Approaching Iapetus - what makes it two-faced?

vogon13 · Sep 11, 2007

No, the delta vee to loft materials from Saturn's rings all the way to Iapetus is large. Iapetus is heavily cratered because the surface is old and no process like wind and rain to erase the craters like on earth. <div class="Discussion_UserSignature"> TPTB went to Dallas and all I got was Plucked !!So many people, so few recipes !!Let's clean up this stinkhole !! </div>

3488 · Sep 11, 2007

Iapetus from 12,221 KM. Enlargement of Voyager Mountains on horizon. This time we are seeing the Voyager Mountains from further around. Voyager Mountains again. Black on White terrain? Here again? Or Here? Iapetus from 6,502 KM. Iapetus from 1,651 KM. Iapetus from 1,987 KM. Iapetus from 7,982 KM. Iapetus from 1,808 KM. Iapetus is just getting weirder. Hi RobNissen, There is no crater removal mechanism at Iapetus, other than, 1). Burial by infalling debris & 2). Fresh cratering to remove older craters. Andrew Brown. <div class="Discussion_UserSignature"> "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". Linda Morabito on discovering that the Jupiter moon Io was volcanically active. Friday 9th March 1979.http://www.launchphotography.com/ http://anthmartian.googlepages.com/thisislandearthhttp://web.me.com/meridianijournal </div>

franontanaya · Sep 12, 2007

There are lots of tiny craters/holes at the crest of those mountains: http://saturn.jpl.nasa.gov/multimedia/images/raw/casJPGFullS33/W00035197.jpg On smaller scale, Martian dunes with CO2 frost looked a bit like that. And there's also something up right that looks like carved in the terrain. <div class="Discussion_UserSignature"> </div>

3488 · Sep 12, 2007

Hi FranOntanaya. I have not really had time yet to study the new images as yet (they have literally arrived within the last hour). I see that quite clearly. I have made a very large enlargement of the mountains here. Don't know what to make of it. I don't think its cryovolcanics, as there appear to be no flow like features?!?!?!?!?! Thank you very much for bringing this to my attention. Andrew Brown. <div class="Discussion_UserSignature"> "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". Linda Morabito on discovering that the Jupiter moon Io was volcanically active. Friday 9th March 1979.http://www.launchphotography.com/ http://anthmartian.googlepages.com/thisislandearthhttp://web.me.com/meridianijournal </div>

franontanaya · Sep 12, 2007

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anthmartian · Sep 12, 2007

Andrew : fantastic images. Will be updating the site soon to include them. As for the dark covering the white. I think its the other way around. on the first example, there are at least a couple of craters half white, half dark. It looks like the white has arrived at the crater site later on. <div class="Discussion_UserSignature"> "Traveling through hyperspace ain't like dusting crops, boy! Without precise calculations we could fly right through a star, or bounce too close to a supernova and that'd end your trip real quick, wouldn't it?"Han Solo - 1977 - A long time ago in a galaxy far far away.... Click Here And jump over to my site. </div>

webscientist · Sep 12, 2007

The latest images of Iapetus are really breathtaking. I see domes but no crater.It seems that the surface is distorted by convection flow. I don't think it's the effect of meteoritic impacts. The assumed flow appears to be too weak to be expelled. Interesting!

3488 · Sep 12, 2007

Hi Anthmartian, I do see what you mean very much. If someone was to ask me, is this white on black or black on white? I would definately say white on black. However JPL seem sure that it is the other way around. Cassini Regio, the huge dark area, is on the leading hemisphere, so there fore if stuff is being swept up by Iapetus, than that is the side that would be contaminated. But I do agree with though, it REALLY does look like white on black, rather than the accepted notion of black on white. I think that Phoebe is still the accepted primary source of the dark material. Below I think is the crater you were refering to. I have blown it up & sharpened it a bit. Black & White Crater on Iapetus. Iapetus from 4,928 KM. Also a strange black on white, or is it white on black landscape???? Iapetus from 4,423 KM. Also a strange black on white, or is it white on black landscape???? Iapetus from 13,209 KM. Transition from dark to light toned hemisphere. Iapetus from 1,776 KM. A deceptively smooth looking landscape. Hi webscientist. I think your brain is playing tricks on you, making hollows look like mounds. MeteorWayne has explained this a few posts up. The image you are referring to is this one: Iapetus from 2,084 KM. I have rotated it. <</safety_wrapper> <div class="Discussion_UserSignature"> "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". Linda Morabito on discovering that the Jupiter moon Io was volcanically active. Friday 9th March 1979.http://www.launchphotography.com/ http://anthmartian.googlepages.com/thisislandearthhttp://web.me.com/meridianijournal </div>

