Land on THAT!!! (or perish in the attempt)

http://www.esa.int/spaceinimages/Images/20..._September_2014

Phil

It's hard to remember that the comet does not have 1g of gravity, any second would expect rocks to tumble.

The preliminary VIRTIS results seem to point towards a carbon-rich, dry, and porous/dusty surface, as one could anticipate from the preliminary Alice results, too:

I am not convinced that all those "boulders" are conventional rocks. I did not expect to see so much rounded original material; many of these look like products of erosion or recomposition. By way of explanation for what I see, I don't expect erosion (except for the evidence of Mars-like "spider flows" where gases may have carved channels under the debris). But I don't discount accretion of volatile materials into new forms, either.

Edit to add that the image scale is still too small to really characterize the roughness of the rocky shapes. Let's hope for a closer view. I'll bet the scientists are just going nuts over the wealth of "never before described" data they are looking at.

That image clearly shows just how amazing the OSIRIS camera really is!

I draped the image onto my work in progress shapemodel so that a synthetic stereo view could be derived:



Cant wait to see more real stereo stuff from OSIRIS.

I see a few distinctly finger or knife edge like 'rocks', as well as more rounded shapes. I wonder if most of what we're looking at isn't the resut of aeons of hydrocarbon materials settling into shpaes due to internal stresses (and vapour flows) as their ice sublimates? WRT surface composition: If the surface material is porous, could a significant amount of ice be caught in those pores, in the near subsurface?

And generally WOW.....

Edit: I didn't see this posted further up the thread: Dust from the comet already being collected

This picture is amazing. To me, as a non-expert, the amazing thing is how earthlike it looks. It looks like a chunk of the Rocky Mountains floating in space. Am I wrong about this? Would any geologists be interested in explaining to a complete ignoramus what is 'alien' about this picture? Like, is there anything about the geology on display in this image that couldn't possibly exist on earth and gives it away as being obviously a photograph of a small asteroid or comet? I'd love to know.

I'm also trying to rationalize the appearances with my own experiences. The rocks we know--igneous and sedimentary rocks of Earth's mountain ranges--are the many-times-recycled grandchildren of the pristine meteor matter embedded in these ices. How about the "tree trunk fortress" on the upper right, or the uniquely thin spires and walls (which look like volcanic dikes but can't be--it's an ice world). The "cliff" seems to present a cutaway of the insides of the head, and I'm struck by the apparent spongy top layer which seems to be laced with flues at least partway down. Rocks that appear to be on a precipitous slope are simply revealing their local sense of where "down" is on this topsy turvy world. Overhangs covered with "drift" seem to have popped out little heaps of rocky material. It's as if mysterious forces have significantly modified this little dirty snowball, and it's truly mindblowing to finally get a close glimpse of things we've never seen before. Science will explain it all in dry PostScript proceedings in coming months, but I'm just gobsmacked, jaw-droppered, twitterpated and salivating at what I see. And those are proper terms most trained geologists are probably using as well right now.

The surface of comet 67P/Churyumov-Gerasimenko can be divided into several morphologically different regions, as shown by a map published by the Max Planck Institute.
http://www.mps.mpg.de/3788997/PM_2014_09_0...Rosetta-Kometen

The images are overexposed in some way.
If part of the comet would be placed somewhere into the Rocky Mountains, it would maybe collapse under its own weight due to its weakness, and end up in a large dust cloud, or some black smelling mud. Taking this aside, it would look pitch-black, much darker than (unweathered) basalt. It would (probably) be almost as light as pumice, at least lighter than water.

With a CI1 carbonaceous chondrite, like Orgueil, you may get an idea of how the comet might be composed near the surface, under a possible black dust layer.

I did away with some of the colorization just to be able to see the image more as it was shot. Is there an untouched version out there?

http://mattias.malmer.nu/wp-content/upload...IRIS_no_map.jpg

I agree that some morphologies on the comet, e.g., shape of the "rocky" outcrops (with pinnacles, sets of fractures and blocky appearance) and adjacent smooth areas and boulders, are reminiscent of reliefs on Earth, e.g., wind eroded granit. Now, the rock type is completely different, perhaps, like Gerald suggested, the most similar rock on Earth is pumice (porous but with strength). My guess is that the similar morphologies derive from similar processes. On the latest OSIRIS image (center up) there is a field of boulders just at the foot of a wall with pinnacles, suggesting (to me) scarp retreat by rockfall. On 67P the retreat might be driven by ice sublimation. On Earth, scarp retreat can be due to physical weathering (changing temperature), wind, ect.

What is alien about it is that despite different gravity and temperature conditions, and despite different rock types (=completely different environment of rock formation) the resulting local-scale morphologies are surprisingly similar!

@Malmer. Great un-colored image: the “unit boundaries” can be better seen now. No, I haven´t found the original image neither.

