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Posted by: Explorer1 Nov 14 2014, 05:17 AM

I think I heard it mentioned during the press conference today, (I can't find it now), about Rosetta itself possibly landing eventually, similar to what NEAR did at the end of the main mission at Eros? Since it's not like there's anywhere else to go with the remaining delta-v left by the end of 2015, and sunlight levels and activity starting to drop after perihelion, and the low gravity makes the difference between orbiting and 'landing' trivial. The whole thing would weigh a kilo or two, right?
Obviously there's a few more pressing concerns right now, but it's something to eventually think about.

Posted by: Gerald Nov 14 2014, 10:39 AM

At some point Rosetta will run out of propellant for orbit corrections.

The mass of Rosetta at regular EOM should be 2900 kg - 660 kg - 1060 kg - 100 kg = 1080 kg.
(Start weight - propellant - oxidizer - mass of Philae, from http://nssdc.gsfc.nasa.gov/nmc/spacecraftDisplay.do?id=2004-006A)
The http://en.wikipedia.org/wiki/Surface_gravity of http://en.wikipedia.org/wiki/67P/Churyumov%E2%80%93Gerasimenko at 2 km distance from the center of mass should be
g = GM/r² = (6.672e-11 Nm²/kg² * 1e13 kg) / (2000 m)² = 1.668e-4 N/kg.
The http://en.wikipedia.org/wiki/Weight of 1080 kg is F = m a = 1080 kg * 1.668e-4 N/kg = 0.18 N.
0.18 N is the force of a mass of 18.37 grams in 9.80665 m/s² gravity.
The actual weight of Rosetta would be a little less due to inertial forces by the rotation of the nucleus.

To be more precise: The http://en.wikipedia.org/wiki/Centripetal_force for a radius of 2000 m and a rotation period of 12.7 h = 45,720 s is m r 4 pi² / T² = 1080 kg * 2000 m * pi² / (45,720 s)² = 0.0102 N.

So we are at 0.18 N - 0.01 N = 0.17 N for Rosetta's EOM weight, corresponding to the weight of a little more than 17 grams on Earth.

That's a model estimate, and may differ, depending on the actual landing coordinates.

Posted by: MahFL Nov 14 2014, 11:35 AM

They have already stated they want to follow the comet during 2016, as it enters the dormant state. They would need a mission extension for that.

Posted by: neo56 Nov 15 2014, 11:01 AM

NavCam mosaic taken on 6 November 2014, with Agilkia landing site on top of the top lobe:
https://flic.kr/p/p7NcbE

Posted by: tolis Nov 15 2014, 11:25 AM

Actually, it will go somewhere, after a fashion.

67P will approach Jupiter to within 0.4 AU in Nov 2018.

Whether Rosetta will be able to do anything about it, out of power and out of fuel, is another matter.

Posted by: astroman Nov 16 2014, 10:07 PM

"rejoined" (forgot password) for this epic event- hopefully it will spawn a co-op esa-nasa cometary exploration program - especially good time being alive for following an historic and species first...


ADMIN: Post moved.

Posted by: SpaceScout Nov 17 2014, 04:08 PM

Deutschlandfunk says the comet's surface remind of corals... Interesting comparison but might lead to some misunderstanding...

Posted by: katodomo Nov 17 2014, 05:48 PM

"Coral reefs under the sea" is what Paolo Ferri supposedly said in a radio interview for HR-Info - which is where Deutschlandfunk took it from, among others. Interview isn't available online (yet?), so can't check it for certain.

Considering quite a lot of people aren't even aware corals are alive i think the extent of misunderstandings will be limited

Posted by: fredk Nov 19 2014, 06:52 PM

From http://www.newscientist.com/article/dn26584-philae-lander-sleeps-but-rosetta-mission-lives-on.html

Posted by: Y Bar Ranch Nov 19 2014, 09:38 PM

Obviously it'd take a lot of precise planning, but if in the end game it was possible to drift down, and then blip the thrusters for the next-to-the-last-time to clean off the overlaying dust from the icy underside...

Posted by: neo56 Nov 20 2014, 09:19 PM

NavCam mosaic of 17 November:
https://flic.kr/p/pbzwPQ

Posted by: Phil Stooke Nov 24 2014, 03:14 PM

The long wait for an OSIRIS color image may be over:

https://agu.confex.com/agu/fm14/meetingapp.cgi#Paper/22395

The AGU abstracts are online and full of good stuff, and a very small number of them contain images, including this one.

Phil

Posted by: ugordan Nov 24 2014, 05:48 PM

The color mottling in that image is very interesting (other than obvious color fringes caused by rotation between frames), I wonder if that's real or an instrument artifact.

Posted by: neo56 Nov 24 2014, 05:52 PM

https://agu.confex.com/agu/fm14/meetingapp.cgi#Session/1556to present the results from the instruments of Rosetta.

Posted by: Malmer Nov 24 2014, 06:38 PM

Made a new animation of navcams draped over my shapemodel. This time with the november 17 navcam quad.

My shapemodel is becoming better with each iteration. The match between features in the images and the shape of the model is surprisingly good if I may say so myself

http://mattias.malmer.nu/2014/11/navcam-november-17/

Posted by: Malmer Nov 24 2014, 07:00 PM

That is one very strange image indeed... the mottling is confined to a broad stripe of the image starting abruptly about 20% in from left and ending about 10% in from the right. It almost looks a little bit like it was added in post. (Scientific DRM?)

The "non mottled" areas look much nicer...

Posted by: climber Nov 24 2014, 07:37 PM

I notice that Rosetta/Philae topics get (so far) about 1500 posts and 300.000 views. Wondering if this beat Curiosity around landing time?

Posted by: Spin0 Nov 24 2014, 08:21 PM

Newly published Navcam images of the region, 2.59 m/pixel: http://blogs.esa.int/rosetta/2014/11/24/cometwatch-20-november/

ADMIN NOTE: Post moved from Philae topic to correct discussion.

Posted by: neo56 Nov 24 2014, 11:09 PM

Very nice animation Mattias, as always

NavCam mosaic taken on 20 November:
https://flic.kr/p/qbuGVV

The shadow of the upper lobe is slightly visible on the coma.

Posted by: fredk Nov 25 2014, 04:23 AM

Very obvious if you extract the saturation channel and stretch:

Very sharp boundary between mottled area and unmottled to the right. The boundary's clearly unrelated to anything on the comet.

Posted by: Malmer Nov 25 2014, 08:37 AM

Yes. And the mottling seems very regular. Like a Perlin noice function...

The parts outside the area are quite nice. One could perhaps work a little on the registration of the images to get less fringing. But you can clearly see the colour of the surface change on the different terrain types. (Especially if you remove the overall red tint)

Posted by: 4th rock from the sun Nov 25 2014, 08:56 AM

Looks like noise / low resolution data. Perhaps some channels are of much lower resolution.

Posted by: ugordan Nov 25 2014, 09:03 AM

Thing is, looking at the rotational state in each of the rgb components, it's suggestive that the source frames cover the entire body, not a case of a colorized greyscale image at the center. Very odd.

Posted by: Gerald Nov 25 2014, 12:06 PM

A strongly hue and saturation stretched (hence false-color) version of the colored OSIRIS image:

My overall, somewhat subjective and qualitative impression is, that bluish spots are correlated to holes/depressions, and reddish spots to peaks/hills.
I can't say, whether this also means some correlation of hue to activity.

From https://agu.confex.com/agu/fm14/meetingapp.cgi#Paper/22395 I've some hope, that the OSIRIS team might have been able to quantify this presumption.

Posted by: Malmer Nov 25 2014, 01:49 PM

My bet is that the image has been intentionally degraded to make sure that it is not used by anyone to do any science.

It is just way to much low frequency noise in the individual channels and there seem to be almost no correlation between surface type and color.
The images from OSIRIS we have seen so far are very very nice. there seem to be no noise pattern of any kind in those.

If one instead looks at the areas outside the noise stripe one is treated to a much higher quality.

Posted by: Michael Capobianco Nov 25 2014, 04:51 PM

Is anyone interested in matching up the diagram of probable Philae landing zones with the recent Navcam images showing those parts of the comet?

Posted by: Floyd Nov 25 2014, 06:33 PM

The zones are just on the other side of the dark grey ridge. Our point of view is 180 degrees off from what we would need to spot Philae.

Posted by: Malmer Nov 25 2014, 11:22 PM

Thank you. I think it is a lot of fun to do. It makes the comet more like a physical object to see it like that. And I get to learn the surface very intimately. I have over 150 surface features that I match over the images. They each have a number. Its strange to have a private toponomy like that.

I go: -ooh look there's a nice image of twelve. Now lets see if i cant find seventeen in this picture. nope. At least I can see 119. that's enough for the camera solve...

Posted by: Phil Stooke Nov 26 2014, 07:25 PM

The jets are really multiplying now! Also, I think this is the first time the dark side has been visible silhouetted against the background coma - we've seen it before with Halley and Hartley-2 but not here.

http://blogs.esa.int/rosetta/2014/11/26/cometwatch-20-november-in-the-shadow-of-the-coma/

Phil

Posted by: SteveM Nov 26 2014, 09:35 PM

Just noticed -- actually just realized what I've been seeing for some time -- that the jets are primarily pointing toward the Sun, while a comet's dust and ion tails point away from the Sun. Can Rosetta observe the process by which the trajectory changes as they become tails, or is Rosetta too close to see that effect?

Posted by: DFinfrock Nov 27 2014, 12:48 AM

Absent any atmosphere, there is no air friction to slow down the jets at they stream outward from the surface. My guess is that as the comet's surface heats up (on the sun-ward side) the jets would be streaming directly away from the surface, or towards the sun. It would only be when the comet falls deeper into the sun's gravitational well, and picks up speed, that the tail is "left behind".

I await someone more knowledgeable about comets to correct me.

Posted by: Phil Stooke Nov 27 2014, 01:16 AM

OK...

http://hubblesite.org/reference_desk/faq/answer.php.id=19&cat=solarsystem

Phil

Posted by: fredk Nov 27 2014, 01:16 AM

My understanding was that it was the pressure of the solar wind that forms the tail(s). So heating on the sun facing side leads to jets towards the sun, which eventually are deflected by the solar wind to form the tail.

If there were no solar wind, particles in a jet pointing towards the sun would presumably get ahead of the comet rather than be left behind (at least prior to perihelion).

Edit: Phil beat me by less than a minute!

Posted by: SteveM Nov 27 2014, 03:52 AM

Thanks for the comments and for Phil's good link. The question remains, however, of what details Rosetta will be able to provide about the process changing jets emerging on the sunward side of the nucleus into tails streaming away from the Sun.

Steve M

Posted by: Gerald Nov 27 2014, 11:28 AM

Small grains should be more susceptible to solar wind and radiation.
The http://sci.esa.int/rosetta/35061-instruments/?fbodylongid=1639 should be well-suited to investigate this question in very detail:

Posted by: SteveM Nov 27 2014, 01:55 PM

GIADA should provide interesting velocity data. Look forward to more GIADA insights into dust particle trajectories since since http://blogs.esa.int/rosetta/2014/09/12/giada-tracks-the-dust-2/ of a few dust particles.

Posted by: neo56 Nov 29 2014, 08:58 AM

NavCam mosaic of 26 November. The rotation of the comet has been substantial in the twenty minutes that passed between the two lower images, resulting in artifacts in the stitching process.
https://flic.kr/p/phnrd6

Posted by: eliBonora Dec 5 2014, 09:11 PM

1 December NAVCAM from 30.1 km

https://www.flickr.com/photos/lunexit/15766808390/sizes/o/

Posted by: ngunn Dec 5 2014, 09:28 PM

Beautiful. Thanks for sharing that. It's amazing to pan around that view. What a place!

Posted by: Dan Delany Dec 7 2014, 01:13 AM

Lovely mosaic eliBonora! The one on the ESA blog has a blurry seam, where the foreground and background limbs meet, that had me scratching my head until I saw yours

Here are a couple attempts at anaglyphs from the Dec 1st and 2nd NAVCAM images, made from the slices where the bottom two (foreground) images overlap. Some artistic liberties have been taken to account for areas which were shaded in one image and lit in the other.

Posted by: eliBonora Dec 8 2014, 04:44 PM

Thank you Dan. Nice anaglyphs.
I think the difference is that we combine these comets by hand and we don't use the software's blending option.

Posted by: neo56 Dec 10 2014, 09:42 PM

My take on NavCam mosaics from 30 November to 7 December:
https://flic.kr/p/q3ANLy https://flic.kr/p/posnFR https://flic.kr/p/qhYF1G https://flic.kr/p/q5R936

Posted by: Phil Stooke Dec 11 2014, 05:33 PM

The latest Navcam blog shows new - or apparently new - features in the neck. Here's a comparison between October and December images (December on the right). I would suggest a close examination of images would probably show more things like this.

Phil

Posted by: Phil Stooke Dec 11 2014, 07:51 PM

Sure enough, here's a comparison between 24 September and 9 December with the new feature on 9 December noted. Differences in lighting and resolution are small enough that I think this is a real change.

Phil

(PS... must work on book... must work on book... aaaargh!)

Posted by: walfy Dec 11 2014, 09:44 PM

Wow, those changes are amazing! Looking forward to the discussions about this.

Posted by: Gladstoner Dec 11 2014, 11:49 PM

I would guess the pit is a low profile feature that produces shadows only when sunlight is at a very low angle. Otherwise, the lack of albedo differences in the smooth material renders it invisible otherwise.

Of course, the very recent formation of a collapse pit would be pretty cool....

Posted by: Phil Stooke Dec 12 2014, 12:15 AM

I don't think the lighting is sufficiently different for the pit to not show up in the earlier image. What you describe is always a possibility in this type of comparison, but I don't think it applies here.

Phil

Posted by: nprev Dec 12 2014, 12:22 AM

If it's all real, and it sure looks like it is, this will set some significant constraints on the life expectancy of comets in the inner Solar System. Could be a huge mission finding.

Well spotted, Phil!!!

Posted by: Phil Stooke Dec 12 2014, 12:27 AM

I spotted the second example, but it was the Rosetta blog:

http://blogs.esa.int/rosetta/2014/12/11/cometwatch-9-december/

which drew attention to the first one. I just illustrated that first one.

Phil

Posted by: Gladstoner Dec 12 2014, 01:49 AM

If the pits did form very recently, then the smoothing process must have been recent as well.

Posted by: jmknapp Dec 12 2014, 11:08 AM

Might the marks be the result of some fragment landing back on the comet after being wafted up by some outgassing activity elsewhere?

Posted by: Gerald Dec 12 2014, 04:34 PM

Non-linear brightness stretched (about quadratic) and 8-fold saturation enhanced version of the http://blogs.esa.int/rosetta/2014/12/12/comet-67pc-g-in-living-colour/:

Brightness-stretching gets the grey value nearer to 50%, nonlinearity avoids more-than-necessary numerical instability near full saturation.

My first out-of-the-hip impression has been, that some of the color could be http://en.wikipedia.org/wiki/Structural_coloration.

Posted by: eliBonora Dec 12 2014, 07:56 PM

We have tried to pull out more color from the OSIRIS image, not because it 's what the human eye could see but because it's interesting to highlight the differences. Of course we can exasperate more and more but we have preferred to maintain a balance with a pleasant look.

https://www.flickr.com/photos/lunexit/16006339535/

Here's also a curious gif created with the three RGB channels splitted:
https://www.flickr.com/photos/lunexit/15820377179/sizes/o/

Posted by: Phil Stooke Dec 12 2014, 08:18 PM

"Might the marks be the result of some fragment landing back on the comet after being wafted up by some outgassing activity elsewhere? "

That's exactly what I would expect for these specific changes.

Phil

Posted by: jmknapp Dec 13 2014, 12:21 PM

Request to the comet gods: puff Philae out of its hole so it lands elsewhere, in the sun and upright of course.

Posted by: wildespace Dec 13 2014, 01:59 PM

Great to finally see the comet in colour! The original OSIRIS composite has greenish cast (common to raw images, it seems, judging by the Mastcam and MAHLI raw images), so I've used "Auto color" in Photoshop to normalise the colours, and then decreased levels to reflect its dark albedo. This also brought out some colours, without the need for enhancing saturation manually:

The neck region seems definitely lighter and somewhat bluer, perhaps it's the un-darkened material being exposed by the comet's activity?

There is interesting golden-red colouration at the bottom of the larger lobe.

Posted by: Explorer1 Dec 13 2014, 05:51 PM

Or just sublimate and crumble the overhang above it while we're in the wishful thinking stage....

Posted by: neo56 Dec 14 2014, 09:38 PM

NavCam mosaic of 9 December:
https://flic.kr/p/q8cP7Y

Posted by: Gerald Dec 15 2014, 12:50 AM

OSIRIS used different color filters for the same CCD, not a Bayer pattern like MSL Mastcam or MAHLI (although Mastcam can also use color filters). So it's more a matter of how the OSIRIS team calibrated colors.

From http://blogs.esa.int/rosetta/2014/12/12/comet-67pc-g-in-living-colour/:

Posted by: surbiton Dec 15 2014, 08:46 PM

Could it be the interior "ice" exposed ?

Posted by: Brian Lynch Dec 15 2014, 09:59 PM

Could it also be that the neck region is occluded by the two lobes so that less dust and other material contributing to the dark colour is able to aggregate on the surface as the comet travels through interplanetary space? Admittedly, I have little expertise in the science of comet formation so that might be nonsensical (ie. is the surface colour even expected to be due to such aggregation?).

Posted by: neo56 Dec 16 2014, 12:09 AM

NavCam mosaic of December 10th:
https://www.flickr.com/photos/105035663@N07/15845836397/

Posted by: Hungry4info Dec 16 2014, 06:04 AM

Focous on the surface change noted by Stooke in the 10 Dec 2014 Navcam image.

