http://www.nasa.gov/mission_pages/dawn/new...wn20110801.html

Phil

Cool rotation movie!! What a cool mini-planet!
http://www.nasa.gov/multimedia/videogaller...ia_id=104094441
I am at JPL now so ironically I can't do my usual quick image processing magic. I will plan to decompose this movie into separate frames and also make an animates GIF later today -- but would be very happy if someone else beat me to it!

The map is at the Photojournal now.

Phil

Whoa, groovy!

False color... interesting splashes.

Well, now we know what the image release policy is going to be in the future...like MESSENGER with a selected processed image of the day.
(But no raw images like MER or Cassini). Ah well.

There will still be PDS releases, right?

This image nicely showcases the equatorial grooves as well as curious dark spots in the dark hemisphere. I wonder what they're all about. Almost look like ejecta spray, but clumpy and more sporadic.

Press release on images presented: http://www.nasa.gov/mission_pages/dawn/news/dawn20110801.html

Yes. I think that's pretty much mandatory for a U.S. mission. Not sure how it will play out with foreign instruments, but I wouldn't expect problems in this case.

Anyone know where/when the recording of the press conference will be available?

Missed the press conference. Is this a close-up of a potential lava flow? (the darker area in the top right)

http://www.nasa.gov/mission_pages/dawn/mul...a/pia14324.html

One major thought I had coming out of the presser was on the comments regarding the formation of the grooves. Now, Chris Russell stated that one idea is that the grooves formed shortly after the SP impact when Vesta was initially compressed in the N-S direction and then rebounded, forming grooves at the equator. But I think there is another possibility: Upspinning. It is possible that the impact sped up Vesta's rotation. Upspinning would cause the equatorial radius to expand and the polar radius to contract, resulting in extension at the equator and compression at the mid- to high-latitudes. Similar upspin/despin/re-orientation scenarios have been discussed for Iapetus (despinning to explain equatorial ridge) and Enceladus (upspinning and polar wander to explain south polar boundary, equatorial fractures, etc.)

Complicating the picture is the possibility that the impact also changed the pole orientation, which may be quite likely as the missing mass associated with the impact crater is now aligned with the spin axis (shades of Enceladus again). A changed spin axis would produce stresses comparable to a spin-up or spin-down about the existing axis.

Excuse me if this was discussed at the press conference, which I missed...

John

In the Enceladus case, change of the axis of rotation can be explained based on polhode phenomenon. But that needs an energy dissipation mechanism, which for Enceladus is based on the tidal lock (as also the possible 'ocean'). But for a free solid body like Vesta, what is the dissipation mechanism?

My first thought about the cracks was we are seeing crustal sloughing into the crater hole. (it's big, for sure, but technically, the missing segment of Vesta is a hole) The tensile strength of the materials surrounding the crater would need to be checked for consistency this idea. Also, the segments between the cracks would be subject to compressive effects as the assemblage creeped (oozed? shifted?) downslope. Not sure I see anything that might be like that at this resolution in the images.

Large Vesta-sized bodies will settle fairly quickly into stable rotation about the minimum moment of inertia after their rotation is perturbed, due to internal frictional dissipation - tumbling will produce internal stresses that will cause motion along fractures, etc., that will dissipate energy and damp out the tumbling (Burns and Safronov 1973).

John

Here is a quick smoothing of the rotation clip. I had to compress a lot it due to 1 MB limit.

Excellent!
Beautiful rotation

The color image is up on the photojournal now.

Phil

http://photojournal.jpl.nasa.gov/catalog/PIA14325


PS before getting too carried away with explanations of grooves, let's consider the other grooved bodies - will the explanation work more generally?

Composed of completely different stuff I know, but it looks remarkably Miranda-esque to me

The crater count looks low over the impact area - I guess that makes sense, what is it - a billion years old?
Seems to be several sites of mass wasting/downslope movement. And those dark areas are fascinating!

Very very rugged, very very cool. Might be a good place for a lightweight instrumented penetrator (if we ever visit again!)!
Although Ceres is the main course, this is a fantastic entree...

P

Very nice!

Fantastic, Tayfun!!!

Man...there's a LOT of interesting features on this little world!

It may be a long wait. I asked about this after the press briefing, and Marc thought that the PDS timeline was 6 months....AFTER they leave Vesta.

In the meantime, I have now decomposed the high-resolution version of the animation into its component frames. Here you go, guys; have fun.
http://planetary.s3.amazonaws.com/misc/Vesta_rotating.zip

Lol, I got to about frame28 before I noticed your message. Oh well. I will work up a few anaglyphs if and when I find my red-blue glasses. I know it is here somewhere.

Mrs. nprev's comment on the movie:

"Huh. Looks like biscuit. Even has lines around the middle like biscuit!"

, but insightful. The grooves sure look like compressional features to me from the south polar impact.

