PDA

View Full Version : Ceres: Odd Round Flat Feature



antoniseb
2015-Feb-25, 07:16 PM
The Feb 19th images (https://lh3.googleusercontent.com/-gcnVA75FaWg/VO30sxheliI/AAAAAAAAy8U/h3q5lSiughA/w612-h341-no/PIA19183.jpg) of Ceres show a very large round smooth feature on Ceres which has a modest sized crater in the center, and four roughly equally spaced modest sized craters near the edge. I am having an interesting time speculating how such a feature was formed, and why none of the other craters on Ceres have this wide perimeter. Speculation?

DaveC426913
2015-Feb-25, 08:09 PM
It is only odd if you assume that the small central crater is related to the large outer crater. The large outer crater looks pretty much like the other large craters, and the small inner crater looks pretty much like the other small craters.

Now, the layout of the four (five) smaller craters is certainly intriguing. Perhaps an asteroid that has been broken up and is travelling as a tight group.

antoniseb
2015-Feb-25, 08:48 PM
It is only odd if you assume that the small central crater is related to the large outer crater. ...
Actually, the big round feature is not like the other big craters. It has a relatively smooth surface, meaning it is relatively new. It IS possible that the largish crater in what appears to the exact center of a new giant crater is a coincidence, but I take the odds of that as fairly low (but uncalculated by me at this time).

One idea I'm exploring is that the central crater was from a very high velocity event, and that the larger circle is not a crater as much as a fracture-zone around the crater. I'm still pretty flexible about the details, and hoping that Dawn's future observations may provide some clues.

IsaacKuo
2015-Feb-25, 10:39 PM
Could it be like a peak ring crater formation? The central crater does look like a normal crater, though.

borman
2015-Feb-25, 11:29 PM
Speculation OK
Perhaps Ceres had its "bell" rung. Suppose that the 4 additional craters are not the result of secondary impacts from the center impact. Suppose that craters regularily covered this area prior to the main impact. The dust lifted covered or buried these craters out to the radius. Suppose that the energy and shape of the impactor was one of Ceres' prefered resonances. The interference pattern could have null nodes where less dust would land. So the craters already located at these symmetry points would get less a covering of dust than other craters within the circle and remain exhumed.

Zartan
2015-Feb-25, 11:38 PM
Actually, the big round feature is not like the other big craters. It has a relatively smooth surface, meaning it is relatively new. It IS possible that the largish crater in what appears to the exact center of a new giant crater is a coincidence, but I take the odds of that as fairly low (but uncalculated by me at this time).

One idea I'm exploring is that the central crater was from a very high velocity event, and that the larger circle is not a crater as much as a fracture-zone around the crater. I'm still pretty flexible about the details, and hoping that Dawn's future observations may provide some clues.

It looks way too smooth for a fracture zone. If it was that, IMO it should have concentric rings like Valhalla on Callisto. Also the central crater does not look exceptionally big.

I think the big crater is actually pretty old?? It is so shallow and smoother over. Sure it's bit weird that there is a smaller crater exactly in the center, but I believe it is just a coincidence.

Cererian surface seems to have somewhat recognizable nature. I find it interesting that we are not actually seeing many, if any, ray systems around the bright features which we assume to represent relatively fresh impact craters. Maybe it's because of low gravity, I dunno.

Trebuchet
2015-Feb-26, 03:18 AM
I've no idea what it is. Or isn't. But isn't this an awesome year to be alive, when we'll get our first close-up pictures of Ceres, and Pluto? And follow a comet on it's way in toward the sun? And see the first Falcon Heavy Launch, and probably the first Falcon first stage soft landing? Wow!

Spacedude
2015-Feb-26, 02:15 PM
Reminds me of a sand dollar........sort of.

ToSeek
2015-Feb-26, 09:49 PM
Emily Lakdawalla is also fascinated: (http://www.planetary.org/blogs/emily-lakdawalla/2015/02251857-ceres-geology.html)


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.

Swift
2015-Feb-26, 10:28 PM
What about if Ceres was rather icey (or icey in that area) and it is an old crater and the ice flowed over a long period of time. The more "traditional" craters are either newer or are in rocky areass?

Trebuchet
2015-Feb-27, 12:55 AM
That's no moon asteroid....

Ara Pacis
2015-Feb-27, 05:28 AM
What about if Ceres was rather icey (or icey in that area) and it is an old crater and the ice flowed over a long period of time. The more "traditional" craters are either newer or are in rocky areass?

My first impression was some sort of "Sea" like on the Moon.

Spacedude
2015-Feb-27, 02:44 PM
deleted, wrong thread, sorry.

Zartan
2015-Mar-02, 10:53 PM
One of the Feb 25th images (http://photojournal.jpl.nasa.gov/jpegMod/PIA18925_modest.jpg) shows the large shallow crater better. It seems to have kind of mound or 'pancake' off-center. There also seems to be smaller 'mountain' or other higher relief feature from East-Southeast of the central crater. (unless I'm looking it wrong and it's actually a small crater).

Ara Pacis
2015-Mar-03, 06:35 PM
One of the Feb 25th images (http://photojournal.jpl.nasa.gov/jpegMod/PIA18925_modest.jpg) shows the large shallow crater better. It seems to have kind of mound or 'pancake' off-center. There also seems to be smaller 'mountain' or other higher relief feature from East-Southeast of the central crater. (unless I'm looking it wrong and it's actually a small crater).

Looks like two or three craters are asymmetrically positions in shallow mounds, which look kinda like outflow. Not saying that's what it is, but that's what the shading makes it look like to me.