Posted by: Gerald Dec 16 2014, 01:48 PM

I think, we've to go back to or even before the formation of our solar system to get most of the interstellar dust the comet is made of.
The net accumulation of interplanetary dust on the present orbit is probably much less than dust ejection. Therefore the currently accumulated dust on the surface - although originally material of the protoplanetary disk - has more likely been material of the comet than been collected recently from interplanetary space.

Exposure to radiation (solar and galactic) might be less in the neck region, leading to a different chemistry over long periods of time. But surface dust is probably reworked due to activity, such that this kind of radiation-induced differences should be hard to detect.
An approach based on activity and varying settlement of cometary dust will probably be more promising.

The dark surface color is (very likely) mostly due to carbon-rich compounds (somewhat similar to soot or asphalt), and to the fine-grained (almost fractal) surface structure (rough surfaces tend to be darker than smooth ones). Grain size influences color. Structural colors (in contrast to pigment colors) are caused by surface structures the size about the wavelength of visible light. Areas on the surface of the comet may vary in their preferred accumulation and ejection of grains of a certain size or structure, and vary in color by this mechanism. Pigmentation (chemical composition) may vary for a similar reason.

Posted by: Bill Harris Dec 16 2014, 03:00 PM

My study of changes on the North Polar Plain 24 September '14 to 10 December '14.

http://univ.smugmug.com/Rosetta-Philae-Mission/Rosetta-Comparative-Series/i-XTTqqmM/0/L/compar_24sept_2oct_9dec_10dec-14_vent_activity-L.png

http://univ.smugmug.com/Rosetta-Philae-Mission/Rosetta-Comparative-Series/

--Bill

Posted by: Habukaz Dec 16 2014, 07:32 PM

Well, the original plans expected Philae to cook to death by March 2015. If it then instead wakes up from slumber; then, with some luck, the total number of months available for science on the surface could exceed the original plans.

IIRC, there was some talk about the possibility to spin up the flywheel as a last-ditch attempt at getting Philae away from its current position before the batteries ran out. If they could successfully pull that off when the insolation at the surrounding planes is habitable, they could possibly extend the lifespan even further.

So I think I'll sacrifice some dry ice for the comet gods in the hope that Philae stays put, for now.

Posted by: neo56 Dec 17 2014, 08:47 PM

NavCam mosaic of December 14th:
https://flic.kr/p/puRbyj

Posted by: Gerald Dec 17 2014, 11:10 PM

That's a quick and very dirty try to get a 3d visualization of http://blogs.esa.int/rosetta/files/2014/12/SCAN_MD_zoom.png as x-eyed stereo flicker, not really recommended, unless you need to know and are ready to risk some head-ache or sea-sickness, more an idea for someone who finds time do better:

raw image: ESA/Rosetta/MIDAS/Space Research Institute (IWF) in Graz, Austria/Mark Bentley
modified by "Gerald"

Posted by: Habukaz Dec 19 2014, 11:55 AM

This cartoon might be the best rendering that we have of the 'dinosaur eggs' for a while...


(via https://twitter.com/Geo_Miles/status/545705614387601408)

Posted by: elakdawalla Dec 19 2014, 05:25 PM

Just to be clear, though, the "dinosaur egg" pictures were not from Philae, they were from OSIRIS. I'll do my best to describe them: imagine a cliff face. Now imagine, instead of the usual kind of striations you'd see in a cliff face, that it was instead made entirely of gumballs. Or maybe peanut M&M's, since they didn't seem quite spherical, but rather slightly non-spherical, but still distinctly round. All of a uniform size. The scale bar on the image was 5m long, and the dinosaur eggs were somewhat smaller than that; Sierks said 2 or 3 meters. It was wacky-looking.

Posted by: Explorer1 Dec 19 2014, 05:30 PM

Yep; kinda wild that those images are being guarded at the same level of secrecy as surveillance satellites...
Presumably an image of Philae on the surface, once acquired, will be released earlier. Surrounding details can be easily cropped out after all.

Posted by: elakdawalla Dec 19 2014, 05:33 PM

They said that images had been acquired in a sequence planned for when Philae should be in sunlight, but that the images weren't on Earth yet. I think.

Posted by: neo56 Dec 19 2014, 05:46 PM

http://wpc.50e6.edgecastcdn.net/8050E6/mmedia-http/download/public/videos/2014/12/029/1412_029_AR_EN.mp4 has been released with NavCam mosaics taken in November and December.
Informations on the making of this movie and files containing both the mosaics and the individual pictures are available http://blogs.esa.int/rosetta/2014/12/19/cometwatch-the-movie/.
They also provide SPICE data for each pictures.
They invite amateurs to do their own mosaics and movie : challenge accepted !

Posted by: jmknapp Dec 19 2014, 09:58 PM

In the image information file, how is "rotation phase" defined?

Posted by: neo56 Dec 30 2014, 09:30 PM

After some work of stitching, here is my animation of the rotation of comet Churyumov-Gerasimenko. Full resolution is available https://www.flickr.com/photos/105035663@N07/16149519312/sizes/o/.

Posted by: neo56 Jan 3 2015, 06:46 PM

I'm working on https://www.flickr.com/photos/105035663@N07/16330253526/.
I have included 7 mosaics yet and I'm pretty happy with the result! Pictures between each NavCam mosaic are interpolated using a morphing software: MorphX on Mac.

Posted by: aholub Jan 3 2015, 08:23 PM

Very nice animation. Much better then ESA original. Thanks for creating and sharing.

Posted by: Jackbauer Jan 6 2015, 10:05 PM

First NavCam image of 2015 :
http://www.esa.int/spaceinimages/Images/2015/01/Comet_on_1_January_2015_NavCam

Posted by: Phil Stooke Jan 14 2015, 02:19 PM

Can't stop, rushing to class, but the newest image has lots of surface changes in it.

Phil

Posted by: Hungry4info Jan 14 2015, 04:31 PM

Some surface changes I've identified comparing it with the 9 Dec 2014 NavCam image. It looks like some of the 'ripples' (I am sure there's a better term) that were first seen in that NavCam image have been erased by surface flow. Many new such features have appeared, however.

Posted by: Phil Stooke Jan 14 2015, 06:36 PM

Here are two close-ups, same features as Hungry4info circled - if you look carefully there are others as well. Also a third post which is derived from my earlier one but adds a third time step. The pits shown with arrows look like the same feature until you check carefully, and they are different.

I have searched other areas on the nucleus in vain, looking for changes there.

Phil

Posted by: flug Jan 15 2015, 09:36 PM

I'm wondering to what degree those are new/changed features, and to what degree they are features that were there in the earlier images but revealed far more clearly by the sun angle/shadows in the later images.

For example, in the 24 Sept/2 Oct/9 Dec image, at first I thought the features indicated by the arrows in the 2 Oct & Dec were the same feature that had moved. But examining the 24 Sept & 2 Oct images more carefully, I think I see the same feature indicated by the arrow in the 9 Dec image. The lighting is just more directly from above in the 24 Sept & 2 Oct images, so there are no visible shadows. On 9 Dec, the sun angle is more oblique, giving far more obvious shadows.

Similarly for the object indicated with an arrow on the 2 Oct image--I can see those outlines in both 24 Sept & 9 Dec as well.

These **might** be pretty much identical features just seen under different lighting. Or they **might** have subtly changed between images--subsidence, perhaps? But I don't think they have **dramatically** changed or shifted.

FWIW this is somewhat informed by some hours spent observing the moon through a telescope. Features that are very obvious under oblique lighting that brings out the shadows will almost 100% disappear under more direct lighting. I'm not the most experienced observer by any means, but these features look in some ways similar to those lunar features that appear/disappear depending on sunlight angle..

I'll be curious what you all think!

Posted by: Hungry4info Jan 15 2015, 10:43 PM

The illumination angles in these images appear to be similar, based on the shadows we see.

Posted by: Gerald Jan 15 2015, 10:47 PM

I think, Phil is (one of?) the most experienced experts in this field, and identifies textural changes much better than me. So if I'm unsure, I'm attributing this to my lack of sufficient experience.

In this special case, the central pair of images shows rather similar illumination. Some subtle features look rather similar (unchanged) in both images, such that I strongly tend to agree with Phil, that some deepenings show up in the right image, exclusively.

But you're of course right, that changing illumination needs to be considered.

Posted by: Jackbauer Jan 16 2015, 02:14 PM

Alléluia !! An image of OSIRIS !! Old (november 22) but spectacular :

http://www.esa.int/spaceinimages/Images/2015/01/Comet_activity_22_November_2014

Posted by: MahFL Jan 16 2015, 03:49 PM

Looks to me the main jet is made up of about 14 jets all combining together, awesome.

Posted by: Jackbauer Jan 16 2015, 06:22 PM

And now the daily NAVCAM image :
http://www.esa.int/spaceinimages/Images/2015/01/Comet_on_10_January_2015_NavCam

Posted by: Phil Stooke Jan 16 2015, 06:41 PM

Look what happens when you stretch the contrast in the OSIRIS image: a beautiful silhouette at the bottom, and the shadow of the nucleus on the coma.

Phil

Posted by: elakdawalla Jan 16 2015, 07:13 PM

Cool. Is it correct to say that the jets appear to curve because material within them is moving radially outward from the comet, while the comet (and hence the jet source regions) is spinning?

I am amused that the first phrase in the blog entry is "In the first OSIRIS image release of 2015..." We're supposed to be getting one per week -- even the ESA bloggers can no longer conceal their exasperation about that!

Posted by: fredk Jan 16 2015, 11:28 PM

I suspect we're not seeing the "lawn sprinkler effect" here - to see curvature in the jets you'd need the speed of the jet material to be not too much more than the rotation speed. I don't know what the expected order of magnitude speed for the jets is.

To me it looks more like we're seeing different (more or less straight) jets in different directions superposed along the line of sight. So one jet in one direction in behind, and other jets pointing in a bit different directions in front. You'd expect jets from separate vents to travel in somewhat different directions.

Posted by: Gerald Jan 17 2015, 12:14 AM

That's an annotated, brightness-stretched resized crop of http://blogs.esa.int/rosetta/files/2015/01/ROS_CAM1_20150110A.jpg:

The streak is probably the track of a dust grain, the red line as a reference line. The streak is curved. This indicates acceleration.
The cause may be drag by gas coming from a different direction, interaction with solar wind, or interaction with photons.
These possible mechnisms may also apply to dust jets.
Small charged grains may also interact with Sun's magnetic field (http://en.wikipedia.org/wiki/Lorentz_force).

So we've several possible causes for the curvature of the jets.
See also http://hubblesite.org/reference_desk/faq/answer.php.id=19&cat=solarsystem, or a little more detailed http://burro.astr.cwru.edu/Academics/Astr221/SolarSys/Flotsam/comettail.html. http://en.wikipedia.org/wiki/Comet_tail.

Posted by: MarsInMyLifetime Jan 17 2015, 12:48 AM

The change of direction seems rather more abrupt than gradual. Is it possible that frozen particles in a conglomerate might finish sublimating in a puff, sending their inert carrier particle in an opposite tangent?

Posted by: Gerald Jan 17 2015, 09:51 AM

Break-up of some hydrated state? I couldn't rule this out, easily. But particles should be of very different size, otherwise we would see a fork.
I've also been considering electrostatic interaction (attraction / repulsion) with the spacecraft. But for this, the motion should be almost perfectly parabolic, which I doubt that it is.
Collisions with fast-moving tiny grains (less than 300 nm diameter to be invisible as individual particles) may be possible, too.

Posted by: Habukaz Jan 17 2015, 11:23 AM

ESA's director general Jean-Jacques Dordain http://www.bbc.com/news/science-environment-30859411 his frustration and sympathies with the current image release policy of Rosetta (and other missions); but no signs of any changes coming soon:

Posted by: Gerald Jan 20 2015, 11:19 AM

Vapor from sublimating ice should relax with about the speed of sound of the specific gas into vacuum.
Very small grains should be dragged the same speed.
Larger grains may be slower, down to zero for larger grains not able to escape from the comet.
With this approach I'd suggest a few hundred meters per second as velocity of the majority of the jets.

I thought I've read 400 m/s without explanation somewhere. The above approach is inspired by this vague memory.

I'm neglecting interaction with solar wind and uv radiation on the current level of activity and proximity to the nucleus.

Posted by: fredk Jan 20 2015, 04:01 PM

Thanks, Gerald. For a 3 km radius, we have roughly 0.5 m/s rotation velocity, which is far smaller than hundreds of m/s. So indeed, for the near-thermal-velocity particles, it looks like we wouldn't expect to see curvature in the jets. Picture a sprinkler rotating extremely slowly...

Posted by: Sherbert Jan 20 2015, 07:14 PM

I was wondering if interaction between the jets and the material of the inner comma may, by friction or ion interactions, tend to curve the tops of the jets as they are, initially anyway, tied to the rotation of the nucleus. The OSIRIS image from 22nd Nov seems to show some curving of the jets further from the nucleus. The very low densities involved would tend to make me think these effects would be rather small. The velocity of inner coma material relative to the surface would need to be known, Rosetta does have instruments to determine that, though.

Posted by: eliBonora Jan 22 2015, 04:58 AM

Last NavCam mosaic: 10, 12 and 16 January

https://flic.kr/p/pTwGmz
https://flic.kr/p/qRfVAu
https://flic.kr/p/qRfVAu

This shows the same view of 2 November but under different lighting
(here in two versions https://flic.kr/p/pEDHFi https://flic.kr/p/pEY7qj)

Posted by: Habukaz Jan 22 2015, 07:59 PM

As per the scientific results thread, 14 newly released OSIRIS images can be found http://www.esa.int/Our_Activities/Space_Science/Rosetta/Highlights/Comet_close-ups. Per https://twitter.com/BBCAmos/status/558346921002434561, the dinosaur eggs mentioned at AGU are here referred to as 'goosebumps' (pic 13).

EDIT 2x: Some more context in http://blogs.esa.int/rosetta/2015/01/22/getting-to-know-rosettas-comet-science-special-edition/.

http://www.esa.int/var/esa/storage/images/esa_multimedia/images/2015/01/comet_from_8_km/15206382-1-eng-GB/Comet_from_8_km.jpg is OSIRIS at full resolution from 8 km - almost like standing on the surface!

Posted by: Habukaz Jan 22 2015, 08:34 PM

What the heck is this thing?

(from the 8 km)

Posted by: MarsInMyLifetime Jan 22 2015, 09:11 PM

If these are possibly raw images from OSIRIS, one explanation could be the shadow of lint that somehow got onto the surface of the sensor (assuming a conventional flat sensor, not push-broom--offhand, I don't know the architecture). Since this is likely a processed science image with known image defects cleaned up, then we could be looking at the shadow of a sharp shard that is pointed toward the camera, and whose top is blended into the background dust layer. I favor that interpretation, as anything stick-like on that surface is unlikely. But I sure think it looks like lint.

Posted by: dvandorn Jan 23 2015, 01:17 AM

These links won't load for me. Perhaps it's just because I'm in the U.S. and the servers are in Europe -- I've noticed speed issues before trying to load images from ESA's websites -- but, for example, I started trying to load the first link about 10 minutes ago and it's still just spinning. The second link started to load an image, loaded about 5% of it, and after about five minutes gave up and said the 5% of the image is all it will load.

Have others here in the U.S. seen the same issue trying to load ESA webpages?

Too bad, I've been waiting for OSIRIS images for a while, here, and now they're out and I can't get them to load...

Posted by: elakdawalla Jan 23 2015, 01:19 AM

I've had no problems.

You can see all the same images in http://t.co/Gc7x5I9UNd.

Posted by: dvandorn Jan 23 2015, 01:21 AM

Thanks! Yeah, it's been a continuing issue for me with the ESA websites. I may need to discuss this with my Comcast rep...

Posted by: TheAnt Jan 23 2015, 01:57 AM

From http://www.nature.com/news/science-pours-in-from-rosetta-comet-mission-1.16777 nice images, names of the various terrains and graphical 3D models with VIRTIS data.

Posted by: atomoid Jan 23 2015, 02:15 AM

yeah, the shadows cast by that heck thing are all backwards in the http://www.esa.int/spaceinimages/Images/2015/01/Comet_from_8_km for that to be er..um..uh.. "something else entirely".. but the exposed chunk directly below it reminds me of the ubiquitous layered chunks at Gale crater.

Posted by: MarsInMyLifetime Jan 23 2015, 02:36 AM

Looking at it enlarged, I think it has all the characteristics of a small fiber on the sensor surface, particularly given the long focal length, which tends to project tight shadows from schmutz in the optical path. I'll be watching for it in any other OSIRIS images that have broadly smooth and light features in that quadrant. I'm surprised it has not been identified as a defect for standard pipeline processing as done for the Curiosity MastCam images that have known dust motes. Anyway, great photos--the foreground of that photo shows clearly a sort of gravelly texture at a centimeters scale.

Posted by: katodomo Jan 23 2015, 06:17 AM

Some of the pictures have resolutions and uncompressed sizes that simply won't work in a browser (or at all on older computers). I'm in Europe, and I get timeouts on the larger files as well. Works considerably better to download them and view them in a dedicated software. The http://www.esa.int/spaceinimages/Images/2015/01/Active_pit for example comes to 13333x6667 px (!), and has an uncompressed size of 254 MB; going with the referenced image resolution of 1m/pix it seems to me they blew it up to about 8-10x size (rule of thumb with the 200m scale given says that picture should be somewhere around 1600px wide at most).

