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Unmanned Spaceflight.com _ Cassini's ongoing mission and raw images _ Iapetus Encounter In January
Posted by: pioneer Nov 29 2004, 04:38 PM
I heard about a peak on Iapetus that may be taller than Olympus Mons on Mars. I was wondering if the RADAR instrument will be used in the January encounter to verify this. What is the maximum distance the RADAR can be used?
Posted by: Decepticon Nov 30 2004, 03:25 AM
I have an animation of this flyby. It shows what to expect during the flyby.
Let me know if you want this.
Posted by: YesRushGen Nov 30 2004, 02:13 PM
Please! Can you post it here?
Posted by: Decepticon Dec 1 2004, 12:48 AM
It's 13.7 Mb
I think I would have to do a file transfer for that. Got ICQ or MSN?
ICQ# 6840999
Posted by: volcanopele Dec 1 2004, 04:41 PM
In addition to the encounter on December 30, we can also look forward to the following encounters:
Nov. 2005 416,000 km (2.5 km/pixel, should show eastern Cassini Regio an d some of the bright terrain)
Jan. 2006 879,000 km (5.3 km/pixel, ring east of Cassini Regio, and eastern Cassini Regio)
Apr. 2006 603,000 km (3.6 km/pixel, southern leading hemisphere)
Sep. 10, 2007 1250 km (12 m/pixel, central cassini regio)
ISS should be able to confirm the heights in the close encounter in 2007 when we might get some great images of those peaks (four of them). Voyager (not sure which one) saw one of the peaks along the limb and Cassini saw the four of them.
Posted by: Bjorn Jonsson Dec 6 2004, 01:03 PM
I did an animation showing 24 hours of the Iapetus flybys around the time of closest approach. It's fairly big (4 MB) but I could upload it temporarily to my website if there's interest in seeing it. However, it's not very impressive, it only shows Iapetus with a lat/lon grid, no instrument FOVs or observations are shown since needless to say I have no information on these. Needless to say I also have stills from the animation.
This is going to be an interesting flyby with images that should be better than the best Voyager 1 images of Rhea.
Posted by: Bjorn Jonsson Dec 7 2004, 08:58 PM
These three stills show Iapetus near the time of closest approach which occurs near 1900 UTC on December 31. This is a very slow flyby, the distance varies by less than 5000 km over the 8 hour interval shown here. The field of view is two times the field of view of Cassini's narrow angle camera.
Posted by: YesRushGen Dec 7 2004, 11:44 PM
WOW!!! 
Posted by: OWW Dec 8 2004, 02:31 PM
In the meantime two smaller Iapetus WOWs 
:
http://photojournal.jpl.nasa.gov/catalog/PIA06146
and
http://photojournal.jpl.nasa.gov/catalog/PIA06145
Posted by: tedstryk Dec 8 2004, 02:55 PM
How close will Cassini come to Iapetus during Tb?
Posted by: YesRushGen Dec 8 2004, 03:52 PM
After T-b near Cassini's apoapsis, near Dec 30th, Cassini will pass (I think) 100,000km from Iapetus - the closest to date by far.
Someone in here said the flyby was originally planned to be closer - but due to uncertainties in Iapetus mass and concerns of Huygen's (in free flight at the time) trajectory being affected decided to increase the flyby distance.
Posted by: volcanopele Dec 8 2004, 05:27 PM
Wow, those images got release quickly 
I anticipated them getting released much later (like nearer to the Iapetus encounter).
A few notes: Note the giant crater near the terminator (EDIT: I see T.R. did mention that in the caption). Iapetus is definitely a battered, ancient world with no less than three giant impact basins on the order of Odysseus in size (relative to satellite radius). That impact structure is on the order of 550 km across
Here, BTW, is a look at those mountains by Voyager 2:
Posted by: volcanopele Dec 8 2004, 05:32 PM
Here, BTW, is a look at those mountains by Voyager 2:
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Posted by: Decepticon Dec 8 2004, 10:14 PM
SO cassini will use Radar on this approach?
Posted by: volcanopele Dec 8 2004, 10:38 PM
SAR doesn't work at 100,000 km. Other modes might be possible but quite frankly I'm not sure what RADAR's plans are for the Iapetus encounter.
Posted by: alan Dec 9 2004, 02:59 AM
Before the last Titan encounter I noticed many raw images that were labeled as pointing at Iapetus almost missed or missed altogether. Anyone know what happened with those. Was there a problem with the pointing? Or were they looking for the dust from Phoebe that some claim as the reason for Iapetus's leading hemisphere being so dark?
Posted by: alan Dec 15 2004, 10:47 PM
the all seeing eye
http://saturn.jpl.nasa.gov/multimedia/images/raw/casJPGFullS06/N00025365.jpg
Posted by: Sunspot Dec 15 2004, 11:03 PM
Some of the members of this forum said it was due to uncertainties in knowing the precise orbit of Iapetus.....
Iapetus sure is a weird place, can't wait to see it up close.
Posted by: CosmicRocker Dec 16 2004, 05:27 AM
No kidding. I didn't realize how weird until I stopped in here and looked at the images being discussed. I found the height of the mountains in that Voyager image amazing.
I also noticed that a lot of the craters seem to display significant changes in elevation. In particular, that larger crater near the terminator in the Voyager image appears to have a large central uplift with greater relief than the rim. Does this suggest it is a body with different physical properties, or is it simply due to lower than expected gravity caused by it's low density?
This should be an eye opening encounter.
Posted by: Decepticon Dec 16 2004, 02:58 PM
Will Cassini start to take some approach images soon?
I'm hoping to see that Huge Impact crater hiding in the Dark area Missed buy Voyager but seen in the Cassini Images.
Posted by: alan Dec 18 2004, 11:25 PM
Some early science results for Iapetus
In the same session at the Division of Planetary Sciences meeting, Bonnie Buratti of the Jet Propulsion Laboratory reported on the first Visual and Infrared Mapping Spectrometer measurements of Iapetus. The encounter was too distant for VIMS to be able to capture pretty pictures as the cameras did. In fact, Buratti got a laugh from the meeting attendees when she flashed her VIMS "image" up on the screen: a mere four pixels covered the entire moon. But she cautioned the scientists not to laugh so quickly. The VIMS image was "fortunate in outline," she explained. "One of the four pixels sits almost entirely in the bright region, and one in the dark region. So these represent the first resolved spectra of Iapetus."
Getting resolved spectra of Iapetus' bright material and dark material means that it's possible for a spectroscopist like Buratti to tell the difference in composition between the light stuff and the dark stuff, and begin to answer the question of how and why Iapetus can have two such different surfaces. The results surprised Buratti. "I may have to eat a lot of stuff that I've published in the past," she said. Looking at infrared wavelengths, she found carbon dioxide bound up in the dark material, just as was seen at Phoebe. This falls in line with the preexisting theory that the dark stuff on Iapetus could have come from Phoebe. But that's not the whole story.
"Phoebe and Iapetus are very different in the visible [wavelengths]," Buratti said. In those wavelengths, Iapetus' dark material looks more like D-type asteroids, which are reddish in color, "like Hyperion." Phoebe, by contrast, most closely resembles a more primitive C-type asteroid. Buratti tried to explain how these differences could arise within the Saturn system. "Exogenic small outer satellites," that is, small bodies that formed outside of the Saturn system and were later captured into distant orbits, "could provide additional material that's reddish in visible wavelengths," which would explain the D-type appearance of Iapetus. This hypothesis is reasonable, Buratti said, because "the small outer satellites do have reddish colors in the visible [wavelengths]." But she can't explain why the reddish coloration doesn't also show up on Phoebe.
http://www.planetary.org/news/2004/cassini_iapetus_1209.html
Posted by: Decepticon Dec 20 2004, 03:55 PM
Help!!!!