anthmartian · Sep 12, 2007

Andrew : The crater that really caught my eye can be seen clicking below. I enlarged a bit, and added the arrow. http://img187.imageshack.us/img187/2568/sept12whiteondarklj5.jpg I just cannot see how this can be dark on white. the crater i have pointed to is definatelly older than the white. One off to the right and just below too is clear evidence for me. In the enhanced image i managed to turn out here, you can clearly see craters under the white also. less defined, even than the eroded old craters covering the rest of the moon. which to me suggests they have been covered. There is also a lot of other evidence here for the white in crouching into numerous other craters. It almost reminds me of glacier fields seen from Earth orbit. i may be wrong, or going against the experts, but it will take some compelling evidence for me to believe otherwise. I think we should be looking at where the white came from, not the dark. If we start doing that, more makes sense. The dark portions of this moon are obviously very old. This moons surface is as dead as a dodo as has been said. If the dark was the newer feature i would expect more definition, it has even less definition than the craters of phoebe, it makes less sense to me for the dark to be newer. It is picking up the lighter stuff from somewhere else i believe. But, i will take that evidence onboard gladly. Mostly because i enjoy logic and what i expect to be turned upside down! lol <div class="Discussion_UserSignature"> "Traveling through hyperspace ain't like dusting crops, boy! Without precise calculations we could fly right through a star, or bounce too close to a supernova and that'd end your trip real quick, wouldn't it?"Han Solo - 1977 - A long time ago in a galaxy far far away.... Click Here And jump over to my site. </div>

3488 · Sep 12, 2007

Thank you very much Anthmartian. http://anthmartian.googlepages.com/thisislandearth I see what you mean. I had not noticed that before (I have not really had a lot of time to look at the new images properly yet). It does look like the white is newer than the black here. Vogon, please help???? I'm getting confused. <img src="/images/icons/crazy.gif" /> I like the images you've posted on your site Anthmartian. That one of the Voyager Mountains you enhanced, I have resaved that. Absolutely stunning. At this rate, I will have more images on YOUR website than YOU do. <img src="/images/icons/laugh.gif" /> <img src="/images/icons/laugh.gif" /> <img src="/images/icons/laugh.gif" /> Mind you I am thoroughly enjoying this encounter very much indeed. Iapetus being faily difficuly=t to reach, due to its large distance from Saturn & relatively inclined orbit, meant that this is the only really close encounter possible with the Cassini spacecraft. So we must make the most of it. Another deceptively smooth looking surface here: Iapetus from 1,646 KM. Andrew Brown. <div class="Discussion_UserSignature"> "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". Linda Morabito on discovering that the Jupiter moon Io was volcanically active. Friday 9th March 1979.http://www.launchphotography.com/ http://anthmartian.googlepages.com/thisislandearthhttp://web.me.com/meridianijournal </div>

anthmartian · Sep 12, 2007

I am a bit busier today, but am trying to get images on the site, not as quick as i would like though. Nothing wrong with your images on there. Especially with things how they are here regarding images. i really think people are enjoying seeing them in one place. that image you were talking about is one of my favourites. it came up a treat. Wonderful detail. <img src="/images/icons/smile.gif" /> http://anthmartian.googlepages.com/iapetus010september2007et3-enhanced-.jpg/iapetus010september2007et3-enhanced--full.jpg http://anthmartian.googlepages.com/iapetusencounter the last two days have been the busiest 2 days on the site so far since i began. Plus, I can put my feet up for a while with you being featured so heavily! lol <div class="Discussion_UserSignature"> "Traveling through hyperspace ain't like dusting crops, boy! Without precise calculations we could fly right through a star, or bounce too close to a supernova and that'd end your trip real quick, wouldn't it?"Han Solo - 1977 - A long time ago in a galaxy far far away.... Click Here And jump over to my site. </div>

vogon13 · Sep 12, 2007

I have been trying to foster looking at the light/dark areas with this in mind: We are not seeing black stuff applied to white areas, and we are not seeing white stuff applied to black areas. Rather, we are seeing a colorless agent (most likely gaseous) applied everywhere. And then upon exposure to solar heat, the agent discolors whatever surface it is in contact with, when that surface reaches a certain temperature. I have made some negative copies of a few of the areas (one mostly white, and one mostly black) and it seems to me once a given sight line to the sun is intercepted by a discolored surface, nothing further along that sight line can be darkened. There are some further 'rules' how this darkening agent works. When Iapetus is directly ahead of Saturn in Saturn's journey about the sun, the sub solar point on Iapetus achieves maximum 'darkening' effect to the greatest altitude. The effect diminishes in altitude as you move away from this point, and the effect becomes more strongly correlated with elevation, darker lower, lighter higher. There is another effect that decreases with distance from this spot, the required angle of the incidence of sunlight on the surface becomes more perpendicular to achieving the darkening. The darkening fades as you approach either pole, as the bits of the surface oriented properly become less prevalent, and the east west extent of the effect is elongated as the sun travels overhead along the equator. The affect having a time componont of activation less than the time it takes Iapetus to orbit Saturn (~80 days). It appears that a given surface is either black or white. The distant 12/2004 pictures did not resolve the dark/white dichotomy, but simply 'averaged' the areal extent covered. I note black spots in the new pictures down to the resolution limits of the camera. <div class="Discussion_UserSignature"> TPTB went to Dallas and all I got was Plucked !!So many people, so few recipes !!Let's clean up this stinkhole !! </div>