Although I'm also not entirely sure whether e.g. http://www.esa.int/spaceinimages/Images/2015/01/Comet_goosebumps and http://www.esa.int/spaceinimages/Images/2015/01/Active_pit the (compressed) jpeg are really supposed to be bigger than the png...

Posted by: 4th rock from the sun Jan 23 2015, 09:59 AM

Don't know about your PC but probably that's due to the video card. Any modern browser will use the video card, so things such as dedicated memory (or lack off) might have an impact.

Posted by: mcgyver Jan 23 2015, 11:05 AM

A bit more comfortable page:
http://lc84.altervista.org/rosetta/immagini.html


These images are weird: at "full resolution" a single pixel is actually made of several pixels, hence it's a zoomed image! What is the sense in doing this?!?

Posted by: Gerald Jan 23 2015, 02:41 PM

"Geomorphological map of comet 67P", with names across the Egyptian mythology:
http://www.sciencemag.org/content/347/6220/aaa1044/F3.large.jpg

Posted by: Mercure Jan 23 2015, 05:17 PM

Nice overview of the info from the latest papers: http://www.bbc.com/news/science-environment-30931445

Posted by: elakdawalla Jan 23 2015, 09:13 PM

Since the images were prepared for a magazine publication, it may be a defensive mechanism against the photo editor complaining about there not being enough pixels in an image. When I prepare my own pictures for magazine articles I've gotten so tired of arguing about how you really can print, say, a NavCam image at larger than 3.3 inches wide (1024 pix x 300dpi) that now I just upsample most images in Photoshop so that they have enough pixels that they could be printed at 11 inches high at 300 dpi. That being said, 13333 pixels is a wee bit of overkill.

Posted by: elakdawalla Jan 23 2015, 10:00 PM

I'm having trouble locating a good global context image to show the location of the "http://www.esa.int/spaceinimages/Images/2015/01/Comet_from_8_km" photo. Can anybody here help me out with that?

Posted by: elakdawalla Jan 24 2015, 12:09 AM

(Sorry to keep talking to myself here)...the more I look at the OSIRIS images, the weirder some of them are. Many of the ones that have been resized are also posterized; the "http://www.esa.int/spaceinimages/Images/2015/01/Crack_extension_in_Hapi" one, for instance, looks like its color table was reduced to 16 gray levels before it was brought into a desktop publishing program for annotation, and when it was exported from there it was exported at a resolution not quite 5 times its original resolution. These images are really munged up

Posted by: MarsInMyLifetime Jan 24 2015, 01:31 AM

At this point, given the uncleaned lint spot and uneven preparation of images for release, I wonder whether ESA has quite the well-oiled processing and staging pipeline we've become used to from NASA's image handling. Perhaps researchers are selecting images from their own processing attempts for the release versions, accounting for the varying consistency of these latest products. Upscaling by zooming blocks is not higher resolution at all!

Posted by: dvandorn Jan 24 2015, 01:38 AM

Do you think the "munging" might be one last attempt by the OSIRIS team to resist releasing their images, by releasing degraded versions? Or does it look more to you like these things are the result of processing by the people who actually published them? I mean, even at the best native pixel resolution, a lot of them look, I don't know, almost de-focused.

Also, am I right in assuming that all of the various releases of these images, including the ones released on ESA's own website, have the same issues?

Posted by: Explorer1 Jan 24 2015, 01:47 AM

Presumably the 'pipeline' isn't the same one that NAVCAM has been using for all the releases since arrival, so there's bound to be issues. Never attribute to malice, etc. etc...

Posted by: Deepnet Jan 24 2015, 02:57 AM

@elakdawalla , I spent some time looking all over the small lobe NAVCAMs for the context of the http://www.esa.int/spaceinimages/Images/2015/01/Comet_from_8_km and couldn't find a match - quite some puzzle.
The image caption gives 15cm / pixel. Times 2048 is ~30m across ( if that refers to the public pixels rather than the originals ? ) , which is few NAVCAM pixels.

Interestingly Holger Sierks is not the Primary Instigator of the OSIRIS project.

Horst Uwe Keller led the team to built Cameras for space missions at the Max Planck Institute, first in Katlenburg-Lindau and now in Göttingen.

Keller was the driving force behind the Halley Multicolor Camera HMC for the Giotto mission.

After the one image success with this camera his team also was selected to built the two cameras on Rosetta.

Sierks took over OSIRIS after Keller retired.

Sierks has stated publicly at AGU that he was opposed to releasing the OSIRIS images, even to other Rosetta teams, giving as reason that others may make discoveries within them before his team.

@Explorer1 , all the OSIRIS images released so far have been very degraded and cropped, so by Occam's Razor this is unlikely a faulty image processing pipeline, Hanlon's Razor does not apply.

Posted by: machi Jan 24 2015, 04:14 AM

Here is very rough comparison with older OSIRIS image.
These "towers" on the head are visible on many NavCam images but almost always from very different angle, so it's not immediately recognizable.

Posted by: elakdawalla Jan 24 2015, 04:29 AM

Ah, you found it, Machi! Thank you.

The "munging" results from these images being prepared for print publication -- they're cropped because they're used as illustrations for the Science magazine articles; they are resized because they're being taken through some sort of desktop publishing software for annotation before being exported to their present format. I'm not saying it's deliberate down-grading of the quality, it's just that these images are meant to be printed in a magazine and were never created with a digital device as an intended end product. But they're all we have to work with at this point.

Posted by: katodomo Jan 24 2015, 08:46 AM

In a TV interview posted http://www.unmannedspaceflight.com/index.php?showtopic=7896&view=findpost&p=216894 Sierks has some DIN A3 and DIN A2 glossy OSIRIS printouts on his table (at about 2:05-2:10), in either case not quite filling the format, and in some cases with the paper cropped (automatic cut). I'd assume these were printed inhouse, which suggests they'd use a plotter with anywhere from 300 to 1200 dpi. At 600 dpi DIN A2 is about 14k x 10k pixels. The pictures might be from the processing pipelines for these or other inhouse printouts.
I'm halfway tempted to run one or two through a plotter at work to see how it'd turn out printing them at that size...

Posted by: Habukaz Jan 24 2015, 10:51 AM

There have been at least two 2048 x 2048 pixel (CCD's resolution) OSIRIS narrow angle releases thus far, including the 8 km one in the most recent OSIRIS batch (and http://www.esa.int/spaceinimages/Images/2014/09/Comet_on_5_September_2014 from September).

I haven't browsed all the scientific papers, but a lot of the poor-quality images appear in these articles, so I guess that there is a possibility that they've simply released most or some of the OSIRIS stuff that they published in the journal (and in a journal, crops tend to be the most relevant, I guess). For example, the 8 km picture is the http://www.sciencemag.org/content/347/6220.cover-expansion for Science, and I am not sure if it's actually used in a scientific context (i.e. it's eye candy?), so it has not been cropped but released as it was given its purpose.

In my interpretation, they simply haven't released that many OSIRIS images specifically for the internet audience yet, which is a shame. The 6 month embargo for OSIRIS data from August (month of arrival) would end in February/March (unless things have changed), so hopefully they'll step up things then.

Posted by: neo56 Jan 24 2015, 06:14 PM

I finished two videos using NavCam mosaics. Frames between each mosaic are interpolated with a morphing software. The gap between some of the mosaics was too big to obtain a single video.

https://www.youtube.com/watch?v=j64aqTWfSBI

https://www.youtube.com/watch?v=qCFEiR6oCeM

Posted by: ap0s Jan 24 2015, 11:20 PM

What are the long term plans for Rosetta's orbit? Will it remain at 30km as it gets closer to the sun?

Posted by: bigdipper Jan 25 2015, 12:42 PM

Is the flex/return between the two lobes at the end of video 2 a morph/processing artifact?

Posted by: Sherbert Jan 25 2015, 01:35 PM

[quote name='Habukaz' date='Jan 22 2015, 08:34 PM' post='217264']
What the heck is this thing?

It took some time to work this out, the shadows at first seem to be all wrong, but it does make sense if you look at it as two steps that merge into one at the near end. I have marked the edges of the steps on the close up below. I have also added a another context image for the OSIRIS 8Km image using the ESA region map.

https://www.flickr.com/photos/124013840@N06/16177086817/

https://www.flickr.com/photos/124013840@N06/16363047795/in/photostream/

Thanks Machi for the context. Another good view from side on can be seen in the middle of the head in this OSIRIS WAC image.

http://www.esa.int/spaceinimages/Images/2015/01/Comet_wide-angle_view

Posted by: neo56 Jan 25 2015, 01:49 PM

It is due to an artifact on one of the NavCam mosaics. The 4 NavCam pictures which compose this mosaic don't overlap really well, resulting in a distorsion.

Posted by: Bill Harris Jan 25 2015, 02:34 PM

In my dust jet study I found one released OSIRIS image from October to be a mirror image of the "original".

http://univ.smugmug.com/Rosetta-Philae-Mission/Rosetta-Dust-Jets

--Bill

Posted by: neo56 Jan 25 2015, 04:48 PM

I made my best to correct this distortion. Here is the https://www.youtube.com/watch?v=qCFEiR6oCeM

Posted by: Gerald Jan 25 2015, 05:44 PM

As the comet becomes more active, they'll probably need a larger safety distance, but they may try fly-by s.
I'd think, they'll prepare two or more plans in parallel to be ready for more than one scenario.

Posted by: Sherbert Jan 25 2015, 10:25 PM

We already know about the February 14th fly-by as close as 6Km from the surface I believe. The current orbit will go out to 140Km before it dives back in towards the comet. A good chance to get close to those larger "grains" in their bound orbits.

Posted by: elakdawalla Jan 26 2015, 03:47 PM

The 6-month clock starts from the date of Philae's landing, not Rosetta's arrival so it'll be May 19 when we can expect data. However, it is extremely common for first data releases to be late, especially from camera teams, both NASA and ESA, so don't hold your breath!

Posted by: Habukaz Jan 26 2015, 04:43 PM

Hmm, OK. That connection doesn't seem to have been made in the http://news.sciencemag.org/europe/2014/11/tensions-surround-release-new-rosetta-comet-data article I read some time ago, hence the confusion.

Posted by: katodomo Jan 26 2015, 05:29 PM

It's rather telling that only the MIRO team has so far posted May 19th as official PSA/PDS deposit date, while the other teams rather conspiciously do not mention that date specifically. It's additionally telling that many of those teams only mention PSA, not PDS - so I wouldn't be surprised if there'll be a difference in deposition schedules.

Posted by: djellison Jan 26 2015, 05:54 PM

Honestly, I'm not expecting anything on the PDS from Rosetta's camera teams in 2015.

Posted by: Gerald Jan 26 2015, 10:38 PM

As far as I understood, Ptolemy measured all m/z up to over 100. Sample collection worked rather unconventional through the exhaust vent, which fortunately is located at the bottom of Philae, such that during 1st td a sample probably got accessible for analysis. That makes data analysis rather challenging.
Therefore I'd guess, that they'll be able to deliver EDRs, but I could imagine that RDRs may need some more time for a final release.
In the meantime it's likely that we'll hear from preliminary analysis results. (I'm hoping for within February to learn more.)

Posted by: stone Jan 27 2015, 06:10 PM

Yes Ptolemy is above 100m/z and COSAC upto 300m/z.
The sniffing is done through gas coming in through the exhaust in both cases. The COSAC exhaust is at the bottom of the lander while Ptolemys exhaust is at the top. The data analysis for a sniffing spectrum is complicated because you see all species at once and due to the 70ev ionization used you get fragmentation and even more peaks. But both Ptolemy and COSAC are in the middle of data analysis and I think the data will be published in the first round of the Lander articles. So you have to wait a little longer for the look on a nice set of organics in the data.

Posted by: eliBonora Jan 28 2015, 09:03 PM

21 Jan CometWatch
seems to be a jet there!

https://flic.kr/p/q2kzvq

Posted by: fredk Jan 28 2015, 09:53 PM

Yes, it's visible in the original frame. And it seems to be coming from the sunlit side of a pit.

This looks similar to the OSIRIS release image, where to me it also looks like the jet is emerging from the sunlit side of the pit (circled in my image), rather than the bottom:

Presumably that's where the most intense heating is.

Posted by: MargaritaMc Feb 6 2015, 06:39 PM

Has anyone any more information about the "little white blobs" on the NAVCAM image posted today on the Rosetta blog?
http://blogs.esa.int/rosetta/2015/02/06/anuket-vs-anubis-cometwatch-31-january/
The blog post says

but are they very small specks near to the camera, or bigger objects nearer to the comet?

Posted by: neo56 Feb 6 2015, 06:49 PM

My take on NavCam mosaics from 16 to 22 January:
https://flic.kr/p/r3dj53 https://flic.kr/p/q7ann6 https://flic.kr/p/r1FTSq https://flic.kr/p/q8mVvN

https://www.youtube.com/watch?v=s3qflVyfCsk between 2 November and 16 January.

I'm working on the very impressive last NavCam mosaic!

Posted by: neo56 Feb 6 2015, 08:33 PM

Here is my take on the latest NavCam mosaic of 31 January:
https://flic.kr/p/r5qDEn

These streams of gas and dust are really impressive! We can even see the silhouette of the nucleus against the comet's coma.

Posted by: flug Feb 7 2015, 03:32 AM

What this reminds me of, is the http://www.unmannedspaceflight.com/index.php?s=&showtopic=7896&view=findpost&p=216807.

What it looks like (to me) in this photo is that similar blobs are all over the place in 'near comet' orbit. Or maybe some of them are above escape velocity and on their way out of there--who knows? Presumably some of them that look like streaks are moving pretty quickly. Without knowing the exposure length of the photos it's hard to say how quickly. But objects going less than 0.1 m/s or so don't get too far above the surface and escape velocity is somewhere around .75 m/s. Objects in bound orbits fairly near the comet will be nearer the upper end of that range. Objects taking a one-way trip off of the comet could be going any speed above that.

If you look at, for example, the bottom part of the image you see the side of 67P that is totally in the dark. Yet above it are numerous white blobs. My take on those is they look like rocks or blobs or particles or whatever that are above the surface enough to be out of the shadow and in the sunlight. Thus they show up brilliantly in contrast with the dark comet behind.

Some of the other white spots surrounding the comet, I suppose *could be* stars (I don't think so just because the exposure level seems wrong etc.; haven't seen stars in other similar photos). But you don't see stars through the dark side of the comet! Those spots showing up above the dark side of the comet must be *something* else.

All speculation, of course. But there are so many of those spots & blobs, they are pretty hard to ignore.

Posted by: flug Feb 7 2015, 06:02 AM

To answer your question more directly, what they look like **to me** is rocks of various sizes more or less surrounding the comet on all sides. Also, this is more or less what you would expect from an active comet that is actively expelling things. If it is expelling dust etc at high velocities, my expectation would be that it is also expelling larger objects at somewhat lower velocities, perhaps ranging in velocity from zero up to the velocity of the dust. That would leave some things, particularly smaller grains perhaps just a bit bigger than the dust, leaving the area of the comet at fairly high speed while other things (often bigger chunks) might be found meandering about quite close to the comet. It's quite possible we're seeing both of those things in the photo.

I don't know any what to prove that is what they are, though, short of several photos taken in fairly quick succession and at known intervals, where you could measure the angular velocity of individual 'blobs' and then see how those angular velocities would fit into various orbital scenarios if the blobs are orbiting or traveling at various velocities.

What they, or some of them, could be:

* Smaller particles near the camera. There is undoubtedly some amount of dust particles near Rosetta--the only questions would be how many are there and how visible they would be in a photo like this.

* Stars. Stars could be ruled in or out by getting the SPICE data & reconstructing the time/direction of the photos and resulting background starfield via software. Or by taking repeated photos and plotting the objects' movement.

* Glitches--cosmic rays striking the detector, bad pixels, dust on the focal plain of the camera, etc

* Maybe something else we haven't thought of yet

Posted by: eliBonora Feb 7 2015, 06:24 AM

Here our 31 Jen CometWatch

https://flic.kr/p/qMSBHG

Posted by: MargaritaMc Feb 7 2015, 01:33 PM

Many thanks for the replies. Very much appreciated!
Regarding (some of) the dots being stars - as was pointed out by flug, the dots that are shown up against the darker background of the comet's unilluminated area can't be stars . But a commentator on Asterisk, the Apod linked discussion forum, madehttp://asterisk.apod.com/viewtopic.php?f=9&t=34418#p239307 for the somewhat similar Osiris image that was a recent Astronomy Picture of the Day.

My ability to work out what stars would be within Rosetta's field of view is inadequate to assess it.

BTW - I've posted ahttp://asterisk.apod.com/viewtopic.php?f=31&t=32292&p=239427#p239427 on the Asterisk board. (I've been a member there for longer than I have been here, and have been routinely contributing to maintaining the Rosetta thread in Breaking Science News.)

Posted by: Gerald Feb 7 2015, 02:01 PM

The range is from sub-millimeter to meter scale grains, the latter in about 150 km distance.
See also http://blogs.esa.int/rosetta/2015/01/22/giadas-dust-measurements-3-7-3-4-au/, http://www.sciencemag.org/content/347/6220/aaa3905.abstract, and http://www.hou.usra.edu/meetings/lpsc2015/pdf/2420.pdf.
Ejected grains are up to a few centimeters. But this may change with increasing activity.

CR hits, stars, etc. are rare.

Exposure times for NavCam are roughly 4 seconds, may become shorter closer to perihelion.

Posted by: Paolo Feb 7 2015, 04:38 PM

I think the detection of meter-sized fragments near C-G may vindicate Giotto's Optical Probe detections of "cometlets" at Grigg-Skjellerupp. opinions anyone?

Posted by: Phil Stooke Feb 7 2015, 07:05 PM

This phenomenon of small fragments moving near the nucleus was also very clearly seen at Hartley 2.

