[X] My Assistant

[Phil Stooke]

On Tuesday (two days from now, for visitors from the future), the first optical navigation image will be taken... hopefully we'll have it in our hands soon after that. So it's time for a new topic. Over the next few months we'll have progressively closer images and full orbit characterization sequences, no doubt including multispectral image sets.

A new world...

This is a bit of reprocessing I have been doing with the Hubble images from a few years ago.




Phil

[dvandorn]

These images, and especially the animation made from them, do give the impression of a cratered body. In much the same way that the early Mariner 10 images gave the impression of a cratered Mercury -- very suggestive, but not enough to say for sure.

Of course, we would most definitely expect Ceres to be cratered -- with no tidal "pumping" I can't conceive of a heat source (internal or external) that would result in ongoing re-surfacing, and every other airless body that lacks an internal heat source (i.e., pretty much all of them except Io, and to a lesser extent Europa and Enceladus) that we've looked at in our solar system has been heavily cratered. Even Enceladus has some heavily cratered terrain far away from its active plumes. It would be the scientific discovery of the decade were Ceres not heavily cratered.

The one nice thing we can say is that we don't have very long to wait, in the overall scheme of things, to get a much better look at this dwarf planet. The Hubble suggestions of an almost Mars-colored world have had me intrigued for quite some time. Now we are very near to knowing, if not the whole truth of the matter, then at least enough data to raise questions we don't even know enough to start asking yet.

-the other Doug

[Habukaz]

Of course, we would most definitely expect Ceres to be cratered -- with no tidal "pumping" I can't conceive of a heat source (internal or external) that would result in ongoing re-surfacing, and every other airless body that lacks an internal heat source (i.e., pretty much all of them except Io, and to a lesser extent Europa and Enceladus) that we've looked at in our solar system has been heavily cratered. Even Enceladus has some heavily cratered terrain far away from its active plumes. It would be the scientific discovery of the decade were Ceres not heavily cratered.

Could not Ceres having formed "alone" compared to the icy satellites of the gas planets who formed right next to giants have an impact on, say, local distribution of radioactive isotopes (and heavier elements in general)?

[dvandorn]

Could not Ceres having formed "alone" compared to the icy satellites of the gas planets who formed right next to giants have an impact on, say, local distribution of radioactive isotopes (and heavier elements in general)?

AIUI, planet formation theory would have it that metals get less and less common in the original protoplanetary disk as you moved away from the Sun, reflected in the relative abundances of metals in the planets as you move outwards.

I have also heard theories that Jupiter once orbited much closer to the Sun, approximately where the asteroid belt is now located, while Saturn was created approximately where Jupiter is now located. As we have seen happen in other solar systems, Jupiter began to migrate closer to the Sun and supposedly began to draw off materials that ought to have contributed to the overall mass of Mars (resulting in Mars ending up smaller and less massive than would otherwise have been expected), but that before Jupiter could move far enough in to begin to disrupt the formation of Earth or any of the other inner planets an orbital resonance with Saturn began pulling it back away from the Sun, in the process tossing Saturn much farther out and likely tossing Neptune out past Uranus.

This all could have affected the formation of Ceres by disrupting its formation at a critical time, such that Ceres had a much larger amount of mass taken away from it by Jupiter. The square-dancing swing-arounds that reorganized the outer planets could also well have been responsible for tossing Ceres into its current, somewhat-skewed orbit -- meaning it could have been a planetesimal that had been forming closer to the Sun than its current location, and thus more enriched in metals than the moons of the outer planets. But it was far enough away from the Sun by the end of its creation that it accumulated a lot of snowballs near the end, accounting for its (potential) resemblance to the icy moons of Jupiter and Saturn.

However, in terms of radioactive heating, most of the planetary formation theories I've read point at Aluminum-26 as the major heat producer in the cores of the inner planets during their early histories. AL-26, however, has a relatively short half-life after it is created in a supernova, so the heating would have contributed only to the initial melting of the rocky planets' cores. None of the other radioactive heat-producing elements that survive to modern times could be contained in great enough quantity in such a small body as Ceres to create a hot core that would have persisted to modern times.

-the other Doug