Approaching Iapetus - what makes it two-faced?

[vogon13]

I rescaled some images from the Saturn Images thread for convenience here.<br /><br /> <div class="Discussion_UserSignature"> <p><font color="#ff0000"><strong>TPTB went to Dallas and all I got was Plucked !!</strong></font></p><p><font color="#339966"><strong>So many people, so few recipes !!</strong></font></p><p><font color="#0000ff"><strong>Let's clean up this stinkhole !!</strong></font> </p> </div>

 

[vogon13]

more:<br /><br /> <div class="Discussion_UserSignature"> <p><font color="#ff0000"><strong>TPTB went to Dallas and all I got was Plucked !!</strong></font></p><p><font color="#339966"><strong>So many people, so few recipes !!</strong></font></p><p><font color="#0000ff"><strong>Let's clean up this stinkhole !!</strong></font> </p> </div>

 

[3488]

Hi vogon13.<br /><br />Like those images very much.<br /><br />I have a few too.<br /><br />Limb of Iapetus.<br /><br />NASA / JPL.<br /><br />Andrew Brown. <div class="Discussion_UserSignature"> <p><font color="#000080">"I suddenly noticed an anomaly to the left of Io, just off the rim of that world. It was extremely large with respect to the overall size of Io and crescent shaped. It seemed unbelievable that something that big had not been visible before".</font> <em><strong><font color="#000000">Linda Morabito </font></strong><font color="#800000">on discovering that the Jupiter moon Io was volcanically active. Friday 9th March 1979.</font></em></p><p><font size="1" color="#000080">http://www.launchphotography.com/</font><br /><br /><font size="1" color="#000080">http://anthmartian.googlepages.com/thisislandearth</font></p><p><font size="1" color="#000080">http://web.me.com/meridianijournal</font></p> </div>

 

[3488]

Iapetus.<br /><br />400 KM wide depression.<br /><br />NASA / JPL.<br /><br />Andrew Brown. <div class="Discussion_UserSignature"> <p><font color="#000080">"I suddenly noticed an anomaly to the left of Io, just off the rim of that world. It was extremely large with respect to the overall size of Io and crescent shaped. It seemed unbelievable that something that big had not been visible before".</font> <em><strong><font color="#000000">Linda Morabito </font></strong><font color="#800000">on discovering that the Jupiter moon Io was volcanically active. Friday 9th March 1979.</font></em></p><p><font size="1" color="#000080">http://www.launchphotography.com/</font><br /><br /><font size="1" color="#000080">http://anthmartian.googlepages.com/thisislandearth</font></p><p><font size="1" color="#000080">http://web.me.com/meridianijournal</font></p> </div>

 

[3488]

Iapetus. <br /><br />Cratered terrain with a grabben & a section of the equatorial ridge. <br /><br />NASA / JPL. <br /><br />Andrew Brown. <div class="Discussion_UserSignature"> <p><font color="#000080">"I suddenly noticed an anomaly to the left of Io, just off the rim of that world. It was extremely large with respect to the overall size of Io and crescent shaped. It seemed unbelievable that something that big had not been visible before".</font> <em><strong><font color="#000000">Linda Morabito </font></strong><font color="#800000">on discovering that the Jupiter moon Io was volcanically active. Friday 9th March 1979.</font></em></p><p><font size="1" color="#000080">http://www.launchphotography.com/</font><br /><br /><font size="1" color="#000080">http://anthmartian.googlepages.com/thisislandearth</font></p><p><font size="1" color="#000080">http://web.me.com/meridianijournal</font></p> </div>

 

[3488]

Iapetus. <br /><br />Trailing night side hemisphere lit by 'Saturnshine'. <br /><br />Long exposure of 82 Seconds has trailed the background stars.<br /><br />The long exposure was necessary to obtain the detail on the surface of Saturn lit Iapetus.<br /><br />NASA / JPL. <br /><br />Andrew Brown. <div class="Discussion_UserSignature"> <p><font color="#000080">"I suddenly noticed an anomaly to the left of Io, just off the rim of that world. It was extremely large with respect to the overall size of Io and crescent shaped. It seemed unbelievable that something that big had not been visible before".</font> <em><strong><font color="#000000">Linda Morabito </font></strong><font color="#800000">on discovering that the Jupiter moon Io was volcanically active. Friday 9th March 1979.</font></em></p><p><font size="1" color="#000080">http://www.launchphotography.com/</font><br /><br /><font size="1" color="#000080">http://anthmartian.googlepages.com/thisislandearth</font></p><p><font size="1" color="#000080">http://web.me.com/meridianijournal</font></p> </div>