I've been trying to view Iapetus from Cassini using this Webpage http://samadhi.jpl.nasa.gov/ Nothing I do makes this Webpage work?!?!
Everyone else seems to have no problem with it?!
What can I be doing wrong?
This is what I get.... http://space.jpl.nasa.gov/cgi-bin/wspace?tbody=806&vbody=-90&month=8&day=29¢ury=20&decade=0&year=4&hour=00&minute=0&rfov=30&fovmul=-1&bfov=30
Posted by: Decepticon Dec 20 2004, 03:55 PM
Double post. 
Posted by: alan Dec 20 2004, 04:42 PM
Strange, it works for cassini up to July 2, 2004 then I get your error message. I can see Iapetus from Dione after that. Maybe they didn't know its path after orbital insertion when they wrote the software?
Posted by: Decepticon Dec 23 2004, 01:27 AM
New PICS!!
And this was from Dec 18! Man I can't wait!!!
http://saturn1.jpl.nasa.gov/multimedia/images/raw/casJPGFullS07/N25973.jpg
http://saturn1.jpl.nasa.gov/multimedia/images/raw/casJPGFullS07/N00025977.jpg
Posted by: CosmicRocker Dec 23 2004, 05:02 AM
Wow!
Posted by: alan Dec 24 2004, 12:10 AM
Looks like only the dark side will be sunlit at closest approach. i guess we'll have to wait for the close up of the monolith 
Posted by: Decepticon Dec 24 2004, 09:24 PM
Looking at this map does anyone know what side will be imaged in Light and what side will be in the Dark?
http://www.monde.de/saturn-iapetus11b.jpg
Posted by: alan Dec 25 2004, 12:15 AM
I can't get JPL's solar sysyem simulator to work for Cassini after July 2 so I found another way to simulate the view. View from sun gives sunlit side
http://space.jpl.nasa.gov/cgi-bin/wspace?tbody=806&vbody=0&month=1&day=1¢ury=20&decade=0&year=5&hour=02&minute=45&rfov=30&fovmul=-1&bfov=30
view from saturn gives phase angle of 110 degrees.
http://space.jpl.nasa.gov/cgi-bin/wspace?tbody=806&vbody=6&month=1&day=1¢ury=20&decade=0&year=5&hour=02&minute=45&rfov=30&fovmul=-1&bfov=30
110-90=20 which should be longitude where terminator crosses equator on your map (sunlit to left)
View from Titan has phase angle of 95 degrees which is close to phase angle at closest approach (94 degrees) So the view from Titan should be close to what Cassini will see at closest approach.
http://space.jpl.nasa.gov/cgi-bin/wspace?tbody=806&vbody=606&month=1&day=1¢ury=20&decade=0&year=5&hour=02&minute=45&rfov=30&fovmul=-1&bfov=30
Would be simpler if they updated the simulato so you could use Cassini as the viewpoint after July
Posted by: Bjorn Jonsson Dec 25 2004, 11:25 PM
Actually the view from Titan is significantly different from Cassini's view since Cassini will be viewing the northern hemisphere. Page 1 in this thread has some renders I did showing Cassini's viewing geometry.
Posted by: alan Dec 26 2004, 03:11 AM
Beautiful work Bjorn. I guess this isn't very useful then
http://ringmaster.arc.nasa.gov/tools/viewer2_sat.html
should have noticed: last updated July 14, 2003
I had the terminator in the right place at least
Posted by: Bjorn Jonsson Dec 27 2004, 12:15 AM
Wow !
http://saturn.jpl.nasa.gov/multimedia/images/raw/raw-images-details.cfm?feiImageID=29377
The highest resolution image ever obtained of Iapetus...
Posted by: Sunspot Dec 27 2004, 12:40 AM
There's a small bump on the limb just past the 3 o'clock position in that image of Iapetus - could that be one of the giant mountains we've heard about?
Posted by: alan Dec 27 2004, 12:50 AM
Upsidedown?
Posted by: volcanopele Dec 27 2004, 12:57 AM
Yep. It's just that tall
Attached is a stretched version to bring out the Cassini Regio features like three of the five (yeah, its five now) giant impacts on Iapetus.
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Posted by: volcanopele Dec 27 2004, 12:59 AM
In the raw images, north is down. In my image, I have rotated so north is approximately up.
Posted by: alan Dec 27 2004, 01:32 AM
Three impact basins? On stretched image I see at 12 o'clock, one at 9 o'clock, is other at 3 o'clock? The mountain appears to be part of rim of impact basin at 9 o'clock.
Posted by: volcanopele Dec 27 2004, 01:39 AM
12, 2:30, and 9, though the mountains are beyond the western rim of impact number 3, labeled in the attached graphic.
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Posted by: alan Dec 27 2004, 03:44 AM
Will Cassini get close enough to determine whether Iapetus has an asymmetric mass distribution?
Posted by: Decepticon Dec 27 2004, 04:26 AM
I thought this moon was werid before, now its just flat out CRAZY!
I'm loving it! This moon looks like Rocky eye in Rocky! 
Posted by: Decepticon Dec 27 2004, 06:07 AM
Check this link out for some refreshed Voyager Maps using cassini data.
http://laps.fsl.noaa.gov/albers/sos/sos.html
Titan WOW!
Tethys
Iapetus
Also Europa was very nicly done!
Posted by: BruceMoomaw Dec 27 2004, 02:15 PM
Jason's stretched image makes it clear that Iapetus' irregular limb -- whioch ahs always intrigued me -- is due to the simple fact, that, for whatever reason, this moon has had the living hell bashed out of it. That largest impact basin looks like the hugely oversized craters that NEAR photographed on the asteroid Mathilde. Is it possible that -- as an abstract I recently saw suggests -- Iapetus is a captured moon, like Phoebe (and Triton)? This could explain its moderately tilted orbit.
Posted by: alan Dec 27 2004, 03:18 PM
Crazy idea: Iapetus was a larger differentiated object: dark outside, light inside; which was shattered by an impact. A large fragment, about one third of the original, was folded together by gravity into a spherical shape with the result looking similar to a baseball. This was later captured by Saturn.
Posted by: David Dec 27 2004, 05:05 PM
But where would the differentiation come from in the first place? If you're supposing that Iapetus' surface is a composite of two different types of materials, why not have one of them come from the impactor itself? Um, and what happened to the other two-thirds of Proto-Iapetus in your theory?
Posted by: volcanopele Dec 27 2004, 05:08 PM
The problem with that is that the bright dark/boundary, on Iapetus, is diffuse. On the dark side, you have bright crater rims and central peaks. On the bright side, you have dark crater floors. Many of the areas on the dark side near the boundary look "frosted" by bright material.
Posted by: alan Dec 27 2004, 06:09 PM
I was thinking if it formed away from Saturn the other fragments would escape. Having the dark material come from the impacter would be simpler though.
Posted by: alan Dec 27 2004, 07:34 PM
Anyone try using an unsharp mask on the images of Iapetus?
Posted by: volcanopele Dec 27 2004, 07:52 PM
I just played with it on the image we have so far and unfortunately the compression on the jpeg is just too much.
BTW, try an unsharp mask in photoshop on my mosaics. You might find a setting you like
Posted by: alan Dec 27 2004, 08:00 PM
Wish I had Photoshop. Looking on the web I see the term unsharp masking used two different ways. This is what I was referreing to.
http://voltaire.csun.edu/masking.htm
Posted by: Decepticon Dec 27 2004, 08:55 PM
^ I wish I understood the question, I'm not that great at adobey.
