Excellent work, Gerald!

Thanks!
A first more or less accurate map will hopefully simplify matching future images. Some areas are still at the very margin of the images available such far, so looking forward to the press conference tomorrow.

Thanks, Gerald - those are really nice. This is a composite... but I really hope it will be outdated as early as tomorrow.

Phil

Click to view attachment

Phil's composite as animated gif, 60 frames, 300 pixels version:

Hopefully the press conference will address those strange markings, Gerald .... they almost look like hieroglyphs!

Oh dear my prediction did not come true, as I said the writing on Ceres would be 'Kilroy was here!'.

As for the bright spots there seem to be 7 of them, with a possibility of a handful more in the areas still only seen at lower resolution.
All appear to be associated with craters, so I go with the long tested Occams razor - that the simplest explanation is the correct one - that we're seeing spots of exposed ice.

Other possible simple explanations for some of the bright spots are slope and local surface smoothness within an overall very rough surface.
The images are heavily brightness stretched, in contrast to usual square-root encoded images.

Some spots remain which can only be explained by high albedo or shinyness.

With the whole raw RC1 and RC2 sequences available the Dawn team, at least the camera team, knows more.

They also have OpNav 4 (highest resolution until 10 April, the next imaging session), and OpNav 5 (yet another new angle that might give new clues) seems to be coming down now.

Briefing on:

http://www.ustream.tv/NASAJPL2

Yes!!! Maps!

Phil

Here are the photos from the press conference:

http://www.jpl.nasa.gov/news/news.php?feature=4496

Here are the the rotation video enhanced to show elevations from the press conference:

https://www.facebook.com/video.php?v=101527...e=2&theater

http://dawn.jpl.nasa.gov/multimedia/Crater...eres_Motion.asp

The OpNav4 image from http://dawn.jpl.nasa.gov/multimedia/Ceres_...nce_gallery.asp

That rotation gif almost shows the faint hint of an outline of the dark side. Is it just an artifact of the creation of the animation? I'm reminded of the images showing 67P's outline against the coma, but a theorized atmosphere at Ceres is far too tenuous, right?

The rotation gif is a computer animation of the global map draped on a spheroid; you can see there's no topography to the limb.

Yeah; I checked again. Way too perfect a circle...

Edit: Just maxed my monitor brightness; machi might be right. I'll wait for the well-informed blog post before drawing conclusions...

Rotation GIF isn't reprojection on the sphere.
Topography is clearly visible on the limb.

The dark area surrounding the brightest spots reappears on the map. The previous crop that I posted had the wrong N/S orientation, so the dark area is visible at current max resolution, too; it only appears more diffuse (and the bright spots still appear at the "left" edge of it). Corrected orientation here:




I also like that I got my own question about the atmosphere answered on the press conference. (<3 the Internet and Twitter)

Yes, sorry. There are two released animations, one a gif made of individual photo frames that does show limb topography, and one a movie made from the map made from that data, draped on a spheroid, which does not show limb topography.

BTW, interesting topography.
I definitely see some shallow canyons on the disc.

LOVE that cross-eye stereo. That's a sphere

Plus there are some interesting albedo regions at the south -- really wish this was in color. Unclear if the regions are due to differing surface texture or material properties.

we are indeed keeping an eye on those 'elongate depressions' too early to tell what they are related.
at this resolution ~4 km/pixel, we get a good layout of the geography but not yet diagnostic indications of how
these features formed. most of the team is still scratching their heads . . .

(btw, Im an uncredited assistant on that global map [having told them the secret of its construction])!

Another one of the bright spots is clearly looking like a rayed/haloed crater when you track it through a Cerean day.



(this one is sitting inside a crater in the northern hemisphere)

This seems like a pretty big clue regarding the bright spots.

When the crater containing the two big bright spots is near the terminator, the spots are visible when the crater floor around them is dark. There are some alternate possibilities, but the most likely one is that they are elevated higher than the surrounding surface. One may be a prominent central peak. The off-center spot seems harder to explain: Possibly a crater within the larger crater? Or a ridge that survived or formed after the crater was formed? A volcanic origin is another possibility.

Then, whatever the explanation for why those places are elevated, yet more possibilities remain as to why elevation would correlate with high altitude. They would get a bit more sunlight than other areas, but not, seemingly, much more. I think it's going to be more about how they formed in the first place. A one-time eruption of ice warmed as impact melt?