 

[3488]

Iapetus. <br /><br />A good old view from Voyager 2. <br /><br />NASA / JPL. <br /><br />Andrew Brown. <div class="Discussion_UserSignature"> <p><font color="#000080">"I suddenly noticed an anomaly to the left of Io, just off the rim of that world. It was extremely large with respect to the overall size of Io and crescent shaped. It seemed unbelievable that something that big had not been visible before".</font> <em><strong><font color="#000000">Linda Morabito </font></strong><font color="#800000">on discovering that the Jupiter moon Io was volcanically active. Friday 9th March 1979.</font></em></p><p><font size="1" color="#000080">http://www.launchphotography.com/</font><br /><br /><font size="1" color="#000080">http://anthmartian.googlepages.com/thisislandearth</font></p><p><font size="1" color="#000080">http://web.me.com/meridianijournal</font></p> </div>

 

[3488]

Iapetus. <br /><br />A New Year's Day 2005 Cassini Spacecraft view. Clearly visible is the 400 KM wide <br />depression & a portion of the lighter toned terrain. <br /><br />NASA / JPL. <br /><br />Andrew Brown. <div class="Discussion_UserSignature"> <p><font color="#000080">"I suddenly noticed an anomaly to the left of Io, just off the rim of that world. It was extremely large with respect to the overall size of Io and crescent shaped. It seemed unbelievable that something that big had not been visible before".</font> <em><strong><font color="#000000">Linda Morabito </font></strong><font color="#800000">on discovering that the Jupiter moon Io was volcanically active. Friday 9th March 1979.</font></em></p><p><font size="1" color="#000080">http://www.launchphotography.com/</font><br /><br /><font size="1" color="#000080">http://anthmartian.googlepages.com/thisislandearth</font></p><p><font size="1" color="#000080">http://web.me.com/meridianijournal</font></p> </div>

 

[jaxtraw]

Looking at those "off-ramps" it's hard to see a hypothesis better than the collapsed ring one.<br /><br />Also, as an old hippie and admirer of the music of Jethro Tull, I propose the feature be named "Dun Ringhill". <img src="/images/icons/smile.gif" />

 

[vogon13]

The symmetrical diverging 'off ramps' force you to think about rings. Realizing the 'off ramps' also describe portions of great circle paths about Iapetus is the clincher. Someone might contort and twist some geological process to generate a cliff or mountain range along or near the equator, but once you see the 3 strands loping away from the common point, and that common point is plausibly the highest point along the equator, you're talking rings.<br /><br />Imagine a smooth celestial body with rings. Through the natural dynamical ring spreading process, eventually, the ring system will plop one particle onto the surface.<br /><br />Then what happens ??<br /><br />The next lowest descending particle smacks the first one.<br /><br />The entire ring system eventually dissipates itself at this point.<br /><br />(I am simplifying quite a bit here to make the point)<br /><br />Realizing inclined elements in the ring system (or conversely, nutation developing in the spin axis of Iapetus) can generate symmetrical diverging 'off ramps' was all the proof I needed. But I concede, for widespread acceptance of this idea, we need more pictures.<br /><br /><br /><br /> <div class="Discussion_UserSignature"> <p><font color="#ff0000"><strong>TPTB went to Dallas and all I got was Plucked !!</strong></font></p><p><font color="#339966"><strong>So many people, so few recipes !!</strong></font></p><p><font color="#0000ff"><strong>Let's clean up this stinkhole !!</strong></font> </p> </div>

 

[jaxtraw]

Yes Vogon, there was no need to explain it again. I'm sorry my post wasn't clearer- I was agreeing with you. I think the "off ramps" are the clincher. I can't wait for some better piccies <img src="/images/icons/smile.gif" />

 

[vogon13]

