But what do the dwarf planet Ceres craters mean or imply for the comet formation theory, comet geology and the EU theory?
The latest (first!) decent image of active asteroid Ceres looks at the palimpsest craters mystery.
A palimpsest crater is where the original sharp form of an impact crater has nearly disappeared over time. On Earth where we use water erosion to explain most surface geology features - sometimes with wind allowed into the party - it would be easy to explain.
Science uses geomorphology (comparison of Earths features to describe and explain other space bodies features) for most geology features on planets and moons but struggles to use geomorphology on these dwarf and mainly ice composed dwarf planets. The same as with comets and asteroids.
Ceres geology - palimpsest craters
Emily Lakdawalla in her blog on planetary.org has looked at the Ceres images of its surface and its massive palimpsest crater. The Electric Universe theory predicted these Ceres craters and surface structures.
But there's one crater on Ceres that made my jaw drop: it's the big one at the center of the view above, (g). It's incredibly flat. You can barely see its rim. Its interior is very smooth and lacks any mid-sized craters, though there are many small ones. On the Max Planck website, they go so far as to say that the large crater is relatively recent, because it contains no middle-sized craters, only small ones.
The main question about such a flat crater, other than its age, is: was it born that way, or did it become flatter over time? On icy worlds, initially deeper craters become shallower when, over geologic time, the warmer ice in the world's interior flows from high places to low places, raising crater floors. But a layer of ice at the surface is so stiff that it still preserves the pre-impact topography. That's how Tethys' huge Odysseus basin still has a rim, a peak ring, and a central peak, even though its floor has risen over time so that it is now convex, continuing the curvature of Tethys' globe rather than concave, like the original bowl shape of an impact crater:
But Ceres' largest visible basin is much, much smoother than Odysseus. There is no pre-impact topography present -- no peak, no peak ring. What happened to the topography? Was it covered up by a volcanic flow, like lava flows filled in the lunar impact basins? Or was there never much any topography in the first place, because the impact happened long ago into a Ceres with a thin crust and a subsurface ocean? These kinds of features are called palimpsests; they don't exist on the mid-sized outer planet moons, but you see them on Europa and Ganymede. The round basin on Ceres is so incredibly smooth that I'm inclined to think it's been filled in, like the terrain in the photo of Triton below, but -- like I said before -- I'm going to remain doubtful of volcanism until I'm left with volcanism as the only interpretation. And we haven't gotten there yet.
At last, Ceres is a geological world