What will that do to the image?
Posted by: alan Dec 27 2004, 09:26 PM
If it is done like in the link I referred to it will reduce the brightness range between the light and dark areas while keeping most of the details. It should make the features in the dark area easier to see. I don't have the software so I don't know if it will work in this case.
Posted by: Roby72 Dec 28 2004, 12:10 AM
Iapetus with its three impacts looms larger and larger each day:
http://saturn.jpl.nasa.gov/multimedia/images/raw/raw-images-details.cfm?feiImageID=29430
Robert Schulz
Posted by: volcanopele Dec 28 2004, 02:59 AM
nice. Looks likes the raw images page is about a day behind us. Tomorrow, there is a color sequence at 4.2 km/pixel.
Posted by: Decepticon Dec 28 2004, 03:08 AM
My try at it.. 
Posted by: tedstryk Dec 28 2004, 03:18 AM
Where did you get the tri-color data? Or did you just colorize the monochrome data?
Posted by: Decepticon Dec 28 2004, 03:22 AM
I colorize the monochrome data.
As said before the Image is very compressed.
I would prefer a Tiff to play with.
Posted by: Decepticon Dec 28 2004, 10:29 PM
Odd, there is very little approach images of Iapetus.
Why the wait for Raw Images?
2 Images in a week!?
Sorry Had to Vent.
Posted by: Sunspot Dec 28 2004, 11:49 PM
Why the wait for Raw Images?
2 Images in a week!?
Sorry Had to Vent.
It's probably just the Christmas holiday
Posted by: volcanopele Dec 29 2004, 12:05 AM
I know.... as soon as yesterday's opnavs show up in the raw image page, I will post my color composites
Posted by: volcanopele Dec 29 2004, 12:06 AM
I know.... as soon as yesterday's opnavs show up in the raw image page, I will post my color composites
Posted by: MizarKey Dec 29 2004, 12:15 AM
Hmmm...when did you change your avatar??? Looks like a new image of Iapetus made it to the board already!
Eric P / MizarKey
Posted by: SFJCody Dec 29 2004, 12:17 AM
They're up
http://saturn.jpl.nasa.gov/multimedia/images/raw/raw-images-list.cfm?browseLatest=0&cacheQ=0&storedQ=0
Posted by: volcanopele Dec 29 2004, 12:43 AM
Hmmm...when did you change your avatar??? Looks like a new image of Iapetus made it to the board already!
Eric P / MizarKey
Why, how did that get there? I'll post my composites shortly.
Posted by: alan Dec 29 2004, 01:00 AM
I've been seeing a faint linear feature along the equator on the raw images of Iapetus. I thought my imaginations was lining up random noise at first but this is the third day I've seen it. I wonder what it is. The large impact basin near the terminator looks like a multi-ring structure, it reminds me of Mare Orientlale.
Posted by: Sunspot Dec 29 2004, 01:06 AM
I noticed that too, I thought at first it might be an JPEG artefact, but it looks real, it also seems to start at the same latitude as the "pimple" on the limb.
Most prominent in this image: http://saturn.jpl.nasa.gov/multimedia/images/raw/raw-images-details.cfm?feiImageID=29463
VERY strange.
Posted by: tedstryk Dec 29 2004, 01:11 AM
Wow, and this is three or four days before closest approach! What is the highest resolution imaging Cassini will attain (on this flyby)? It has been said before, but with all the changes made, I am a bit confused.
Posted by: volcanopele Dec 29 2004, 01:18 AM
here they are
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Posted by: volcanopele Dec 29 2004, 01:20 AM
here is a time sequence
Updated middle frame
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Posted by: AlexBlackwell Dec 29 2004, 01:23 AM
From my understanding, with C/A at ~117,500 km ISS should get about 705 m/pxl resolution in the highest-resolution imagery, which is ~10x better than the imagery acquired in October. Note that with the flyby taking place at Cassini's apoapsis, the flyby velocity is relatively slow; in fact, it would be more accurate to say that Iapetus will fly by Cassini.
Posted by: SFJCody Dec 29 2004, 01:31 AM
So... what's going on? Is this a world-spanning ridge of giant equatorial cryovolcanoes that spew dark material onto the ice?
Posted by: volcanopele Dec 29 2004, 01:33 AM
That would be pretty inconsistent with the age of the surface which quite frankly looks like its the oldest surface in the Saturnian system. Not saying I know what's causing the bright streaks. Could be a fault, a la Dione.
Posted by: alan Dec 29 2004, 01:40 AM
heres the fault in an earlier image look how high it is
http://saturn.jpl.nasa.gov/multimedia/images/raw/casJPGFullS04/N00022208.jpg
Posted by: SFJCody Dec 29 2004, 01:50 AM
Operating on the 'see what sticks' principle-
Could the light material be some kind of polar deposit? The non-polar distribution could be related to historical changes in Iapetan obliquity.
Posted by: volcanopele Dec 29 2004, 02:06 AM
Could the light material be some kind of polar deposit? The non-polar distribution could be related to historical changes in Iapetan obliquity.
but then again, satellites like Tethys and Dione look ancient but do shows signs of having had tectonic activity.
Posted by: David Dec 29 2004, 03:00 AM
Why, they must be the Death Star trench and superlaser dish!
Posted by: Decepticon Dec 29 2004, 03:11 AM
Where is Iapetus equator in that image volcanopele?
I'm trying to get a bearing as where this is on the Voyager Global Maps.
Posted by: alan Dec 29 2004, 03:35 AM
How about this: Iapetus is hit head on by a centaur, that huge impact basin near the terminator looks like a likely spot. Some of the debris from the centaur ends up in a retrgrade orbit and lands on Iapetus's leading side.
Posted by: volcanopele Dec 29 2004, 04:31 AM
I'm trying to get a bearing as where this is on the Voyager Global Maps.
Here is my best shot at placing a grid on these images. Not very good, I know... But I think that bulge is real..
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Posted by: alan Dec 29 2004, 04:38 AM
Decepticon, I think the dark area is is centered on the equator, light areas in the latest images are on the poles.
Posted by: alan Dec 29 2004, 04:40 AM
Or maybe not 
Volcanopele responded while I was typing
Posted by: alan Dec 29 2004, 05:37 AM
A giant grabbed hold of it and twisted it until it cracked and the insides leaked out of it. those aren't impact basis, they are his fingerprints. 
Posted by: alan Dec 29 2004, 06:30 AM
This looks similar to the crater at the top center of the dark region
http://photojournal.jpl.nasa.gov/catalog/PIA01054
Posted by: Decepticon Dec 29 2004, 12:00 PM
I'm trying to get a bearing as where this is on the Voyager Global Maps.
Here is my best shot at placing a grid on these images. Not very good, I know... But I think that bulge is real..
Thanks!
http://photojournal.jpl.nasa.gov/catalog/PIA01054
Interesting. They do look alike.
Posted by: alan Dec 29 2004, 06:55 PM
I remember people commenting that Iapetus didn't quite round back in October. I assumed it was an optical illusion caused by the contrast beween the light and dark areas. It shows up well in this image.
http://saturn.jpl.nasa.gov/multimedia/images/raw/casJPGFullS06/N00024963.jpg
How well does it line up with the anti-saturn point?
Posted by: Decepticon Dec 29 2004, 08:41 PM
Cassini Page Update! Video Flyby.
Next up for Cassini is a flyby of Saturn's icy moon Iapetus on Dec. 31. Iapetus is Saturn's two-faced moon -- one side is very bright, and the other is very dark. The spacecraft will pass about 65,600 kilometers (40,800 miles) of the frigid moon.