Phil


http://science.nasa.gov/science-news/science-at-nasa/2010/18nov_cometsnowstorm/

Posted by: Ron Hobbs Feb 10 2015, 03:43 AM

Universe Today is showing a new Navcam image from Rosetta, Feb. 3. I don't see it posted on the Rosetta page, but it is a fascinating image. This is going to be a wild ride.

http://www.universetoday.com/118901/rosettas-comet-really-blows-up-in-latest-images/

Posted by: katodomo Feb 10 2015, 06:58 AM

It was posted on the blog yesterday: http://blogs.esa.int/rosetta/2015/02/09/last-waltz-at-28-km-cometwatch-3-february/

Posted by: neo56 Feb 10 2015, 01:59 PM

My take on the NavCam mosaic of 3 February:
https://flic.kr/p/r63a93

Posted by: dvandorn Feb 10 2015, 06:13 PM

It may just be a function of the viewing angle, but, in the February 3 image, for all the world it looks like there are jets coming off of the near lobe of the comet pointed almost directly away from the camera, flowing parallel to the neck and then striking and flowing off of the far lobe. I can understand the striations on the underside of the neck leading up into to the far lobe, if that's what's happening -- they're the result of "wind" erosion.

-the other Doug

Posted by: scalbers Feb 10 2015, 06:19 PM

Looks to me like some shadowing effects to sort out with this interpretation.

Posted by: fredk Feb 10 2015, 06:57 PM

This is a spectacular view!

I think that we may be seeing time-variability in jet activity. If we compare what appear to be sunward-directed jets from sunward-facing sides of pits, the jets seem to have changed over the interval between neighbouring frames - compare the arrowed features:

Of course the viewing angles have changed a bit between those frames. But it would be interesting to see a series of frames to look for fluctuations in the jets...

Posted by: Fran Ontanaya Feb 10 2015, 07:00 PM

Are any of the jets pointed to the inner side of the opposite lobe? It would be nice to see the rate of erosion from particles hitting it.

Posted by: mcgyver Feb 13 2015, 10:25 AM

Summary: OSIRIS cam revealed at list 350 micro-satellites orbting around comet, sized from 4 cm to 2 meters.
This means several pixels in each image, apparently being surface features, are actually "flying" features.
Unfortunately it is impossibile to distinguish "surface pixels" from "orbiting pixels" without a 3d image. But I don't think Rosetta is capable of taking 3d pictures of moving objects.

Posted by: Sacha Martinetti-Lévy Feb 13 2015, 06:10 PM

(Apologize my poor English)

Velocities might be low. There is also the parallax. A sequence of pictures with a good time step can be used for 3D images at such distance. When I travel with plane, I like to take clouds, mountains, others planes with two, or three seconds between shots, and make 3D with. It is the same process. Like an anaglyph of a planet made with its rotation (like Dawn, on another topic.) If moving objects are slow enough and/or far, may be it is possible.

But I don't know how fast are the cameras. And albedo is so low... Thought, there are great 3D masters, here, who I lurke since a decade. I am sure they have an idea, and better than mines

Posted by: neo56 Feb 14 2015, 01:14 PM

A composite of the two NavCam pictures of February taken more than 100 km away from the comet:
https://flic.kr/p/qTNWQ1

Posted by: Explorer1 Feb 16 2015, 02:38 PM

Flyby navcam's are up:


http://blogs.esa.int/rosetta/2015/02/16/cometwatch-14-february-flyby-special/


Some of those 'cosmic ray hits' are suspiciously large (from the zip file).

Posted by: Gerald Feb 16 2015, 08:50 PM

Some rather bright ejected grains, yes.
Fortunately none of the really big ones hit Rosetta.

Posted by: Explorer1 Feb 16 2015, 09:23 PM

Given enough time, one could figure out their trajectories and orbits; maybe arrange for a close look at one later in the year?
That paper said some might be as big as Rosetta itself, correct?

Posted by: Gerald Feb 16 2015, 11:47 PM

At present moderate activity level we still see probably two populations in terms of grain size. The freshly ejected grains resulting in the streaks on the Navcam images will be up to the centimeter range, whereas the distant grains in bound orbits may reach up to a few meters diameter comparable to Rosetta without the solar panels.
But who knows when the next outburst may eject large grains in the meter scale.

The distant large grains in bound orbits should be near a velocity of 10 cm/s (about 7 cm/s at 150 km distance) relative to the comet, such that if one really decides to visit one of those bound grains from some distance, it would be possible to aim almost straight to it. Better of cause would be a three-dimensional map of the bound grains by stereo imaging and trajectory estimates. I could well imagine, that the OSIRIS team is working on such a survey, particularly since they've numbered the grains in one of the papers. Such a survey would also make sense in order to compare bound grains before and after maximum activity to esimate the evolution of the bound grain population over longer periods of time.

Posted by: ngunn Feb 17 2015, 12:23 AM

Would it really be so bad if one of these low velocity lumps encountered Rosetta? Philae during its bounce took a few knocks which altered its rotation state yet it survived to take images of its landing site. Rosetta presumably would be able to recover from an unplanned change to its rotation state.

Posted by: dvandorn Feb 17 2015, 01:16 AM

I'd imagine that would depend on the size and mass of the lump, its velocity and where on the spacecraft it hits Rosetta. Also, a lump or clump could hit in a bad spot -- on the outer lensing of OSIRIS, say -- and leave enough material to degrade the imaging.

Fingers and toes crossed, nothing terribly untoward will happen. But I gotta think the mission planners knew they'd be running such risks when they planned extended operations inside the coma of an active comet.

Posted by: Explorer1 Feb 17 2015, 01:17 AM

An unplanned science interruption is probably not on the science team's list of priorities. Managing to close in enough to resolve some of them as more than just points probably is though!

It's funny that C-G as a miniature planetary system with moonlets (micromoonlets?) has gone pretty much unreported; even Phil Plait's recent blog post just assumes they are cosmic ray hits (to be fair, so would anyone after this many years of seeing raw images): http://www.slate.com/blogs/bad_astronomy/2015/02/10/rosetta_new_images_of_comet_show_it_outgassing.html

Posted by: Phil Stooke Feb 17 2015, 01:33 AM

Nice!

Phil

Posted by: katodomo Feb 17 2015, 07:13 AM

The paper gave an upper boundary of up to 2 meters based on albedo estimates. Rosetta is 2.8x2.1x2.0 meters with a solar panel wingspan of 32 meters.

Posted by: eliBonora Feb 17 2015, 09:23 AM

Some flyby's processing

https://www.flickr.com/photos/lunexit/15935505634/

https://www.flickr.com/photos/lunexit/16550376871/

https://www.flickr.com/photos/lunexit/15928651694/

Posted by: Sacha Martinetti-Lévy Feb 17 2015, 12:26 PM

Great pictures as usual, Eli. You don't forget the albedo, even it's useful for human perception of space objects, it's rare and difficult without colors.
.
The 2nd and third are awesome. Full of detail.

Posted by: neo56 Feb 17 2015, 03:34 PM

My take on the flyby mosaics:
https://flic.kr/p/rdoEX5 https://flic.kr/p/rdrqf3

https://flic.kr/p/qVZG7u https://flic.kr/p/qWZ5XT

And two close-up on Imhotep region from the 3rd mosaic:
https://flic.kr/p/rdvgam https://flic.kr/p/qWcqzv

Posted by: jasedm Feb 17 2015, 04:07 PM

Fabulous mosaics - thank you Eli and Neo!

Posted by: Sherbert Feb 17 2015, 09:02 PM

Thanks to Eli and Thomas for the lovely mosaics.

I am fascinated by the right hand close up of the Imhotep region. The formations on the far side of the plain have a "glassy", sort of shiny appearance. This is certainly a phase angle effect, but for me it lends credence to the composition ratios suggested by the ESA teams. That is about 70% dust, 25% volatile ices and 5% organics. It looks a lot like rock, but the reflectivity is all wrong. Most of all, the way all the material appears SO eroded on a body with no atmosphere to speak of, no surface fluids either. This for me is the most clear evidence that 67P is made of material totally alien and incomparable to anything on Earth.

Posted by: SteveM Feb 18 2015, 02:06 AM

Great work with the mosaics. I can't help thinking that if we're getting images this good from Navcam, what will the OSIRIS images look like?

Posted by: Sherbert Feb 18 2015, 10:03 PM

So what are we to make of theses layers seen in Phil's image and visible in Eli and Thomas's mosaics, as well as many other images over the last six months. This NASA article and the attached paper make interesting reading.

http://www.nasa.gov/jpl/rosetta/why-comets-are-like-deep-fried-ice-cream/index.html

The estimated porosity of 70-80% for 67P strongly suggests it has an inner core of Amorphous Ices. Recently the OSIRIS team suggested a layer of surface, as much as 20m thick, is lost during the weeks around Perihelion. The critical temperature mentioned in this article of 150K would thus move further below the surface and initiate the formation of new layers of "chocolate covered ice cream". In the process, the phase change would release considerable amounts of energy and a significant change in volume allowing sublimated gases and possibly liquids to collect below the surface in high pressure pockets, the Cryovolcanic equivalent of magma chambers. All sorts of mayhem could then ensue at that point. The oily organic boundary may lubricate, or even create, large area fracture planes just to add to the show. I have numbered some of the more readily discernible layers at Imhotep.

https://www.flickr.com/photos/124013840@N06/16387284287/in/photostream/

The previous orbit of 67P had a Perihelion twice as far from the Sun as the current one, surface loss would be much, much less, leading to thinner crystalline ice layers. Unfortunately for this idea the layers appear to be upside down. The thicker upper layers may well be due to various possible forms of resurfacing like Cryovolcanism, a large increase in coma fallout and dispersal of debris during major activity at Perihelion, all scenarios made possible by the recent change of orbit.

I wouldn't really rate this idea as a viable theory, but maybe some discussion might bring enlightenment.

Posted by: Gladstoner Feb 18 2015, 10:57 PM

Interesting paper, Sherbert.

I believe the fine layering is due to coma fallout that occurred during and after multiple perihelion passages (as you mentioned). The beds are probably not primordial or really ancient, since they have not been mixed up (time averaged) by eons of impacts. The regular jointing (barely visible) may indicate that they didn’t form in the very recent past (i.e. last few orbits or so; the smooth surface, on the other hand, is likely a very recent layer).

Perhaps there is a ‘'battle'’ between deposition and erosion. In other words, the particles are deposited as they slowly drift back to the surface after being expelled, while outgassing and surface disruption removes them again in places (see the ‘swept clean’ areas in some of the mosaics above. By chance, as in this case, there will be patches or areas of layering that manage to survive disruption. It kind of reminds me of the earth’s rock cycle in miniature -- with ancient basement rock, old strata, and recent sediment -- but with radically different processes in play (of course ).

Posted by: Sherbert Feb 19 2015, 09:52 PM

I have to agree with you Gladstoner, layering due to deposition was my main thought until I read the NASA article. It is perhaps a too Earth centric view though. Sediments form consolidated, hard rock layers on Earth, in large part due to the Earth's gravity providing the high pressure to compress them, via the weight of subsequent deposition layers. The minuscule gravity of 67P, I would think, would be insufficient to compact the dust/gravel to form these seemingly solid, rock like, layers. Also this dust/gravel once at the surface, even more so once expelled, is virtually devoid of volatiles, so if the outer sub-surface layers of the comet are compressed dust and coma fallout, sublimation activity would surely be minimal. In my view, this rules out dust and coma fallout deposition as a large scale structural process.

Right from our first views of 67P in August, I have been convinced that the surface is predominantly a volcanic landscape. Until now I could not really come up with a regularly available energy source well below the surface to account for this apparent Cryovolcanism. An intermittent source from impacts was the best I could do. I may therefore, be clutching at straws, but pockets of pressurised, molten material, dozens, or hundreds, of metres below the surface created by the change from Amorphous ices to a more compact, lower energy, crystalline form, could readily explain many of the features we see at the surface as well as the expected kilometre scale, supersonic "jets".

I do like the "battle" between deposition and erosion idea as a predominant comet resurfacing process. It certainly helps to explain the observed, surprisingly, homogeneous colour of the surface layer. In the Northern "Duckiesphere" deposition appears to be in the ascendancy, in the "sunnier" South, erosion. In the equatorial region it seems fairly even, some dust/gravel, but lots of rubble, the energy flux not being enough to eliminate larger stone and boulder sized pieces from the surface.

Posted by: Gladstoner Feb 19 2015, 10:43 PM

I understand, but with the extremely weak gravity and complete lack of disruptive processes (wind, precipitation, etc.), some very minor compaction and weak electrostatic attraction may be enough to hold the outcrop together. That is, until outgassing and mass wasting removes it. Plus, there may be components of comet composition (organics?) that could bind the particles together.



Yes. I think there is a valid analogy between the comet's surface and a volcanic landscape. I'm reminded of the Ubehebe maar craters in Death Valley NP, California. Venting/explosions excavate the pits, ash and cinders settle over the landscape, process repeats:



Perhaps the amorphous-to-crystalline change does play a role. I must say I'm still struggling to imagine how the heating from limited sunlight can cause huge outbursts from below the surface (particularly with the repeating activity of 17P/Holmes).

Posted by: Sherbert Feb 20 2015, 06:47 PM

I have often wondered how solid the apparently solid outcrops actually are too. Once the solid, frozen volatiles have sublimed, you are essentially left with a pile of dust, which seems to retain its shape by, as you say, weak Van de Waals forces, maybe some "glue" like properties of the organics, one early suggestion was the organics were akin to tar, and the interlocking of the jagged surfaces of the dust grains at a micro scale. It is interesting to see how far Phillae's foot buried itself in a seemingly solid formation at the rear of its alcove/cave.

I also share your doubts about the production of large scale activity from the energy of sunlight acting on the very top surface layers alone. The limited small scale activity seen up until now, yes. This is just simple diffusion of the sublimating gas from the very low volatile content, top sub-surface layers at relatively low pressures through the dust layer, in the process, carrying away small amounts of dust at a few metres per second. Only 1% of the surface area of the comet being active is enough to produce the observed activity, as at December, we have been told.

Even the fourfold increase in the energy of the sunlight at Perihelion is not going to produce activity capable of producing the major terrain changes that have clearly taken place. Some other energy producing process must be involved. Some have suggested rotational energy, others tectonic activity resulting from mass loss, or gravitationally created stresses, particularly in the Hapi region. These are probably all viable, but are localised to specific areas of the comet.

I should say at this point, this theory of the amorphous ice/crystalline ice boundary is not new. I just thought the layering was possibly some visual evidence of it occurring. An "onion" analogue for cometary structure has been proposed, but I am not familiar with the details and the mechanisms proposed. The concerted attempt to determine the temperature gradient through the surface layers by both Rosetta and Phillae is in place to investigate this very process. The limited CONSERT data so far, will certainly hinder this investigation and the lack of any real seismic data from MUPUS. For me, it answers too many questions for it not to be the key mechanism in the evolution of 67P.

Posted by: Gladstoner Feb 24 2015, 02:46 AM

But yet, we see the tremendous outbursts and dramatic surface changes....



Perhaps pockets of highly volatile ices (CO2, CO, NH3, CH4, and/or something else?) sublime and are released vigorously when overburden is sufficiently weakened by some of the processes mentioned above. Speaking of volcanic analogies, I'm reminded of the explosive release of gas when the side of Mt. St. Helens slid off in 1980.



It's possible that all of the processes mentioned already, as well as some that no one has even thought of yet, could play a role to a degree. I'm afraid a complete answer won't be possible until a drill core sample can be properly examined in the lab.

Posted by: atomoid Feb 24 2015, 06:31 AM

I keep thinking the only significant source of energy is absorbed infrared conducting inward to dissociate the liquid glues holding together outcroppings of aggregates, and it would seem all the action is limited to the outermost onion skin boiling away as a layer of chunky grime, seeming hardly enough to do much in one pass, though perhaps plenty over tens of millions.

I'm wondering what kind of radiation environment may result during a direct CME hit and how much energy may that produce and at what distance below the surface could such energy be released?
it brings to mind (and i am completely out of my depth here) how reactors use boron to slow down the radiation enough so that it can interact, otherwise it shoots by and that energy is not captured.

Posted by: DFortes Feb 24 2015, 08:34 AM

This is because boron has one of the largest neutron absorption cross sections of any element. Other comparable elements are cadmium and gadolinium, which we use as shielding foils in neutron scattering experiments.

See the NIST tables of neutron scattering data and look at the right-hand column (Abs xs) for each element.

http://www.ncnr.nist.gov/resources/n-lengths/

Posted by: Gerald Feb 24 2015, 12:10 PM

Based on the left image of figure 3 of http://www.srl.caltech.edu/ACE/ASC/DATA/bibliography/ICRC2005/usa-mewaldt-RA-abs3-sh12-poster.pdf, the definition of http://en.wikipedia.org/wiki/Electronvolt, and the http://en.wikipedia.org/wiki/Solar_constant here my back-of-an-envelope calculation:
1e11 protons per cm² with an estimated average energy of 10 MeV during a large SEP event results in an energy of
1e12 MeV/cm² = 1e16 MeV/m² = 1e22 eV/m² = 1e22 x 1.6e-19 J / m² = 1.6e3 J/m².
Assume the peak of the SEP lasting 1 hour (see figure 3 of the paper, the SEP actually lasts longer), we get less than
(1.6e3 J/m²)/3600s = 0.44 W/m².
The solar (almost) constant is about 1.36 kW/m² at Earth distance from the Sun, hence about 1.36/9 kW/m² = 151 W/m² at 3 AU.
So we are below 1/100 for the energetic particles relative to the total solar irradiance during a SEP event.

