From this video, schedule until october:
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That's tentalizing! Similar features were seen on Wild 2 and interpreted as possible erosion-resistant fumaroles. Check out Figure 6 in this article. With the resolution of OSIRIS I would expect to see summit pit on these pinnacles.

Also, 67P seems to have a lot of structural features, such as parallel linear ridges and scarps that, if I remember correctly, were rarely seen on previous comets. These structures characterize both the head and the body and might be primary structures, supporting the idea that head and body are genetically related, i.e., they formed on an originally single object.

Greetings to all

Monster!!

This is 180° rotated version of yesterday's image from NavCam camera.
Credit: ESA/Rosetta/NavCam.

... bleeding at its neck out of a deep wound?

Monster? Duck?? Myself, I thought I saw a lion head one day. But whatever the "view of the day", depending on sun angle and/or one's imagination, sooner or later order needs to be created out of the chaos that this irregularly shaped comet presents to the scientific world. I asked via the ESA Rosetta blog whether they would decide on a cartography system at the start of the mapping phase (10th Sept) but no answer (yet).

Googling, I found a most telling statement about this interesting subject. Quote: "cartographic options for non-spherical worlds have until recently been very limited"

See http://adsabs.harvard.edu/full/1992acm..proc..583S

The author?? Our one-and-only Philip J. Stooke!

Are there any plans to take RGB images of the comet with OSIRIS? (I'd love to see an overal true-colour image of the comet, before Rosetta starts mapping the surface close-up)

Also, I can't find any information or specifications about the NAVCAM, which has been giving us these amazing images of the comet so far. Is it an unfiltered camera? What is its wavelength sensitivity?

The Rosetta blog works! A follow-up post provided a link to an animation by DLR, the national aeronautics and space research centre of the Federal Republic of Germany, regarding possible landing sites on 67P - including a polar and coordinate system overlay on 67P.

See http://youtu.be/CNGu7KbXzOs

OSIRIS has lots of "color" filters (for NAC: far uv, near uv, blue, green, orange, hydra, red, ortho, near ir, Fe2O3, IR), see this status update, p.15. So they could.
As I understood, they've at least taken a green image (press conference august 6), already, and color images from a distance (status update p.20).
Taking color spectra and looking for color variations are science objectives (status update, p.21).

Some specs here, although nothing about filtering.

I didn't notice anything in the special volume of Space Science Reviews (128) about navcam - maybe someone else did?

I'm curious about how solar illumination varies throughout the cometary "year" and if that would explain a history of erosion that might have formed the neck from an initially more spherical ("more", not "extremely") body.

Alternately, I think about Iapetus and even Callisto as analogues and wonder what happens to the non-icy material when outgassing takes place. Does some of that non-icy material settle elsewhere on the comet, or does it effectively depart into space? If it deposits onto non-outgassing locales, there could be a positive feedback loop of some areas having too much non-icy material in the regolith to outgas, while other areas have accelerated outgassing.

I guess we'll know when Rosetta's finished its mission.

There may not be any unambiguous vents (yet!) but looking at this image of the comet's outgassing I can see three, maybe four, distinct plumes. They all seem to come from sources distinct but near to each other, which might imply a more vent like outgassing than generalised sublimation

Here's a recent light curve of C-G as seen from Earth (at bottom), so we can get a rough idea of the projected activity increase. Note some of the brightening would be from the viewing and solar illumination geometry, while some would be from more intrinsic activity.

http://aerith.net/comet/catalog/0067P/2015.html

NavCams are not filtered (they are two NavCam cameras).

After hipass filtering (30 pixels), and appropriate non-linear stretching, it looks to me like the four-plumes version (or more). Here a false-color version of the OSIRIS image, after rgb-channel-combining the original (red) with the processed image (green/blue) :
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I guess the smooth and brigther areas on the comet are good candidate for landforms formed by deposit of non-icy material

I don't suppose there are any images with a regular exposure length taken near then time of the over-exposed one? It'd be intruigingn to narrow down which part of the neck the plumes are coming from, even just which side.

You could come very close by comparing the silhouette in the original long exposure image below to corresponding silhouettes of short exposure images taken as the comet rotates.

http://www.esa.int/spaceinimages/Images/20...n_2_August_2014

That's a combined (registered, averaged, brightened and stretched before and after averaging) version of screenshots of this video of the press conference on August 6, starting at about 1:27:20:
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Thank you, I've been packing for a family holiday so time has been a bit short for me. Looking at that, and the larger images on the esa site, it seems the 'jets' roughly originate from an area of the bright white deposits which has a family of large boulder-like features scattered about. While I like the idea of 'smokers' the first thought I have is that the boulders are more heat absorbent, get the sun easier because they stick up, and the emission is caused by sublimation of material around their bases...

