[X] My Assistant

[Decepticon]

Nov. 2005 - 416,000 km - 2.5 km/pixel - eastern and central Cassini Region, northern bright terrain

http://space.jpl.nasa.gov/cgi-bin/wspace?t...porbs=1&brite=1

Buy this weekend (Nov 4,05) we will be getting some great views of Iapetus. Comparable to these images. http://ciclops.org/view.php?id=624

And buy Nov 11 will be within 417,000 km

I can't wait to see these images. 

I hope we get some approch images soon.

[Rob Pinnegar]

I hope we get some approch images soon.

It will be nice, but as has been pointed out elsewhere in this forum, for the most part we're going to be seeing parts of Iapetus that we've already seen at closer range (during the New Year's flyby).

[Decepticon]

Raw Images have started. http://saturn1.jpl.nasa.gov/multimedia/ima...5/N00042490.jpg

[tedstryk]

Raw Images have started. http://saturn1.jpl.nasa.gov/multimedia/ima...5/N00042490.jpg

Yes, but the angles and illumination are a bit different. Which, as far as making nice pictures to look at, is very exciting.

[Decepticon]

Oddly I can't find the name of that crater right hand side. Does anyone know if its been named?

That the central peak looks very prominent from this distance.

[tfisher]

Raw Images have started. http://saturn1.jpl.nasa.gov/multimedia/ima...5/N00042490.jpg

Here's an attempt at a color merge using two IR images, green, and UV. I pulled up the contrast a bit to try to bring out detail in the dark areas, but it is mostly JPEG artifacts in the raw data there.

[jmknapp]

The IR images show the dark area to be a bit hotter compared to UV:



If you take the ratio of the brightness of the dark to light areas, the ratio is almost 2x greater in the IR image.

To be expected I guess... like asphalt on a sunny day.

[jmknapp]

Oddly I can't find the name of that crater right hand side. Does anyone know if its been named?

That the central peak looks very prominent from this distance.

It's not listed at the USGS site. Maybe it's unnamed as yet?

Here's a mercator map showing its location as about 6N 324W:

Iapetus map

The size looks to be about 180km across (15 pixels at ~2,000,000 km).

There's nothing in the USGS list that matches that lat/lon:

USGS Iapetus nomenclature

Reportedly most of the features are named after characters in Chanson de Roland, or rather the British translation by Dorothy Sayers, Song of Roland.

[tedstryk]

The IR images show the dark area to be a bit hotter compared to UV:



If you take the ratio of the brightness of the dark to light areas, the ratio is almost 2x greater in the IR image.

To be expected I guess... like asphalt on a sunny day.

I was wondering wonder if you are right in an absolute sense. In other words, I wonder if the dark area is actually brighter causing the contrast to be less, or if the bright area is dimmer. With autostretch, there is no way to tell. I am not that confident with my Cassini color skills, but I decided to see if the trend showed up in Voyager OGV data. I took the highest resolution (and also least smeared) set, and carefully reprocessed them (the images I posted before had been cosmetically toyed with a bit, and I wanted to make sure I wasn't enhancing my own foolings with the channel mixer). Sure enough, when I enhanced the color, and overlayed it on a high-pass filtered image, the redness of the area was clear (well, orangeness, but based on what we are seeing, it seem that this trend continues further into the red and infrared).

[um3k]

Just take a look at this image and you will see the browness of Cassini Regio. http://photojournal.jpl.nasa.gov/catalog/PIA06167

[tasp]

Just take a look at this image and you will see the browness of Cassini Regio. http://photojournal.jpl.nasa.gov/catalog/PIA06167

Would you characterize the color of the dark bottoms of the craters of Hyperion to be brown also?

[um3k]

Would you characterize the color of the dark bottoms of the craters of Hyperion to be brown also?

I haven't seen a color image, so I can't answer that question.

[scalbers]

Yes, but the angles and illumination are a bit different.  Which, as far as making nice pictures to look at, is very exciting.

Nice to see the entire eastern edge of Cassini Regio in context. This is higher in resolution (~75%) than some of the previous imagery that I've used (e.g. PIA06100) and thus ought to be able to add some addtional details into my map. It also has a higher phase angle with more shadows to give contrast.

For comparison, my map with the previous imagery is at http://laps.fsl.noaa.gov/albers/sos/sos.html#IAPETUS

[JRehling]

Nice to see the entire eastern edge of Cassini Regio in context. This is higher in resolution (~75%) than some of the previous imagery that I've used (e.g. PIA06100) and thus ought to be able to add some addtional details into my map. It also has a higher phase angle with more shadows to give contrast.

