The raws are very confusing due to their high contrast, but it's amazing the detail you can get by a slight adjustment.

In this image it appears that landslides in some of the craters have uncovered the bright material below a thin dark coating.

http://saturn.jpl.nasa.gov/multimedia/imag...3/N00092155.jpg

This is Alan's image from the above post, specially processed to bring out detail in bright and dark - a process that causes false bright fringes around some bright patches.

My impression is more that dark dust has slid over white patches. Does bright stuff flow in places? Not sure.

Phil

Click to view attachment

I still cannot imagine a mechanism that would produce the features we see. If the dark material impacted Iapetus, it is not going to slide around the surface or puddle in the bottom of craters like we have seen. Is it possible that in the past, Iapetus retained a thin Mars-like atmosphere that perhaps blew the stuff around?

My version of the big mosaic:


Maybe some color will be coming this way, too, depending on how hard it turns out to match all those 45 frames...

At the moment, here's that mosaic at 1/4 resolution with wide-angle color overlaid:

It's not registered very well, but I haven't really tried.

P.S., does anyone know a good image hosting service that allows big images and files over a couple of megabytes? Big mosaics such as this look awful at 1 megabyte limit this forum enforces.

Very, very nice... now that image (or a future version) should be the title image for Iapetus' wikipedia entry.

Took me 18 straight hours....

color composite from 3 images (well 9 if you are counting the filters).

is there enough on there to do a full disc at this resolution?

and if there is… is there a reason to take a stab at it when you know ugordan will just do it 20x better than i will?

the hires is here:

wanderingspace.net

its about 2000x2869 pixels huge there.

Ahhh, I probably shouldn't bother then...

When can we expect to see that beast?

so when y'all say overlaid… are you saying that you use a lo-res color image to “colorize” the hires clear filter? wouldn't that only color the image as well as say… how they colorized “it’s a Wonderful Life”?

Nice work Gordan and mgrodzki. A high res, fully registered color version should be great.

Some "complex" hydrocarbons may actually be volatile.

One way to degas (and purify) benzene:

1) Put benzene in a stopcocked flask connected to a 3 way tube with stopcock and connected to a vacuum line and also connected to another stopcocked flask (the receiver)
2) Freeze it (-78 C in dry ice/acetone bath is an easy way to do it in the lab, even though benzene melts at 5 C)
3) Open stopcocks to vacuum. Pull vacuum on entire system
4) Close stopcock to vacuum.
5) Remove cold bath under benzene-containing flask.
6) Move cold bath to empty flask.
7) After material transfers over to receiver flask, close stopcock, let benzene thaw. (You can now transfer flask into a drybox while still under vacuum, or put benzene under argon for air-sensitive reactions.)

Benzene sublimes in the vacuum, then recondenses into the cooled flask.



Wild idea, and not to well thought out on my part, but I wonder if it is possible if some of the ices we are seeing may be organic ices? Some might be volatile enough to transfer around. And some might even turn dark after enough exposure to light (UV photochemistry).

This could put a whole new level of complexity into the system (nicely described in the graphic by SFJCody here), with a thin coating of white stuff (ice), and a thing coating of white/dark stuff (organic ices) being mobile.

Is there any spectral data out there that could nip this hypothesis in the bud?

-Mike

speaking as a non-scientist… has anyone suggested that it looks EXACTLY like it was hit by a paintball? is there anything in the realm of possibility that it was hit by something not exactly solid, but kind of wet and liquid? is that insane?… i mean, i imagine slapping that thing with a ball of paint (already with craters) and it then makes sense the way that material seems to be lying on peaks and depressions.

Those "landslides" remind me more of this.

No idea.

If you are looking for something to do, why not try the 2909 mosaic from ORSHIRES001, in color? Admittedly, my will to get that done in color is waning...

[...]

This is the best explanation I've seen yet; it leaves in place the dark regions as the result of an exogenous process, but it doesn't require the visible dark material to also be the cause of the process.

and we are thinking the source of heat to cause this happen is…?

also thinking this is a negative on any plume activity?

I decided to give the color a shot after all, this is still a rough work in progress, roughly 1/3 is done:

[...]

Yes! - see my post yesterday.

What's so frustrating about this is that whether you believe white-on-black or black-on-white, most images contain at least several aspects that "prove" your hypothesis, sometimes even in the same crater. What we wouldn't give for one nicely-resolved (1m/pixel) image of a transition area!

You're gona make it to APOD Ugordan, and may be more.
I like this World.
Thanks

Gordan's mosaic is now posted at full resolution and less compressed on the blog.

Thanks Gordan! Keep these coming!

--Emily

Magnificent mosaics Ugordan (but you should have put a warning on the biggest one!)

Oh yes - and thanks for turning it north upward. I can now stop standing on my head in front of the computer.

Here's a preliminary (and quick) 1K map with special thanks to Gordan for allowing me to use one of his recent B&W mosaic versions. A couple of approach images are in there as well. I note that Claude (western basin) looks a little funny shaped. This is probably (in addition to the latitude effect) due to remapping from the triaxial ellipsoid into planetocentric coordinates.

Click to view attachment

I want to share what the "snowy" part of this world remind me :

Click to view attachment

Click to view attachment

Steve, do you keep progressive versions of your maps? I'd be amused to see what Iapetus looked like post-Voyager, post-B/C flyby, and then post Rev 49...