I've been thinking towards freshly exposed material with less dust cover, and higher abundance of volatiles, maybe as a consequence of exterior or interior mass wasting (a bit like tectonics). In the latter case there could have formed cracks, releasing volatiles.
Release of volatiles may remove more dust, and accelerate exposure of fresh interior material.
Reduction of net gravity (due to changing rotation) reducing the protective pressure of the dust layer might be a more remote possibility.

Just did a totally oversimplified model calculation, ignoring all attractive forces besides gravity:
No errors assumed, a roughly spherical dust particle of density 1 g/cm³, temperature 205 K, and a diameter of about 40 nm will immediately escape a body with an escape velocity of 0.46 m/s, as estimated for 67P/C-G, by its Brownian motion allone.

(Setting translational kinetic energy E = 3/2 k_B T_k equal to E = 1/2 m v², with Bolzmann constant k_B, kinetic temperature T_k, mass m, escape velocity v.)

This might allow for a "dust atmosphere" of particles larger than about 40 nm diameter.
Electrostatic repulsion due to positive charging by photoeletricity may add additional "pressure", and increase this minimum particle size.

Edit: Replaced 400 nm by 40 nm, one decimal digit.

Brownish motion is the result of impacts upon a particle by the molecules of the fluid it's suspended in (i.e. dust floating in an an atmosphere or in suspension in a liquid of some sort)

How does that apply here?

We get the same kind of vibrations at surfaces or within a dust layer, if not cemented or bound otherwise. Dust particles (may?) take the role of molecules in a liquid or in a gas due to the very low gravity.

Edit: Think of dust as loosely bound macro-molecules.

So you assumed all of the thermal energy was in the form of bulk kinetic energy of the dust particle? That's a pretty good approximation for very small molecules, but why should we ignore the internal thermal energy of a 40 nm particle?

From ESA blog.. 667P/C-G in 3D


http://blogs.esa.int/rosetta/2014/08/14/comet-67pc-g-in-3d/

WOW...!

and no obvious craters either.

I spotted one...

Wow ! The side of the upper lobe is covered in striations everywhere that is not covered by debris. Fractures from an ancient impact or layering from changing conditions during the formation of a much larger body? It looks like freshly broken rock, although the material and scale are vastly different.

The smooth area of fines in the top center seems to be draped over a cliff while that in the right center neck area is very sharply delineated from the clean fresh icy area. Can't wait to see all this in more detail.

That's a good point. Thus the size of particles escaping by Brownian motion should be (much?) smaller. Details (particularly vibrational modes) are rather tricky.

Normal to the possible "layering", there seems to be some "ridges". How did they formed...perhaps mass wasting in low-gravity environment?

Or are these erosion-resistant conduits seen in section?

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I made cross-eye version from the amazing OSIRIS images.
It looks that StereoPhoto Maker can do slightly better job in its automatic alignment mode.
Credits for original images: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA.

Amazing! Look's like the left side of the top lobe almost looks like it could crumble and slide down at a any time. Everything looks so fragile and soft (even that lone crater)


Today's navcam taken after another manoeuvre:

http://www.esa.int/spaceinimages/Images/20...t_2014_-_NavCam

The boulders on the neck almost look wind carved in this shot. Is it me or do they seem to be lined up, like the tips of ridges? A couple of them have protrusions near their peaks that are similar to wind carved formations I've seen in the Scottish highlands.

Looking at the upper left hand quarter of the image I linked in my previous post I can see a couple of steep sided pits... could they have formed through a process like that?

I wonder if the whitish area to the right of center is the source of the jets seen on the August 2 long exposure image.

It seems very clean with no traces of dust or debris and looks like it is subliming/eroding away and eating into the dust-covered surface, especially on the right side with all the non-volatile components being lifted away from this area.

as for craters, unless there is a better explanation i suspect many of the deep circular 'pockmarks' are actually very old craters from larger impacts having been evolved through sublimation and other erosional processes. perhaps newer and ostensibly more common small ones like Emily found appear classically clean because they don't persist very long but get averaged out by sublimation and settling? (or maybe deep space is just a very empty place and older ones date back 'billions and billions'). heres a crosseye of a section at top of a group of 3 possible crater relics. why would such crater walls persist? alternation and hardening due to impact melt?
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Runaway outgassing for some period of time looks like a plausible cause for theses pits, probably not too recently - due to the debris fill.
But it's too early to rule out other options.
It could also have been a more virulent event.


This would be my first choice, too.

Resublimation / precipitation of water ice and organics could work (as cement for the dust/regolith).
Or just compactification, if the cause has been a virulent event (e.g. an explosive gas eruption).
Since the gravity is low, the walls don't need to be very strong.