For comparison, my map with the previous imagery is at http://laps.fsl.noaa.gov/albers/sos/sos.html#IAPETUS

It is interesting to see the white, vaguely peninsular, intrusion into eastern Cassini Regio. It is possibly similar to the white mountains that stick up out of western Cassini Regio. In both cases, it seems to be a continuation of the equatorial ridge, but broken in the western case, and at both ends of Cassini, bright instead of dark. Getting a better look at the "black eye" crater east of Cassini is also turning up some clues -- the identification of a central peak is new. More significant, it seems as though the darkening is, to the west of that crater, on the OUTSIDE of the rim, not the inside. If the dark stuff was blasted ballistically, this is a key distinction: was it landing on eastern Cassini Regio from the east, or from the west? If it came from the east, then likely all of Cassini Regio was laid out from east to west. If it came from the west, then likely all of Cassini Regio was emplaced from the inside (and/or above) OUT. What we don't get to see on this encounter are the craters to the east of that one, which are smaller and also have darkened rims. Whether the three rims were darkened west to east or vice versa, then we have a new significant clue regarding the creation of Cassini Regio. But we don't find out anything more until later.

[scalbers]

It is suggestive indeed to look at the white peninsular region on the eastern edge of Cassini Regio. It does appear somewhat continuous with the white peaks on the western side. The trick though is that a close look suggests that the white peninsular region is slightly inclined to the equator, assuming I have the night-side image navigated properly. The new imagery should also help me to get the navigation of various images to fit better.

Is there any chance the 2007 encounter will show us a close-up of the white portion of the equator?

[Michael Capobian...]

Iapetus in Saturnlight

It's interesting to compare the albedo patterns in this picture of the "black eye" taken in Saturnlight with the new image. There doesn't appear to be any correspondence between the dark stuff and central peak.

Michael

It is interesting to see the white, vaguely peninsular, intrusion into eastern Cassini Regio. It is possibly similar to the white mountains that stick up out of western Cassini Regio. In both cases, it seems to be a continuation of the equatorial ridge, but broken in the western case, and at both ends of Cassini, bright instead of dark. Getting a better look at the "black eye" crater east of Cassini is also turning up some clues -- the identification of a central peak is new. More significant, it seems as though the darkening is, to the west of that crater, on the OUTSIDE of the rim, not the inside. If the dark stuff was blasted ballistically, this is a key distinction: was it landing on eastern Cassini Regio from the east, or from the west? If it came from the east, then likely all of Cassini Regio was laid out from east to west. If it came from the west, then likely all of Cassini Regio was emplaced from the inside (and/or above) OUT. What we don't get to see on this encounter are the craters to the east of that one, which are smaller and also have darkened rims. Whether the three rims were darkened west to east or vice versa, then we have a new significant clue regarding the creation of Cassini Regio. But we don't find out anything more until later.

[Decepticon]

New stuff in. Lots of pics of empty space.

http://saturn1.jpl.nasa.gov/multimedia/ima...5/N00042609.jpg

[edstrick]

I keep looking at the best available images of the big crater right at the end of Cassini Regio to see if I can see Arthur C. Clarke's black monolith standing there.....

(Note: Go back and read the book "2001, A Space Odyssey"....... The Stargate Monolith is on Iapetus, not orbiting Jupiter... In the middle of a bulls-eye target crater) ;-)

[Decepticon]

[ljk4-1]

I keep looking at the best available images of the big crater right at the end of Cassini Regio to see if I can see Arthur C. Clarke's black monolith standing there.....

(Note:  Go back and read the book "2001, A Space Odyssey"....... The Stargate Monolith is on Iapetus, not orbiting Jupiter... In the middle of a bulls-eye target crater)  ;-)

In the same 1968 novel, Clarke also mentioned the dozens of rings circling Saturn, back when the planet was thought to have only 3 or 4 large ones.

Dare I suggest we ask the Cassini team for a closer look at Iapetus' large crater?

[jmknapp]

In the same 1968 novel, Clarke also mentioned the dozens of rings circling Saturn, back when the planet was thought to have only 3 or 4 large ones.

Dare I suggest we ask the Cassini team for a closer look at Iapetus' large crater?

In a few days (Nov. 12 @14:36 UTC) Cassini will come close enough (~416,000) to fill over half a NAC frame with Iapetus--although said crater will be in shadow:



The above uses Steve Albers' map. The science plan says they're going to be taking NAC shots of Iapetus up to 05:41 UTC: VIMS_017IA_IAPETUS006_PRIME

[tasp]

The above uses Steve Albers' map. The science plan says they're going to be taking NAC shots of Iapetus up to 05:41 UTC: VIMS_017IA_IAPETUS006_PRIME

[/quote]


Figures, the expected view is 180 degrees around from what I want to look at.

I appreciate the humor in this. And am still happy to have more Iapetus pictures. I just think the source crater for the emplaced ring material is on the other side.

Should be good pictures, though, Voyager never exceeded half a NA frame on Iapetus, did it?

[Decepticon]

New update today.

Can anyone give them a little color? http://saturn1.jpl.nasa.gov/multimedia/ima...5/N00042784.jpg

http://saturn1.jpl.nasa.gov/multimedia/ima...?browseLatest=1

[tedstryk]

Should be good pictures, though, Voyager never exceeded half a NA frame on Iapetus, did it?

Not even close. Here is that color super-res view I posted earlier, inset on the full, raw 800x800 clear filtered image from the highest resolution sequence.



Here is the same image, with the Voyager image to scale with one of the November 5 Cassini images.

[djxatlanta]

Long-time lurker, first-time poster. Here's a color image of Iapetus I processed last night from the new images released yesterday... although looking at it again this morning, I see one of the green stacked images is off by just a touch.