I mean canyon simply as linear feature with prominent topography.*
I haven't idea how those depressions were formed (but I'm happy that they are there! )

EDIT: *_ Nice BS which I wrote. Of course I meant canyon as some kind of linear depression.




Here is version for anaglyph lovers:

by any other name, right?
we will be looking at that area carefully in April. It will be frustrating in that we wont get anything as old as this again until mid-April, as we move into prosition to make our first orbit.

For the central brightest spot, elevation may be a factor. But I think what we're mainly seeing is bit depth. Notice that the brightest spot is considerably fainter in that frame than in the earlier frames. So we may simply have a situation where most of the crater floor is down at 1 density value or less, while the bright spot is still at higher levels. In fact some of the crater floor is also visible when you tweak the gamma:
Click to view attachment
Toss in unknown stretching/clipping and there's no need (yet) to rely on higher elevation.

Yes, but...Take a look at the change in brightness of the secondary bright spot during the rotation. It dims considerably as the two bright spots move into shadow. Assuming a similar origin, it seems that the main spot and secondary spot (or should I say spots?) both reflect the most light from directly above and diminish in apparent brightness as the rotate towards the terminator.

Doesn't that pretty much eliminate an active cryovolcanic origin since that type of activity would produce some brightness without reflective light? I don't know whether the base material is more reflective in direct sunlight or if something is blocking some of the sunlight on the high altitude peaks as the spots rotate away. But, it seems that its reflective light causing the brightness not intrinsic light.

Of course, infrared readings would provide a big clue but we have to wait for those.

Andy

I did note that also in the animation, and you provided a still of the phenomenon also - that it remain bright up to the very moment until it do not even get reflected light from the far crater wall.

And I think Habukaz got it right, I agree now that the number of potential ice sites got fewer with these images.
Even so a few of them might be ice that have dusted over, but it seem more likely that several could as well be rubble and ejecta from impacts on this very dark surface.

Ceres really are a wonderful little world that certainly deserve to be called 'Dwarf planet' so it not is bundled together with the other silly asteroids.

Not any more than liquid water/slushy ice glows.. (but ongoing activity would glow in the right infrared wavelengths since it's hotter than the surroundings).

EDIT: The map image in the presentation is not the full 360 degrees.

I was curious to see how the recently observed features lined up with old Hubble et al. observations (from Ceres Wikipedia page):

Click to view attachment

Interestingly, the long-known 'Piazzi' feature corresponds with a topographically unremarkable area between the smooth-floor basin and the large crater to its northeast, yet the albedo variations are notable:

Click to view attachment

If you compare the new Dawn map with the version posted earlier here - Gerald's reprojections and my combination of them - you can see many errors in what we did. It's only natural, as we didn't have the proper pointing information. But now the Dawn map can be used to do some better work.

This shows, on the left, the northern hemisphere in a polar azimuthal (equidistant) projection. On the right, I have added parts of Gerald's reprojections, each one itself projected to azimuthal and merged with the Dawn map. Most of the polar area is filled in.

Phil

Click to view attachment

Here are all the individual frames from pia18920 paired for cross-eyed stereo. Lot's of neat stuff going on.

Click to view attachment

I also did a cross-eyed gif animation, but decided it didn't bring much to the party (plus it's over 7MB).

Great!

Last few images are especially interesting.

Yeah, that rayed crater really "pops" in 3D -- vivid rays, sharp rim, and looks like a flattish white floor, with sunlight reflecting off the east rim.

The north pole is really battered with craters (presumably older) compared with the rest of Ceres.

A few details that caught my eye.

(left and right images are taken from different frames and thus represent different lighting conditions; contrast or brightness has not been altered)

Exhibit A:



an unusually dark crater wall or area of a crater


Exhibit B:



chevron-shaped feature?

Exhibit C:



a crater with several bright spots within and around it (barely visible in the left crop)? Also appears to have darker surface materials surrounding at least some of it, a bit like the crater with the brightest spots.

Exhibit D:



a basin with arms

Matching up some features on old and new maps:

Click to view attachment

That angled escarpment is striking.

Exhibit E:

Click to view attachment Click to view attachment

The (possible) mound within the upper right portion of the large crater.

It does indeed look like something is casting a shadow on the lower part of the crater wall in that area of the crater. Alternatively, it could be a depression I suppose.

WOW! Lots of goodies to drool over. A surprising number of linear features running roughly North to South, with many more in the Southern hemisphere. Some may be mosaic issues though. The latest images do tend to confirm the relaxation of the craters, the surface in general in fact. The upper mantle appears to be somewhat "squidgy". The evidence of two or maybe three large scale resurfacing events is a bit clearer too. The visible elevation changes marking their southern margins could well be responsible for the darker regions that were looking like a canyon or crater system in the OPNAV1 & 2 images.

