In your opinion which part of that is bad news ?

First of all, I'd like to express how ABSOLUTELY, TOTALLY, FREAKING AWESOME this mission is. If the "bad" part thus far is that at this distance four images need to be taken to get a global view with much less than four times gain in resolution (and all the stitching problems), I'll take it. I'm sure Explorer1 just forgot the quotes around "bad news".

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What are the axes, and what are the orange blocks and coloured symbols here?

It would be nice with a "crescent" one just for aestetic purposes.

The orange blocks are symbols of the camera positions when the images have been taken.
The object in the center should reperesent the comet.

The quaternions together with the names/dates of the images would may be useful for people working on the same topic.

that little jumble of blue dots in the middle is the comet. The orange blocks represent the camera positions in relation to the comet for each shot.

The axes and scene scale are arbitrarily selected right now.

Yes, centsworth, that's what I meant by 'bad' news; we can't see the whole nucleus in the daily image release anymore. We haven't gotten an OSIRIS in a while either...

Were the landing site subframes based on OSIRIS or Navcam data? I supposed them to be peeks into the most recent OSIRIS planning photos.

The reason we haven't seen any of those is simply because Rosetta has not been on that side of the comet. We've stayed over the dayside for surveying purposes.
See this video.
https://www.youtube.com/watch?v=hplkIritIn8

Yes, the landing site "zooms" were eeny weeny crops of OSIRIS data, 540 pixels square out of the 2048-pixel CCD.

What's funny (or even ridiculous) is the apparently deliberate pixellation of the full-frame images.

My interpretation of the pixelation has been the resizing of an image, which has previously been composed of reduced images, to the 540pixels/km scale.
Large images are simply more difficult to work with. The idea of rescaling may have emerged after the image has been prepared, and the post needed to be released.

Did ESA not already say some info will be withheld due to the scientists rights to the info to make their discoveries. ESA has it's own and different release policy from NASA/JPL.

Quite natural if you are making a 300dpi image for a press release, composed of individual lower resolution images.

I'm wondering whether they'll set up a live landing show for Philae like for Huygens?Anyone heard about this?

Yes : affirmative. I'm working on it as TPS with Societe Astronomique de France and Ciel & Espace magazine for a huge show we are organizing with ESA for France to give a live coverage of the landing to a large audience. It will be very much organized like the live show we set up with ESA for the Huygens landing on Titan in 2005

VM, will there also be a webcast accessible to international viewers?

Yes : I think there will be an event in Darmstadt that will be broadcasted on TV.
But I dont't know about similar general audience events like the one we are setting-up in France.

ESA Challenged us to make a Mosaic from Rosetta's four NAVCAM images. Here's my try using Hugin.

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Image ESA/Rosetta/NAVCAM/Steve M

Here is my version rotated by 180° and resampled to 5 meters per pixel (close to real resolution ~5.2 m/pix).

easy enough using Nip2 and a few tie points


now do to camera rotation each image has about 5 extra pixels at the center corner ( the area that is vignetted )

Oh that's just astonishing! Great work guys. What an amazing piece of debris this is.

(Hugely speculative, and based on a few images):

It looks like two planetesimals of dense material have come together during the early stages of the solar system to form a contact binary, planetary migration then scattered them to a location where they accreted a few tens of metres of ice across the pair as a coating. A chance gravitational encounter then flung them into an elliptical sunwards orbit, with the ice being progressively sublimed away with each perihelion passage, partially revealing the denser and darker two bodies beneath.

Hey, I can hand-wave with the best of them.......

I'll have a try at it as well. The scree that lies on the large body side of the neck appears to fill in some pre-existing but no longer active sublimation pans (craters, if you will, but they are too close and consistent in size to convince me that they were formed that non-randomly). Sides of the large body also appear to be sloughed off at some more recent time in the comet's history. Given the neck appears to be the most active area the moment, my hand wave is that a larger original body became very thin in the middle and the "head" simply rolled back to a more gravitationally stable location against its larger part, where many years of continued wasting from the scar have laid the talus slopes inside the neck. It's all hand-waving until the scientists give us their interpretation, but for me this hypothesis avoids dealing with collision energies for low-strength objects. Back to more plausible fiction now...

There is scheduled an "ESAHangout: Where will Philae land?" in a little more than an hour (16h CEST, 7 a.m. PDT).

I'll take a shot...I think I'm in this camp. My theory is comet shrinking is an unstable process in that once the object departs from spherical to something more ellipsoidal, there is a trajectory of slighter lower energy to depart from the comet at the midpoint/minor axis and so that's where more erosion occurs. Stuff that doesn't depart accretes on the remaining lobes. If one lobe is bigger than the other, it steals from the smaller.

It would be fun and fascinating to run a simulation of this sort of thing. I imagine someone someplace is already doing it.

You made that statement before, but the opposite is in fact the case. The midpoint is the place on the comet's surface where gravitational potential is lowest, therefore material there requires more energy to escape than surface materials at other locations. Escape velocity depends only on the potential at a given point, not on the local value of the field strength. Saltating material (stuff that doesn't depart) would tend to migrate toward the neck, not away from it. The neck should act as a dust trap whilst the comet is far from the Sun and relatively inactive.

Once activity starts, however, my guess is that the ejection processes easily overcome the comet's weak gravity - irrespective of position on the comet. There are all sorts of possible reasons why the neck might be an active location - different material, looser packing, differences in insolation (was it a cold trap for volatiles at some point?), release of gravitational energy due to mutual settling of the two lobes, etc. etc.

It would be interesting to see a map of where "down" is in the different surface areas of the comet. A temporary one could be made by just using the 3D model and supposing homogenous density. If ESA at a later stage manages to identify mass concentrations the map could be refined.

