles) and 1% nuclei
of other heavier elements [HZE ions]
These energies are the same or greater than particle accelerators. If you took a rock, coated it with ice in proportion to an ice layer that might exist on Ceres with a subsequent coating of a thick layer of mud; then were able to introduced this model of Ceres into the particle stream of a working particle accelerator, and let it sit there for 2 to 4 billion years, would you expect the ice to still be present?
It's not a perfect analogy, but you get the idea.
On the other hand, magnesium is the 9th most abundant element in the universe. According to information curated and published by Mathematica and Wolfram Research, Inc, magnesium is 12% of meteorites for example. (
http://periodictable.com/Elements/012/data.html)
According to my favorite theoretical model, there is a strong likelihood that magnesium would be present on Ceres in abundance. Evidently, magnesium only occurs naturally in combination with other elements. Given the general abundance of hydrogen and oxygen in our solar system, we could expect magnesium hydroxide and magnesium oxide (which are white substances), but we could also expect magnesium sulfate (due to an abundance of sulfur in the parent nebula for our solar system) and similarly, we can expect magnesium carbonate. All of these are white or colorless.
A magnesium sulfate mineral found on neighboring planet Mars is meridianiite. It is clear to colorless and would reflect light nicely.
Also, diffusive losses from the bombardment of meridianiite (and other magnesium sulfates) would include water vapor.
I learned from the Russell interview that Ron-Astro posted, that this idea of the bright spots being due to certain salts is one of the contenders that Dawn Team is considering (meridianiite and other magnesium substances qualify as salts).
Chris Russel wrote: from
http://www.space.com/28776-nasa-dawn-ce ... rview.html
But there are people who are holding out for salt — not necessarily table salt, but salts of various minerals that may be white in appearance. So we have sort of a dichotomy of opinion in the team as to whether this has a dry or wet explanation. But we'll get to the bottom of this when we can resolve the bottom of the feature.
I have missed participating in this discussion with you all. [I did not stop discussing due to lack of interest, but was detained by work.]
† Cosmic Rays
http://imagine.gsfc.nasa.gov/science/ob ... rays2.html
* Energies:
http://www.gizmag.com/cosmic-rays/28997/;
Wonder if Ceres is on DST? 