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?

I have an animation of this flyby. It shows what to expect during the flyby.

Let me know if you want this.

Please! Can you post it here?

It's 13.7 Mb


I think I would have to do a file transfer for that. Got ICQ or MSN?


ICQ# 6840999

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.

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.

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.

WOW!!!

In the meantime two smaller Iapetus WOWs :

http://photojournal.jpl.nasa.gov/catalog/PIA06146
and
http://photojournal.jpl.nasa.gov/catalog/PIA06145

How close will Cassini come to Iapetus during Tb?

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.

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:

Here, BTW, is a look at those mountains by Voyager 2:

SO cassini will use Radar on this approach?

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.

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?

the all seeing eye
http://saturn.jpl.nasa.gov/multimedia/imag...6/N00025365.jpg

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.

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.

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.

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

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?t...vmul=-1&bfov=30

Double post.

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?

New PICS!!

And this was from Dec 18! Man I can't wait!!!

http://saturn1.jpl.nasa.gov/multimedia/ima...lS07/N25973.jpg
http://saturn1.jpl.nasa.gov/multimedia/ima...7/N00025977.jpg

Wow!

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

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

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?t...vmul=-1&bfov=30

view from saturn gives phase angle of 110 degrees.
http://space.jpl.nasa.gov/cgi-bin/wspace?t...vmul=-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?t...vmul=-1&bfov=30

Would be simpler if they updated the simulato so you could use Cassini as the viewpoint after July

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.

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

Wow !

http://saturn.jpl.nasa.gov/multimedia/imag...eiImageID=29377

The highest resolution image ever obtained of Iapetus...

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?

Upsidedown?

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.

In the raw images, north is down. In my image, I have rotated so north is approximately up.

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.

12, 2:30, and 9, though the mountains are beyond the western rim of impact number 3, labeled in the attached graphic.

Will Cassini get close enough to determine whether Iapetus has an asymmetric mass distribution?

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!

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!

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.

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.

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?

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.

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.

Anyone try using an unsharp mask on the images of Iapetus?

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

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

^ I wish I understood the question, I'm not that great at adobey.

What will that do to the image?