New update today.

Can anyone give them a little color? http://saturn1.jpl.nasa.gov/multimedia/ima...5/N00042784.jpg

http://saturn1.jpl.nasa.gov/multimedia/ima...?browseLatest=1

[Decepticon]

^ Welcome!

Nice work.

[Decepticon]

Oh wow. http://saturn1.jpl.nasa.gov/multimedia/ima...5/N00042815.jpg

http://saturn1.jpl.nasa.gov/multimedia/ima...heQ=0&storedQ=0

[Rob Pinnegar]

Some interesting topography there near the terminator -- 'seem to be some parallel canyons there. Kind of puts one in mind of the "tiger stripes" on Enceladus, but it's hard to imagine they could be the same type of feature.

[volcanopele]

Tiger stripes are much finer structures than what you see here. Remember, Iapetus is...lumpy. I know that on the limb you have both a 350-km wide impact basin and just north of that you have the equatorial ridge.

[dilo]

False color composition (MT2+Green+UV); normal and enhanced tones versions.
Methane red dominate on the dark terrain, "green" spots are intriguing...

Attached thumbnail(s)

 

[Decepticon]

Nov 10 Update! http://saturn1.jpl.nasa.gov/multimedia/ima...heQ=0&storedQ=0
I wonder if those "Scratches" are fractures caused by that Massive Basin.

Is it me or is jpg compression killing these images.
I expected much bigger pictures buy now.

[Decepticon]

I hope this resolution will help in Steves Albers Map of Iapetus.

[tedstryk]

Well, remember that the best images now are from 639,742, and closest approach is about 416,000, so we should be seeng some significantly closer images than these. Nothing like around New Years, but it should be good.

[scalbers]

The terminator is moving as the higher resolution images are coming in. So from a mapping perspective it is turning out to be an interesting tradeoff in terms of which image to use over a particular location. The sun has also moved to more northerly latitudes over the past year adding to the new revelations of this flyby.

[Decepticon]

Here she is in all her glory!

http://saturn1.jpl.nasa.gov/multimedia/ima...heQ=0&storedQ=0

[tedstryk]

Here she is in all her glory!

http://saturn1.jpl.nasa.gov/multimedia/ima...heQ=0&storedQ=0

Great images. But closest approach is 416,000, and these are about 480,000. So we probably have not seen the best yet. I cant wait to do a super-resolution image with some PDS products of this. Also, Decepticon, it seems we are getting some nightside images that you like. This is turning into a most interesting flyby.

[Decepticon]

Great!

Nov 14 Cassini will have a great opportunity for that.
I hope its done. http://space.jpl.nasa.gov/cgi-bin/wspace?t...porbs=1&brite=1


I wonder JPL could have changed this Non-Targeted for a closer flyby.

[Toma B]

Isn't this one lovely untargeted flyby???

[tedstryk]

Isn't this one lovely untargeted flyby???     

Great mosaic!

[Rob Pinnegar]

In spite of their different sizes, some of the adjacent images in the above mosaic work not too badly as stereo pairs. Any chance we could see all of them at the same apparent size? Fourteen images means thirteen sets of stereo pairs -- that would give a really nice idea of Iapetus' shape.

[Decepticon]

Now that's a Excellent peace of work!

Now someone take out a set of crayons and color these bad boys!

[alan]

Iapetus in color

Images N42987, N42988, N42989 merged using ImageJ
http://rsb.info.nih.gov/ij/

[David]

It's scary just how many huge impacts Iapetus has taken; I count six super-sized craters just on this side of the moon. Especially the one that produced that massive crater in the middle of the dark zone. Isn't that bigger, proportionally, than Mimas' Herschel crater?

[Decepticon]

I think the crater it's self is bigger than Mimas altogether!

I made this a while ago showing mimas compared to Tethys impact basin Odysseus.

[Rob Pinnegar]

I think the crater it's self is bigger than Mimas altogether!

Not only is it bigger than Mimas, but it's bigger than Enceladus as well, by about 50 kilometres.

[ljk4-1]

It's scary just how many huge impacts Iapetus has taken; I count six super-sized craters just on this side of the moon.  Especially the one that produced that massive crater in the middle of the dark zone.  Isn't that bigger, proportionally, than Mimas' Herschel crater?

It makes one wonder just how many more moons Saturn had in the past.

And why don't the other gas giant worlds have rings as magnificent as Saturn's?

[Rob Pinnegar]

It's scary just how many huge impacts Iapetus has taken; I count six super-sized craters just on this side of the moon.

There is another huge one in the southern part of Roncevaux Terra. It is almost as big as the Cassini Regio basin that dominates the recent Iapetus shots. The one in Roncevaux Terra is on the side of Iapetus that faces away from Saturn, so it can't be seen in the images from the New Year's flyby, or the one a few days ago.

However, it was imaged from a distance as Cassini was approaching Saturn (and will be imaged at much better resolution in September 2007). If you look in the "Latest from Saturn" section on the Cassini main page and select "Iapetus", you can find some old shots of it there (they're on the second page).

