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Dawn's first orbit, including RC3, March 6, 2015- June 15, 2015
MarsInMyLifetime
post May 11 2015, 08:02 PM
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It may soon be time for some underexposed frames that shift the washed out zones into the gray scale for analysis. Given that there seems to be some sensible scale to the size of some of these dots, any detail or sense of relative brightness between them is still washed out.


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Habukaz
post May 11 2015, 08:04 PM
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There's also this feature that looks like a three-pronged mountain:


Attached Image Attached Image Attached Image


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Zelenyikot
post May 11 2015, 09:36 PM
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It look like volcano



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Phil Stooke
post May 11 2015, 09:59 PM
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Wow, that is really good! Thanks.

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ZLD
post May 11 2015, 10:15 PM
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I'd say its a good candidate for a volcano like feature. If you watch closely to the first few frames, you can see what would appear to be a depression in the top center of the mound.

Added some deconvolution sharpening.

(click to animate)


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Bjorn Jonsson
post May 11 2015, 10:16 PM
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QUOTE (Zelenyikot @ May 11 2015, 09:36 PM) *
It look like volcano


Very interesting feature and a really cool animation. The mountain apparently has some albedo features but I also get the impression that some of the bright features are at least partially due to illumination geometry changes.

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Sherbert
post May 11 2015, 11:23 PM
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To take stock after the RC3 images. In addition to huge numbers of craters, there appear to be sundry other features, gouges, plateaus, basins rough and smooth and gullies. There are a large number of "polygonal" craters mainly pentagons and hexagons, which should tell those who know about such things something about the composition of the surface layers. There appear to be "stretch marks", which either indicate tectonic activity or are the result of expansion and/or contraction in the past. The numerous bright spots all appear to be of indigenous origin from their shapes, possibly as Gladstoner suggests from seepage of material from below the surface. THE bright spots have the appearance of salt lakes and the odd "spiky" shapes of a couple of other spots suggest they too are the result of fluid deposition. The fascinating mountain is most probably a volcano, since other mountain building scenarios seem in short supply in this area, that is, its not a central peak in a crater or the remains of a crater rim. I just wonder if it is not a giant "Iceberg" that has been thrust up through the surface from below, just to introduce a left field possibility. Different densities and phases of water ice might lead to odd occurrences such as that.

So lots to ponder on still and still we require better resolution. Dawn is due to take a couple of sets of images as it spirals into the next survey orbit, we await further enlightenment.
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Gladstoner
post May 12 2015, 01:19 AM
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Speaking of left field ( smile.gif ) ....

I can't help but be reminded of Middle Butte near Idaho Falls, Idaho:

Attached Image


When I saw this butte some years ago while traveling through the area, I figured it was a cinder cone (one of several along the Snake River valley). As it turns out, though, Middle Butte formed when a volcanic intrusion pushed up the overlying rocks in a piston-like fashion.

The mountain on Ceres has a roughly similar appearance -- isolated, with (mostly) steep slopes and (an apparently) flat top. Since there is a lack of obvious geologic context here, I figure this is either a volcanic (or 'volcanic') construct or a tectonic uplift. Since it is hard to imagine sustained eruptions producing a 4 km high edifice on Ceres, I'm leaning toward an uplift of some kind.

If this is a tectonic uplift, it may provide a valuable cross section of the upper crust. When I strain my eyes while watching the animations, I think I can just make out a sandwich-like structure in the slopes, i.e. bright-dark-bright. These variations of albedo are probably a combination of outcrops and talus/debris. Since there appears to be some of the high-albedo material present, this could help sort out its nature and origin.

Also, the steepness of the slope on the mountain's north face may be partially due to the impact crater just below it.
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MarsInMyLifetime
post May 12 2015, 03:10 AM
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I have to agree that this hill is volcano-like in appearance. But if it is due to a geologic process, then why, over geologic time, haven't many others also appeared? Perhaps this one is unusually large and the others are lurking just below the present limit of resolution... more geyser-like in form than built up from durable "ash." What I'm missing so far in the surface is a sense of history of repeating processes (as in Europa's criss-crossing ice ridge sequences).


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Habukaz
post May 12 2015, 09:33 AM
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It's certainly a very interesting-looking feature. It might be related to what was mentioned by a project scientist in a link posted earlier:

QUOTE
“There are domes, things pushing out from the inside,” he continued, “and bright spots that suggest that material from inside has come to the surface in some sort of volcanism.”


If the feature is caused by internal geological processes, there might be more of them. This might be the one that grew the biggest, it might be the youngest one or it might be the one that is the most resistant to erosion.


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Webscientist
post May 12 2015, 10:31 AM
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Well found!

I've performed a rough calculation based on the perspective of this view and I obtain a diameter of the mountain/volcano (from left to right) of 18.52 km.

(16 px / 842 px *974.6 km = 18.52 km.)


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ZLD
post May 12 2015, 02:57 PM
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Heres another way of viewing the mound in RC3. Centered and rotated the frames to reproject a flyover of the area. The mound appears to be sitting on either highlands or an uplift of some sort. Interesting!


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fredk
post May 12 2015, 03:12 PM
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QUOTE (MarsInMyLifetime @ May 11 2015, 09:02 PM) *
It may soon be time for some underexposed frames that shift the washed out zones into the gray scale for analysis. Given that there seems to be some sensible scale to the size of some of these dots, any detail or sense of relative brightness between them is still washed out.

In frame 15 the solar illumination is at a very low angle and the region 5 spots are apparently not overexposed. However, if you carefully align frames 15 and 16 (this involves rotation as well as squashing the minor axis of the crater in frame 16), it looks like the morphology of the brightest part (in the centre of the crater) changes:
Attached Image

In particular, frame 15 shows the central part clearly resolved into two spots, but in frame 16 it looks like a new bright spot/region has appeared just to the right of the two central spots. If the two spots were simply getting brighter as the sun rose, and hence overexposing and getting larger due to the brightening of the tails of the PSF, then the two central spots in frame 15 should simply get brighter and larger and eventually merge into an elongated shape. Instead, we see what looks like a third central spot/region.

One possibility here is an actual change on the surface, with a new bright region turning on due to solar heating (I think we heard some speculation about this earlier from the team). But perhaps it's more likely that this is simply due to topography: the third central spot is in shadow in frame 15 and in sun in frame 16. We had hints of this in previous releases.

(Like usual, we need to be careful about pixel-scale details, although here we're clearly signal-dominated.)
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alk3997
post May 12 2015, 03:52 PM
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Could the change in frame 16 just be the result of the CCD sensor becoming saturated? It looks to me that the brightness has increased significantly between frames 15 and 16 and therefore frame 16 no longer resolves the individual points.

Andy
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fredk
post May 12 2015, 04:23 PM
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Definitely they get brighter, but they also develop a "bump" off centre, indicated by the intersection of the white lines:
Attached Image

This is the puzzling thing. Conceivably CCD bleeding could do this, but if it was bleeding there's no sign that the bleeding gets worse (longer) as you'd expect as the spots move further into the sun and brighten considerably.
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