The penetration depth is probably in the mm scale for most of the protons in terms of energy, see e.g. http://www.sciencedirect.com/science/article/pii/S0169433212021630, and consider porosity.
Some high-energy end particles in the GeV range may penetrate up to the meter scale. But that's probably less relevant in terms of integrated energy release per area or per volume in that depth.

Posted by: Holder of the Two Leashes Feb 24 2015, 02:18 PM

One small correction here. Boron is used to capture neutrons in a reactor, stopping the reaction. It is carbon, hydrogen, deuterium, and/or oxygen that are the stuff used to slow them down without significant capture, increasing the reaction. And I think it's the latter that atomoid had in mind.

Posted by: Sherbert Feb 24 2015, 09:30 PM

I am rather hoping that what we have seen up until now are just powder puff stuff compared to what occurs around Perihelion. Monitoring of the activity around Perihelion has previously only taken place from Earth, when a few "jets" were able to be identified after extensive image processing of a coma extending over tens of thousands of Kilometres from the nucleus. The ESO VLT image of 67P taken in August already showed the coma and developing tail extending around 19,000 Km. The dust columns we have seen of a few kilometres in size are just not going to be seen in that sort of glare. Hence the expectation of activity way more dramatic than what we have seen so far.


It is the mechanism for the formation of pockets of volatiles that is the issue here if we are to explain the surface of the comet as we see it now. Larger amounts of volatiles are postulated to be found well below the surface, but the vast majority of energy from the Sun is not going to penetrate that far into the comet. That tiny amount of energy that does trickle down to the amorphous ice layer however, may be enough to trigger the phase change to crystalline forms of ice, releasing energy and reducing the volume of the ice. The volatile ices rapidly sublimate to fill the space created, resulting in a pressurised void beneath the surface. The loss of surface material and its thermal properties, are therefore, critical to new pockets being formed.

The layers of material above such pockets, could be many metres thick and although porous are going to enable higher gas pressures to build up. In some places natural fissures and cracks will allow the gas to escape to the surface fairly quickly taking large quantities of dust with it, weakening and eroding the structure of the material beneath the surface. The surface will then collapse to fill the void, creating depressions and pits. In other places, the pressure will build up and up, distorting the surface above into a dome shape until, at some point, there is a catastrophic failure, as at Mt. St. Helens, and large amounts of comet material are displaced. The huge caves and overhanging crater rims are the result.

Such may be the build up of vapour pressure in these pockets, the water ice could melt to become liquid water that then mixes with the dust and organic goo to form Cryovolcanic lava. This liquid, or semi-liquid, mud is expelled by gas pressure from the caldera and flows over the surface until it freezes. Since the surface of the comet is around 220K the first outpouring would instantly freeze very close to the outflow point, successive layers would build up creating a rim of frozen material, depleted in volatiles and subsequently more resistant to erosion by sublimation. Once the release of pressure means the vapour pressure can no longer maintain liquid water, or prevent the filling of the hole in the surface with frozen material, the "lava" will freeze into a solid lake of frozen mud with a level surface. Subsequent sublimation of the remaining volatiles near the surface will result in a flat plain of dust surrounded by a rim. This rim would be layered, each layer a slightly different mixture of dust, organics and volatiles. The circular mounds of all sizes in the Imhotep depression are perfect examples of this, some even show evidence of material flowing down the outside of the rim. Those eruptions that occur on the side of slopes leave an overhang, bits of which later through erosion, fall onto the flat frozen lake below. Hence we see many of the dust circles with rubble strewn on one side.

The gas escaping into the vacuum will be travelling at huge velocity and will likely carry debris of many sizes to a height hundreds, or even thousands of Kilometres above the comet's surface. Terrestrial volcanoes can expel huge chunks of material many Kilometres into the atmosphere, against a gravity 10,000 times greater than 67P's and the weight of a column of air many miles thick. On 67P there is no atmosphere, so no weight of atmosphere to slow things down. These are the "Jets" I am looking forward to.



Agreed, 67P is a complex system of many processes linked together. Given the porous nature of the comet interior it would seem probable that much of the heavier dust migrates to the lobes due to centripetal forces, leaving the region around the axis of rotation richer in volatiles and the ends of the lobes richer in dust. Slabs of this denser material could be flung off the comet by its spin, if a layer of newly crystallised ice forms below the surface with a layer of oily organics exuded at its surface to create a "lubricated" boundary plane. What look like large fracture planes can be seen on the ends of the big lobe.

Would the shift in mass to the ends of the lobes start to stretch the comet, creating fissures and cracks near the axis of rotation exposing the volatile enriched material below? Result, more rapid erosion creates the neck region. One such crack is clearly visible currently which appears to extend along the Hapi region under the dust layer. Deposition of activity and coma fallout clearly has a large part to play in the near homogeneous composition and colour of the surface. Small and medium scale sublimation processes along with thermal cycles clearly play a key role, as erosion mechanisms, in it's appearance too. Internal mass loss should result in buckling and fracturing of the sintered ice crust. Such "mountain forming" is evident around the belly of the big lobe in particular.

As we have now reached the end of the initial close mapping and comet characterisation phase, these are some of the ideas I have been formulating and collecting, based on what has been revealed so far. It does seem to fit together with some degree of plausibility, but there are plenty of other revelations and mysteries to come no doubt, to shatter that illusion.

Posted by: Gerald Feb 24 2015, 10:13 PM

Regarding the cryovolcanos: This may need some adjustment, since inner heat is unlikely. Heating comes from the Sun. Water ice usually doesn't melt below 273 K within a reasonable pressure range (see http://en.wikipedia.org/wiki/File:Phase_diagram_of_water.svg). Under near-vacuum conditions, however, there may be some moderate pressure build-up at 220 K (between 1 and 10 Pa).
The main source for higher pressure potential comes from CO2, CO etc. (http://en.wikipedia.org/wiki/File:Carbon_dioxide_pressure-temperature_phase_diagram.svg) Virulent outbursts should therefore be driven by these highly volatile gasses.
See also the http://en.wikipedia.org/wiki/File:CO2HydrPhaseDiagram.jpg as an option.

Posted by: Gladstoner Feb 24 2015, 11:55 PM

I wonder if certain highly-volatile ices could become superheated even with the extremely low temperatures that one would expect within the nucleus -- even near perihelion. To me, that seems to be the only possible driving force for explosive activity.

Is it possible to estimate the internal temperature of the nucleus, or are there too many unknowns?

Posted by: Sherbert Feb 25 2015, 12:51 AM

Hi Gerald. I am assuming the volatile ices contain a number of different molecules. Carbon Dioxide and Water being the most abundant it would appear from the data released so far. Yes vapour pressures would have to be very high and the energy released by the phase change from amorphous ice to crystalline ice substantial to allow for liquid water, but the presence of Methanol, Ammonia and other volatiles in the mix, which lower the melting point of Water ice, may well change the equation. Methanol and Ethanol mixing with Water is an exothermic reaction too to add a bit more heat to the mix. I also have no idea at what depth this ice phase change might happen. This would have a large bearing on the confinement of any evolved gases. No matter what the pressure, pure liquid Water can not exist below ~253K, so it is asking a lot. The other problem is the lack of pressure at the surface, especially over areas more than a few square metres. So I think its plausible, but a lot more information about the ice mixture and the effect the large amount of dust and the organics have on the possible phases of the volatile ices mixture would be needed.

Certainly the main driver of the gas pressure is likely to be Carbon Dioxide, it has no liquid phase and the change in volume from solid to gas is massive. Nitrogen expands a vast amount when going from solid to gas, but it would seem to be in short supply on 67P. Solid Nitrogen would only be likely in the very centre of the comet in the coldest spots. If conditions do occur that allow some sort of fluid state, I would imagine it would be infrequent and very short lived at the surface, but some type of molten or semi-molten material has flowed on the surface. The other possibility is some sort of plastic flow of this peculiar mixture that makes up the comet. That is a pure guess as I know next to nothing about the mechanisms of plastic flow. As you know I tend to deal in ideas rather than numbers and as I have already said, I am not sure it is a viable theory even without knowing many numbers, but it would explain many of the large scale features on the surface.

I'll leave it to the proper scientists to work out the details.

Posted by: Gerald Feb 25 2015, 10:39 AM

I'm very sceptical about http://en.wikipedia.org/wiki/Superheating in the presence of dust (as nucleation sites).
Carbon monoxide has a boiling point of 81.6 K at normal atmospheric pressure. It will be one of the first ices to sublimate, unless chemically bound.
Since sublimation needs energy, sublimation of (abundant) CO will keep the inner of the nucleus near the melting/sublimation/boiling point(s) of CO (probably the sublimation point at low pressure), until almost all CO is gone. So my guess is, that the inner of the nucleus will stay a little below 70 K.

The covering layers of the nucleus certainly provide some protection of the inner layers, not just in terms of thermal insulation, but also in terms of pressure. That way removal of the top layer at some location may cause a run-away sublimation process due to exposure of highly volatile ices (and might be liquids), think of accidents with pressure cookers.
The process will slow down either after cooling down due to sublimation or due to exposure of deeper layers which have been left below the sublimation point of the respective exposed ices.

Posted by: Sherbert Feb 25 2015, 11:32 PM

Some further thoughts on the possibility of liquids at or near the surface of 67P.

If one looks at molten rock, lava, on Earth as an analogy, its temperature is many hundreds of degrees higher than the ambient temperature at the surface, it does not freeze instantly and can continue to flow for many Kilometres. This often occurs in lava tubes, where a surface skin has solidified insulating the hotter liquid inside. Lava on Earth takes many forms depending on the chemistry of the rock and to a large extent on the amount of gas dissolved in the rock. There is the hot flowing version of lava, but also the slow crumbly, creeping version, various states in between and Pyroclastic flows. Different textures of material with different physical characteristics can be seen associated with possible Cryovolcanic activity on 67P, compositional differences and initial temperature conditions of the original molten, or semi-molten cometary material might account for this in a similar way. The high specific heat capacity and lower melting points of aqueous solutions also contributes to slowing the freezing process due to temperature. So the temperature at the surface might not be so much of a problem as I initially imagined.

The more problematic issue of very low pressure at or near the surface, still remains. The scenario, as imagined, is that at an undetermined depth, but reasonably assumed to be well below the surface, a layer of crystalline ice, made mostly of Water and Carbon Dioxide, but with many other volatiles within it, is formed by a phase change from Amorphous ices at some critical temperature. This releases heat energy, there is a decrease in the volume the ices occupy, creating empty space. This vacuum is immediately filled by the most volatile substances, Carbon Monoxide, Nitrogen and Carbon Dioxide being the primary candidates. These gases are confined by the previously formed crystalline layers above and hence compressed, increasing their temperature and pressure. At some point the local supply of these more volatile volatiles will be all converted, but such is the increase in temperature, the less volatile chemicals would start to sublimate/melt, such as Methanol, Ethanol, Sulphur Dioxide, Water, Ammonia and Methane. All the time these fluids are confined the temperature and pressure will increase, the volume of the pressure bubble increases, more material is eroded from the insides of the chamber. Space is now being taken up by a large percentage of incompressible solid, the dust which makes up around 70% of the cometary material. Thus we start a runaway, self sustaining, growing pressure bubble, within which the temperature is increasing, pressure is increasing, liquids are able to exist, in which gases can now dissolve, Carbon Dioxide being particularly good at this in Water. The material in the pocket can now be considered to be "hot" compared to the surrounding cometary material.

At some point containment is broken and a pathway to the surface and the vacuum is created. The "hot" dust/liquid/gas mixture, "frothy mud", will immediately travel towards the surface. If through narrow cracks, at extremely high speed, further increasing the temperature and pressure, eroding and collecting more material and gas along the way. Turbulence in these flows could be the cause of the "goosebumps" seen by OSIRIS. The highly visible result at the surface, would be your huge supersonic jets. All the time the pressure maintains a high velocity of flow, the temperature and pressure within the jet will maintain the phases of the material. Once confinement is escaped, dissolved gases will start to escape adding to the vapour pressure in the flow of material, the amount of collimation of the jet will then determine how long conditions within the jet can maintain a liquid phase. At the suggested supersonic speeds even a few seconds could mean liquids travelling great distances, Kilometres even, before freezing. That distance will get less and less as the pressure in the pocket is reduced and the size of the eroded caldera increases. Eventually the flow of "hot" material will reduce and the dust/liquid mixture will deposit around the caldera, soon solidify, to form a layered crater rim as the composition of the ejecta changes. Eventually the ejected material will fall within the created caldera rim to form a lake of "warm, fizzy, mud". This will freeze once its temperature and the rate of sublimation and dissolved gas escaping, falls below a level sufficient to keep the "mud" liquid. Eventually the surface layers above the pocket, depleted in solid ice, unable to maintain there own weight, will collapse into the now empty pressure bubble and form a pit or depression.

The longer containment below the surface is maintained the higher the temperature and pressure get, the bubble gets larger until it starts to distort the surface, creating a "pressure dome". More and more liquid could exist containing less volatile, larger organic molecules such as Ethylene Glycol, antifreeze. The heat would also travel down into the comet releasing more energy. At some point a catastrophic failure of the surface will occur and the pressure rapidly released over a large area, propelling large chunks of the surface in all directions. The dissolved gases rapidly expand creating the equivalent of Pyroclastic flows of dust, gravel, shattered cometary "rock" and gas which at their base would maintain a temperature and pressure sufficient to sustain liquified material, which is able to flow over the surface of the comet. In effect Cryovolcanic lava flows. The vast amounts of pulverised cometary material making up the dust cloud of the Pyroclastic flow would travel across the surface of the comet and deposit themselves over huge areas, the dusty looking plains of the Northern Hemisphere. At the top of Hathor cliff there is a distinct surface layer of lighter fine grained material many metres thick, which reminds me of the ash deposited at Pompeii from Pyroclastic flows.

The lack of any such activity up to now suggests this process, if it does occur, happens only at or soon after Perihelion, when the heat flux within the comet's surface layers is at it's maximum. At some time in the past, with supplies of amorphous ice existing closer to the surface, less energy from the Sun would be required, so even though 67P was more distant from the Sun, these processes could still occur, probably over larger areas of the surface too. The big depressions at Imhotep and Hatmehit may well be very ancient. The notorious variability of comet activity, could also be explained. Previously available volumes of Amorphous ice have been used up and until surface loss occurs to enable enough energy to reach deeper into the comet, vigorous activity will be curtailed.

I hope you like the story, its all basic geophysics, but it relies entirely on the assumption that sufficient heat reaches the postulated amorphous ices inside the comet and the overlying crystalline ice layers together with the proposed sintered ice layers making up the comet's "crust", have a structural integrity sufficient to maintain confinement for sufficient time. I am still not entirely convinced, there are one or two too many assumptions involved and entirely too much use of the word "porous" when describing cometary material, but that is the nature of speculation I suppose.

Posted by: tedstryk Feb 26 2015, 12:07 AM

Amazing work!

Posted by: Gladstoner Feb 26 2015, 01:10 AM

Very interesting scenario. I would love for Rosetta to catch the process in the act.

A question about the amorphous/crystalline transition....

Could a reduction in confinement pressure alone be sufficient to trigger the phase change? If so, perhaps solar heating indirectly causes the process as outer layers are slowly weakened as they sublimate.

Posted by: Gladstoner Feb 26 2015, 01:37 AM

The comet 29P/Schwassmann-Wachmann 1 has periodic outbursts (~1 per year) despite its large perihelion distance of 5.76 AU.

http://en.wikipedia.org/wiki/29P/Schwassmann%E2%80%93Wachmann

http://cometography.com/pcomets/029p.html

The solar radiation at that distance is quite feeble, so there is something else going on with this comet, particularly since it has been close to its current orbit since at least 1908.

Posted by: Gerald Feb 26 2015, 10:00 AM

Did you consider the microgravity environment of the comet? Escape velocity is near 1 m/s.

Posted by: Sherbert Feb 27 2015, 12:12 AM

That's one fly in the ointment certainly. How much gas and dust in the inner coma would act to spread out the emerging material is also unknown. As I am assuming these events only take place around Perihelion, the density of the inner coma could be significant enough to deflect back to the surface a percentage of the material. It is interesting to look at the ROLIS images taken at Agilkia. The suggestion in the AGU talk was that the regolith has been mobilised. There is very little dust, it is mainly granular along with numerous pieces of shattered cometary material, so heavier material inconsistent with sublimation residue. This region being one that I suggested might be covered in Pyroclastic flow material, I see this as good evidence that at some point in the fairly recent past this area of the comet was resurfaced in this manner, more likely as low flying fallout given the tiny gravity, rather than as the ground hugging flows we see on Earth.

Also to be considered is the angle to the local surface the rupture occurs. Many of the cave like features appear to have been from sideways ruptures that would eject material closer to parallel to the surface. The escaping gases and dust would tend to carve out the semi-dome shape of these caves while depositing most of the ejecta on the surface. A really good example of this is in the Hapi valley near to the former landing site A, "The Amphitheatre" as Bill H. dubbed it.

https://www.flickr.com/photos/124013840@N06/16631605386/in/photostream/

Such use of Earthly analogies is fraught with danger, but as it is the only reference and language we have, it is petty difficult to avoid. Perhaps this phenomena, however it visually and physically manifests itself, should be called a "Cryoclastic Flow".

Another issue Gladstoner alluded to is the conditions under which this phase change observed by the NASA team occurs. Their experiment involved a critical temperature at the surface of the Amorphous ice, which itself was exposed to vacuum. The cometary ice analogue used contained PAHs (Polycyclic Aromatic Hydrocarbons) to simulate the organic content, but as I understand it, no dust analogue. The critical temperature was 150K under these conditions, but may be different under confined conditions and of course may not occur at all in the presence of a high percentage of dust. So well does this imagined scenario appear to produce the morphology of the comet surface, I am inclined to think that at some level below the surface the conditions are present for the transition to occur. A sort of circular argument I know, but hey I'm not writing a scientific paper here, just figuring it out as I go along.