Understanding (finally) what precisely is occuring at the contact point is helpful too.<br /><br />The differential ring spreading process is the primary mechnism that causes the lower edge of the ring system to descend towards the surface. While this process is relentless, it is excrutiatingly slow. We have a particle (for convenience, the lowest one) that is passing over the pinnacle on every orbit. Every orbit, the particle is 'bumped' slightly lower. The degree of lowering is much smaller than the average size of ring particles. Therefore, when the particle does contact the highest fixed point along the orbital ground track, the contact is always glancing and skidding. No big splat.<br /><br />Now, contact with the pinnacle will cause the particle to fragment to shatter, it might even spin up and shatter. Whatever, we now have a blast of snow, zipping along the top of the ridge, depositing a thin layer as it goes along. The particle on contact, also slows down a bit, and due to the shallowness of the slope of the ridge, the 'snow' might be overtaken by trailing ring particles that while they may not have contcted the pinnacle, their physical size is still large enough for them to interact with the pulverized particle they are over taking. These particles no longer have circular orbits about Iapetus, and will dip towards the surface for 180 degrees, and then climbing back up to the height of the pinnacle. Depending on the random amount of decel, these particles have the opprotunity to impact an appropriately high 'Voyager Mountain' along the ground track.<br /><br />The pinnacle along the ring's orbital ground track remains <i>fixed</i> throughout the emplacement process. (sorry I didn't figure that bit out sooner) <div class="Discussion_UserSignature"> <p><font color="#ff0000"><strong>TPTB went to Dallas and all I got was Plucked !!</strong></font></p><p><font color="#339966"><strong>So many people, so few recipes !!</strong></font></p><p><font color="#0000ff"><strong>Let's clean up this stinkhole !!</strong></font> </p> </div>

 

[3488]

I really hope to that we get some really high res of the 'Off Ramps' too.<br /><br />Hopefully we get to see a Map of Iapetus soon showing the different resolution, that<br />different areas will be imaged at,<br />like this one of the Iapetus, December 2005 encounter.<br /><br />Andrew Brown. <div class="Discussion_UserSignature"> <p><font color="#000080">"I suddenly noticed an anomaly to the left of Io, just off the rim of that world. It was extremely large with respect to the overall size of Io and crescent shaped. It seemed unbelievable that something that big had not been visible before".</font> <em><strong><font color="#000000">Linda Morabito </font></strong><font color="#800000">on discovering that the Jupiter moon Io was volcanically active. Friday 9th March 1979.</font></em></p><p><font size="1" color="#000080">http://www.launchphotography.com/</font><br /><br /><font size="1" color="#000080">http://anthmartian.googlepages.com/thisislandearth</font></p><p><font size="1" color="#000080">http://web.me.com/meridianijournal</font></p> </div>

 

[3488]

Only EIGHT days left & counting to Iapetus.<br /><br />Andrew Brown. <div class="Discussion_UserSignature"> <p><font color="#000080">"I suddenly noticed an anomaly to the left of Io, just off the rim of that world. It was extremely large with respect to the overall size of Io and crescent shaped. It seemed unbelievable that something that big had not been visible before".</font> <em><strong><font color="#000000">Linda Morabito </font></strong><font color="#800000">on discovering that the Jupiter moon Io was volcanically active. Friday 9th March 1979.</font></em></p><p><font size="1" color="#000080">http://www.launchphotography.com/</font><br /><br /><font size="1" color="#000080">http://anthmartian.googlepages.com/thisislandearth</font></p><p><font size="1" color="#000080">http://web.me.com/meridianijournal</font></p> </div>

 

[jaxtraw]

I don't think these have been posted-- first a website from one of the imaging team which has lots of fascinating detail including the flyby's schedule blow-by-blow<br /><br />http://www.geoinf.fu-berlin.de/projekte/cassini/cassini_fu_iapetus_flyby.php<br /><br />And also an animated .gif (about 800kb) showing the specific areas which the cameras will target which is quite mesmerising to watch <img src="/images/icons/smile.gif" /><br /><br />http://www.planetary.org/image/Ia049_all_ftprts_sph_anim.gif<br /><br />I'm all quite thrilled to bits about this. 10m per pixel isn't something we get every day <img src="/images/icons/laugh.gif" />

 

[3488]

Post deleted by 3488 <div class="Discussion_UserSignature"> <p><font color="#000080">"I suddenly noticed an anomaly to the left of Io, just off the rim of that world. It was extremely large with respect to the overall size of Io and crescent shaped. It seemed unbelievable that something that big had not been visible before".</font> <em><strong><font color="#000000">Linda Morabito </font></strong><font color="#800000">on discovering that the Jupiter moon Io was volcanically active. Friday 9th March 1979.</font></em></p><p><font size="1" color="#000080">http://www.launchphotography.com/</font><br /><br /><font size="1" color="#000080">http://anthmartian.googlepages.com/thisislandearth</font></p><p><font size="1" color="#000080">http://web.me.com/meridianijournal</font></p> </div>

 

[3488]

