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Dawn Survey Orbit Phase, First orbital phase
belleraphon1
post Jul 18 2011, 10:36 PM
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Thanks DAWN team for releasing these.

A lot to look forward to in the coming 12 months!

Mirandian indeed.

Craig
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Drkskywxlt
post Jul 18 2011, 10:59 PM
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Is that picture facing the south pole?

For somewhat not geologically-minded, what is reminding all of you about Miranda? I don't see the similarities really...
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ugordan
post Jul 18 2011, 11:09 PM
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A faux-color version based on color derived from Hubble WFPC2 F673N and F439W filters:

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belleraphon1
post Jul 18 2011, 11:19 PM
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Drkskywxlt:

Call it exhuberance.

Mirandian was perhaps more prominant in the lower resolution view from July 9th. Go to NASA photojournal and explore
Miranda.

Miranda has what I would call sectional terrain (not a geologist either nor do I pretend to be). Odd blocks of internal resurfacing surrounded by cratered terrain.
As we get closer the comparisons do seem to break down a bit. Is this a demonstration of how small bodies go through an early stage of internal processing?

But is it not wild that we can even make subjective comparisons of bodies so far apart in space and time!
That is what some 50 years of solar system exploration has given us.

Glad I was born to see it from the start.

Craig
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kap
post Jul 18 2011, 11:54 PM
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QUOTE (ugordan @ Jul 18 2011, 03:09 PM) *
A faux-color version based on color derived from Hubble WFPC2 F673N and F439W filters:
]


Nice work. What does everyone think of that big scarp on the upper right area of the image. Could that be the edge of the southern hemisphere impact crater?

-kap
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Juramike
post Jul 19 2011, 12:03 AM
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QUOTE (kap @ Jul 18 2011, 06:54 PM) *
What does everyone think of that big scarp on the upper right area of the image.


That's a neat cuspate scarp, and another just beside it. I'm looking at the small wavy pile of stuff right in front and wondering if material slumped to reveal an abrupt scarp.


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MarkG
post Jul 19 2011, 12:07 AM
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Boys and girls, it's "Rampant Speculation Time...."
The patterns on the South Pole crater floor do resemble both Miranda, and Earthly sea-floor spreading. Perhaps a shock-melted mantle zone convected for a while, rafting surface debris and local volcanics into linear rows from spreading crack centers. Fun to speculate.
Vesta had it's "bell rung" pretty good with the impact, maybe there was a surface wave interference pattern that distributed things in the pattern seen.
Relaxation after impact, with the core wanting to re-center, and perhaps migration of the rotation axis, could cause some of the features we see. Also the floor striations could be caused by compressional wrinkling from this relaxation, plus landslides and collapse blocks from the crater rim.
Is the central mountain a volcano, an intrusive diapir, an infall debris pile, a garden-variety crater central mound, or a combination?
Stay tuned!

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belleraphon1
post Jul 19 2011, 12:25 AM
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"But is it not wild that we can even make subjective comparisons of bodies so far apart in space and time!"

My quote from my last post here.

Miranda and Vesta...far away in space but perhaps not in time. The period of resurfacing may have been in the same period of time. Early in solar system history.
Once again are we seeing how smaller bodies go through an early period of furious internal resurfacing that is restricted to segregated internal blocks of activity.
A herterageneous stew that cooks in spots but stays stone cold in others.

Shaken... not stirred?

Craig
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MarkG
post Jul 19 2011, 01:35 AM
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There is a big difference between Miranda and Vesta, however. The difference is the presence of ice and tidal forces on Miranda, both largely absent on Vesta.
Ice is quite ductile, and small gravity can cause it to flow, but plain rock, like on Vesta, don't flow unless it is pretty much hot enough to melt, and the interior pressures in Vesta, with it's light gravity, are not going to contribute that strongly.
One of the big questions is how warm was the interior of Vesta at impact? We already know (pretty much) that Vesta got hot enough early to differentiate its core/mantle/crust, and then we can ask how much of this heat was left at impact. Since the planet as a whole did not re-spherize itself, it must have been largely cooled to a solid at impact time. Perhaps some of the core was still liquid -- radioactive decay might have kept it going a while.
On the other hand, Quite some time might have passed since the planetary system formed and cleared out the nebula and most debris before the impact. We know that a significant amount of asteroidal objects are dynamically related to Vesta and are shards of the great impact. The surface of Vesta also does not appear to be crater-saturated. (With further imaging, crater counts should be able to give a rough age estimate -- looking forward to that.)
So it seems (arms waving wildly) that the energy for reshaping parts of Vesta had to be delivered by the energy of impact. How much shock melting could accomplish is unclear, and a better answer is in the hands of the planetary modelers and the mega-computers.
An interesting idea is the possibility that accumulated surface volatiles were stirred up by the impact and ablated by solar and impact heating, and Vesta was a giant comet for a while...
Well, I think I've embarrassed myself enough for now. Its a free country, gotta love it.
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Steve G
post Jul 19 2011, 01:36 AM
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Sometimes it's easier just to rotate and crop, and just look at a single feature at its best orientation. I just love these cliffs!
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nprev
post Jul 19 2011, 01:36 AM
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I think we'll definitely need a true global view before we'll be able to understand what we're seeing now, but my working hypothesis is that Vesta was damn near remelted globally after this tremendous impact. However, it probably cooled quite quickly as well; we may well be seeing a landscape frozen in time after a catastrophe, perhaps like the ancient Earth (sans atmosphere & oceans) after the big whack that formed the Moon.


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Explorer1
post Jul 19 2011, 01:44 AM
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How far will coverage of the northern hemisphere go; will it stay mostly in shadow for the full duration of Dawn's visit?
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belleraphon1
post Jul 19 2011, 02:06 AM
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Shaken or stirred?

That is the question.
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Gladstoner
post Jul 19 2011, 03:13 AM
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On second thought (or third), it looks like material from the original crater 'wall' has slumped toward the center -- basically the same as what occurs in craters on the moon and Mercury. In this case, though, the slumps have slid all the way to the central peak/uplift, and continued to flow as they were displaced by more material sliding down from above. After eons, a jumbled flow was the result.
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MarkG
post Jul 19 2011, 04:02 AM
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Replies...
My understanding is that the North pole of Vesta will just begin to be illuminated at the end of the Vesta mission, so there will be eventual global photo coverage by Dawn.
Also, mass wasting from the crater sides does not seem to explain the 5-km-ish spaced parallel ridges on the crater floor. I'm wondering if they are ridges of olivine....
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