Posted by: neo56 Feb 27 2015, 07:48 AM

Thanks a lot jasedm, Sherbert and Ted!

Posted by: Gerald Feb 28 2015, 01:09 PM

Maybe in the somewhat metaphorical language of volcanoes, the presumed eruptions on the comet resemble a bit a http://en.wikipedia.org/wiki/Phreatomagmatic_eruption or better http://en.wikipedia.org/wiki/Phreatic_eruption eruption resulting in a http://en.wikipedia.org/wiki/Maar.
The analog ends at the heat source, since it's the Sun in the case of comets, heating the nucleus from the outside, until the heat diffuses to a deeper region with highly volatile compounds, which eventually cause the outburst.

The "eruption" ejects boulders analog to volcanic bombs; gases and smaller grains are lost, since most of them are accelerated to beyond escape velocity. Some medium-sized grains may just hover or dance at some distance over the surface for some time in cases where the interplay of inertia, gas drag and gravity are balanced. The latter may share some properties with pyroclastic flows (except the "pyro") or mudflows.
Things not leading to escape are happening in slow-motion of a few decimeters per second at most (like Philae's landing).

Posted by: dvandorn Feb 28 2015, 04:47 PM

And, what you just postulated perfectly describes the formation of the dust and gas tails (the gas and small grains that achieve escape velocity) and the coma (the material that hovers around the nucleus and eventually falls back).

So, working it from the nucleus end, as you just did, results in what we see from a distance in the coma and tails. Good work!

-the other Doug

Posted by: Sherbert Feb 28 2015, 05:39 PM

Thanks for that Gerald. Pretty much the scenario I was describing, the heat source is different, but the rapid conversion of volatile ices into gas should give similar surface morphologies . These Maars look very similar to that big circular feature at Imhotep and the other smaller ones dotted about in the same area. The image of the phreatomagmatic eruption deposition layers is remarkably similar to what can be seen at the top of Hathor cliff where there is a darker rubbly aggregate layer below a lighter fine grained layer.

https://www.flickr.com/photos/124013840@N06/15866204623/

In other places, the outcrops at the edge of the Anubis and Seth region, show repeated light and dark layers.

https://www.flickr.com/photos/124013840@N06/16278376168/in/photostream/

From the 2003 and 2009 appearances of 67P, maximum activity occurred about a month after Perihelion, implying the transmission of maximum solar energy to the source of the major activity takes a period of time. More evidence that this is a process that takes place well below the surface. Looking at the latest NAVCAM image, there is a long, large cliff running along the edge of the Khepry region, which could be a crystalline ice layer and it appears to be highly consolidated. It may be as porous as a sponge, but its appearance gives me encouragement that there are dense enough layers within the comet to provide sufficient gas containment.

http://www.esa.int/spaceinimages/Images/2015/02/14_February_close_flyby_16_12_GMT

I am liking the physical model more and more, but the crucial evidence for the energy multiplying phase transition actually occurring inside 67P, as opposed to on the surface during the NASA lab experiment, is still missing. I can imagine your information about Carbon Monoxide possibly sublimating deep within the comet, may actually lower the critical temperature under confinement conditions, by providing some internal gas pressure already. MIRO data suggests temperatures below the surface fall from 160k just below the surface, to 30k in the centre. The proposed critical transition temperature of 150K may be only a few metres below the surface, so for the comet Gladstoner mentions, which is much larger, and way less active, the Amorphous ices layer may still be only these few metres below the surface. Its orbit is pretty circular, but over 5 AU from the Sun so sufficient energy transfer from the surface is going to be very slow and major activity limited, but could occur at almost any point in its orbit.

All thats needed now is some CONSERT information to show Amorphous Ice below Crystalline Ice layers, some thermal gradient data to these depths, and some detailed compositional data from a very high speed jet. Let's hope Philae wakes up again before Perihelion, when it might all kick off.

Posted by: JTN Feb 28 2015, 09:53 PM

http://blogs.esa.int/rosetta/2015/02/27/cometwatch-the-challenges-of-a-close-flyby/: a new Navcam image from the close flyby, and an account that suggests we had quite a lucky outcome:

Posted by: Malmer Mar 3 2015, 09:51 AM

Temporary loss of star tracker only affects pointing right?

So there was really never any physical danger. Only risk of loss of science?

Posted by: JTN Mar 3 2015, 09:53 AM

Gosh, an OSIRIS image, at 11cm/pixel: http://blogs.esa.int/rosetta/2015/03/03/comet-flyby-osiris-catches-glimpse-of-rosettas-shadow/.

Posted by: Ames Mar 3 2015, 10:21 AM

Those jagged features are cliff edges.
There are some rocks that appear darker in the bright region (Heiligenschein). A difference in composition?.

Posted by: Habukaz Mar 3 2015, 10:41 AM

The weird curved/bent feature from the 8 km OSIRIS picture released earlier has returned again at the exact same spot, and this time it is easy to see that it is an artefact.

Posted by: ugordan Mar 3 2015, 12:57 PM

I like how the OSIRIS/NAVCAM context image and even the shape model are available in uncompressed PNG form, but the actual high res NAC frame is a substantially compressed JPEG. Classy.

Posted by: Weywot Mar 3 2015, 01:43 PM

Credits: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA

Hi-res: http://www.esa.int/spaceinimages/Images/2015/02/14_February_close_flyby

Rosetta has captured its shadow during the 6 km fly by. Resolution is about 11cm/pixel.

More info in german http://www.mps.mpg.de/3943019/PM_2015_03_03_Rosettas_Schatten_auf_dem_Kometen at the Max Planck Institute, which is in charge for the OSIRIS camera system.

Edit: I missed the link above. But anyways. really cool image of the detail in the Imhotep region. Picture is 228mx228m across. I really hope, the OSIRSI archives are released in a way, that is easyly accessable. When it is released...

Posted by: MahFL Mar 3 2015, 03:10 PM

They won't put the craft on an orbit that collides with the comet, so loss of science would have been the problem if it went into safe mode.

Posted by: Sherbert Mar 3 2015, 08:33 PM

I can't disagree with that this time.

Posted by: fredk Mar 3 2015, 09:14 PM

It would involve strong assumptions to suppose that the compression was intentionally high to reduce what could be seen in the image. We've seen before oddly super-sampled images (and other resolution oddness recently with Dawn, eg) that were likely the result of press release requirements, and almost certainly not the choice of the science team. Similarly here, we know nothing about who determined the degree of compression or why.

Posted by: Phil Stooke Mar 13 2015, 05:51 PM

Wow, look at this great false-color image!

Phil

http://www.esa.int/var/esa/storage/images/esa_multimedia/images/2015/03/false_colour_comet_hapi_region/15307441-1-eng-GB/False_colour_comet_Hapi_region.jpg

Posted by: MarsInMyLifetime Mar 13 2015, 07:05 PM

That image shows the one meteor crater originally spotted by Emily. In the black of the lower right quadrant there seems to be a tinier crater that looks rather similar (the tiny hole on the ridge terminator, just below center here):

Posted by: Sherbert Mar 14 2015, 03:02 AM

It has been noted elsewhere how colour images are so much easier to unravel and pick out patterns and features. This wonderful OSIRIS image is a perfect example. The deformation of surface layers by a pressure bubble forming well below the surface can clearly be seen on the far side of the valley, The resulting catastrophic failure and explosion has ripped a huge gapping hole in the comet. Molten material forced up from the interior has frozen and solidified as a dark igneous type material in a huge plug, totally different in appearance to the lighter surface layers.

The huge chasm extends the other side of the valley and is seen as the void above the Amphitheatre, where the darker igneous type material is seen again. Diffusion of dust through the porous interior to the tops of the lobes, seems to have left the axial regions richer in volatiles, increasing the size and likelihood of these gigantic Cryovolcanic events in the neck region. Less dust, less insulation, heat travels deeper into the comet. Thus a large trench has been blasted out around the axis of rotation to create the neck. Well its an idea, not sure how provable it is, but we seem short on explanations for the neck still, so I'm offering this as my suggestion as a further consequence of the Amorphous/Crystalline ice phase change energy source.

https://www.flickr.com/photos/124013840@N06/16185307724/

Posted by: Herobrine Mar 18 2015, 06:50 PM

Can you help me confirm something?
I'd like to verify that we are only a couple days away from the latest possible date for 6 months worth of raw post-hibernation OSIRIS data to be made publicly available in the archives (or at least, the latest it is supposed to be made publicly available, assuming the statements made by ESA on its blog are true).

It was stated in June 2014:
"All Rosetta science instrument data have a proprietary period of 6 months, after which they will be publicly available in our archives" ( http://blogs.esa.int/rosetta/2014/06/25/comet-67pc-g-in-rosettas-navigation-camera/ )

This was confirmed in July 2014:
"With Rosetta, all data from its 21 instruments (11 on the orbiter, 10 on the Philae lander) are subject to a 6 month proprietary period." ( http://blogs.esa.int/rosetta/2014/07/16/access-to-rosetta-data/ )

Two months ago, I inquired on ESA's blog about why PSA didn't yet contain any post-hibernation OSIRIS data, despite the instrument having been returning data for well over 9 months. ( http://blogs.esa.int/rosetta/2015/01/12/cometwatch-6-january/#comment-322770 )

I was told, at that time, that "the release of science data that is on a six-month proprietary period is made six months after the end of the previous six month period", meaning that the actual longest time there could be from acquisition to release was 12 (6 + 6) months, and that the release would contain all of the data from 12 months prior to release, to 6 months prior to release (so, a six month chunk of data, ending 6 months before it had to be released). I was slightly disappointed to find out the wait time was really about 9 (+/- 3) months rather than "6 months" being the longest that teams could hold the data, but at least I'd been informed of the real maximum delay between acquisition and release (12 months), so that didn't really bother me. I never expected (though I had hoped for, of course) an automated 6-months-behind stream anyway. Storing the data in 6 month chunks and copying the previous one into the archives when the current one is finished, is certainly easier (plus the teams get the additional benefit of making the proprietary period of 6 months last 9 months, on average ).

I remember reading a comment that a person made on this forum, where that person said the 6 months started on the date Philae landed. I don't believe that person explained how they came to that conclusion, and it's a conclusion that seems, at least immediately, inconsistent with statements made by ESA on their blog, and since the mission lasts longer than 6 months after the landing, the data could not possibly all be released 6 months after that point, so I'm inclined to disregard that comment, at least until I find anything that explains how that conclusion may have been drawn.
It's also possible that that person had inside knowledge of the release cycle and was simply stating that one of the 6 month periods ends on that date, giving them 6 months from that point to make the data from that period publicly available. If that be the case, however, then you can substitute this entire post with a different question, which would be: if they chose that date as the end of one of their 6-month cycles (12 May 2014 to 12 November 2014), then they would have had to release all of the data from the previous cycle (end-of-hibernation to 12 May 2014) by that date, so where is it? I'm not aware of that happening, and the PSA doesn't show any OSIRIS data from end-of-hibernation to 12 May 2014, so I'll assume for now that what ESA has been saying on their blog is true instead.

I know OSIRIS resumed producing data at least as early as 20 March 2014 (a couple days short of a year ago) based on a press release from Max Planck about OSIRIS ( https://www.mps.mpg.de/3323535/PM_2014_03_27_Rosetta_A_glimpse_of_the_comet ) that says "This image taken with the Wide Angle Camera on March 20 shows a wide field 25 times larger than the diameter of the full moon."

I also know post-hibernation OSIRIS data has not been included in any data release so far (that I'm aware of), and given that post-hibernation OSIRIS data has been accumulating since at least one year (minus a couple days) ago, I can conclude that the latest the first 6-month batch of post-hibernation data would be released is 20 March 2015 (or earlier, if OSIRIS resumed returning data earlier than 20 March 2014). Additionally, I can conclude that the OSIRIS team hasn't opted for a release cycle shorter than the 6 month maximum (if they had, then the first set of post-hibernation OSIRIS data would have already been released), so the imminent data release, a couple days from now at the latest, must be a release that includes 6 months worth of OSIRIS data.

I don't believe I've made any mathematical errors, so that should be correct. I was wondering if anyone can confirm that all of that adds up and that we should expect to see all raw OSIRIS data from 20ish March 2014 through 20ish September 2014 released in the archive by the end of this week, or next week if it takes them a couple days to get the data into the archive for some reason (they are engineers, not network storage specialists, after all).

Thanks

Posted by: elakdawalla Mar 18 2015, 07:44 PM

I can confirm that it's six months after landing, or May 19. http://www.planetary.org/blogs/emily-lakdawalla/2014/07291014-rosetta-update-long-journey.html

That being said, the odds of the OSIRIS team actually complying with this requirement are pretty much zero.

Posted by: djellison Mar 18 2015, 08:10 PM

The OSIRIS team will deliver when they deliver - the efficacy of data delivery agreements within ESA seems to be very poor.

I've said elsewhere - I'd be surprised if they delivered anything to the PSA in 2015.

Posted by: Herobrine Mar 18 2015, 10:09 PM

Ah, thank you. I felt silly when, shortly after I posted this question here, the same question that had been "waiting for moderation" on ESA's blog for two days finally got through, and with a reply. ESA is now saying on their blog the same thing you're saying (minus the bit about the OSIRIS team not being likely to comply with the requirement). They also mentioned that the "next block of data, corresponding to 'escort phase 1' from 19 November to 10 March, should be delivered to ESA on 10 September."
I think that, though they try their best, perhaps the people who run the blog don't always get the most accurate/complete information from the people they consult when trying to respond to questions posted there, and I think that's what led to both my initial impression that data would be publicly available 6 months after the teams got their hands on it and my later impression that they split it up into 6 month chunks that get released 6 months after the end of the chunk.
So, my understanding of how long the teams get to keep the data to themselves has gone from 6 months, to 12 months, and now to 16 months (in the case of the first chunk of post-hibernation science data) or however long they want, based on how they choose to group the data into phases. If the teams had thought to do so, they could have labeled all of the science to do with 67P as a single phase; then they could have kept it from anyone else getting to work with it until June 2016, six months after the 'end' of the mission.

I'm curious though, why both of you are pretty sure they won't actually hand over the data to ESA when they're 'required' to do so. I can't help but suspect there's a story behind that prediction.

Posted by: elakdawalla Mar 18 2015, 11:11 PM

Not much of a story -- first data deliveries from missions' main science phases are often delayed, the more so when it's a team that has been reluctant to share data. Even without that, first data release delays do happen on many missions for benign reasons -- the team's busy doing science on their first real data, so archiving is a much, much lower priority. And then there's the team personality. It's not just OSIRIS we're waiting for, remember, it's also ROLIS and CIVA.

At least we'll have NavCam!

Posted by: DoF Mar 21 2015, 08:03 PM

The NAVCAM pictures at 10km are already quite stunning, so I will be very happy to see all of them.

In other news, it looks like 67p is http://www.bbc.com/news/science-environment-31965458. The previous perihelion passage had the opposite effect, although a spin up later might of course still be in the cards.

Posted by: Phil Stooke Mar 31 2015, 03:20 PM

Lots of new Navcam images are now available at the Rosetta image archive:

http://imagearchives.esac.esa.int/

Including Earth and Mars flyby and CG approach.

Phil

Posted by: neo56 Apr 1 2015, 06:32 PM

First NavCam mosaic taken during flyby of 28 March:
https://flic.kr/p/qXC9yx

Levels adjusted to show jets of gaz and dust:
https://flic.kr/p/rA6Jta

Posted by: Lewis007 Apr 3 2015, 06:49 AM

Scary times for Europe's comet-chaser Rosetta

Europe's pioneering probe Rosetta battled breakdowns with navigation and communication with Earth after it ran into blasts of dust and gas from the comet it is tracking, mission control said Thursday.

source: http://www.spacedaily.com/reports/Scary_times_for_Europes_comet-chaser_Rosetta_999.html

ADMIN EDIT: No need to post the entire media release when members can read it at the original source. A headline and teaser is sufficient.

Posted by: neo56 Apr 3 2015, 07:57 PM

Here is the second NavCam mosaic taken on 28 March:
https://flic.kr/p/qZkX86

And a zoom on Hapi region:
https://flic.kr/p/rDNaBv

Posted by: neo56 Apr 9 2015, 05:01 PM

The third NavCam mosaic taken on 28 March:
https://flic.kr/p/rZTCpW

Levels adjusted to show the jets:
https://flic.kr/p/s3bQAT

Posted by: jasedm Apr 9 2015, 05:22 PM

Thanks Neo for posting all these mosaics - very much appreciated!

Posted by: neo56 Apr 9 2015, 06:41 PM

Thanks jasedm

Posted by: neo56 Apr 10 2015, 09:39 PM

NavCam mosaic taken from a distance of 137 km of the comet:
https://flic.kr/p/rLHa9L

Levels adjusted to show jets of gaz and dust as well as the shadow of the largest lobe on the coma:
https://flic.kr/p/r7u99r

Posted by: Hungry4info Apr 14 2015, 04:42 AM

This image appears to show the south pole of Churyumov-Gerasimenko in detail better than I have seen before, thanks to reflected light off the larger component.
http://www.esa.int/spaceinimages/Images/2015/04/Comet_on_25_March_2015_NavCam

Posted by: wildespace Apr 19 2015, 05:59 AM

http://www.facebook.com/mattias.malmer.5 created this great tool to visualise Rosetta's view of 67P. Image updated every 10 minutes.

http://mattias.malmer.nu/rosetta-now/

Posted by: abalone Apr 20 2015, 02:39 PM

Rosetta's comet throws out big jet

http://www.bbc.com/news/science-environment-32380793

Posted by: fredk Apr 21 2015, 03:49 AM

More details http://blogs.esa.int/rosetta/2015/04/20/osiris-catches-activity-in-the-act/

(Always best to get as close to the horse's mouth as possible.)