[tasp]

If we find Iapetus today pretty much where it formed 4+ billion years ago, then perhaps we can infer a few things about it's past.

Considering the large potential volume of space Iapetus had to 'sweep' up in its' pokey ~80 day orbit, can we assume Iapetus took longer to form than the rest of Saturn's moons interior to it?

If the formation was slow enough, would Iapetus have had time to radiate impact heating and radio-nuclide heating early enough in its lifetime to have finished its accretion stage with a solid crust? Was Iapetus molten period unusually short for an object of its mass?

Would the large impact craters now visible be a record of a final stage of accretion that we apparently don't see on any other moon to this extent?

[JRehling]

If we find Iapetus today pretty much where it formed 4+ billion years ago, then perhaps we can infer a few things about it's past.

Considering the large potential volume of space Iapetus had to 'sweep' up in its' pokey ~80 day orbit, can we assume Iapetus took longer to form than the rest of Saturn's moons interior to it?

If the formation was slow enough, would Iapetus have had time to radiate impact heating and radio-nuclide heating early enough in its lifetime to have finished its accretion stage with a solid crust?  Was Iapetus molten period unusually short for an object of its mass?

Would the large impact craters now visible be a record of a final stage of accretion that we apparently don't see on any other moon to this extent?

Certainly, Iapetus is an extreme outlier as a large satellite so far out. Any other satellite that far out is much smaller; any other satellite that large is much closer to its primary.

Your idea of radiogenic heating having run its course prior to accretion's completing is an interesting one. Alternately, it could be that gas giants gave off enough heat in their early history to melt their satellites' surfaces. That could explain why Callisto and Rhea are not as rugged as Iapetus. The contrast between Rhea and Iapetus is especially interesting, since they are the same distance from the Sun and nearly identical in size -- yet so different, mainly in ways that make Iapetus unique and Rhea dull.

[ugordan]

  Great!

Nov 14 Cassini will have a great opportunity for that.
I hope its done. http://space.jpl.nasa.gov/cgi-bin/wspace?t...porbs=1&brite=1
I wonder JPL could have changed this Non-Targeted for a closer flyby.

It's great how Cassini's pointing at Iapetus during the whole encounter has been perfect, keeping Iapetus in the center of the NAC frame the whole time. I remember the "close" approach to Iapetus (around 1 MKm, IIRC) about a year ago where the pointing was so bad that most of the shots were off, clipping Iapetus off, it was very frustrating , remember this was before the New Year's flyby. Funny that only those images that got the pointing slightly off could stand a chance of capturing the whole (still pretty small) crescent...

[Decepticon]

However, it was imaged from a distance as Cassini was approaching Saturn (and will be imaged at much better resolution in September 2007). If you look in the "Latest from Saturn" section on the Cassini main page and select "Iapetus", you can find some old shots of it there (they're on the second page).

I must be blind! I can't find it.

[Ian R]

I must be blind! I can't find it. 

Only the eastern rim is visible in the second image, while the floor of the basin can be seen in the third, black & white, picture.

[tasp]

The big 'bite out of the apple' crater on the terminator in the center picture seems elongated. (granted a nice fully illuminated shot would help interpretation)

Would like to keep a close eye on this during the 2007 flyby (my impression is we see this area of Iapetus in that flyby), am considering this to be a candidate crater for consideration of being the source crater for a grazing impact in the same vein as the possible Orpheus impact with earth.

May have some relevence in Pluto studies too.


Of course the white equatorial peaks are fascinating too.

Appreciate the pix posting, {my computer skills aren't up to that sort of thing}

[TritonAntares]

....
Of course the white equatorial peaks are fascinating too.
...

Hi,
here is something about what we'll expect in Sep.2007:

The 'white mountains' will be in prime focus...
In detail:
http://saturn.jpl.nasa.gov/multimedia/prod...HARM_050125.ppt (21 MB)
--------------------------------------------------------------------------------------------------------------
I wonder about the name of the prominent crater at the terminator:

Is it 'Roland' ?

'All named surface structures are named after persons and places from the german 'Roland-Song'. Tale tells Roland was one of 12 paladines of Karl the Great.
He fought against the Basks in Spain and died 778 in Roncesvalles.'

Bye,
TritonAntares

[Jeff7]

If we find Iapetus today pretty much where it formed 4+ billion years ago, then perhaps we can infer a few things about it's past.

Considering the large potential volume of space Iapetus had to 'sweep' up in its' pokey ~80 day orbit, can we assume Iapetus took longer to form than the rest of Saturn's moons interior to it?

If the formation was slow enough, would Iapetus have had time to radiate impact heating and radio-nuclide heating early enough in its lifetime to have finished its accretion stage with a solid crust?  Was Iapetus molten period unusually short for an object of its mass?

Would the large impact craters now visible be a record of a final stage of accretion that we apparently don't see on any other moon to this extent?

Molten period....that just brought up an odd theory for that ridge. Something to try:
on a very cold (sub-freezing) metal surface, place a drop of water there. Once it freezes, look at the top - there is a point.
Now granted, water and rock may behave very differently as they solidify....but, if Iapetus was gooey or liquid, and it began to freeze up again, this could have created that ridge, in a similar manner to the point on a drop of water.