+ Image Details
+ Iapetus Flyby Animation
http://saturn1.jpl.nasa.gov/home/index.cfm
Posted by: alan Dec 29 2004, 10:23 PM
Description of Iapetus flyby
http://www.planetary.org/news/2004/cassini_iapetus_plan_1229.html
Posted by: tedstryk Dec 30 2004, 12:54 AM
From the Cassini website?
_____________________
Target: Iapetus - December 29, 2004
Next up for Cassini is a flyby of Saturn's icy moon Iapetus on Dec. 31. Iapetus is Saturn's two-faced moon -- one side is very bright, and the other is very dark. The spacecraft will pass about 65,600 kilometers (40,800 miles) of the frigid moon.
___________________
Has this not been updated to reflect the change in trajectory or has there been some other development that I have somehow missed?
Posted by: AlexBlackwell Dec 30 2004, 01:00 AM
_____________________
Target: Iapetus - December 29, 2004
Next up for Cassini is a flyby of Saturn's icy moon Iapetus on Dec. 31. Iapetus is Saturn's two-faced moon -- one side is very bright, and the other is very dark. The spacecraft will pass about 65,600 kilometers (40,800 miles) of the frigid moon.
___________________
Has this not been updated to reflect the change in trajectory or has there been some other development that I have somehow missed?
Yes, this C/A figure is outdated. Frankly, I wouldn't be surprised if that blurb was written months ago.
Posted by: Decepticon Dec 30 2004, 01:46 AM
Even at the current distance the Images must me Mouth Watering.
I just can't wait to see these Images!
My father says Iapetus looks like a walnut in yesterdays images. 
Posted by: BruceMoomaw Dec 30 2004, 06:44 AM
(1) Ah. So, judging from the Planetary Society's description, radar scatterometry of Iapetus WILL be obtained during this flyby. (By the way, Jason, you never did confirm for us that Cassini missed some of its planned measurements -- including the radar -- during its recent Dione flyby, or explain what caused the problem.)
(2) It turns out that some researchers have been WAY ahead of us in noting both Iapetus' nonspherical, lumpy shape and the apparent implication that this moon has had the very devil knocked out of it at some point -- and that its whole developmental history has been radically different from that of Saturn's inner moons:
http://protostar.aas.org/publications/baas/v32n3/dps2000/329.htm
http://www.lpi.usra.edu/meetings/lpsc2000/pdf/1596.pdf
http://www.lpi.usra.edu/meetings/lpsc2000/pdf/1660.pdf
Posted by: MizarKey Dec 30 2004, 03:38 PM
(2) It turns out that some researchers have been WAY ahead of us in noting both Iapetus' nonspherical, lumpy shape and the apparent implication that this moon has had the very devil knocked out of it at some point -- and that its whole developmental history has been radically different from that of Saturn's inner moons:
http://protostar.aas.org/publications/baas/v32n3/dps2000/329.htm
http://www.lpi.usra.edu/meetings/lpsc2000/pdf/1596.pdf
http://www.lpi.usra.edu/meetings/lpsc2000/pdf/1660.pdf
Bruce, thanks for the excellent links!
You've got to love the internet...during the Voyager days I waited patiently for every issue of Sky & Telescope and Astronomy magazine to come out so I could see the new images and read about the exciting discoveries. Now it's a matter of hours / days before we get the information. And not just that, we get to converse with some of the people who are working with the craft / data!
My sincerest thanks to all of you who are making this happen and keeping us informed! And thanks to Doug and Bruce for the best forum on the web!
Eric P / MizarKey
Posted by: tedstryk Dec 30 2004, 03:58 PM
I remember going to the library to scope out every newspaper I could that might, just might have Neptune coverage. Then I would keep checking Science News. Then, at last, Sky and Telescope and Astronomy would have the latest. I am still an S&T subscriber. But I think it is an old habit - I haven't taken it out of the plastic-wrap in months!
Posted by: Decepticon Dec 30 2004, 04:18 PM
Before the Internet Space News was very hard to get your Hands on.
When it did come out it was amazing stuff.
When Voyager passed Neptune PBS did a Live broadcast from JPL.
I was so excited.
Posted by: volcanopele Dec 30 2004, 05:11 PM
(2) It turns out that some researchers have been WAY ahead of us in noting both Iapetus' nonspherical, lumpy shape and the apparent implication that this moon has had the very devil knocked out of it at some point -- and that its whole developmental history has been radically different from that of Saturn's inner moons:
http://protostar.aas.org/publications/baas/v32n3/dps2000/329.htm
http://www.lpi.usra.edu/meetings/lpsc2000/pdf/1596.pdf
http://www.lpi.usra.edu/meetings/lpsc2000/pdf/1660.pdf
1) Not surprised considering the apparent difference in surface materials, between the Callisto-style Cassini Regio and the Rhea-style Reuxeveux Terra. I'm not certain what happened to that data. All I know is that some of the Dione data, other than ISS, was lost.
2) The non-spherical nature of Iapetus is not a new discovery, but it does provide for some annoyances.
Posted by: DEChengst Dec 30 2004, 05:32 PM
Those were the times
I still remember watching the live report from Darmstadt as Giotto flew by Halley's comet. There I was, only ten years old watching the images arrive in the middle of the night.
Posted by: tedstryk Dec 30 2004, 05:41 PM
I remember "Neptune All Night." I was 10 in 1989, and my parents made me stop watching a little past midnight to go to bed.
Posted by: Decepticon Dec 30 2004, 06:30 PM
I was 14 years old during the neptune flyby. Triton was a gem of a moon.
To bad this encounter is not live.
At least we have the Huygens landing. I'm looking forward to seeing the first Europa Subs with my son in the future. (I belive 100% of subsurface Oceans 
)
Posted by: David Dec 30 2004, 06:35 PM
It does seem that in addition to various bumps, lumps, and seams, that Iapetus is a bit egg-shaped; but it also seems that we're still able to impose a global latitude and longitude coordinate grid upon it. How irregular does a moon or asteroid have to be before that's impossible? Could you impose the same type of grid on Phoebe? Or Hyperion?
Posted by: alan Dec 30 2004, 07:56 PM
I noticed something odd about the latest images of Iapetus: the shadows are wrong. The insides of the craters are dark on the sides closest to the poles and brighter on the sides closest to the equator when it should be the other way around. Is this caused by impacts redistrubing the light and dark material? How old would the dark material have to be to show this effect?
Posted by: Decepticon Dec 30 2004, 10:32 PM
Mapping Coverage...
http://saturn.jpl.nasa.gov/multimedia/images/image-details.cfm?imageID=1265
Posted by: AlexBlackwell Dec 31 2004, 01:53 AM
http://www.jpl.nasa.gov/news/news.cfm?release=2004-300
Jet Propulsion Laboratory
December 30, 2004
Posted by: alan Dec 31 2004, 04:26 AM
I've noticed some interesting features near the poles I'd like a closer look at. Any chance of getting one before Monday?
Posted by: alan Dec 31 2004, 05:37 AM
If you look just at the rims of the craters the dark material continues almost to the poles.
Posted by: alan Dec 31 2004, 07:08 AM
Anyone else see a huge impact basin here? Or am I just imagining things in the noise?
http://s02.imagehost.org/view.php?image=/1148/impact_basin.jpg
it appears to be split apart by a rift
original image is here
http://www.nasa.gov/mission_pages/cassini/multimedia/pia06146.html
Posted by: Decepticon Dec 31 2004, 05:20 PM
If it is, that is 1 HUGE Impact.
Posted by: alan Dec 31 2004, 07:49 PM
I'm having some doubts about it now. I don't see it in any of the Voyager images.