As a starting hypothesis, the largest impacts are most likely to have occurred earlier in Ceres's evolution when it is proposed there could still be a liquid ocean beneath an icy crust. The nest of not quite so bright spots on the equator, corresponding to the higher albedo area seen in the Hubble images, seems to be roughly at the centre of the resurfaced area and most of the other bright spots fall within the resurfaced area. Low crater counts suggest this may not be an ancient event and the ocean might by then be only remaining in the equatorial regions, this resurfaced area would, in theory, have a cleaner, far less dusty composition. The freezing liquid would develop cracks and ridges like those on Europa. Later impacts could more easily expose cleaner brighter ices, or their steeper slopes with a thinner layer of dust might reflect more light. The Great White Spot(s) could be a low angle impact, as suggested earlier, that skipped. The first would be deeper exposing more ices, the second less deep. It would probably have to be a pretty recent event too, the photochemical reactions and sublimation residue on the surface would eventually darken the ice to the same colour as the rest of the surface. Different ages, or different slopes, different brightnesses.

Cryovolcanism at this stage looks a long shot, but the slow sublimation of volatiles, to in effect erode and smooth the surface as well as "soften" the crater rims, seems probable. It might be worth looking to see if Ceres has a tail. The Infra red results are going to be the main interest here. Water ice has been talked about most, but Carbon Dioxide is surely also present in significant amounts. The surface morphology "looks" reasonably straight forward, if time consuming, to unravel, for those that know about these things.

These are possibly the edges of one of the large resurfacing events I postulated in my post above.

Exhibit F:

Click to view attachment

The scarcity of craters in this otherwise rough area may indicate resurfacing. Can't wait to get a closer look.....

In regards the CWS, I disagree strongly with the analysis made in the press conference that there is no elevation feature associated with it. It strongly appears to me that it is either a structure that makes up a central peak unit, or an impact on an existing central peak unit. The way it dims as its host crater goes into the terminator, but stays visible while the crater floor around it is in shadow, is almost definite in it reaching higher than the shadowed far crater rim.

I really don't buy that this is some odd kind of processing artifact. It shouldn't appear at all when the crater floor is in shadow, if it's a reflection feature, unless it stands up well above the crater floor.

-the other Doug

The white splotch being visible as it has passed into the terminator could be a very high albedo material, such as snow, being illuminated by light reflected from the far wall of the crater that is poking up into the sunlight while the floor remains in shadow.

I see it as possible support for my iceberg impact proposition.
The second white patch may indicate a pile of snowy debris from the original impact due to the angle of the incoming projectile relative to the surface of Ceres.



It seems to be very over saturated in comparison with the rest of Ceres.

I have decided to make the dustbin lid my backup.

Looking over the 3D views, that big relaxed "sand dollar"-shaped feature seems like the key to much of what we're seeing.

Click to view attachment

Clearly it is relatively young, based on the low crater count. The current low relief is deceptive -- the impact which created it must have been one of the largest to hit Ceres, kind of like Herschel crater on Mimas. The impact would have splashed ejecta (presumably mostly ice/water) all around Ceres, leaving a thick mantling deposit which softens the appearance of the underlying landscapes. The north polar region seems to have escaped the worst of it. It happened long enough ago that the crater and ejecta have had time to relax almost to level, but it would have been the defining event for much of what we see today. Perhaps the impact punched through into liquid ocean, in which case the water would have filled it and frozen, bringing it rapidly to level. Quite a story there.

A very interesting pentagram shape for such a large impact structure.



What could the resulting boundaries of this impact indicate about the object it was formed on.

The overall shape of Ceres, the impactor, or both.

EDIT:
Well done algorimancer, while I was scrawling with an image editor, you had finished. I like the sand dollar association.
Agreed, it does look like a re-solidified melt, with a little aging showing.

I see a starfish. :

Click to view attachment

The valleys marked in red are probably its secondary impacts.

I'd bet the basin is extremely ancient. The resurfaced floor, on the other hand, could be another matter.

I was just using that wonderful post by algorimancer of all the pia18920 and the cross eyed 3D technique.
The grooved terrain is crossing over and through some older large impacts.
So, those impacts pre-date the terrain grooving event.
I can only think it indicates a possibly solidification of a liquid mantle and it has expanded Ceres somewhat.