Thank you very much jaxtraw. <br /><br />That is superb. <br /><br />vogon13 will like the 20 metre & 50 metre resolution observations of the Voyager Mountains, <br />(mind you, so will I) <img src="/images/icons/laugh.gif" /><br /><br />The occultaion with Nunki / Sigma Sagittari will settle once & for all, if Iapetus is <br />completely without an atmosphere. I suspect that to be the case. <br /><br />Yes 10 metres per pixel is extremely good. <br /><br />It looks like we also get to see the southern polar region quite well too as <br />well as the Moat Crater in Saturnshine. <br /><br />Can't wait. <br /><br />SEVEN days & counting. <br /><br />Below, Iapetus in monochrome & in approx true colour (UV, Green & near IR filters). <br /><br />NASA / JPL. <br /><br />Andrew Brown. <div class="Discussion_UserSignature"> <p><font color="#000080">"I suddenly noticed an anomaly to the left of Io, just off the rim of that world. It was extremely large with respect to the overall size of Io and crescent shaped. It seemed unbelievable that something that big had not been visible before".</font> <em><strong><font color="#000000">Linda Morabito </font></strong><font color="#800000">on discovering that the Jupiter moon Io was volcanically active. Friday 9th March 1979.</font></em></p><p><font size="1" color="#000080">http://www.launchphotography.com/</font><br /><br /><font size="1" color="#000080">http://anthmartian.googlepages.com/thisislandearth</font></p><p><font size="1" color="#000080">http://web.me.com/meridianijournal</font></p> </div>

 

[3488]

First image of Iapetus taken during the approach by the Cassini Spacecraft for the close <br />encounter next Monday.<br /><br />A very slim crescent. <br /><br />BTW I had to enlarge & enhance it somewhat.<br /><br />Taken on: Monday 3rd September 2007 from approx: 1,449,143 kilometers.<br /><br />Getting exciting this. <img src="/images/icons/laugh.gif" /><br /><br />NASA / JPL.<br /><br />Andrew Brown. <div class="Discussion_UserSignature"> <p><font color="#000080">"I suddenly noticed an anomaly to the left of Io, just off the rim of that world. It was extremely large with respect to the overall size of Io and crescent shaped. It seemed unbelievable that something that big had not been visible before".</font> <em><strong><font color="#000000">Linda Morabito </font></strong><font color="#800000">on discovering that the Jupiter moon Io was volcanically active. Friday 9th March 1979.</font></em></p><p><font size="1" color="#000080">http://www.launchphotography.com/</font><br /><br /><font size="1" color="#000080">http://anthmartian.googlepages.com/thisislandearth</font></p><p><font size="1" color="#000080">http://web.me.com/meridianijournal</font></p> </div>

 

[3488]

A further enlargement & contrast enhanced verion of crescent Iapetus.<br /><br />Monday 3rd September 2007 from:1,449,143 kilometers away.<br /><br />NASA / JPL.<br /><br />Andrew Brown. <div class="Discussion_UserSignature"> <p><font color="#000080">"I suddenly noticed an anomaly to the left of Io, just off the rim of that world. It was extremely large with respect to the overall size of Io and crescent shaped. It seemed unbelievable that something that big had not been visible before".</font> <em><strong><font color="#000000">Linda Morabito </font></strong><font color="#800000">on discovering that the Jupiter moon Io was volcanically active. Friday 9th March 1979.</font></em></p><p><font size="1" color="#000080">http://www.launchphotography.com/</font><br /><br /><font size="1" color="#000080">http://anthmartian.googlepages.com/thisislandearth</font></p><p><font size="1" color="#000080">http://web.me.com/meridianijournal</font></p> </div>

 

[jaxtraw]

Hey Andrew, don't post too many of these, the tension is nailbiting already. It's like watching a woman striptease who's taking a week to get her coat off <img src="/images/icons/laugh.gif" /><br /><br />Seriously tho thanks for the image <img src="/images/icons/smile.gif" />

 

[CalliArcale]

I am drooling over the images too, and eagerly awaiting the flyby. I am pinning this thread through the flyby. <img src="/images/icons/wink.gif" /> <div class="Discussion_UserSignature"> <p> </p><p><font color="#666699"><em>"People assume that time is a strict progression of cause to effect, but actually from a non-linear, non-subjective viewpoint it's more like a big ball of wibbly wobbly . . . timey wimey . . . stuff."</em>  -- The Tenth Doctor, "Blink"</font></p> </div>

 

[CalliArcale]

