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Dawn's Survey Orbit at Ceres
Habukaz
post Jun 19 2015, 05:42 PM
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At first I thought it was some other bright material, but I guess you are right. It's kind of counterintuitive that the bright material inside the crater should be visible from this angle.


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ZLD
post Jun 19 2015, 06:15 PM
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That does seem pretty strange. Must be peering just over the crater rim.


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ngunn
post Jun 19 2015, 07:25 PM
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As I mentioned before don't forget that the curvature of Ceres applies as much along the line of sight as it does around the limb. Big craters have convex floors.
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eliBonora
post Jun 19 2015, 08:40 PM
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QUOTE (wildespace @ Jun 19 2015, 08:13 AM) *
Perhaps you could use that colour information in your images? I'd imagine that the surface's appearance at near-infrared would be similar to what it looks like at red wavlengths.


Yes, I know, it would be possible but maybe be worth waiting for better definitions .. and they are coming! smile.gif


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scalbers
post Jun 19 2015, 10:50 PM
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Today's image also helps in mapping some of the terrain just south of spot #5.

Attached Image


Full 8K resolution and polar views are here.


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eliBonora
post Jun 20 2015, 05:50 AM
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Here a Ceres mosaic (PIA19575 and 19576)



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antipode
post Jun 20 2015, 07:04 AM
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Now that basin is fascinating, not just for the radial valleys, but for the darker mare-like features on its floor. Someone needs to do some crater counting there when the resolution gets good enough!
Also, whats with that lobate feature to the right of the basin which terminates near those fossae? Almost looks like the basin has overflowed (cryo?)mare materials in the past. Does anyone else see that?

P
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TheAnt
post Jun 20 2015, 08:49 AM
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QUOTE (antipode @ Jun 20 2015, 09:04 AM) *
Also, whats with that lobate feature to the right of the basin which terminates near those fossae? Almost looks like the basin has overflowed (cryo?)mare materials in the past. Does anyone else see that?


Of course we do see it. smile.gif That part immediately caught my eye also on the image composite that eliBonora provided.
It seem that the crater walls might be slowly filling slowly, if that turn out to be correct they truly would be doing so at a glacial pace.
I cant stop wondering if those larger chunks might be ice or aggregations of the darker surface material that stick together.
In addition there appear to be terrace all round the southern half of the crater that make it seem that the southern region got a higher elevation.
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alk3997
post Jun 20 2015, 03:11 PM
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If Ceres still has a glacial fill process that continues today, shouldn't we see some of those small to mid-sized craters partially filled or at least distorted? To me the current surface still looks old. I see Ceres as a body that was one-time active but has now cooled to a point that the surface is no longer active. Any modifications are only done by crater impacts.

Below the surface, we'll have to wait and see what the data says.

Andy
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TheAnt
post Jun 20 2015, 05:25 PM
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Distorted craters could indeed show us something.
Now that the area right of that large crater show quite less craters than on average, whereas areas north of the crater are literally peppered.
Do this mean that craters have been removed, and only later replaced more recently by a few small craters just at the limit of the image resolution?
And yes, one of the largest ones near the right side of the image actually is distorted.
But we will need higher resolution images before this little hypothesis will fly or be turned over end, most craters in the area are too small to show any detail yet.
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ZLD
post Jun 20 2015, 06:36 PM
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QUOTE (alk3997 @ Jun 20 2015, 09:11 AM) *
To me the current surface still looks old. I see Ceres as a body that was one-time active but has now cooled to a point that the surface is no longer active.


The surface certainly looks old and battered yes but much younger than a lot of other icy bodies that have been studied. For floating in the asteroid belt, Ceres appears remarkably smooth in a lot of places suggesting some amount of occasional resurfacing in those areas in geologically recent times.

I haven't heard much about the possibility of a periodic atmosphere around Ceres recently. Has there been any more debate on this? We are unfortunately nearly in the dead of winter on Ceres right now. Has this been laid to rest since that article? There wasn't ever much as far as details on the speculation anyway.


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ngunn
post Jun 20 2015, 10:11 PM
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QUOTE (ZLD @ Jun 20 2015, 07:36 PM) *
The surface certainly looks old and battered yes but much younger than a lot of other icy bodies that have been studied


Could be just a little bit younger if all the big land-forming action happened early on. The process exposing the white spots on the other hand must be recent and ongoing.
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Steve5304
post Jun 21 2015, 04:07 AM
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QUOTE (Gladstoner @ Jun 19 2015, 04:46 PM) *
Spot #5 is nearly on the horizon in today's image:

[attachment=36162:spot_5.jpg]




This image makes ice look plausible...as much as i want it to be somthing like diamonds or aliens.. I am still not convinced the bright spots anomaly was almost entirely blown out of proportion by exposure of the camera.
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alk3997
post Jun 21 2015, 02:09 PM
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QUOTE (TheAnt @ Jun 20 2015, 11:25 AM) *
Distorted craters could indeed show us something.
Now that the area right of that large crater show quite less craters than on average, whereas areas north of the crater are literally peppered.
Do this mean that craters have been removed, and only later replaced more recently by a few small craters just at the limit of the image resolution?
And yes, one of the largest ones near the right side of the image actually is distorted.
But we will need higher resolution images before this little hypothesis will fly or be turned over end, most craters in the area are too small to show any detail yet.


Yes, all good questions.

The large craters with the apparently filled-in, but cratered, floors have intrigued me. Perhaps at a large enough kinetic energy an impact breaks through the crust into the subsurface ocean and allows the floors to be filled for a very short period of time. Over time the crust has become thicker and so more kinetic energy is needed to break on through to the other side - the subsurface ocean and allow flows to occur. The deeper the ocean, the shorter the time before the opening freezes again.

This is why only the big craters show signs of resurfacing and yet have middle to small craters within them. Over geologic time it has required more and more impact kinetic energy to cause a flow to occur. The crust near the equator is shallower than near the poles which would explain the differences in large crater density between the equator and the poles.

Andy
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JohnVV
post Jun 22 2015, 02:42 AM
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QUOTE
Perhaps at a large enough kinetic energy an impact breaks through the crust into the subsurface ocean and allows the floors to be filled for a very short period of time. Over time the crust has become thicker and so more kinetic energy is needed to break on through to the other side - the subsurface ocean and allow flows to occur. The deeper the ocean, the shorter the time before the opening freezes again.

this thing is way too small and there is no "jupiter" to tug at it

it has been a solid bit of ice and rock for a VERY long time
and has been DEEP COLD for a very long time

impacts on "high ice " content are VERY different than on a rock or on nickel /iron

you get very FLAT floors on the impacts in ices
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