Probably not what happened; just a wild guess.

[volcanopele]

I wonder about the name of the prominent crater at the terminator:
http://saturn.jpl.nasa.gov/multimedia/imag...5/N00042980.jpg
Is it  'Roland' ?
http://solarsystem.dlr.de/HofW/nr/051/Iapetus.gif
'All named surface structures are named after persons and places from the german 'Roland-Song'. Tale tells Roland was one of 12 paladines of Karl the Great.
He fought against the Basks in Spain and died 778 in Roncesvalles.'

Bye,
TritonAntares

Yep, that's Roland

[tasp]

I think I have mentioned this before, the tidal breaking effect of Saturn would have been unusual, too.

Because of the distance Saturn's tidal effect on Iapetus would have been quite weak compared to the closer satellites. That Iapatus is tide locked now, verifies the effect but does not clue us in how long it did take.

Due to the protracted braking, the internal heating evolved would have had longer to dissipate.

I think we have an object here with a uniquely ancient crust (for its size). That the surface of Iapetus exhibits a degree of 'lumpiness', an amazing array of extremely large craters is seemingly consistent with these musings.

And the icing on the cake, Cassini Regio and the equatorial ridge......

[tedstryk]

It isn't over yet!

[Rob Pinnegar]

Man. Look at that huge dent in the upper-left-quadrant limb. That's gotta be part of the huge topographic basin that has been discussed here previously. It's in the right part of Iapetus -- north central Cassini Regio.

[volcanopele]

Man. Look at that huge dent in the upper-left-quadrant limb. That's gotta be part of the huge topographic basin that has been discussed here previously. It's in the right part of Iapetus -- north central Cassini Regio.

No, think bigger...

[Decepticon]

Whoo Hoo! Saturn shine!

Having a tough time getting any detail.

[volcanopele]

Whoo Hoo! Saturn shine!

Having a tough time getting any detail.

hmmm, the quantization due to the stretch, the jpeg compression, and the 12-bit to 8-bit conversion does do a number on how much detail you can get out of these jpegs in the region illuminated by Saturn-shine. Not to mention the scattered light

[Ian R]

hmmm, the quantization due to the stretch, the jpeg compression, and the 12-bit to 8-bit conversion does do a number on how much detail you can get out of these jpegs in the region illuminated by Saturn-shine.  Not to mention the scattered light

Jason, where can we find the topographical data from the January flyby that revealed the existence of the large basin?

Thanks!

[volcanopele]

Jason, where can we find the topographical data from the January flyby that revealed the existence of the large basin?

Thanks! 

I don't know of a graphic available online, but it is described in Bernd's DPS abstract:

http://www.aas.org/publications/baas/v37n3/dps2005/82.htm

[Ian R]

I don't know of a graphic available online, but it is described in Bernd's DPS abstract:

http://www.aas.org/publications/baas/v37n3/dps2005/82.htm

Thanks Jason.

[Ian R]

Whoo Hoo! Saturn shine!

Having a tough time getting any detail.

This is the best I can get out of the nightside from the raw JPEGs:

[Ian R]

Night-side in context:

[Ian R]

[47.08] The topography of Iapetus' leading side

There is an old 800 km impact basin centered at 270 degrees E, 40 degrees N with rim topography of more than 10 km extending over scales of 300-400 km

http://www.aas.org/publications/baas/v37n3/dps2005/82.htm

Judging from this abstract, this should be the rough postion and extent of the large basin:

[Decepticon]

Another download. http://saturn.jpl.nasa.gov/multimedia/imag...heQ=0&storedQ=0

[Toma B]

Here's updated version of my "Iapetus flyby" image...

P.S.
IT IS FREE FOR ALL WHO WANTS TO HAVE IT AND SHOW IT TO ANYBODY ANYWHERE...
NO COPIRIGHTING LIKE SOME GUYS LATELLY DID...!!!
(yes it took me some time to make it but I don't own this picture anymore than NASA/JPL does...)

Thanks NASA/JPL Cassini...Everybody...

[TritonAntares]

Here's updated version of my "Iapetus flyby" image...
...
Thanks NASA/JPL Cassini...Everybody...

Thanks only to Iapetus himself...
... he owns his right of picture ...
----------------------------------------------------------------
Bytheway, really great montage...
... wish to own it as poster.

Bye,
TritonAntares

[tedstryk]

Here's updated version of my "Iapetus flyby" image...

P.S.
IT IS FREE FOR ALL WHO WANTS TO HAVE IT AND SHOW IT TO ANYBODY ANYWHERE...
NO COPIRIGHTING LIKE SOME GUYS LATELLY DID...!!!    
(yes it took me some time to make it but I don't own this picture anymore than NASA/JPL does...)

Thanks NASA/JPL Cassini...Everybody...

Great mosaic.

[Toma B]

... wish to own it as poster.
TritonAntares

OK I will send you 16 times bigger image if you pay me $126 or (150.000 pesos)...
I know it' not verry cheap but you know I had to download ALL THE RAW images and then there is a price of image editing software , not to mention my WORK...