As Cassini approaches Iapetus (the flyby will occur on New Years' Eve), we come nearer to possibly learning the truth of one of the great mysteries of the Saturn system. Just recently, Cassini revealed that the mysterious white streaks on Dione's surface weren't streaks at all, but rather long cliffs. Nobody knows what created those cliffs, so while one mystery was solved, another popped up in its place.<br /><br />The same may well happen when Cassini encounters Iapetus. Iapetus is a strange moon. It was discovered centuries ago by the astronomer Cassini himself, who noted that he could only see it when it was on one side of Saturn, correctly deducing that it must be very bright on one side and very dark on the other. The Voyager probes returned images showing that it is tidally locked with Saturn and that its leading hemisphere is as dark as lampblack while its trailing hemisphere is as bright as newfallen snow, making it a bizarre study in contrasts. Why is Iapetus like this? Was material kicked off of Phoebe and then swept up by Iapetus? Or is some internal process responsible? Is it something else entirely? What is the deal with Iapetus?<br /><br />Guesses, anybody? <img src="/images/icons/wink.gif" /> Also, does anybody have any guesses about what new mysteries may be revealed? You've got just a few days before Cassini starts its closest study yet of the enigmatic moon, although I have no doubt that the mystery will linger for a long time to come. <div class="Discussion_UserSignature"> <p> </p><p><font color="#666699"><em>"People assume that time is a strict progression of cause to effect, but actually from a non-linear, non-subjective viewpoint it's more like a big ball of wibbly wobbly . . . timey wimey . . . stuff."</em>  -- The Tenth Doctor, "Blink"</font></p> </div>

 

[brellis]

Careful you don't stick Andrew with your pin, he's had his hands all over this thread <img src="/images/icons/cool.gif" /> <div class="Discussion_UserSignature"> <p><font size="2" color="#ff0000"><em><strong>I'm a recovering optimist - things could be better.</strong></em></font> </p> </div>

 

[3488]

Thank you all for your kind comments.<br /><br />Thank you also CalliArcale for making this a stickie.<br /><br />At least brellis, people will know where I am if i'm pinned here!!! <img src="/images/icons/laugh.gif" /><br /><br />I am afraid that there are no fresh Iapetus images today, just checked, so the<br />most recent are those above. Cassini yesterday made more Saturn observations.<br /><br />From the JPL website:<br /><br /><font color="black">"Cassini successfully flew by Titan on Aug. 31, 2007, imaging the Huygens <br />probe landing site and studying the composition and geology of Titan's surface. <br />This flyby placed Cassini on a course to conduct the closest flyby of the odd <br />moon Iapetus that it will perform during the entire mission. On Sept. 10, <br />Cassini will come about 1,640 kilometers (1,000 miles) from Iapetus's surface. <br /><br />Iapetus is a world of sharp contrasts. The leading hemisphere is as dark as a <br />freshly-tarred street, and the white, trailing hemisphere resembles freshly-fallen snow. <br />Scientists want to know more about the composition of the dark material that coats <br />Iapetus. They also want to learn more about Iapetus' distinctive walnut shape <br />and the chain of mountains along its equator".</font><br /><br /><font color="white">So it does look very, very good indeed for next Monday. <img src="/images/icons/cool.gif" /><br /><br />So keep checking back, if anything new pops up, I intend to reveal it on this thread. <br /><br />I am having trouble with British Telecom yet again, but hopefully, that will not cause me <br />too many problems in keeping this thread up to date.<br /><br />Andrew Brown.</font> <div class="Discussion_UserSignature"> <p><font color="#000080">"I suddenly noticed an anomaly to the left of Io, just off the rim of that world. It was extremely large with respect to the overall size of Io and crescent shaped. It seemed unbelievable that something that big had not been visible before".</font> <em><strong><font color="#000000">Linda Morabito </font></strong><font color="#800000">on discovering that the Jupiter moon Io was volcanically active. Friday 9th March 1979.</font></em></p><p><font size="1" color="#000080">http://www.launchphotography.com/</font><br /><br /><font size="1" color="#000080">http://anthmartian.googlepages.com/thisislandearth</font></p><p><font size="1" color="#000080">http://web.me.com/meridianijournal</font></p> </div>

 

[jaxtraw]

As the Iapetus approach, er, approaches, I'm wondering what we should look for in the images to support or invalidate the "Ring Hypothesis". I would imagine a mountain chain formed by uplift would be geologically (iapetologically??? <img src="/images/icons/smile.gif" /> ) different to one formed by accumulated ring particles.<br /><br />Off topic, but as you've mentioned ISP problems, just thought I'd mention that after a lot of irritations with broadband ISPs, I've been with Zen for quite some time now and the connection has been entirely trouble free. It costs a bit more, but I've only had to contact support once, over a change of DNS servers. I don't have any financial interest in Zen, by the way <img src="/images/icons/smile.gif" />