Posted by: volcanopele Dec 31 2004, 07:58 PM
First set of Iapetus images are down. That is a HUGE ridge
Posted by: volcanopele Dec 31 2004, 08:03 PM
It's there. The moat is seen in the coverage map made of only Voyager images. It was uncertain whether that was an impact basin, but new opnav images from Dec. 18 show a that it is.
Posted by: volcanopele Dec 31 2004, 08:07 PM
Wow, that was quick. You can see it for yourself.
I was wrong it is not a fracture. Sue me.
http://saturn.jpl.nasa.gov/multimedia/images/raw/raw-images-details.cfm?feiImageID=29522
Posted by: volcanopele Dec 31 2004, 08:09 PM
Bright-dark dichonomy:
http://saturn.jpl.nasa.gov/multimedia/images/raw/raw-images-details.cfm?feiImageID=29520
Posted by: Decepticon Dec 31 2004, 08:36 PM
OMG
I'm in shock! Amazing!
Posted by: Decepticon Dec 31 2004, 08:51 PM
My first try at stiching. What you think?!
Posted by: Decepticon Dec 31 2004, 08:56 PM
A colour try. Remember I'm new at this...
Posted by: alan Dec 31 2004, 09:26 PM
Decepticon, part of the dark area is gray rather than brown. Why?
Posted by: djellison Dec 31 2004, 09:30 PM
http://img126.exs.cx/my.php?loc=img126&image=iapetus4ve.jpg
I love it when PTGui says the control points are "too good to be true"
Posted by: alan Dec 31 2004, 09:37 PM
It's there. The moat is seen in the coverage map made of only Voyager images. It was uncertain whether that was an impact basin, but new opnav images from Dec. 18 show a that it is.
I wasn't referring to the moat. I pointed out what I thought was an impact basis nearly half the size of Iapetus. I see a low area in the Voyager images and some fractures but I can't tell if the fractures are related. I probably connected some unrelated fractures.
Posted by: alan Dec 31 2004, 09:48 PM
Dark material looks like dust to me. Is it just me or does the edge of the light terran look polished to anyone else?
Posted by: Decepticon Dec 31 2004, 10:15 PM
I was cheating when I colored it.
Posted by: Sunspot Dec 31 2004, 10:23 PM
Wow, that was quick. You can see it for yourself.
I was wrong it is not a fracture. Sue me.
http://saturn.jpl.nasa.gov/multimedia/images/raw/raw-images-details.cfm?feiImageID=29522
WOWWWWWWWW...... how high do you think that might be?
Posted by: alan Dec 31 2004, 10:45 PM
I was thinking looks like wind blown streaks must be dust. How do you get something that looks llike wind blown streaks with no atmosphere 
Posted by: djellison Dec 31 2004, 11:36 PM
By orbiting thru a cloud of it ?
Doug
Posted by: alan Jan 1 2005, 02:51 AM
Another theory:1)Iapetus had a subsurface ocean like Europa. 2) The equatoral ridge was present before the largest impact basin. 3)The impact compressed the other side of Iapetus driving the liquid out of the fissure at enough pressure for it reach escape velocity. The liquid freezes and darkens and is swept up by Iapetus.
Posted by: BruceMoomaw Jan 1 2005, 06:53 AM
Alan is thinking along lines roughly similar to mine. My own version: This utterly gigantic and incredible ridge seems to run smack through the middle of the dark region, and it looks like an enormous version of the double ridges crisscrossing Europa. Could it possibly be a gash out of which methane from Iapetus' interior gushed as gas before freezing back down onto the surface as methane frost -- which was then gradually darkened into dark organics by solar UV and Saturn's radiation (as is hypothesized to see the very dark patches we can already see on Pluto)? And could the few bright patches that seem to be sprinkled along the length of the gash ( http://saturn.jpl.nasa.gov/multimedia/images/raw/casJPGFullS04/N00022208.jpg ) be the few regions where water was extruded out of the gash and refroze AFTER the gash had stopped emitting methane?
Second wild speculation: that famous huge "dark ring" first seen by Voyager and now more clearly seen by Cassini ( http://www.nasa.gov/mission_pages/cassini/multimedia/pia06146.html ) turns out to just contact the outer corner of the main dark region -- and, as Alan said earlier, it looks like the lower outer floor perimeter of a gigantic crater with a raised hummock in the middle (like the Callisto crater at http://photojournal.jpl.nasa.gov/catalog/PIA01054 ). Could it be that, since this was where the methane cloud gushed from the ridge was just approaching its limits, the gas was able to flow along the surface in the depressed ring without coating the surface at the higher central hummock, so that it formed a methane frost layer which later became radiation-darkened in the "moat" around the central hummock?
Posted by: alan Jan 1 2005, 07:27 AM
What would happen to liquid (water, methane, ammonia) if was exposed on the surface of Iapetus? Would it vaporize explosively creating something like a pyroclastic flow? (cryoclastic?) Would this create steep sided mountains like Mt. St. Helens?
Posted by: alan Jan 1 2005, 07:30 AM
I looked at the images from the 27th again. What appeared to be wind blown streaks is probably a group of parallel ridges with dark material on one side.
Posted by: BruceMoomaw Jan 1 2005, 08:54 AM
"What would happen to liquid (water, methane, ammonia) if it was exposed on the surface of Iapetus? Would it vaporize explosively creating something like a pyroclastic flow? (cryoclastic?) Would this create steep sided mountains like Mt. St. Helens?"
Methane would, I think -- the moons of Saturn are still above its vacuum vaporization temperature. Water and ammonia almost certainly would not. What I'm thinking about that ridge is that -- as hypothesized for Europa's ridges -- it may be a region in which liquid water-ammonia mixture oozed upwards to the surface and then froze, later being pushed up by more liquid coming up from benetath it -- and that methane mixed with this, when it reached the vacuum at the surface, exploded outwards as gas. (It might indeed have contributed to pyroclastic phenomena around the immediate vicinity of the ridge -- or not, depending on forceful its release was. Alternatively, it might have vented outwards relatively gently.)
Posted by: centsworth_II Jan 1 2005, 02:37 PM
Yeah, I think cryoclastic sounds good and gives a better impression of the type of event being discussed.
Posted by: alan Jan 1 2005, 04:27 PM
The ridge may have formed as the last remnants of a subsurface ocean frove. As the outsides of a pocket of water froze it would compress what remained in the center. It would squeeze out at a weak spot like a crack that already present.
Posted by: SFJCody Jan 1 2005, 04:46 PM
The second batch is http://saturn.jpl.nasa.gov/multimedia/images/raw/raw-images-list.cfm?browseLatest=0&cacheQ=0&storedQ=0
Posted by: Decepticon Jan 1 2005, 05:21 PM
^ Oddly I don't see them?!
Link?
Posted by: Bjorn Jonsson Jan 1 2005, 05:25 PM
You need to do a Ctrl-Refresh if using IE.
Oddly, the distances in the image 'captions' are incorrect, they seem to refer to the old trajectory which had a closest appoach of roughly 60,000 km. However, the closest approach was about 120,000 km. It's extremely frustrating that the exact image times are not given; in that case I could calculate the correct distance myself.
Posted by: Decepticon Jan 1 2005, 05:30 PM
Thanks!
The might side Images are amazing!
This will help alot to map this moon out.
Bjorn have you been working on a global map for this moon?
Posted by: alan Jan 1 2005, 05:34 PM
Wow, I see five craters in the graylight images where the crust has sunk creating basins rather than rims.
http://saturn.jpl.nasa.gov/multimedia/images/raw/casJPGFullS07/N00026380.jpg
The "moat" and the curves leading from it were probably created by a broken object like Comet Shoemaker-Levy 9.