Man I'm gonna be rich in no time!!!
.
.
.
.
.
.
.
.
JUST KIDDING!!!

[Phil Stooke]

This:



is my version of the saturnshine image. It's a composite of the two images from that sequence. That is one way to reduce those hideous JPEG artifacts in these early release images. It will work better on the later earthshine sequence as there are more images to merge.

Phil

[dvandorn]

Hmmm... let's see, Earthshine ought to correlate pretty well to Sunshine at Saturn's distance... but I imagine there might be a small strip around the terminator that would see Earth and not the Sun.

I must say, I'm impressed with Cassini's cameras, that they can get images only from the small amount of light reflected all the way from Earth to Saturn...



Just kidding, Phil -- I just couldn't let than one lie there. As typos go, it was one of the more entertaining.

-the other Doug

[Phil Stooke]

Poo! Yes, a blunder. To make up for it, here's the other sequence in - uh - planetshine:



Just two of the better frames from the sequence merged (after individual processing).

Phil

[JRehling]

is my version of the saturnshine image.  It's a composite of the two images from that sequence.  That is one way to reduce those hideous JPEG artifacts in these early release images.  It will work better on the later earthshine sequence as there are more  images to merge.

Good work -- as usual!

The craters to the east of Cassini Regio are of intense interest, I think. They are laid out about like a snowman, a sequence in decreasing size from west to east. About three large ones show various degrees of "black eye". This is interesting because it's clear that CR's dark stuff (henceforth, CRDS) was deposited, at the margins, ballistically. At the borders, the deposition reflects topography, and when topography is known, the patterns reveal the trajectory of the source material.

We can probably say there are about three good candidates for the trajectory of the CRDS.

1) Endogenous: Coming from inside CR and spraying outwards. If this is what happened, the CRDS border should everywhere show an in-to-out pattern.
2) Exogenous and "above": Some sort of "cloud" was in front of Iapetus, and either in one sweep or multiple sweeps, Iapetus overran the CRDS. This would generate a border that is in-to-out also. Any asymmetries in CR (and we know it is significantly asymmetrical) would reveal the trajectory of Iapetus through the cloud.
3) Splash: A very large impactor struck Iapetus and the remains of that body is the origin of CRDS. The CR border patterns should reveal the location of the source of the impact.

Let's call the snowman craters A, B, and C, in order of decreasing size, west to east.

The snowman craters east of CR make (1) and (2) hard to support. But here is the key question: Does the CRDS show that it was deposited in them east to west (which would clinch origin (3) decisively) or west to east? The location of the dark stuff is easily seen in saturnshine:

http://photojournal.jpl.nasa.gov/jpegMod/PIA06168_modest.jpg

But this image makes it very hard to determine the topography. We only have one field of information, and if it indicates albedo, we can't also perform shape from shading!

In that image, snowman crater B seems to show CRDS deposited on the west inner rim, which would decisively indicate that theories (1) and (2) are kaput. Yet it is also clear that some in-to-out deposition of CRDS occurred in the general vicinity: Note the Tsaichovsky-looking crater to the left of the snowmen, near the left edge of the image.

But it's hard to tell what is going on with Snowman A. Is that "black-eye" pattern on the inside of the west rim, or the outside? This image:

http://saturn.jpl.nasa.gov/multimedia/imag...5/N00042486.jpg

makes it seem like the outside rim may have deposits -- higher resolution would be incredibly useful!

But note the central peak: it appears not to have CRDS. If the crater rim has CRDS, then Snowman A is older than the CRDS event -- but the central peak shows no CRDS although Snowman B and C do -- how could CRDS "leap" over Snowman A's central peak and deposit onto the smaller Snowman craters? One resolution would be if Snowman A *was* the CRDS event (or a contemporaneous part of the process). Imagine a series of dark impactors hitting Iapetus in a large chain. It appears as though Snowman B overlaps the other two Snowman craters -- perhaps they were formed in the same minute, leaving dark rims but white interiors, as a possible fourth and larger impactor hit inside what is now CR, splashing its dark contents outward, leaving in-to-out patterns around most of CR's boundaries, with the exception of the Snowman craters.

At first glance, this seems unusually complex for a simplest explanation. Yet, the quirk of the CRDS pattern on the Snowman craters demands something more complex than theories (1) and (2). Any explanation that can't explain the Snowman craters is dead on arrival.

[Toma B]

Final image of this Iapetus flyby...
Thanks for watching...

[Rob Pinnegar]

Any explanation that can't explain the Snowman craters is dead on arrival.

Agreed, but I wonder whether we are ever going to get decent resolution Sunshine images of the Snowman region. From the looks of things, that part of Iapetus is going to be in darkness during the close flyby of 2007. Saturnshine shots will certainly help at that time, but I guess that from such close range blurring has got to be a problem over long exposures. At least the recent images of Snowman on the terminator should help with the topography.

I agree that Snowman is key to understanding the CRDS mystery -- but these million-kilometre snapshots just don't quite cut it. Keep those fingers crossed for the extended mission.