Posted by: dvandorn Apr 21 2015, 06:44 PM

Interesting that this jet comes from a surface in shadow. It also occurs to me that some of the first jets observed came from the shadowed parts of the neck region.

Is there possibly a mechanism working here that would cause jets to break through more often when the surface is shadowed? Or is it more likely that the new jet actually started while that region was sunlit and we only saw it after it went into shadow?

Posted by: atomoid Apr 21 2015, 09:58 PM

it seems clear it apparently began in shadow (or it may have been active in sunlight and we didnt get an image of it until the same region later re-burped for the camera as activity was still subsiding while in shadow):
"..camera captures the moment a jet bursts into action. The first image was captured at 06:13 GMT on 12 March, the second two minutes later."
http://www.esa.int/spaceinimages/Images/2015/04/Comet_jet_awakens

Posted by: ngunn Apr 21 2015, 10:10 PM

The heat pulse delivered to the surface each day will take some time to propagate down to the level where there are still volatiles to sublime. I don't see any mystery in the jet first appearing at night.

Posted by: katodomo Apr 22 2015, 05:18 AM

This one appeared within minutes before local dawn as I understand that Rosetta Blog post.

My complete layman hypothesis:

Local volatile depot within the comet is heated and expands; the interior of the comet consists of voids connected through ducts and cracks between material that the volatiles expand through; on the sunlit side, thermal expansion of the comet material partially closes off these microscale ducts, leading to the expanding volatiles being ducted preferably towards the dark side (or rather: increases friction between comet material particles, thus making it harder for escaping volatiles to "push" them aside).
The microscale ducting would be what shapes the jet velocity and extent and the material taken up by the jet is material taken along from the duct surface once the jet gains sufficient drive. The "heated volatile bubble" escapes through such a duct in a timeframe dependent on its size and heating profile within the comet; short jets would then come from relatively isolated reservoirs quickly exhausting themselves, with the larger jet there may be a ducting mechanism connecting multiple (or many) reservoirs within the local comet area.

Such a mechanism should create jets preferably on the not-yet-lit side near the terminator or in other unlit areas nearby lit areas, such as deeper craters or behind cliffs, as observed by Rosetta.

Posted by: atomoid Apr 22 2015, 10:39 PM

In regards to the last two posts, I have heard that geologists refer to the temperature pulses as 'waves' of thermal energy propagating downwards, and that its possible to use that temperature profile and extrapolate record of average temperatures going back decades or more, but i wasn't able to find much information on how fast these 'waves' are expected to travel by googling around.

Assuming this is mostly conduction it depends upon material/density to determine the timespan, with the comet being somewhat uncertain to characterize along those lines unless these current outbursts, if applicable to such an approach, can be used to characterize a model profile. Its also hard to characterize whether thermal expansion should tend to be maximized at these thermal pulses as well, thus working counter to 'seal off' any escape cracks leading from the very areas that are subjected to sublimation.

So assuming that residual thermal waves should eventually propagate to the very center and presumably least outgassed portion of the comet at some point, however long that may take, if thats an extended period, we may see significant outbursts long after perihelion.

Posted by: fredk Apr 23 2015, 04:21 PM

I'm wondering whether there might be a possibility for this new jet to have originated on the sunlit portion of the comet. The obvious interpretation of the image is that the source of the jet is on the shadowed side, and once the jet has travelled far enough out it gets into the sunlight and so is visible. For this to happen the jet clearly has to travel out of the comet's umbra.

But another idea is that the jet originated in the sunlit region around where I put the black dot:

Notice that due to the comet's rotation that area has just entered into sunlight when this frame was taken, so would be subject to heating. Now to explain why the jet is only visible farther out, you'd have to assume that the source of the jet was a transient burst, ie the jet you see farther out came from the burst, which is now turned off and so no jet is visible near the source.

There are a couple of problems with this idea. First, the jet in question is composed of a couple of sub-jets, which converge below where I drew the dot, on the dark side. I'd say it's more likely (though not certain) that the source of the jet is closer to the convergence point. Second, I don't recall seeing any other jets terminating in space, as you'd expect from other transient bursts. So my guess is that the source is indeed on the dark side. If there were more frames taken soon after this one that would decide it for sure.

Posted by: DoF Apr 26 2015, 01:45 PM

Notice that in the blog post they speculate that the jet actually originates from a sunlit face of a cliff/outcropping. It's just that due to the viewing geometry Rosetta can't see this sunlit area.

Posted by: scalbers Apr 26 2015, 03:47 PM

A hidden sunlit area seems harder for me to visualize, given the relatively low phase angle. Perhaps this can be explored with Malmer's shape model?

Posted by: Malmer Apr 28 2015, 09:26 PM

I took the timestamp and generated the viewing geometry and direction of the sunlight from SPICE data.

I then let this planar surface catch the shadow of the comet and moved it around until it had was lit as the little jet in the OSIRIS frames.

That gives us a reasonable lock on the location.

Posted by: fredk Apr 28 2015, 10:28 PM

Really nice, Malmer. To answer scalbers' question, I can't see any sign of a cliff or outcrop near Malmer's source of the jet that's in the sun. And at earlier times the sun was even farther from that source location.

Posted by: Malmer Apr 28 2015, 10:41 PM

The sun did not hit the "underbelly" of the duck until about one hour and 15 minutes later. And that area had been in shadow for five and a half hours or so.

Posted by: nprev Apr 29 2015, 12:57 AM

Hmm. All this may be telling us something about the thermal inertia of the comet as well constraining things like internal structural models and volatile composition/mix.

All in a very coarse sense, of course, but these are the sorts of key observations expected from Rosetta.

Posted by: Phil Stooke Apr 29 2015, 12:19 PM

Internal plumbing? A pathway through the lobe, heated at one end, losing material at both ends?

Anyway, enough of such speculation - it's time to go nuts:

http://blogs.esa.int/rosetta/2015/04/29/major-release-of-navcam-images-800-to-30-km/

Lots of new Navcams from as low as 30 km.

Phil

Posted by: Paolo May 18 2015, 06:33 PM

today is one of those rare days we are treated with am OSIRIS release
http://blogs.esa.int/rosetta/2015/05/18/osiris-spots-boulders-in-balancing-act/

Posted by: Phil Stooke Jun 10 2015, 11:13 AM

Another OSIRIS release - a really nice one of jets emerging from shadows:

http://blogs.esa.int/rosetta/2015/06/08/sunset-jets/

and a Navcam view of the southern hemisphere:

http://blogs.esa.int/rosetta/2015/06/09/cometwatch-1-june/

Still lots going on with Rosetta!

Phil

Posted by: DoF Jun 11 2015, 10:55 PM

http://i.imgur.com/SpSU18G.png is a rough guide on where those jets are on a NAVCAM image from back in October. The pink line shows that maybe one of them have its origin in a small depression in the dust layer. Emphasis on maybe. I think the large jet and the potential origin shown with the cyan line is also worth taking a look at. I'm curious if the "dunes" that goes towards the right is formed by that jet. http://i.imgur.com/M5eUKCZ.png of the area. The yellow arrow is only pointing at the general area of where some jets seemed to be. The cyan and pink arrow once again points towards what might be actual sources. It's easier to see the dunes I were talking about at this angle as well. I wish to underline that these are all just crude guesses.

The original NAVCAM images are ROS_CAM1_20141008T021835_P and ROS_CAM1_20141008T140825_P that were recently released on the http://imagearchives.esac.esa.int/. Credits: ESA/Rosetta/NAVCAM – https://creativecommons.org/licenses/by-sa/3.0/igo/ and ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA.

Posted by: Sherbert Jun 13 2015, 07:06 PM

Good work DoF. Just finding some good alternative views of the right area helps a lot. I would tend to agree with the pink source site. It looks like it might be a source established on the previous orbit, the loss of volatiles from below the surface has created a depression. The area of the yellow jets seems about right too. Any jet source must, because we can see it in images, have a source of dust. It follows sites of bright jets are going to be covered in a large supply of dust. The source of the jets, the reservoirs of volatiles powering the jets, are below the surface, their shape and the escape routes to the surface are hidden.

In the microgravity of 67P the effect of capillary action on fluids becomes a significant determinant for how they behave and move. See NASA's microgravity coffee cup. With this in mind, some possibilities for discussion.

The evidence is that there are no large amounts of volatiles at or near the surface, they have sublimated away. Large amounts of volatiles are leaving the comet, so they are coming from below the surface and one way they could get to the surface, once the Sun's energy is sufficient to reach them, is by capillary action through the porous material and tiny cracks within it. During the long cold 67P winter some volatiles will freeze, most importantly Water, to seal off these cracks and fissures allowing pressure to build up below as the energy from above seeps deeper into the comet. Spring arrives, the comet crosses the ice line, the ices in the subsurface tiny cracks and pores, sublimate and the pressure from below is released, gas is pushed by pressure and dragged by capillary action to the surface. The deeper the pocket of volatiles is buried the longer it takes the route to unfreeze and the longer it takes for the Sun's energy to percolate down to them. In the neck area the depth of any volatile pockets is limited and together with it being a cold trap for condensing material from the coma, makes it the most likely area for the first jets.

If an aggregate of planetesimals of variable composition is how 67P initially formed, variously sized, volatile rich packets, would be randomly spread throughout the comet and would presumably have a general "potato" or "dinosaur egg" shape. What is left behind when all the volatiles have gone, a large pile of dust and a roughly spherical empty space. As the entire surface slowly erodes, several hundred metres was estimated as being possible by the OSIRIS team, these empty spaces and their lake of dust collected in a basin at the bottom, are exposed at the surface. A familiar formation on the surface, some showing evidence of collapsed roofs. The original volatile rich planetesimals also aggregated with variable composition, so boulders of more refractory materials are likely to be found within. These get left behind resting on the lake of dust, example Cheops and the rocks on the floor of the Imhotep depression, which themselves hint at being aggregates of smaller boulders of variable composition cemented together by an ice and dust mortar formed on the surface of each planetesimal in the same way as on the surface of 67P. This seems a fundamental construction technique on the comet, from the nanometre scale to the Kilometre scale and leads to that same diversity in scale in the appearance of a number of common visual features, the "horseshoe" shape for example.

Before sublimated gas from below can escape to vacuum, it must get through the dust layer. We have seen from Rosetta's dust collection, this is likely to be made of extremely fragile aggregates of micron sized dust particles, which offer even more scope for capillary effects to take over. The aforementioned coffee cup uses capillary action to create a self sustaining flow/stream of fluid in microgravity, as long as the astronaut keeps allowing the fluid to run into their mouth, the fluid will flow until every last drop leaves the vessel. This would suggest that the dust/gas interaction forces the fluid gas into micro sized streams, which combine at the surface to create a broader collimated stream, its direction determined by the vector of the force from the gas pressure below. Not all the energy in the gas column comes from the Sun's energy and the expanding gases. Capillary action still works in the dark, at least until the subsurface micro cracks freeze, closed again. Super volatiles like Carbon Monoxide, Nitrogen and Carbon Dioxide may well keep a small percentage of routes to the surface open and still escape at night or when the surface is in shadow, as seen in the ROSINA data.

Pressure from gas build up in volatile rich reservoirs below could lead to jets then, but simple diffusion through the porous comet material and the pressure gradient created by the vacuum at the surface, will also allow sublimated gas from widely dispersed, un-concentrated volatile sources, to move towards the surface, only this time with far less energy and with a more random set of velocity vectors. Capillary action in such low gravity would act in all directions, not just perpendicular to the surface, moving the tiny dust particles along with it. The dust layer acts like blotting paper for the sublimating gases, capillary flows dispersing the gas in all directions out into the dust layer. Pour a liquid through filter paper and it exits as a collimated stream.

In effect, because of the micro, even nano, sizes of the dust particles, the gas/dust mixture takes on the properties of a fluid, a fluidised bed, which is just heavy enough to largely remain on the surface. A number of comments have been made that the dusty plains look like seas and we have seen dunes and ripples in the dust as if it were behaving as a fluid. A percentage of gas will attain escape velocities sufficient to carry dust a small way above the surface. Once 67P crossed the ice line the halo of ejected dust all over the surface started to become visible. In the latest images that wispy halo has become a solid curtain tens of metres high, wherever there are areas covered in dust, where the increasing energy from the Sun is releasing larger quantities of dispersed volatiles with greater energy.

Capillary action/surface tension in microgravity has been intensively modelled in recent years, how fluids behave in space systems has become critical, fuel flows, hydraulic systems, lubricants and human environment systems, all need to take account of this effect. Can those equations and models be adapted to the surface environment of a comet? Constraints on particle sizes in the dust, its mechanical properties and energy flux figures are available from the ROSETTA and PHILLAE data, so one might hope the challenge is taken up. This represents a possible model for, very low energy, long time scale, erosion processes, akin to those performed by wind and water, on Earth. Such long timescale erosion is clearly taking place on the surface, the uncanny resemblance to eroded "rock" on Earth has been evident right from the first images of surface formations.

The numbers and models may show such fluidisation of the dust layer is not possible via this mechanism, but I am sure some outcomes are expressed in the topology of the surface. Of course it could be just another of my crazy theories, but maybe it will plant a seed in someones mind who knows a lot more about fluid surface tension in microgravity than I do. :-)

Posted by: Gerald Jun 14 2015, 06:41 AM

Not sure, what you mean with "fluid". A dust gas mix can behave similar to a fluid in some aspects.
But a true fluidized gas in the cometary subsurface doesn't appear likely due to low pressure; water (https://en.wikipedia.org/?title=Triple_point#Table_of_triple_points pressure 611.73 Pa), CO (15.37 kPa), and CO2 (517 kPa) are ruled out as fluids; ethanol (0.43 mPa at 150 K, according to the table) might be a feasible candidate, but its abundance is too low.
You would need such a fluid phase for https://en.wikipedia.org/wiki/Capillary_action. If interpreting a gas/dust mix as a fluid, its surface tension would be too low to cause relevant capillary forces, since https://en.wikipedia.org/wiki/Van_der_Waals_force mostly responsible for https://en.wikipedia.org/wiki/Surface_tension reduce rapidly with the distance between dust grains. But you need this distance between the grains to make them behave remotely similar to a liquid.
The gas phase shows https://en.wikipedia.org/wiki/Diffusion with probably https://en.wikipedia.org/wiki/Effusion as a special case.

Edit: There might be a scenario with capillary forces involved: Provided the crust of the comet turns out to be enriched in complex organics, they might show a tar-like behaviour, i.e. some softening under solar illumination, gluing dust particles together. This gluing might involve capillary forces. But that's rather speculative.

Posted by: Malmer Jun 14 2015, 10:09 AM

Posted by: scalbers Jun 14 2015, 02:45 PM

Impressive match between the shape model and OSIRIS image. The partly shadowed jets in the center look to be pretty close to Philae's location, if Philae is where we have been thinking.

Posted by: Bill Harris Jun 14 2015, 03:42 PM

Speaking of shape models-- what is the best 3-D Printing template/file available today? I'd held off having one of the early 3D files printed, waiting for them to mature.

Great that we've found Philae, it looks like she landed in rough terrain. I was hoping that this wouldn't turn out to be another "Elvis Sighting"...

--Bill

Posted by: Malmer Jun 14 2015, 08:08 PM

I think mine might still be the best one out in the open:

http://mattias.malmer.nu/wp-content/uploads/2015/05/67P_HD_2015-05-09.zip

If you print it. Please send pictures.

Posted by: Sherbert Jun 14 2015, 10:36 PM

Thanks for your thoughts Gerald.

A gas is a fluid and as I understand it, can be subject to capillary forces. There is vapour pressure from the sublimating gas below which is increased when the gas is forced into a smaller volume, inter molecular forces and viscosity then become significant factors in the gases behaviour and it assumes many of the properties of a liquid. The narrow channels required to achieve this are on the molecular scale, but the evident porosity of the solid looking comet bulk material suggests this is a realistic scenario. The spaces left behind by already sublimated ices being the obvious mechanism by which such channels could form. The number of such channels would be dependent upon the ratio of the different volatiles and a comet's orbital and seasonal configuration. An explanation for apparently random, or regular, fluctuations in cometary activity maybe?

The possible fluidised gas/dust mixture at the surface is a whole different ballgame. This I imagine might behave more like aerated flour or cement dust, the reduction in friction between the particles from the gases percolating through it, giving it some fluid like behaviour, in particular the ability to mix and flow. The depth and permeability of the dust layer together with any cohesion provided by "sticky" organic molecules is probably key to the extent of any fluid like behaviour. It is clear from the activity we have seen that the vast majority of gases reaching the surface, leave it, carrying varying amounts of dust along with them, but I still think random diffusion and micro-scale capillary action would disperse the gases and saturate the surface dust layers as part of a dynamic equilibrium, at the very least leaving each dust grain with a boundary layer of gas molecules surrounding it.

The freezing of this gas/dust/organics mixture creates the solid material visible on the comet. Seasonal, orbital and diurnal temperature changes combined with coma fallout seem to be the basis of a sedimentary deposition scenario for which there is considerable visual evidence on 67P, the ROLIS images at Phillae's final landing spot for example. There has to be some mechanism whereby the ices, dust and organic material are thoroughly mixed and then deposited as layers to form the comets visible solid material and this is a suitably cyclical, long timescale and scalable mechanism that is a plausible fit. It of course remains for others with greater knowledge and access to the evidence to embellish or eliminate.

