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Dawn's first orbit, including RC3, March 6, 2015- June 15, 2015
Phil Stooke
post Jun 11 2015, 03:08 AM
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Please link to the original images at the Dawn website, rather than some image hosting site with pop-up ads.

Phil



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TheAnt
post Jun 11 2015, 03:37 AM
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QUOTE (Habukaz @ Jun 10 2015, 03:56 PM) *
Also in the release is, among other things, a nice mosaic of one of the two big craters in the southern hemisphere. These scratch marks north (?) of it have an interesting appearance:


Yes that feature did catch my eye also, it resembles glacier shearing, and might be a comparatively young feature.
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Gladstoner
post Jun 11 2015, 07:25 AM
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Ceres spot in the parking lot? smile.gif

Attached Image


Fracture/conduit? Check.

Salt deposits? Check.

There is even a dark halo, but the origin of this one is quite different.
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ZLD
post Jun 11 2015, 01:56 PM
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And is that a giant pair of feet?! Aliens confirmed on Ceres! News at 11!


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Gladstoner
post Jun 11 2015, 06:14 PM
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New image, contrast enhanced:


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stevesliva
post Jun 11 2015, 06:32 PM
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QUOTE (dvandorn @ Jun 10 2015, 03:12 PM) *
Yeah -- the dark streak appears to be a shadow cast by a ridge of some type, as the sun is coming from the bottom of the image.


If you look at this earlier image, in the craters lower in the image, especially right above the caption, there are dark deposits that really do not appear to be shadows.
http://solarsystem.nasa.gov/news/display.cfm?News_ID=49244

I would not bet that all the low albedo features in the image you're discussing are shadows.

Here, too, there are dark features on the crater slopes that don't seem to all be shadows:
QUOTE (Gladstoner @ Jun 11 2015, 01:14 PM) *
New image, contrast enhanced:
Attached Image

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ngunn
post Jun 11 2015, 06:45 PM
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Great view of the 'sand dollar' in the upper right there. This is a good orbit from which to capture the whole of the Ceres's biggest features within a frame. Soon we will be too close for that.
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Gladstoner
post Jun 11 2015, 07:26 PM
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QUOTE (stevesliva @ Jun 11 2015, 01:32 PM) *
Here, too, there are dark features on the crater slopes that don't seem to all be shadows:


Indeed. This darkish area (Piazzi) has been noticed since the early Hubble observations.
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Gladstoner
post Jun 11 2015, 10:36 PM
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QUOTE (dvandorn @ Jun 10 2015, 03:12 PM) *
.... things that occur to me, looking at the zoomed-in image:

1) The secondary white spots look like a long quonset-style building, with smaller outbuildings arranged around it...

2) The main spot looks like the saucer section of a Constitution-class starship, with the longer piece representing the engineering hull. Not much left of the nacelles, just a few small pieces, so they must have blown apart upon impact...

wink.gif

Or maybe it's where the underpants gnomes stash their contraband.
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John Broughton
post Jun 12 2015, 06:01 AM
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This is a section of the floor of the western of the two southern basins, including light and dark markings seen since January. North is at top.
Attached Image


As mentioned earlier, I suspect both light and dark markings represent volcanic deposits in regions where the crust is weak. That's why light and dark markings are often found on fault lines and in proximity with one another.

My suspicion is that light-toned spots represent salt gradually deposited over a period, and therefore should show varying degrees of positive relief, depending on how long each site was active. I'm yet to see any spots displaying definite signs of impact-related excavation (the consensus explanation in this forum since day 1). The light-toned area left of centre appears to include a ridge on a fault line. If I'm not being fooled by the lightng angle, two thirds of the way along it is a steep cone-shaped mountain. Judging by other large Cererean basins, that mountain looks too small and steep to be its original central peak. The ridge itself could represent a piece of crust that has been broken and tilted prior to formation of the mountain on top.

And I suspect dark markings result from impacts elsewhere, forcing water to explode through those weak points in the crust, spraying and flooding the area with mud -- the basin floor right of centre has clearly ruptured, just where it is darkest. By the way, just at the top of that rupture is a curious mound with two depressions in it that seems to have formed there sometime after the groove it is sitting on.
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Gladstoner
post Jun 12 2015, 10:47 PM
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In the newest release, another crater with a central pit:

Attached Image


This seems to be a recurring theme.
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dvandorn
post Jun 13 2015, 12:29 AM
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I'm agreeing a lot with John's points above. Especially where he notes that the darkest albedo unit seems to overlay the area around the cracks on the right of the image. This looks like a classic example of fissure volcanism, where the Cerean equivalent of fire fountains sprayed from the fissures, emplacing the Cerean equivalent of pyroclastic material over the surrounding terrain. Compare this to the black/orange/red/brown volcanic glasses on the Moon that were emplaced by ancient fire fountains. (Look up the orange/red soil and dark mantling found at Apollo's Taurus-Littrow landing site for good examples.)

The thing I wonder about is how ancient are the landforms we're seeing? Except for impact alteration, any volcanism (even cryovolcanism) on Ceres driven by internal heat would have to have shut down gigayears ago. I wonder if Ceres would have looked pretty much exactly as it looks now three billion years ago?

-the other Doug


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Julius
post Jun 13 2015, 06:51 AM
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QUOTE (Gladstoner @ Jun 11 2015, 07:14 PM) *
New image, contrast enhanced:


Attached Image


Are we sure that is an impact crater?
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Ian R
post Jun 13 2015, 11:18 AM
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The Piazzi dark feature, and its proximity to the nearby impact structure, reminds me of the dark pyroclastic halo on the southern rim of Mare Orientale (albeit far more diffuse):

Attached Image


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TheAnt
post Jun 13 2015, 02:02 PM
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QUOTE (Gladstoner @ Jun 13 2015, 12:47 AM) *
In the newest release, another crater with a central pit: This seems to be a recurring theme.


Indeed, yet smaller craters do seem to often have that central peak we've learned to expect. Even in that image there's a few such craters at lower right.
So was that central pit a bright area similar to spot 5 in the past? If that turn out to be correct, the case for ice grow stronger, since a pit would suggest something have been removed/evaporated, salts could remain though leaving the pit bright so have they dusted over or darkened by some other mechanism.....?
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