Posted by: alan Jan 1 2005, 05:43 PM
Look at those star trails. Excellent job tracking on those long exposures.
Posted by: alan Jan 1 2005, 05:57 PM
And another mountain at the edge of the dark terrain. I think there is a fault continuing from it into the light terrain. How far does that equatorial ring go?
Posted by: Bjorn Jonsson Jan 1 2005, 06:43 PM
I was planning to do a map but it's probably going to be complicated to make due to the fact that Iapetus isn't spherical, I'll need to partially reverse engineer the viewing geometry and preexisting maps are almost useless for doing so.
Posted by: DEChengst Jan 1 2005, 07:33 PM
A very quick-and-dirty Iapetus mosaic:
http://paranoid.dechengst.nl/saturn/Iapetus1.jpg
And yes it's dirty. One part has duplicate craters
Posted by: Decepticon Jan 1 2005, 07:37 PM
Looks nice! I've been trying to do that all morning and I failed.
Posted by: alan Jan 1 2005, 08:59 PM
Every time I look at the dark side of Iapetus it gets even more bizarre. What I thought was a crater chain before now appears to be the end of a narrow wedged shaped sunken area. I see at least two other "craters" that have the same sunken area leading from them and a number of large cliffs.
Posted by: alan Jan 1 2005, 09:02 PM
Some the collaped areas have deposits of dark material just outside the top of the cliffs. I think the dark material was vented when they collaped.
Posted by: alan Jan 1 2005, 09:35 PM
I see lots of sunken areas, uplifted areas, fractures and cliffs on Iapetus except near the ridge. I think a subsurface ocean expanded as it froze causing the crust to stretch forming horst and graben in many areas. This didn't happen around the ridge because the slushy material was squeezed out through the fault releasing the pressure.
Posted by: alan Jan 1 2005, 09:45 PM
color images
http://www.planetary.org/news/2005/cassini_iapetus_firstimages_0101.html
Posted by: tedstryk Jan 1 2005, 10:08 PM
Maybe this is superficial, but Iapetus is starting to remind me of the Uranian moon Umbriel. Particularly with the bright crater rim and whisps Umbriel has (and considering our coverage is limited to the southern hemisphere of Umbriel, there could be more elsewere). Of course, this could just be superficial.
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Posted by: alan Jan 1 2005, 10:21 PM
I see some color variations in the large vrater on the left in this image. Are they real? If so are they different materials or just different lighting?
http://www.planetary.org/news/2005/images/iapetus1_lg.jpg
Posted by: alan Jan 1 2005, 10:55 PM
Some of the small craters in the light material on the trailing side have dark floors, the large ones do not, i see one midsized crater with a dark ring and light center. There could be a thin layer of dark material under the bright material on the trailing side.
Posted by: alan Jan 2 2005, 01:11 AM
Alternate explanation: dark material around rims of collapsed areas is layer of dark material being revealed by landslides. This would explain why it is widespread in this area. Of course this leads to more questions: How thick is the dark material? Is it they same as what is on the leading side? How did the dark material get covered by the light material?
Something odd: I see craters with central peaks in the clean area on the darkside but not it the jumbled area. Were they destroyed or are they camoflaged?
Yes I am starting to quote myself.
Anyone else interested in throwing around half baked theories or wild speculation. You only have until Monday when they have the press conference and give us the official explanation..
Posted by: volcanopele Jan 2 2005, 02:49 AM
I am favoring an endogenic process right now. I have never liked exogenic theories but when images showing an ancient dark terrain started showing up, I thought I was going to have to eat my hat. But all this discussion has reminded me that endogenic processes don't necessarily mean lava flows but could just mean pyroclastic deposits.
Posted by: Decepticon Jan 2 2005, 05:32 AM
I wonder how tall that Crater wall is.
http://saturn1.jpl.nasa.gov/multimedia/images/raw/casJPGFullS07/N00026298.jpg
I hope Cassini gets some super High Res of that.
Also Can we expect more Images or thats it for the sweet stuff.
Posted by: alan Jan 2 2005, 06:05 AM
I found a diffuse patch in the nightside images. Could it be an active vent or just an area sloped away from the light source.
http://s02.imagehost.org/view.php?image=/1157/diffuse_patch.jpg
Posted by: alan Jan 2 2005, 06:51 AM
I may have posted this before. It describes ice volcanos along the shore of Lake Superior
http://mivo-sys.tripod.com/cryo.html
Posted by: alan Jan 2 2005, 08:11 AM
I think I have a way to darken material on the sides of craters closest to the poles while leaving the opposite side bright. If it darkened by exposure to sunlight the sides that are shaded or are sloped away would be exposed to less and would remain bright. Another way to darken it may be exposure to the solar wind. Is Iapetus outside of saturn's magnetic field? Of course this doesn't exlain why its on the leading side only. It would be easier if the ridge ran all way along the equator on the leading side. Perhaps it is buried under debris from the large impact basin.
Posted by: DEChengst Jan 2 2005, 01:58 PM
Redid the first mosaic and made a new one:
http://paranoid.dechengst.nl/saturn/Iapetus1.jpg
http://paranoid.dechengst.nl/saturn/Iapetus2.jpg
Posted by: alan Jan 2 2005, 04:08 PM
I read that Titans orbits is near the edge of Saturn's magnetophere so Iapetus should be outside ot it. I wonder what effect passing through the magnetotail would have.
Posted by: BruceMoomaw Jan 2 2005, 04:23 PM
Alan's latst theory, alas, will not work at all. First, both sides of Iapetus are exposed to sunlight equally often.
As for possible darkening by Saturn's radiation belts: this might be a conceivable explanation if Iapetus were within them -- although it would actually have to be LIGHTENING of the material on Iapetus' trailing side instead, since Saturn rotates faster than Iapetus revolves around Saturn, and so the charged particles dragged along by its magnetic field would be smacking into Iapetus' light-colored trailing side. Such radiation-induced color changes are, in fact, noted on the trailing sides of Jupiter's Galilean satellites, although they're very mild by comparison (they're due mostly to sulfur atoms that are expelled by Io, ionized and then dragged around Jupiter by its rotating magnetic field, smacking into the trailing sides of the three big icy moons). Nitrogen ions from Titan are likely to get rammed into the trailing sides of the inner icy moons of Saturn in the same way, although any color changes this produces are subtle. (I believe that Pioneer 11, by sheer chance, actually flew close enough to Epimetheus to detect the low-radiation wake which that moon, like all of Saturn's inner moons, plows in Saturn's radiation belts on its leading side.)
But Iapetus is actually far outside Saturn's radiation belts (indeed, Titan is only within them part of the time) -- and so this explanation won't fly either; just as both sides of Iapetus are equally exposed to sunlight, they're equally exposed to the solar wind. Whatever has colored one side of Iapetus, it's more than radiation exposure that has produced it -- although this still leaves the possibility that the dark material is methane frost on one side of it that has been darkened by exposure to solar UV and/or charged particles in the solar wind and in Saturn's long trailing nightside "magnetotail". This, as I said, is one of the leading explanations for the dark patches that are so dramatically evident on Pluto that we can see them even from here.
Posted by: alan Jan 2 2005, 04:54 PM
Bruce, I was using the varied exposure to sun light as an alternate theory to explain the brightness variations with latitude and in particular the brightness variation of the crater rims at highter latitudes which would naturally occur if Iapetus was orbiting through debris. I did mention that it didn't explain why it is on the leading side only.
Posted by: alan Jan 2 2005, 05:26 PM
Something I just thought about, if orbiting through debris would result it the craters near the poles having one dark rim and one light rim then the craters near the east and west edges should show the same effect but with the the variation being east/west rather than north/south. I don't see this is the night side images.