[scalbers]

I have an updated version of the Iapetus map now posted (as of 11/17). This has several of the flyby images as close as 480000km included. Interesting to see a basin I hadn't noticed before on icy terrain just outside the NE edge of Cassini Regio and NW of the Snowman craters. I plan to do some additional cleanup and such on the map.

http://laps.noaa.gov/albers/sos/sos.html#IAPETUS

[TritonAntares]

Hi Steve !

Would also be nice to see a north polar stereographic projection like this one:


There have been so many new pics from the north side of iapetus, that such a map should give some more information than the old one,
especially about the crater and basin sizes.

Bye,
TritonAntares

[Toma B]

Just added last 2 picture of Iapetus from this flyby...
Now it's complete...
I hope you will like it...

[alan]

View of Iapetus from North using Titan24 with Steve Albers latest Image

[ugordan]

Looks like they're really persistent with the NT imaging sequence:

http://saturn.jpl.nasa.gov/multimedia/imag...eiImageID=54545

1,4 mil km out and still shootin'

This ought to make for a great color flyby movie once the images are on the PDS, it's gonna kick the heck out of the Voyager Iapetus flyby sequence

[edstrick]

These extreme crescent images don't show much terrain, but give accurate limb profiles on the illuminated limb to build up a precise global shape model.

Also of interest is the difference between dark and light materials photometric functions at high phase angle.... tells something about the physical / optical properties of individual grains of the materials.

[TritonAntares]

...
Interesting to see a basin I hadn't noticed before on icy terrain just outside the NE edge of Cassini Regio and NW of the Snowman craters.
I plan to do some additional cleanup and such on the map.
...

I'm not quite sure which basin you mean Steve, but a really large bassin - if it is really one - can be seen on images taken on October 22, 2004 from 1.6 Mio. km:

or this one:
http://saturn1.jpl.nasa.gov/multimedia/ima...5/N00022974.jpg

I mean the bright walllike structure about 2 diameters NNE of the biggest Snowman crater (not NW?!). Is it the eastern rim of a very large basin?
----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Another question is about upcoming Iapetus-far-encounters in 2006:

(I) January 25 - 879.000 km - 5,3 km/pxl
http://space.jpl.nasa.gov/cgi-bin/wspace?t...vmul=-1&bfov=30
Mainly known terrain, but more southern latitudes; probably the Snowman craters in saturnshine.
(II) April 11 - 603.000 km - 3,4 km/pxl
http://space.jpl.nasa.gov/cgi-bin/wspace?t...vmul=-1&bfov=30
Southern regions of the leading side, for sure parts of the giant basin found in summer 2004; probably in saturnshine?

Are there any animations of these encounters available?
Any more infos?

Bye
TritonAntares

[scalbers]

Triton-Antares,

The basin I'm looking at shows up nicely on alan's Northern orthographic projection at about latitude 55N, longitude 335 (about 4 o'clock). Interesting wall you are also pointing out.

Good to hear we have some more NT encounters in 2006. We certainly have some animation experts in this forum who might be able to show us what they will look like. I can run Celestia on my desktop to see such animations, though I can generally post just still screenshots. For example, here is a view from April 11, 2006 at this URL:

http://laps.noaa.gov/albers/celestia/celestia.png

[Decepticon]

Where can I get that program?

It provides excellent views!

[TritonAntares]

...
The basin I'm looking at shows up nicely on alan's Northern orthographic projection at about latitude 55N, longitude 335 (about 4 o'clock). Interesting wall you are also pointing out.
...

Hi Steve !

Aah, you meant one of those huge craters at the terminator during the november encounter.
Maybe a mid-size basin...
I'm glad to read you recognized this wall...
I thought it could also be an artificial structure in this low quality image...

------------------------------------------------------------------------------------------------------------------------------------------------
Again, to all animation experts:

Are there any animations of these Iapetus-far-encounters available?
(I) January 25 - 879.000 km - 5,3 km/pxl
(II) April 11 - 603.000 km - 3,4 km/pxl

Many thanks,
TritonAntares

[scalbers]

Where can I get that program?

It provides excellent views!

Hello Decepticon...

Celestia is freeware - the price is certainly right - at http://216.231.48.101/celestia

The software is user configurable, so that I've been adding in my maps to its texture database. It has Cassini's location pre-programmed into it. Good luck with it.

[Bjorn Jonsson]

Again, to all animation experts:

Are there any animations of these Iapetus-far-encounters available?
(I) January 25 - 879.000 km - 5,3 km/pxl
(II) April 11 - 603.000 km - 3,4 km/pxl

I made a quick animation of the April flyby and will make another one tomorrow if someone doesn't do so before me.

I used a slightly modified version of Steve's map.

The animation starts on April 7 2006 00:00 and ends on April 16, 2006 15:00. The distance to Iapetus at the start and at the end is a little over 1,000,000 km. The field of view is 0.15 degrees.

The animation can be downloaded here (7 MB; encoded using DivX):

http://www.mmedia.is/bjj/misc/css_stuff/mi...tus_apr2006.avi

[TritonAntares]

...
The animation starts on April 7 2006 00:00 and ends on April 16, 2006 15:00.
The distance to Iapetus at the start and at the end is a little over 1,000,000 km.
...