I defer to superior knowledge....but the outlines of some of the surface features made me wonder if processes akin to those responsible for snow chimneys (transport of materials by escaping gas) might be at work.

Thanks for your anaglyph Malmer, it's awesome!

Thanks for all the answers to my question!

It is more beautiful than I could have imagined

Click to view attachment


http://blogs.esa.int/rosetta/2014/09/10/ro...elfie-at-comet/

Very nice! If you really stretch the view of the comet, the jets are revealed again.

Click to view attachment

Phil

Mosaic of NavCam pictures taken on 7 september:

Could that also be lens glare going on? The spacecraft itself is also causing similar glare near each bright spot.

There is fuzziness elsewhere in that image which might be just glare, but this is right over the neck area, so I think this is jets.

Phil

Because several images were merged for admittedly pictorial impact, the data's integrity for interpretation is iffy to me. But man, what a pretty selfie!

These recent views, unlike earlier ones, are looking into the light. From this angle the jets should be more prominent relative to the cometary surface, similar to what we have seen in Cassini's images of Enceladus. So my bet is on Phil: that image does show the jets.

The latest ESA mosaic has a phenomenon that might be useful going forward: each adjacent pair happens to have enough overlap to yield a nice cross-eyed view of that section of landscape. In these views that I cropped and lined up (generally Sun coming from top or left for ease of visual sensemaking), the elevations of the platforms and furrows become much more clear, at least to me. Hoping this happenstance of the mosaic overlap is of use to somebody. In clockwise order:

Click to view attachment Click to view attachment Click to view attachment Click to view attachment

Edit: A tap or two of Ctrl+ helps to get the scale up to where stereo merging is easier.

Yes those mini stereo strips are really cool. It is a nice little extra perk. I eill try to make little mini 3D dem:s out of them. They make it easier to understand just how rough and hostie the surface really is. But I'm hoping that we get another osiris stereo pair at some point.

Thanks MarsInMyLifetime! Looking at the steep sided, flat topped, mound just to the lower right of the center of the image I've left in the quote... can anyone say if the bright top the result of a lighter deposit, or angle wrt the Sun?

Totally agree with you, Phil.
They are jets indeed, because they are oriented towards the Sun.
I made my own processing yesterday of the nucleus for some friends in France, haven't seen your post, and I obtained the same results...
Click to view attachment

That feature was exactly what got me to investigating the possible stereo effect. The shadow shows that it is projecting a rounded top onto the terrain, so it is definitely not at surface level (just a bright spot) or flat topped. It is boulder-like, unlike the rampart structures which are generally quite a bit larger. I'm looking forward to explanations why it and the series of smaller bright objects above it are not draped in the same dark stuff that covers the rest of the landscape.

The pan in the middle left has some interesting furrow features that look like fingers reaching into the circle. I'm starting to see these furrows/tubes in many places now. They may have something to do with the transport of volatiles to the surface (and then end up exposed as fossil features once their former substrate sublimates away).

I'm glad to hear you say that, I was thinking I was imagining things - there are linear features, and even sets of narrowly spaced parallel furrows, in the images I've seen. My guess would be gas transport to, but who knows (yet)? Fascinating!

The science editor of a reputable Dutch newspaper reported today that the Philea landing site selection process is becoming tense, as the sheer roughness of the 67P surface is becoming increasingly evident at the candidate landing sites. There are flatter (less rough) areas on 67P but these are unfavorable for the required amount of sunlight for Philea. What will the landing team decide? I can’t wait to hear their decision and rationale on Monday!

(below left) interesting bright circular patch at top right in sept 10 release.
Nice resolution in this release, also nice is the subtle illumination of the dark inner-facing 'side' between the two lobes.
the same area is covered on sept 1 aug 16 aug 8 aug 3, but the aug 7 release has it (below right), seems theres nothing there, perhaps a sort of camera artifact?
Click to view attachment Click to view attachment

Here is the spectacular image taken by Rosetta's NavCam on September 10, showing the nucleus of comet 67P/Churyumov–Gerasimenko, and fully cleaned and processed to show you its backlighted shape. The night side of the front lobe is now seen thanks to the sunlight coming from the other lobe... Enjoy !
Click to view attachment

Really impressive image Olivier !

Impressionnant, Olivier !
La présentation pour La Villette avance ?

Recent update from ESA Where Will Rosetta's Philae's Lander land on comet 67P/churyumov-Gerasimenko?

No matter what happens on touchdown, there will be loads of science data from Philae: quite the checklist, including a 'farewell' image from CIVA of the deployment!
Looks like the surface temperature is the main limit on lander lifetime as perihelion approaches.