Posted by: Decepticon Jan 2 2005, 06:25 PM
Made this using alans great stich job and Bjorn Lat/Log Map.
Posted by: alan Jan 3 2005, 01:11 AM
Looks like the guy who posts the raw images has sunday off. Anyone know if they have a press conference scheduled next week.
Posted by: alan Jan 3 2005, 01:48 AM
I zoomed one of the images of the leading side to look at the cliff. I noticed something odd: near the top there is a darker layer, yes darker than the rest of the dark terrain.
http://saturn.jpl.nasa.gov/multimedia/images/raw/casJPGFullS07/N00026259.jpg
Posted by: BruceMoomaw Jan 3 2005, 02:22 AM
Michael E. Adams of the Jupiter List has stitched together an absolutely superb mosaic of Cassini's Iapetus pictures: http://www.meawebdesign.com/space/iapetus_mosaic_bw.jpg . Unfortunately, when you magnify those craters on it, the resolution of the photos is not just not quite high enough to determine whether we're looking at central pits or at central peaks that have had the dark material slide down their outside slopes to expose light ice underneath. I'll have to review the craters seen on various other icy moons to determine whether any of them show central pits instead of peaks.
What we do see is unmistakable streaking of the dark material at the dark region's edges -- which really does look more like the pattern from ejecta than from methane gas, which I'd think would spread out more evenly. But the gigantic ridge does indeed run smack through the midline of the dark Cassini Regio -- so is this pure coincidence, or was the dark material indeed expelled from Iapetus' interior through the ridge? At any rate, we have here still further confirmation that the Solar System is dead set on continuing to surprise us.
Posted by: alan Jan 3 2005, 02:34 AM
I thought this crater looked strange. Seemed too unlikely that three imacts each smaller than the previous would hit the same spot.
http://s05.imagehost.org/view.php?image=/0624/iapetus_v2_81a.jpg
http://s05.imagehost.org/view.php?image=/0624/iapetus-v2-81b.jpg
Posted by: alan Jan 3 2005, 02:38 AM
Bruce I was refering to DARK pits in the small craters not the bright spots in the large ones.
Posted by: alan Jan 3 2005, 02:52 AM
Never mind about the geyser/volcanos I got confused by the bright sides of the large craters and forgot which direction the light was from.
Posted by: BruceMoomaw Jan 3 2005, 05:10 AM
It's rather easy to do that with this particular world I suppose tomorrow we'll all know a great deal more.
Posted by: alan Jan 3 2005, 06:33 AM
Was this area melted?
http://s04.imagehost.org/view.php?image=/1468/N00026259a.jpg
Looks kind of fishy to me
Posted by: alan Jan 3 2005, 06:50 AM
The trailing side looks like someone shook out a paint brush on it. Seems more likely that its ejecta although it could be methane settling in low areas, that side does look quite rough. On the trailing side I was thinking of a dark solid mixed in the liquid with most of the liquid boiling off leaving leaving dark deposits behind.
Posted by: ilbasso Jan 3 2005, 05:53 PM
With Michael Adams' new stitch, turned in a different orientation than the ones we've been looking at, suddenly I find myself wondering if the dark stuff wasn't there first and the light material came in later! I can almost convince myself that at the interface area between the dark and light portions, the light stuff seems streaked into the dark areas. And many of the craters near the boundary have light material on the crater walls facing the light side of the moon. So couldn't that argue for the light material coming afterward??
Of course, that doesn't explain the ridge. That part of Iapetus looks like an almond shell or the seam on a (american) football!
Posted by: David Jan 3 2005, 06:59 PM
I have been wondering about this myself, though I know too little about possible processes to be able to opine. Iapetus looks like a big donut-hole that's been dipped in confectioner's sugar or a white glaze.
I was looking at the point at which the "seam" disappears, or at least becomes very shallow in elevation. I noticed that all of the craters in the same area seem to be flattened as well. Is there some sort of event which could 'melt' the topography and cause it to flatten, without destroying all traces of the topography in the process?
Posted by: Decepticon Jan 4 2005, 12:40 AM
More images have come up...
Some Great night side Images!
http://saturn1.jpl.nasa.gov/multimedia/images/raw/raw-images-list.cfm?browseLatest=0&cacheQ=0&storedQ=0
Posted by: tedstryk Jan 4 2005, 02:18 AM
Here is a mosaic of the new crescent imagery. This is one amazing flyby! This was a fun one to assemble, though the large depression on the limb confused me for a while.
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Posted by: alan Jan 4 2005, 03:19 AM
Give this a try: increase the brightness on one of the nightside images then rotate it 90 degrees. I can see lots of fractures running parallel to the equator when I do this. So many that I'm wondering if speculating that the entire dark side being an impact basin wasn't so crazy after all.
Posted by: Decepticon Jan 4 2005, 06:24 AM
^ I tried but don't see it alan.
Got a example?
Posted by: alan Jan 4 2005, 07:24 AM
Try it with this one
http://saturn.jpl.nasa.gov/multimedia/images/raw/casJPGFullS07/N00026439.jpg
It needs to be brightened a lot before you can see anything. Look for the dark lines running sideways near the southern (curved) horizon, helps if that is at the top. They look like the tops of uplifted blocks to me.
Posted by: alan Jan 4 2005, 08:40 AM
Somethings weird is going on here
http://s05.imagehost.org/view.php?image=/0631/N00026245odd.jpg
Posted by: chris Jan 4 2005, 12:08 PM
Alan,
I'm a newbie here. What exactly is weird?
Chris
Posted by: volcanopele Jan 4 2005, 05:05 PM
I'm a newbie here. What exactly is weird?
Chris
I think he means the "wind streaks". To me, it just means that what ever deposited the dark material was low to the ground at those latitudes.
Posted by: alan Jan 4 2005, 05:21 PM
Its not just the "wind streaks" the craters looks odd. The have rings of light and dark material inside of them and the ejecta looks "wet" like the they formed in slushy material. One group of them is in a lobe of bright material. Some of the larger craters look like one of the rims is sliding downhill.
Posted by: volcanopele Jan 4 2005, 07:54 PM
A couple of notes:
1) RADAR detected Iapetus. According to Arecibo results, the dark material and the bright material are indistinguishable, suggesting that the dark material is less than a radar wavelength deep (3 m or 13 m, not sure which Arecibo used). Should be interesting to see what Cassini RADAR found.
2) There is a press "activity" on Friday. Some good mosaics should be presetned then.
Posted by: alan Jan 4 2005, 09:35 PM
I think after the ridge becomes shallow it becomes a rift, spreading rather than compressing, the surface would be softer resulting in flatter craters.
Posted by: Decepticon Jan 5 2005, 03:53 AM
1) RADAR detected Iapetus. According to Arecibo results, the dark material and the bright material are indistinguishable, suggesting that the dark material is less than a radar wavelength deep (3 m or 13 m, not sure which Arecibo used). Should be interesting to see what Cassini RADAR found.
2) There is a press "activity" on Friday. Some good mosaics should be presetned then.
I hope we see a new global map.
It's a little upseting to see very little press releases.
I hope 05 turns out better with Color images and pre and post orbit science.
Posted by: alan Jan 5 2005, 04:34 AM
I think the outer rim of the largest impact basin is where the crust cracked and settled rather the rim of the crater. A couple of craters along the rim look like they are split or shifted as it settled.
http://s04.imagehost.org/view.php?image=/1485/N00026263Ro.jpg
Posted by: alan Jan 5 2005, 06:23 AM
What would happen if methane calthrate was erupted onto the surface? Would it be stable? I'm thinking if there were patches of it on the surface the methane could be released by impacts. This would settle in any holes that had formed in the dark blanket and darken with exposure to sunlight. I see this as a way to create fresh dark material after Iapetus cooled too much to drive volcanism.
