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Small Body Grooves - Redux, Vesta bets?
Guest_Morganism_*
post Mar 30 2011, 01:06 AM
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Anyone seen any published papers out there on the grooves yet?

Thinking we are going to see them on Vesta......
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stevesliva
post Mar 30 2011, 01:38 AM
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Vesta's pretty much another order of magnitude larger than Lutetia, which is also much bigger than Phobos, meaning... who knows?
http://www.lpi.usra.edu/meetings/lpsc2011/pdf/1366.pdf
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Guest_Morganism_*
post Mar 30 2011, 02:06 AM
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Am trying to keep an eye out for binary asteroids, and ones with sattelites and see if it is relevant for this idea, but havn't seen anything new lately there either, other than a size limit paper
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elakdawalla
post Mar 30 2011, 04:45 AM
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OK, I'm going to go out on a limb and predict we won't see grooves on Vesta; it's too big. It may have lineaments from impacts but I'm hypothesizing it won't have Phobos-like grooves.


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tedstryk
post Mar 30 2011, 01:52 PM
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If it is indeed a relatively intact piece of a protoplanet destroyed in an impact, it is difficult to know what we will see. And Olbers, assuming it is a crater, is larger in size relative to Vesta than Herschel is to Mimas. Mimas doesn't have groves like Phobos or Lutetia, but it clearly has had effects on a global scale. I even wonder if we might be totally surprised and find a rocky Miranda analogue. I can't wait for Dawn's arrival!


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Explorer1
post Mar 30 2011, 06:01 PM
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If the grooves were of the same scale they are on Phobos, they'd probably be big enough for Hubble to spot them anyway (assuming the bottom crater is their source).
They're either smaller or not there at all: Dawn will prove it of course.
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Phil Stooke
post Mar 30 2011, 08:05 PM
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Have you seen the Hubble images of Vesta? It would have to be a Grand Canyon of a groove to be visible to Hubble.

More to the point, let's hope some good navigation or distant imaging frames show up during the approach so we can get a decent look at it! A virtual Mars Bar for the first person to spot a crater other than the south polar basin.

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Explorer1
post Mar 30 2011, 10:51 PM
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Yeah, I was just exaggerating quite a bit; we're all hoping for early images (nothing actually scheduled yet right)?
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Holder of the Tw...
post Mar 31 2011, 05:14 AM
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My wild guess is yes, there will be some grooves of some type on Vesta (and not just crater chains), but only random and just here and there. Nothing even close to Phobos. No particular reason, just the way I imagine it.

Mostly looking forward to what may be a noticeably multi-colored little world, albeit in subtle, pastel shades.
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ElkGroveDan
post Mar 31 2011, 05:30 AM
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I'd say it's going to have cratering similar to Eros and Mathilde and otherwise appear unremarkable except for north polar, concentric, globe-circling fractures/ridges.


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algorimancer
post Mar 31 2011, 02:57 PM
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Getting a little side-tracked here... but if the decaying ring theory is correct as a source of the ridges (and I've been an advocate of this), then where are the ridges on Mercury? It seems to have all the right ingredients, no atmosphere, reasonably spherical, and deep in the Sun's gravity well such that it should regularly get whacked by asteroids/comets, a good fraction of which should have grazing impacts which would generate a ring. Possibly the problem is that the gravity is TOO great, so that the fraction of grazing impacts which generates a ring is very small, implying (as I may have mentioned before) that there is an optimal mass range where grazing impacts yield (largely non-equatorial) rings which decay to yield ridges as the body rotates during decaying-ring/planet interaction events. I really wish I knew enough about the physics involved -- not just orbital dynamics but also impact and fluid dynamics -- to do a good simulation of the process. All I have is mental models :/

Speaking as a statistician, we need more samples to say anything definitive. Vesta and Ceres will help. My mental model isn't good enough to make a believable prediction with regard to whether we'll see the grooves on Vesta or Ceres; it would be neat to see grooves on both, but with a declining trend due to increasing mass.

EDIT: Actually, looking at this linked image of Mercury from Phil Stooke (from the Messenger section):
QUOTE (Phil Stooke @ Mar 31 2011, 10:49 AM) *

I note an awful lot of elliptical or wedge-shaped craters and crater chains. Perhaps this is what happens (as opposed to ridges) at the high end of the mass range as an impact-derived ring decays. Interesting.
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antipode
post Mar 31 2011, 10:02 PM
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A recent Icarus paper posited that Vesta might be noteworthy for large deposits of 'mega ejecta' - emplaced after the giant polar impact as Vesta spun underneath the material on its ballistic trajectories. IIRC, the paper suggested that the asymmetrical emplacement of that ejecta might at least partially explain Vesta's shape (along with the aforementioned crater of course).

I guess we will know soon!

P
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DDAVIS
post Apr 1 2011, 10:10 AM
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I wonder if there are maria basalts in some lowlands...
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Guest_Morganism_*
post Apr 5 2011, 12:23 AM
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Dang, this crater chain and groove thing is starting to infect my other views. Saw that APOD pic of Mars with Valles Merineris front and center, and started thinking, what it Deimos was a sheperd moonlet .....

I just changed my Mars sample target. want to see in one of the little craters at the end of the Valles. Be interesting to find a chunk of Phobos right there...

Especially now that they found all the subsurface water is on the opposite side of the planet from the Valles M.
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Phil Stooke
post Apr 5 2011, 02:27 PM
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That infection can be treated!

Phil


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