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






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).

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.

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.

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.

Click to view attachment

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.

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.

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).

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?

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

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.

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?

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

New stuff in. Lots of pics of empty space.

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

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?

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

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

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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?

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

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.

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.

^ Welcome!

Nice work.

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

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

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.

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.

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

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.

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

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.

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.

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.

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.

Isn't this one lovely untargeted flyby???

Click to view attachment

Great mosaic!

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.

Now that's a Excellent peace of work!

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

Iapetus in color
Click to view attachment
Images N42987, N42988, N42989 merged using ImageJ
http://rsb.info.nih.gov/ij/

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?

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.

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

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?

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).

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.

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...