Posted by: alan Jan 6 2005, 05:14 AM
What time is the press activity?
Posted by: alan Jan 6 2005, 05:46 PM
A mosiac of sunlit cresent and the night side was posted here
http://www.markcarey.com/cgi-bin/mt/mt-view.cgi/18/entry/21706/discussion_page?start=41&show=20
Posted by: AlexBlackwell Jan 7 2005, 07:27 PM
There is a press "activity" on Friday. Some good mosaics should be presetned then.
What time is the press activity?
I'm not sure about "press activity," but maybe Jason was referring to today's CICLOPS release "http://ciclops.lpl.arizona.edu/view_event.php?id=9"?
Posted by: tedstryk Jan 7 2005, 09:04 PM
I don't mean to be rude, but the new release http://photojournal.jpl.nasa.gov/catalog/PIA06166
is the worst version of that mosaic I have seen anywhere - the limb is entirely washed out. And several other images seem like very compressed jpegs compared to amateur versions, even though the versions I downloaded were .tiff files. I can understand a motive for releasing limited imagery in terms of not wanting to be beaten to scientific results by those not on the team. But with the images in the "raw" section being much better than the public release quality this time around, it seems to have little point. I fear the Cassini team is failing to understand the importance of "instant science in creating public interest in the mission.
Posted by: volcanopele Jan 7 2005, 09:16 PM
is the worst version of that mosaic I have seen anywhere - the limb is entirely washed out. And several other images seem like very compressed jpegs compared to amateur versions, even though the versions I downloaded were .tiff files. I can understand a motive for releasing limited imagery in terms of not wanting to be beaten to scientific results by those not on the team. But with the images in the "raw" section being much better than the public release quality this time around, it seems to have little point. I fear the Cassini team is failing to understand the importance of "instant science in creating public interest in the mission.
When I sent that image out to the team, it looked fine with no compression artifacts. I understand that a unsharp mask filter was run, but the ones I did weren't that bad, and the others that Tilmann Denk did showed NO compression artifacts.
Posted by: volcanopele Jan 7 2005, 09:22 PM
is the worst version of that mosaic I have seen anywhere - the limb is entirely washed out. And several other images seem like very compressed jpegs compared to amateur versions, even though the versions I downloaded were .tiff files. I can understand a motive for releasing limited imagery in terms of not wanting to be beaten to scientific results by those not on the team. But with the images in the "raw" section being much better than the public release quality this time around, it seems to have little point. I fear the Cassini team is failing to understand the importance of "instant science in creating public interest in the mission.
When I sent that image out to the team, it looked fine with no compression artifacts. I understand that a unsharp mask filter was run, but the ones I did weren't that bad, and the others that Tilmann Denk did showed NO compression artifacts.
okay, here is what happened. I sent around a jpeg version of a mosaic I created. People liked it so I was asked to send out a tif version. I did. Apparently, no one bothered to go and change the image from the JPEG I sent earlier to the new tif version.
GRRRRRRRRRRRRRRRRRRR!!!
Posted by: tedstryk Jan 7 2005, 09:25 PM
I didn't mean to offend anyone. I just couldn't understand why the jpeg compression was there. Good to here it was just a mistake.
Ted
Posted by: volcanopele Jan 7 2005, 09:47 PM
One complaint I have is the way the unsharp mask was done. I usually a smaller boxfilter size, usually less than 1 pixel. This greatly reduces edge effects.
Posted by: Decepticon Jan 8 2005, 05:22 AM
Please tell me that JPL will use exposure times imaging on other moon flybys!?
This adds to images during each moon encounters.
Iapetus global maps will benefit a great deal using this method.
Posted by: tedstryk Jan 8 2005, 05:33 AM
What do you mean by that? Are you referring to the images taken of the part of Iapetus in Saturnshine? Such imaging might be possible, but the spacecraft, at aphelion, was not moving very fast. For the other moons, this might prove difficult or impossible.
Ted
Posted by: Decepticon Jan 8 2005, 01:45 PM
Yes.
Posted by: tedstryk Jan 8 2005, 02:08 PM
In addition to being more difficult because of spacecraft motion, Cassini will have many more non-targeted opportunities often not listed in lists of non-targeted flybys (100,000 - 250,000 km) to do gapfill on the moons inside Titan's orbit. The next closest Iapetus flyby other than the targeted flyby in 2007 will be this fall at ~415,000 km(Better than the nearly full view used in Jason's little icon (~700,000 km) but not nearly as good as this flyby. I wish I had a list of the flyby distances for major moons for all orbits, like we did with Galileo. But I guess that was a lot easier when we were only dealing with four major moons at Jupiter. Also, without Galileo's bottleneck, the Cassini people probably have a lot more observations to plan.
Posted by: Decepticon Jan 8 2005, 07:50 PM
You would think this info would come out before each encounter!
Sadly its not.
Posted by: tedstryk Jan 10 2005, 11:57 PM
VIMS and CIRS data for Iapetus has been released. Check out photojournal.jpl.nasa.gov
Jason, any word on the Dione VIMS data?
Ted
Posted by: volcanopele Jan 11 2005, 12:41 AM
Jason, any word on the Dione VIMS data?
Ted
Thanks!! I've been waiting for those to show up. For VIMS, the most important results are in the transition zone between the dark and bright terrain, showing predominantly CO2 and bound water ice. For CIRS, they found a surface with a very low thermal interia, suggesting a fluffy surface. This is consistent with our interpretation of the landslide crater, that the materials that filled that crater were "fluffy" but CIRS has shown that this is the case for the entire dark region. Still waiting for RADAR results. Arecibo results suggest that the dark terrain is thinner than 13 meters thick, but those were not disk resolved results. RADAR should gives us a better idea on the thickness of the deposit.
Still no word on Dione data. My understanding is still that RADAR and either VIMS or CIRS lost their data, not sure how and if that is still the case.
Posted by: alan Jan 11 2005, 03:46 AM
I find it interesting that the CO2 peaks at mid latitudes and has holes in it. Perhaps there is more than one type of dark material: a thick layer containing minerals from inside Iapetus concentrated near the equator, and a thin layer containing the CO2 from the outer moons like Phoebe that is more widely distributed.
Posted by: scalbers Oct 11 2007, 03:37 PM
I noticed Ted Stryk's excellent 12/2004 image in this post that I'll link here:
http://www.unmannedspaceflight.com/index.php?showtopic=4561&st=690&p=101828&#entry101828
I was wondering which PDS or raw images this was made from. Ted's processed image may be worth substituting over certain areas in my map if that's OK, or I could go to the original images. Is this from about 700000km out on approach? I'd be interested in any background info on this. For some reason these aren't showing up when I do simple searches on the PDS or the raw images page.
Might be fun to help complete this dormant thread. This is the approach image I'm http://laps.noaa.gov/albers/sos/saturn/iapetus/gridded/ortho15_gridded.jpg in the map. Is Ted's image a sharpened version of the one I'm using?
Thanks,
Posted by: ugordan Oct 11 2007, 04:30 PM
The images you probably want were taken on 2004-12-27, target is listed as UNK, not IAPETUS. Here's my quick take on the IR3/GRN/UV3 shot, desaturated to approximate natural colors and contrast-reduced to bring out CR:
http://i108.photobucket.com/albums/n15/ugordan/2004-12-27near-true.png
Posted by: tedstryk Oct 11 2007, 04:39 PM
Yes. Same dataset. I applied a variant of Tim Parker's super-resolution technique to the images and made a color overlay.
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