To me it looks like the smaller lobe was originally attached to the long end of the bigger one, but then the neck broke and it rolled over to lie parallel. Maybe the cracking occurred at that time.

An excellent 3D of the comet from ESA.

I took the liberty of "improving" it, at least for my eyes, by adjusting the relative position of left and right channels. L and R images in the original tend to drift from sharing same horizontal plane in some regions, very uncomfortable for the eyes! I'm guessing the drifting is due to the vantage point of Rosetta not being directly above the comet's equator, where you would get perfect positioning for parallax as the bizarre object rotates. Here's a tweaked lower half of the released image:

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...and the upper-half.

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imho, the image currently foaming in my head is a surface dominated on most outfacing areas by overlapping ancient impact crater relics modified by sublimation and other types of erosion discussed here. the more recognizable crater relics remain remarkably deep and circular perhaps due to melting-imposed cohesion of the walls by cementation of a regolith/ice surface and steadily deepened by sublimation of an underlying material composed mostly of ice. but I haven't heard (nor have i been paying attention) of any official speculation about the density or composition of 67PCG at this point so its just ephemeral imaginings in the dearth of facts.. like this nice one with its high cemented walls in that view could have been formed by the walls persisting as the surrounding surface sublimates around them, finally becoming undermined and crumbling into boulders rolling downhill at what must be a comically slow pace.. (its interesting to note there do not appear to be any boulder tracks, if they could have enough 'weight' from the fall to leave any sort of impression in what seems at least by apparent smoothness to be a signifficantly deep dust field)
Click to view attachment EDIT: wall edge has apparently sublimated away here leaving a fantasical top-heavy.. 'Armegeddon'-esque formation

It looks to me like the internal structure of the comet as exposed in the valley wall is characterized by a fabric of vertical to radiating fractures. Most seem to radiate from the center of the mass, but others form shorter fan-like arrays. Maybe this structure reflects some original crystallization (mega-crystal faces) or a later re-crystallization or cooling fabric (columnar to prismatic jointing).

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I hate to admit it, but they got it mostly right in the movie Armageddon!

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The eroded crater (right side of the body) in today's ORISIS image is interesting in that it is looks to be very fragile and the shadow profile in the lower right of the crater has what looks somewhat like a balanced 'rock' as cropped above. Bright spot is the 'rock' at 9 o'clock and the top heavy shadow is at 3 o'clock.

I've seen mentioned before that there may be 'rocks' on pedestals as sublimation occurs around the base of insulated masses of ice (balanced rocks).

I think that when the resolution increases in low orbit a few weeks from now, several arches/holes with diameters of a few meters will be found in areas such as this with thin walls. They would likely be short-lived structures, perhaps lasting only 1 orbit of the sun or even just days near periapsis.

One of my first thoughts after looking to these structures has been the largest crystals of needle ice "ever".
(Google for "ice needles minnesota" as a supercool(ed) example.)
But the idea first appeared too weird to post.

Interesting spire? from today's image release (8/14 image) Looks very monument valley like assuming it is actually a spire. Would love to see in 3D from 30 km orbit.

I really wondered about that one too! A good use of the question mark there, lets wait and see for more clear images. If it really is one such feature they will likely wish to have a better look. =)

Here a picture of all current images. I annotated some features I think I identified. Maybe I totally wrong, but this comet is really a strange one...


green: B means body, H means head
A: Deep black crater
B: crater
C: Line of bolders on the neck ("necklace")
D: tongue like feature
E: depression
F: Flat field with one side steep slope (cirque-like?)
G: elongated flat field
H: Crater field
I: Flat field
J: Pan cake like feature / crater
K: winding wall
L: great wall with fractures
M: Crater
N: tower montain
P: Deep Crater
O: Bay like feature

After rotating a bit the leftward image, this interesting crater renders a little easier for the eyes, though the original is still pretty awesome. I also sharpened it just a touch. The 17 minutes between the L and R shots shortened the shadows, so they throw off the 3D effect a bit in those areas. (My guess is that it was morning there when the shots were taken.) Anyway, this crater is pretty mind blowing, as well as the whole comet. A big thanks to ESA and the Rosetta team for all the updates!

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Just one more from a different part of the comet, with a little processing to the image:

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Excellent video from ESA depicting orbital insertion of Rosetta:

https://www.youtube.com/watch?v=Mf1zsACcXc4

And accompanying blog post:

http://blogs.esa.int/rosetta/2014/08/18/wh...p-with-rosetta/

The craggy rim of the large depression (crater?) at the centre is reminiscent of the Icy Spires of Callisto:

http://spaceflightnow.com/news/n0108/23callisto/