I made an animation with the two OSIRIS pictures taken on August 7 using MorphX for Mac, to give a sensation of depth:

https://www.flickr.com/photos/105035663@N07/14939113547/

And here is my take on the stitching of NAVCAM pictures of August 31:

The awakening of the comet 67P!
New images from NavCam clearly shows jets from the neck:
Credit for original images: ESA/Rosetta/NavCam.

It's alive alright.

The 2 jets seem very focused and appear to emanate from the bright clean face in the center of this image cropped from the Aug 7 ORISIS image.
The earlier overexposed NavCam image also shows multiple focused jets.

It doesn't seem like a relatively flat surface would give jets like these...

Wouldn't any 'jets' be broader (hemispherical) and more diffuse as the sublimation occurs and the expanding gas/dust leaves the 'flat' surface? I don't see anything in this suspected source area other than flat faces with little debris and no pits of any significant size.

It appears that as the volatile surface material sublimes, nonvolatile material accumulates at the bottom of the slope(s). The only thing I can figure is that a cover of debris heats up and the volatilized material escapes through a narrow opening to give the observed jets.

Perhaps someone will be able to narrow down the source of the jets on the surface from this and possibly other contrast enhanced images.

The question of how jets become collimated like this has vexed comet scientists for a long time. One suggestion - I think from J. Crifo, is that the volatiles come from several sources near each other, and the dusty component is caught where the expanding gas cones intersect. Two sources would focus dust into a sheet where the two cones intersect, but three would focus it into a jet, and multiple gas sources would create multiple jets between triads of gas cones.

I don't know if that can work here but it's an interesting idea.

Phil

One question I have is: does this jet come from the part of the neck visible in this navcam frame, or does it come from a part of the neck just "over the horizon" and hence not directly visible. In the latter case the direction of the jet would have a component away from us.

But I think we can rule the latter possibility out, since enhancement appears to show the jet in front of the overhanging portion of the smaller comet lobe:
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In the area I circled, the jet appears to be visible against the shadowed portion of the overhang.

Therefore (unless I've got the overall lobe geometry horribly wrong) the jet appears to have a component towards us, and that should mean that the region of emission on the neck is indeed visible in the same navcam frame. One loophole might be that the jet is emitted close to horizontally from the surface. I don't know how likely that would be. But this should give us better confidence in locating the source.

I agree that the emission region seems to be visible in that navcam frame, or is at least close to the horizon. I'll try with this (very) tentative location. I have also broadly located the region in the 8 August frame.
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The emission region might be related to the flat area of the neck, but not exactly where the "boulders"/spurs outcrop from the "dusty" surface. Or am I going too far with the interpretation?

I have split the fascinating discussion on generating 3D models of the comet to its own thread. (Still working on moving a few more posts...)

EDIT: Done. There were two almost completely independent discussions happening here, and I wanted the 3D modeling one to be able to continue seamlessly after this thread ends with the beginning of the next mission phase.

Very nice image! What I'd like to know is, are we seeing an entirely undifferentiated body that's primarily eroding in the middle, or could perhaps the comet be a small piece of a larger, partially differentiated parent body, and better described as having an eroding, volatile-rich region in the middle that was sort of cementing together two chunks of more refractory material (the lobes). If the latter is the case, it might help explain the "dead comets," like (3200) Phaeton. Hopefully we'll find out!

Landing site A may be even a greater place for a view, with source of streaming jets just below. Though a direct view to the very bottom of the "neck" might be had only in select locations from that perch. From Doug's excellent rendering:
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Might not be such a good place once activity increases further, especially if the eroding neck breaks at perihelion.

If C-G breaks up it would be a bumpy ride regardless of where the probe lands--might as well get crushed rather than flung from the surface...

Spotted today at work.
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What's the name of the comedian?

The closest I could get with this annotated stereo
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is: very close to the horizon.

The lines try to connect the peaks of the grey levels in each of the two images.

I see two separate jets, originating from slightly different locations and pointed in different directions. They criss-cross in this image:

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I adjusted the levels to highlight the jets, then superposed the normal image with 50% opacity. It seems there is another jet on the right of the neck. But I checked on the individual NavCam images and when I adjust the levels, the jet is not here... So it may only be an artefact from the stitching process.

"Might not be such a good place once activity increases further, especially if the eroding neck breaks at perihelion."

@ngunn: Maybe that would be the best place ever in history of watching comets. The ESA could then make a new movie blockbuster "Armageddon 2: Breaking comet".
I really hope that there will be a major break up.

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Great image. I think I can see a suggestion of a third jet on the left of the neck? To me it looks as though the lines of the jets lie something like in the attached image. It's not at all clear to me what angle the jets are relative to the local surface, or that they lie in the same plane, so I couldn't say where any originated except somewhere along their centre lines.

Early results from the Alice instrument:
http://www.jpl.nasa.gov/news/news.php?release=2014-297

I'm wondering about the chemical composition and the microscopic structure of the surface. The very low albedo in the far uv as well as in visible light makes me thinking of soot or other large organic molecules (carbon-rich tholin, asphalt, PAHs).

A very rough surface on the micrometer and nanoscale might also be able to explain the very low albedo on a wide range of wavelengths (far uv, and visible).

In terms of the Alice results, does this mean the neck wouldn't have at least a slightly higher albedo and some exposed water ice?

This talk from San Francisco's Exploratorium gives a great rundown of the comet, the craft, the mission so far, with nice illustrations and demonstrations:
http://www.youtube.com/watch?v=lBSwyIdxJoA...zltLN_WumwIBC3Q