Posted by: antipode Jun 15 2015, 04:04 AM

Sorry Malmer, I couldnt help it.



Now please back to the science

P

Posted by: Phil Stooke Jun 15 2015, 04:15 AM

Yes, back to the sci - no, there's just time for this latest bulletin - lander spotted at last:

Phil

Posted by: Ron Hobbs Jun 15 2015, 04:51 AM

LOL

Gosh, I so love this forum.

Posted by: JohnVV Jun 16 2015, 01:53 AM

now the question is
dose only one of those have BLUE plasma and gasses shooting out ( mouth)
or
do both have blue plasma and gasses (mouth and vent)

Posted by: DoF Jun 16 2015, 09:03 PM

I love that visualization Malmer, you've really done great work. Too bad my desktop is so old by now that it can't really deal with your 3d model, otherwise I'd like to play around with it a bit more. Could I bother you with rendering a version that's the same as the middle render (i.e. where you try to match the OSIRIS image), but with the light direction changed so there wouldn't be any shadows in the area? Because it's the same angle it'd make it easy to overlay the OSIRIS image to better see where the visible parts of the jets area in relation to the underlying comet.

As for scalbers, you got the position of Philae a bit wrong. Basically from this viewpoint if you start from the centre of the Hatmehit depression and go directly left that's where you should find the lander, it's not at the same place as these jets.

Posted by: scalbers Jun 16 2015, 09:27 PM

Thanks for the clarification DoF. I think I was using some poetic license by saying "pretty close". It is in the same general part of the comet and perhaps close enough for Philae to see them (in the eastern sky jutting above the right edge of Perihelion Cliff)? Maybe it's around 60 degrees azimuth between Philae and the jets from an imaginary viewpoint at the center of Hatmehit.

The neat thing is that this could be a testable hypothesis.

Posted by: MahFL Jun 23 2015, 01:10 PM

Rosetta mission extended.

http://blogs.esa.int/rosetta/2015/06/23/rosetta-mission-extended/

Posted by: neo56 Jun 29 2015, 02:02 PM

I made a montage of 18 NavCam pictures taken between 28 March (top left) and 5 June (bottom right) drawing inspiration from what was done by ESA.
Contrast was increased to show streams of dust and ice particles.

https://flic.kr/p/vj8VWQ

Posted by: Malmer Jun 30 2015, 02:11 AM

Thank you! and sure:

Posted by: Herobrine Jul 2 2015, 12:08 AM

It's entirely possible that I'm just crazy, but it seems to me that the latest release of NAVCAM images happened silently this week.
NAVCAM images for "Escort Phase 1" from 2014-11-21 to 2014-12-19 appear in PSA (and in the NAVCAM image browser), apparently deposited on 29 June.

I don't see a blog post about this or any mention of it anywhere. Did I miss something?


ftp://psa.esac.esa.int/pub/mirror/INTERNATIONAL-ROSETTA-MISSION/NAVCAM/RO-C-NAVCAM-2-ESC1-MTP010-V1.0/
http://imagearchives.esac.esa.int/index.php?/category/66

Posted by: Explorer1 Jul 2 2015, 01:21 AM

It was on the official Twitter feed; presumably that's more well-read?

Posted by: Herobrine Jul 2 2015, 02:38 AM

Probably. I don't use Twitter on a regular basis; I guess that explains why I didn't hear anything.
Kind of surprised it hadn't been mentioned here, though. I suppose now it has.

Posted by: Herobrine Jul 2 2015, 03:08 AM

Speaking of data releases...

44 days (that's 12% of a year) after 19 May, precisely 0 science data from the first phase have made it into the PSA, from what I can tell (NAVCAM not included).

I'd like to think that after the media coverage of the data release policy in November, with headlines like "Tensions surround release of new Rosetta comet data", "Concerns over ESA’s Data Release Policy Amidst Rosetta Comet Landing", and "Rosetta will prompt science images rethink", that it would be in the instrument teams' best interests to fulfill their data delivery requirements in a timely manner if they hope to continue that sort of data policy for future missions.

Has anyone heard anything from anyone about the status of any of the science data from any of the instruments/teams, or when any of it might actually get released? Or is it possible that much of the data has been released, and I'm simply looking in the wrong place?

Posted by: dvandorn Jul 3 2015, 12:31 AM

It has also been mentioned here, in a number of different contexts regarding ESA mission scientists and their contributions to the PSA, that they are not always made in a timely manner.

AIUI, there is little in the way of enforcement of the submission deadlines, and from observation, they seem to be recognized more in the breach than in reality.

In other words, while the data should get there eventually, don't get too upset if they aren't submitted to the PSA right on schedule, there is precedent for such submissions to run significantly later than the scheduled dates. And that's about all I can really say, here. Though I'd love to hear from Emily her feel for the timing. She talks to those people one heck of a lot more often than I do...

-the other Doug

Posted by: djellison Jul 3 2015, 12:49 AM

It'll show up when it shows up.

I learned long long ago to never expect a data release on any schedule from ESA. That way, 5+ years later, when it does show up...it's a nice surprise.

Posted by: JohnVV Jul 3 2015, 01:35 AM

no kidding
the Vesta data just showed up SO quietly that NO ONE noticed until Bjorn noticed it 6 months later
http://www.unmannedspaceflight.com/index.php?s=&showtopic=7266&view=findpost&p=210479

Posted by: machi Jul 3 2015, 10:37 AM

http://www.unmannedspaceflight.com/index.php?showtopic=7266&view=findpost&p=194406
UMSF community knew almost immediately about Vesta's data in PDS. But as only few of us processed those data so it wasn't so visible.
Another problem is that all images from Dawn are strictly speaking scientific (for mapping purposes) and there is no "kodak" moment
and because of that images aren't so catchy.

Posted by: PaulH51 Jul 4 2015, 01:50 AM

I realize that we have seen many subtle changes in many surface features since Rosetta arrived at 67P C-G. However, with the comet moving ever closer to the sun, and the ever increasing activity, has there been any noticeable reduction in the comets size? Or is it just that the losses are just too small, or maybe not easy to measure using the images that have been released so far? Apologies if this is a less than smart question, but I was just curious.

Posted by: chuck0 Jul 4 2015, 08:17 PM

I think the losses on the northern hemisphere which we have been observing most of the time until now will not be too drastic. The southern hemisphere i think will be a different story... we have only seen a few illuminated images of that part of the nucleus, but at least to me it seems like it has been heavily eroded away (it is somewhat flattened). I think there is actually a paper by the OSIRIS team who predict up to 20m surface erosion on the southern hemisphere...

http://blogs.esa.int/rosetta/2015/02/09/seasonal-forecasts-for-67pc-g/


Btw, i added malmers shape model to my small webgl application (works best with chorme and to a lesser extent with firefox... and i am not 100% sure i got the comet rotation right )

http://www.googledrive.com/host/0B_Y5O4C6aiKmfktCSlJEb2N1d2h0WElIcEs1R081OXdfUS01MFV4Ukk4RGFGUllPMFNZZms

currently there is spice data for as far as July 15th. Rosetta seems to keep in its scanning pattern for contacting Philae.

Posted by: JohnVV Jul 4 2015, 09:00 PM

from " h t t p : / / w w w .googledrive.com/host/0B_Y5O4C6a...RGFGUllPMFNZZms "
the orbits look to be making 60 degree orbital changes
http://imgbox.com/Y9E6D1QB

what spk files are you using ? ( RORL_DL_??????????? .bsp)

Posted by: chuck0 Jul 4 2015, 09:05 PM

@JohnVV those orbits are from the early mapping phase from the end of last year. You can use the slider below the 3D window to go to the current date.
I am using RORB_DV_????.BSP for rosetta and CORB_DV_????.BSP for 67P. Comet frame of reference comes from CATT_DV_????.BC, though i am not completely sure i applied that 100% correctly.

Posted by: Herobrine Jul 6 2015, 04:02 PM

@chuck0 I agree that you probably don't have the orientation of 67P quite right in your web app right now. I compared ROSETTA NOW!, which I believe has been shown in the past to definitely have the correct orientation for 67P, to the approximate (had to zoom in, so perspective is off) view from Rosetta in your web app for the same minute and it looks like yours may be off by 90 degrees about the rotation axis? Or something like that.

(I rotated the image to align with the ROSETTA NOW! image above)

Posted by: chuck0 Jul 6 2015, 06:01 PM

Thanks for that tip. It seems like a 90 degree rotation around the north south axis improved things considerably... now the philae deployment looks pretty consistent with the video pusblished by ESA.

Posted by: chuck0 Jul 8 2015, 09:37 AM

Some really interesting info about the optical navigation they are using around 67P
https://www.youtube.com/watch?v=_3k03Jb3dgQ&feature=youtu.be

Posted by: Explorer1 Jul 14 2015, 08:45 PM

http://blogs.esa.int/rosetta/2015/07/14/hello-pluto/

Apologies, but I couldn't resist...

EDIT: and the next day, a more serious release:

http://www.esa.int/Our_Activities/Space_Science/Rosetta/Highlights/Boundary_conditions

Corresponding blog post:

http://blogs.esa.int/rosetta/2015/07/15/getting-to-know-rosettas-comet-boundary-conditions/

Posted by: chuck0 Jul 15 2015, 09:16 PM

Aside from the Pluto image there has been a release of some more OSIRIS images in this blog post about geologic regions

http://blogs.esa.int/rosetta/2015/07/15/getting-to-know-rosettas-comet-boundary-conditions/

Posted by: chuck0 Jul 19 2015, 11:39 AM

Seems like Rosetta will now restart doing full orbits oround 67P.

( see http://www.googledrive.com/host/0B_Y5O4C6aiKmfktCSlJEb2N1d2h0WElIcEs1R081OXdfUS01MFV4Ukk4RGFGUllPMFNZZms )

Posted by: PaulH51 Jul 20 2015, 08:51 AM

ROSETTA AND PHILAE STATUS UPDATE : Posted on 20/07/2015
http://blogs.esa.int/rosetta/2015/07/20/rosetta-and-philae-status-update/
Extract:

Posted by: Sherbert Jul 20 2015, 04:34 PM

Some more OSIRIS NAC images available here! Our cup runneth over. Thanks Holger and team, some really nice goodies here.

http://www.esa.int/Our_Activities/Space_Science/Rosetta/Highlights/Inside_Imhotep

Posted by: Sherbert Jul 23 2015, 09:49 PM

This intermittent communication with Philae is concerning.

67P is now spraying out large, dense columns of finely powdered dust, ice crystals and gas. Doing so at considerable velocity. Electrostatic discharges within fine powders are an extremely hazardous phenomenon here on Earth. (Oxygen has a bit to do with that too.). Nothing messes up radio communications like electrostatic discharges. Shifting slightly to the dark side of the terminator might be an option, further from the peak daytime activity, possibly a wise precaution with Perihelion approaching.

Posted by: chuck0 Jul 23 2015, 11:30 PM

Yeah, i think Philae is really going to have a hell of a ride... not only because of the interference which might be generated by the dust but also because the southern hemisphere is supposed to loose up to 20m of material during perihelion ( http://blogs.esa.int/rosetta/2015/02/09/seasonal-forecasts-for-67pc-g/ ). I think it is no wonder that Philae might be moved around quite a bit in the coming weeks. If it still can keep in shadow long enough to stay cool it would be really really nice to see an up to date image from the surface (i think the sequence they are trying to blind command is containing at least a rolis image... wish they could also get a new CIVA pano).

Posted by: Sherbert Jul 24 2015, 04:42 PM

The increasing brightness of the coma should enable a sneak peak at the missing Southern hemisphere. Might be a useful "before and after" exercise.

Posted by: nprev Jul 24 2015, 05:16 PM

Given the increasing level of activity on the comet combined with Philae's issues it's not at all surprising that the team is not able to provide updates as frequently as some would like. I'm sure that they're struggling to keep up with rapidly changing circumstances on all fronts.

Posted by: Astro0 Jul 26 2015, 10:43 PM

ADMIN NOTE: About 10 posts above were removed that related to the OSIRIS team policy on image releases. We don't need to go over old ground on this one and it is a clear breach of http://www.unmannedspaceflight.com/index.php?act=boardrules. Thanks all.

Posted by: chuck0 Jul 26 2015, 11:59 PM

@Sherbert yes i am also really looking forward to seeing more pictures of the southern hemisphere. I hope that they will publish some nice navcam images early on. Rosettas trajectory will give it a good view of the south for two weeks starting somewhere around tomorrow. It seems like there is also one last Philae listening pass planned around August 17th. After that they will actually leave the terminator plane and back off quite a bit more behind the comet.

Posted by: Herobrine Jul 31 2015, 06:28 PM

A new block of NAVCAM data was released today.
http://imagearchives.esac.esa.int/index.php?/category/67
ftp://psa.esac.esa.int/pub/mirror/INTERNATIONAL-ROSETTA-MISSION/NAVCAM/RO-C-NAVCAM-2-ESC1-MTP011-V1.0/

Posted by: remcook Aug 3 2015, 08:44 AM

And pre-landing data in the archive now! http://blogs.esa.int/rosetta/2015/08/03/first-release-of-rosetta-comet-phase-data-from-four-orbiter-instruments/

Posted by: Paolo Aug 3 2015, 08:50 AM

actually, for OSIRIS

I would call it pre-arrival, rather than pre-landing

Posted by: Bill Harris Aug 3 2015, 03:16 PM

I would barely call it "approach".

http://www.esa.int/var/esa/storage/images/esa_multimedia/images/2014/06/comet_on_4_june/14582721-1-eng-GB/Comet_on_4_June_node_full_image_2.png

Posted by: katodomo Aug 3 2015, 07:35 PM

The OSIRIS data release actually also includes the asteroid flybys and the gravity assist swingbys, which i think hadn't been released before (not sure). On the ESA Archive Image Browser, which is a lot more public-user-friendly than PSA.

The copyright notice in the ESA Archive Image Browser for OSIRIS pictures may also be noteworthy:

http://imagearchives.esac.esa.int/index.php?/page/copyright_information

Although i'm not sure how to interpret that.

Posted by: Herobrine Aug 3 2015, 07:55 PM

Making the earlier datasets accessible from the Archive Image Browser is new, but they have been available in the Planetary Science Archive for several years; the only newly-released OSIRIS data (of which I am aware) are 4 datasets that span the 85 days from 2014-03-20 to 2014-06-12.
Delivery of OSIRIS data from the post-hibernation phase up until the end of Philae's post-landing activities and Rosetta's post-separation maneuvers on 2014-11-19 was due to ESA on 2015-05-19, with delivery to be expected then or very soon after from the team. The next block of OSIRIS data, corresponding to "Escort Phase 1", from 2014-11-19 to 2015-03-10, should be delivered to ESA on 2015-09-10. It's unclear to me, based on that blog post, whether they expect to meet that due date. The way the post reads makes it sound to me that, "by September", they intend to release a second version of the same datasets they just released. I can't gather from that blog post when they expect to receive the rest of the OSIRIS data that was due 2015-05-19; perhaps it will be included in the release of the "second version".

Edit: Corrected 2014-11-14 to 2014-11-19

Posted by: stevesliva Aug 12 2015, 12:48 AM

OSIRIS images of a very short-lived outburst on July 29:
http://www.jpl.nasa.gov/news/news.php?feature=4687

Posted by: belleraphon1 Aug 13 2015, 04:06 PM

A lot of good stuff in this 2 HOUR hang out from this morning...video with a new outburst caught in the act last night, etc.

ESAHangout: Rosetta mission's day in the Sun
https://www.youtube.com/watch?v=TaBZbc6WGLs

Craig

Posted by: Herobrine Aug 13 2015, 06:48 PM

All of the MIDAS data from the Pre-Landing phase was published to PSA yesterday.
ftp://psa.esac.esa.int/pub/mirror/INTERNATIONAL-ROSETTA-MISSION/MIDAS/RO-D-MIDAS-3-PRL-SAMPLES-V1.0/

Posted by: Bill Harris Aug 14 2015, 11:07 AM

Here is a little light reading on "The Joys of Perihelion":

http://blogs.esa.int/rosetta/2015/08/13/rosettas-big-day-in-the-sun/#comment-505564



and these are .PDF papers on various comet processes that might be related to the perihelion passage:

"Heat and Gas Diffusion in Comet Nuclei"
http://www.issibern.ch/PDF-Files/SR-004.pdf

"The outburst triggered by the Deep Impact collision with ..."
http://faculty.cua.edu/ipatov/di-mnras.pdf

"Physical Mechanism Of Comet (and Asteroid ..."
http://www.hou.usra.edu/meetings/metsoc2015/pdf/5002.pdf

"Cavities as a source of outbursts from comets Sergei ..."
http://arxiv.org/pdf/1103.0330

Memorable Comets of the Past
http://cometography.com/past_comets.html


Enjoy.

--Bill

Posted by: Herobrine Aug 20 2015, 05:08 PM

The raw data collected by Rosetta's Ion Composition Analyzer (RPC-ICA) from 2014-03-26 through 2014-11-20 became available in PSA on the 14th.
ftp://psa.esac.esa.int/pub/mirror/INTERNATIONAL-ROSETTA-MISSION/RPCICA/RO-C-RPCICA-2-PRL-RAW-V1.0/

The raw data collected by Rosetta's Ion and Electron Sensor (RPC-IES) from 2014-03-24 through 2014-11-20 became available in PSA on the 7th or 12th. Not sure how I missed this one until now.
ftp://psa.esac.esa.int/pub/mirror/INTERNATIONAL-ROSETTA-MISSION/RPCIES/RO-C-RPCIES-2-PRL-V1.0/