Yes, it's fascinating to look at each part of landscape from its own "local level" as it were. The closest terrain appears scoured to me, suggesting that some venting occurs laterally, perhaps out from underneath rocky layers. Considering the eons of activity on this world, I'm actually surprised there is not much more buildup or selective puddling of boulders on the surface. Do they get ejected regularly, or is it a case of actually very low populations of boulders that are too heavy to leave the gravity well?

Thanks Polaris, Thanks Neo
Oui, ca avance bien mais Gilles doit faire un point très vite avec l'ESA, car la mission est gérée un peu aussi au "jour le jour". Le noyau est extremement cabossé à l'échelle du mètre de ce nous avons compris et meme sur les sites retenus l'atterrissage sera dangereux. En plus, ils n'ont aucune idée dans quoi va se ficher les grappins pour que la sonde s'aggrippe au noyau... En bref, c'est "chaud", plein de surprises et on est suspendus aux décisions. Du coup, je suis en retard sur ma presentation et Gilles aussi ! Je vous tiendrai au courant...

Thanks Polaris , Thanks Neo
Yes, AC is progressing well but Gilles must make a point quickly with ESA, because the mission is managed a little as the " day to day " . The core is extremely dented across the meter that we understand and even to the selected sites will be dangerous landing . In addition , they have no idea what will file grapples for the probe aggrippe kernel ... In short , it is " hot" , full of surprises and is suspended from the decisions. So, I 'm late on my presentation and Gilles too! I 'll keep you posted ...

In about an hour, the landing site will be announced.
http://www.esa.int/Our_Activities/Space_Sc...on_announcement

Edit:
Site J is the Primary site.
Site C is the secondary site.

If I understood right, they think they see some hints of activity from near the site, which they believe is associated with some of the cyllindrical pits we're seeing.


Edit2: new images of primary landing site.
http://www.esa.int/spaceinimages/Images/20...ry_landing_site
http://www.esa.int/spaceinimages/Images/20...g_site_close-up

And backup site.
http://www.esa.int/spaceinimages/Images/20...up_landing_site

Interesting that the landingsite 3D view looks like it is made using a digital elevation model with a picture draped over it.

The signal to noice ratio is just fabulous with the osiris camera!

How accurately can they target the lander ? I know it just floats down due to the comets gravity.

From http://www.esa.int/Our_Activities/Space_Sc...setta_s_lander:
"The descent to the comet is passive and it is only possible to predict that the landing point will place within a ‘landing ellipse’ typically a few hundred metres in size."

This is actually a quite good dispersion zone for this method of placement. Let's hope everything goes well with the release process and the calculations!

I don't think, that they really know the accuracy of the landing (at the moment). Roughly 1 square kilometer.

The actual landing position is highly sensitive to the velocity vector (amount and pointing) after separation of the lander. They first accelerate the orbiter roughly towards the nucleus onto a hyperbolic orbit, then separate Philae from Rosetta, and return to an elliptical orbit for Rosetta. Separation after accelaration towards the nucleus reduces the descent time, and the sensitivity of the trajectory regarding the field of gravity of the comet, and regarding the initial velocity vector after separation.
Neither the result of the first burn nor the momentum provided to Philae by the separation are known precisely.
There is some sensitivity to the mass of the nucleus. This mass cannot be determined exactly, since the orbit of Rosetta is influenced by the gravity as well as by gas emanated from the nucleus; this orbit is used to determine the mass and field of gravity of 67P/C-G.
There is some more subtle dependency of Philaes's trajectory from the detailed field of gravity of the nucleus.

Overview of the operations for landing (cropped screenshot of today's press conference) :
Click to view attachment

This is the area they are considering for site J to estimate the risk induced by slope (another screenshot):
Click to view attachment

... and the winner is ...

http://www.esa.int/Our_Activities/Space_Sc...osetta_s_lander

The caption says they used two images to make the anaglyph.

First, I thought, they would provide a complete recorded version of the press conference immediately after the conference. Seems not. So here some of the slides:
Click to view attachment

Edit: Quite some more background info about the selection process last week-end is described in this CNES article (in French).
Two things I didn't see elsewhere thus far have been, that Philae is expected to set on site J with 0.95 m/s, and site C won't be suitable for Consert.

here is the replay of today's landing site announcement:

http://www.esa.int/spaceinvideos/Videos/20...te_announcement

I made a detailed 3D model of the landingarea:

http://mattias.malmer.nu/wp-content/upload...07C90EBCBD8.mov

You can play with the 3d model if you like. (3D print?) Here is the obj file:

http://classic.syndicate.se/image/space/Landingsitemodel.zip

Up to now, I still haven't see on what axis the comet rotates. This is an important matter for simplifying the landing operation and the illumination factor. By the way, Click for an interesting NASA report.

for the rotation see the thread that was split off this one
i have posted many images with the X axis as the axis of rotation
http://www.unmannedspaceflight.com/index.p...st&p=212592

http://www.unmannedspaceflight.com/index.p...st&p=212594