--Emily

Ugordan: WWWWWWWOOOOOOOOOOOWWWWWWWWWWW!

Ugordan, I use lunarpages.com for web hosting. They give you 350 GB (!) of storage for hosting for under $100 / yr. Try http://www.lunarpages.com.

- John Sheff
Cambridge, MA

Am I right in thinking that the dark markings at the very left (western) edge of the newly added material are actually shadows, and not intrinsically dark? They don't show up dark on previous versions of the map.

Beautiful work, Gordan.

You need a UMSF nickname. How about "Mosaic Master"?

Thanks, everyone. Alex, that would be unfitting as this is by far the largest mosaic I ever did. This may be routine stuff to some MER experts, but it sure isn't for me.

Anyway, here's the (probably final) product, an approximately natural (I hope) color view:


60 narrow-angle frames to go through...
I think I'm gonna lay off of Iapetus for the time being...

[...]

Mike.... the VIMS and CIRS on CASSINI will give us spectral and temperature data. That info may take awhile to reduce.

Ugordon .... magnificant image work... I think this will view will be the iconic Iaptus image for some time to come.

The sum is greater than the parts. Spencer model still holds up..... wanna see the VIMS and CIRS information. That simple dark albedo sublimation model can have some complex effects..... complexity from simple initial forces that build and feed on each other to make bewildering surfaces like what we see on Iapetus.

Not sure how valid this is but I went back to look again at the "boring" moon Rhea imaging and notice that Rhea also shows that strange sloppy half-melted look we see but without the albedo mix. At high res I think most of the mid size Saturn moons show some of this effect.
From DeChengst (great mosaic...)
http://www.unmannedspaceflight.com/index.p...ost&p=97858

Interesting.

Craig

So... the ridge. Does it disappear once it gets to Roncevaux Terra?! It certainly looks that way... but maybe it's just the angle we're looking from.

If the ridge is only in the dark bit, that would be unbelievably weird...

Yes David they are shadows near the terminator. It may look deceptive as I'm colorizing ugordon's B&W mosaic so shadowed areas would look falsely like the brownish dark terrain. Perhaps if I try some color images (e.g. ugordan's new color masterpiece) this can be remedied. The trick then is to have reasonably consistent color within the context of "natural", "near-true", "enhanced", and such.

Just a reminder to everyone, our mosaic master's first name is Gordan.

My apologies Gordan

Fantastic work... and as I mentioned... think this will be THE iconic Iapetus image. At least until some lands there.

Craig

[...]

I've been visiting Steve's page for quite some time now, and I have a lot of versions of Steve's maps.
Here's a little animation:

That is so cool!

Has anyone gone back over Black et al. [2004] to see how their radar observations match up with the latest imagery? Indeed, Porco et al. [2005] merits another read.

Here's my try at a non-linear stretch of the white mountain closeup. I used the "image/adjust/curves" tool in Photoshop <5.5> and kept the slope positive at all image levels, but it was nearly horizontal between the histogram peaks of the light and dark materials.

Great work, Ed...and I still have no idea what's going on here! Good grief, we might have to send a rover to find out...

Oh, and lest I forget: all hail the Mosaic Master!!! Showed your image to several of my co-workers today, Gordan; their jaws literally dropped.

I enhanced the contrast of this image using equalize histogram in ImageJ.

Click to view attachment

Works best on the Iapetus images with significant areas of both bright and dark terrain

I thought the ridge was rather neatly explained as the remnants of an infalling ring. That was a pretty convincing paper, as I recall (http://www.agu.org/pubs/crossref/2006/2005GL025386.shtml).

Speaking of the ridge, aside from the contrast between the dark & bright terrain (apparently a cosmetic feature), the distinctive thing here is the ridge. I'm led to wonder whether there might be a connection between the two. Consider the possibility that typical satellite impact velocities are such that under normal impact conditions the dark material is is chemically dissociated by the heat of the impact, whereas decaying ring particles could dump their gravitational energy gradually via friction rather than instantly, so that upon impact they have only the energy of low Iapetus orbit, allowing the dark material to survive intact. Alternately, per the notion that the dark material is already mixed into the surface and simply needed something to kick-start the sublimation which exposed it, perhaps the low-energy decay of the ring provided that trigger. Of course, sometimes a coincidence is just a coincidence.

that gordan hires is A+MAZE+ING. that spells spectacular.

OK -- for those who feel the bright surface is overlaying a dark substrate, how do you explain the "streams" of dark material which extend hundreds of kilometers into the trailing side? These are linear features made up of mostly contiguous dark material. Sometimes they separate into discrete pits or craters with dark floors, but for the most part they are dark "stains" that do not seem to follow fracture patterns or even organized crater chains.

It looks for all the world like jets of dark material sprayed from the leading edge back to the trailing edge...

-the other Doug

I think they are exactly that: streams of dark material, from a comparatively recent impact somewhere in the location of the snowman. Maybe the big snowman crater itself. They seem to radiate outward from a point.
If the dark material were present as an extremely thin layer, there might not be enough material to produce such a large and prominent ray system, so I see this as evidence for snow on gunk rather than gunk on snow.