Excellent Bjorn,

seems that we'll see some new fairly unknown parts of the southpolar cap.
Also interesting, Iapetus starts in half phase about a million km away and than shrinks into cresent.
The huge basin - found in july/august 2004 - will not be visible.
I'm quite sure it's situated on the hemisphere that never gets saturnshine due to Iapetus looked rotation...

Nevertheless 9 day long far-encounter......

Bye,
TritonAntares

[edstrick]

Is this another basin? We only saw part of the big basin that's fully illuminated here in the image sequence last January. I tried to trace the equatorial ridge into the terminator, but it was too close to the basin's rim and presumably was pretty much obliterated.

In the new flyby sequence, we get views further east, and I keep suspecting another badly damaged basin, almost contacting the big one. I've noted it's possible rim with red radial marks.

The equatorial ridge seems absent in this region, but may have been obliterated by the new basin I suspect I see. I've marked a (bad... it's probably too far south) extrapolation of the equatorial ridge into the suspected basin with green X's. where there may be faint traces of it where I've marked, but this "new" basin may explain it's more or less absence in this region.

Attached thumbnail(s)

 

[Decepticon]

This moon really needs more close ups.


I found the exposure times for the Saturn shine where shorter this time.
Compared to the last 2 times.

So much more surface mapping could have been done if longer exposure of the night side where planned better.

[ugordan]

I found the exposure times for the Saturn shine where shorter this time.

Where did you find that information? SPICE kernels or estimation from star trails?

So much more surface mapping could have been done if longer exposure of the night side where planned better.

Don't be so quick to judge the imaging team. They probably had their reasons for shortening the exposures. My guess would be the possible image smear due to small jitters during target motion compensation. This time Iapetus was not nearly as large (angularly) as during New Year's Eve flyby when the angular scale of larger surface features was greater than uncertainties of motion tracking. If they took longer exposures now, they would have risked more potential image smearing due to such attitude wobbling. Cassini is very accurate when the pointing needs to be steady, but it's not as precise when actually tracking a target. IIRC, it comes down to the resolution of its star trackers. However, it's still much more precise than similar probes were.

Besides, just because we don't see much detail among JPEG artifacts, doesn't mean the original raw images aren't downlinked at the full 12-bit dynamic range.

[tedstryk]

This moon really needs more close ups.
I found the exposure times for the Saturn shine where shorter this time.
Compared to the last 2 times.

So much more surface mapping could have been done if longer exposure of the night side where planned better.

Depends. The shorter time may have led to sharper images, which, if stacked, could compensate for the sorter exposure time if it wasn't severe. It is hard to tell from the stretched jpegs though. Suffice it to say that there must have been a good reason - They spend so much time on this encounter, when not much else was going on, and I can't believe that such a change is an oversight.

[Decepticon]

I see.

[scalbers]

Is this another basin?  We only saw part of the big basin that's fully illuminated here in the image sequence last January.  I tried to trace the equatorial ridge into the terminator, but it was too close to the basin's rim and presumably was pretty much obliterated. 

In the new flyby sequence, we get views further east, and I keep suspecting another badly damaged basin, almost contacting the big one.  I've noted it's possible rim with red radial marks. 

The equatorial ridge seems absent in this region, but may have been obliterated by the new basin I suspect I see.  I've marked a (bad... it's probably too far south) extrapolation of the equatorial ridge into the suspected basin with green X's. where there may be faint traces of it where I've marked, but this "new" basin may explain it's more or less absence in this region.

Ed,

When looked at in context (e.g. on my map) the features you outline seem to me as part of the "Iapetean Tiger Scratches". These of course wouldn't really be like the features on Enceladus, though their horizontal extent may be similar. To me it looks like a series of canyons or valleys that terminate at the edge of Cassini Regio.

http://laps.noaa.gov/albers/sos/sos.html#IAPETUS

[Bjorn Jonsson]

And here is an animation of the January 2006 flyby:

http://www.mmedia.is/bjj/misc/css_stuff/mi...tus_jan2006.avi

It starts on January 21 2006 12:00 and ends on January 31 2006 00:00. The field of view is 0.1 degrees and the distance at the start and at the end of it is a bit over 1.5 million km.

[edstrick]

scalbers: "When looked at in context (e.g. on my map) the features you outline seem to me as part of the "Iapetean Tiger Scratches". These of course wouldn't really be like the features on Enceladus, though their horizontal extent may be similar. To me it looks like a series of canyons or valleys that terminate at the edge of Cassini Regio."

I grabbed the current map, wrapped it around so I could see the entire east end of Cassini Regio, and contrast stretched it. The result is attached. I wasn't really aware of these tiger scratch features, not sure if they're "alpine valleys" like the one radial to the Imbrian basin, or the valleys radial to the Orientale basin on the moon.. very odd, and not well imaged yet.

I still get a hint of a ruined basin, but it's ceatainly not well constrained by the current images, it if exists at all. I will be most interested to see the form / structure / geology of these scratches when we get good images. Other than the equatorial ridge belt, limited evidence of endogenically driven geology seems to survive the basin and crater population on Iapetus, and these could be examples.