What can make a series of long, straight grooves along the equator of an isolated self-gravitating body?
Debris collapse into extension cracks is one possibility. But what would cause straight cracks at the thickest part of the body?
In the South Pole impact, as the debris was blasting away, the center of mass of Vesta became shifted towards its North Pole, and the area around the crater rim became very high ground. The result static force on the equatorial region would have been compressive.
However, the dynamic situation would have been different. In solids, compression waves travel faster than shear waves, and the bulk (2/3) of the momentum transfer (apart from vaporization heating) from the impact would be transferred by the shear waves, especially an angular momentum change.
With Vesta getting its bell rung so hard, the equator could have been the mega null/shear zone between torsional resonance modes. With debris falling on/in/around the cracks and partially filling them, we could end up with the current distribution.
With limited information coming from Dawn, they'll just have to put up with theories from the bleachers (cheap seats for the Brits).

Despite the Dawn team wanting this to be a very primitive body dating back to the Dawn of the solar system, there's no particular reason why it could not have been larger at a very early date and to have lost a lot of mass though large impacts to become what we see today. I only suggest this to say that the grooves may be explained by events whose records are no longer visible to us. It's like Phobos - everybody wanted the grooves to be the result of Stickney despite the fact they have no geometric relationship to it at all. At least we can lay the old story of Mars ejecta to rest at last!

Phil

Wow. It looks like baling wire is holding the asteroid together....

It never ceases to amaze me how new types of features keep showing up on these newly explored worlds.

Speaking of new features, this little image artifact

Click to view attachment

looks a lot like Tsiolkovskiy on the moon:

Click to view attachment

Mashup of 3 images: full frame image coordinated to global mosaic, overlain by a warped false color view of IR data (?) PIA14325:

Click to view attachment

Full resolution on flickr: http://www.flickr.com/photos/31678681@N07/6000679166/

Gladstoner you read my mind.


I can't wait to see close ups of that crater.

I was excited when I first saw that too until I decomposed the animation and realized that it is in fact an artifact -- a bit of dust somewhere or something. Here's a teeny window on that little "Tsiolkovskiy" -- it doesn't move as Vesta rotates beneath it. There's a few other black specks that don't move from frame to frame.

Heh, I suppose the group of blemishes can be used to calibrate the cropped and blown-up images that are released to the media.

Man, you are really crafty!!!

A recording of the Vesta press conference can be seen here http://www.youtube.com/watch?v=DJBcxfxNo-M...nel_video_title

and here
http://www.space-multimedia.nl.eu.org/inde...;catid=1:latest

I shall call it the "Tsiolkovskiy Artifact"

And the next two largest specks can be "Grimaldi" and "Plato".

These are indeed artifacts present in the raw image. We can correct for most of them by using a flat field.

It won't work on Phobos, since the grooves on that body tail off on the trailing hemisphere.

It will be interesting to see the extent of these grooves on Vesta.

Here is a little article from the AP about Vesta

http://news.yahoo.com/scientists-stunned-s...-204550456.html

the last line has a 20th century kinda of feel to it:

....The team does not plan to post raw images online as other NASA missions have done. Instead, there will be just one picture released daily ....

Pablo, this community is nothing if not crafty.


I was very happy when Alicia (who has, several times, been nearly the only reporter besides me present onsite at Von Karman for a press briefing) asked that question, because I figured I'd worn out my welcome with such questions.

Don't worry about it Emily, I think we're just going to have to accept that we're not going to make the mission's Powers That Be change their minds. It's a great shame, but it seems that, unlike the MER team for example, some of them just don't get how much they're going to miss out on having a hugely-enthusiastic community of space enthusiasts and image manipulators on their side, working with their raw images to create exciting new products that would benefit them. I think it's a huge, huge mistake, I really do, and jaw-droppingly short-sighted in this modern age of data sharing and "citizen science" when we're all encouraged to be part of the space missions we follow so devoutly. I don't "feel a part of" DAWN, I feel like I've been told I can watch what's going on but only if I go stand over there, out of the way, and don't make a nuisance of myself.

I'm hugely supportive of the mission, and very grateful for every image we have been shown, but oh, it could be so, so much better than this. Oh well. Roll on MSL!

Don't give up; they may very well change their minds for Ceres.

I was hoping for some numbers (dimensions, mass, density) at the press conference to compare with the previous estimates based on very distant observations. Guess we'll have to wait awhile longer for those.

IIRC, the question was whether all raw images will be made available as they were received (like MER), but was there a follow-up question as to why not?

Any chance of showing Tayfun Oner's wonderful smoothing of the rotation movie to the Powers That Be? They could be getting stuff like this done *for free* by UMSF.

If these were politicians getting out of line then we, as citizens, would have the option of not re-electing them next time around (this happened in my county a few years ago). In the case of mission PI's, I suppose an equivalent option would be to advocate appropriately to our elected representatives when the next round of mission funding occurs. Not all missions are going to get funded, so we can at least see about ensuring that the ones that do have an immediate data-release policy in place. For that matter, this mission will presumably be seeking a post-Ceres extension....

It's an orbital mission. Do the ones in orbit around the moon, mars, and mercury release everything immediately?

Cassini?