anthmartian · Sep 12, 2007

Vogon : Where would this gas be coming from? Does this imply then that the whole moon is being frosted with this gas settling on the surface? If this process is happening relatively quickly i assume, would that distort the views that this is an exceptionally old and worn landscape. What i mean by this is would this settling have a smoothing effect? tricking the viewer into believing something was old. Rather than covered up and potentially quite new, with previously defined edges which are now hidden? <div class="Discussion_UserSignature"> "Traveling through hyperspace ain't like dusting crops, boy! Without precise calculations we could fly right through a star, or bounce too close to a supernova and that'd end your trip real quick, wouldn't it?"Han Solo - 1977 - A long time ago in a galaxy far far away.... Click Here And jump over to my site. </div>

tdamskov · Sep 12, 2007

These recent images are incredible - the more we see the more the mystery deepens. Anthmartian (and Andrew), thanks for excellent work on your site, your images are a great inspiration. Here's my own small contribution: An animated Flash sequence showing the flyby of the Voyager Mountains. I've only done a quick and dirty auto-contrast on the raw CL2 images and a slight colour tinting for pure artistic effect. http://www.td4.dk/space/IapetusRoundTheSpine.html I wanted to keep the trip fairly "straight" but somewhere in the middle, the angle of the camera is changed. I've manually adjusted the position of the frames and added some stretched pixels to the sides of the images where necessary to make it look less jarring. As a note of interest.. The raw image sequence actually does contain another two images at the end of this sequence where the camera is pointing almost straight down at the Voyager Mountains. They didn't really fit in the animation (too much difference in angle) but they do overlap some of the terrain visible in the animation. I might do another high-res version with more focus on single stepping through the images. I hope better calibrated/processed images will appear soon.

vogon13 · Sep 12, 2007

Gas is transported to Iapetus (and Hyperion!) as it traverses Saturn's magnetotail (always anti-sunward to Saturn, btw). That is why there is the time component in the darkening. Additionally, as the gas is used up, the composition changes a bit, and we note a slight color change in the 'dark crud' from west to east across Iapetus. The gas is from Titan's atmosphere, btw. And per our students of color science, we note that brown (Iapetus) and orange (Titan) are pretty much the same color with different degrees of saturation. (that's why there is no brown in the rainbow, yet it is a color.) <div class="Discussion_UserSignature"> TPTB went to Dallas and all I got was Plucked !!So many people, so few recipes !!Let's clean up this stinkhole !! </div>

anthmartian · Sep 12, 2007

Vogon : Thank you for that explanation. That makes a lot of sense. feel a bit dumb now. With the Titan gasses and all. tdamskov : Awesome work there! What a thrill riding with Cassini! <img src="/images/icons/smile.gif" /> I have made quite a few animations from Cassini data. But never of a flypast such as this. We discuss here the hows, and why's of this mysterious moon. But this brings home the sheer drama of what has happened. a space ship has flown within 1,300 km of a moon in the outer solar system! I got very excited seeing that. Thankyou. <img src="/images/icons/smile.gif" /> <div class="Discussion_UserSignature"> "Traveling through hyperspace ain't like dusting crops, boy! Without precise calculations we could fly right through a star, or bounce too close to a supernova and that'd end your trip real quick, wouldn't it?"Han Solo - 1977 - A long time ago in a galaxy far far away.... Click Here And jump over to my site. </div>

jaxtraw · Sep 12, 2007

Sorry Vogon13, I don't see how that explains only the leading hemisphere being darkened. The entire moon is equally sunlit during each orbit (except the short term when the Sun is occulted by Saturn).

vogon13 · Sep 12, 2007

Gas is 'applied' to Iapetus as it passes behind Saturn (as viewed from sun) and is just about totally used up in ~40 days. Maximum effect occurs at 20 days (90 degrees). Iapetus takes ~80 days to go 'round Saturn. <div class="Discussion_UserSignature"> TPTB went to Dallas and all I got was Plucked !!So many people, so few recipes !!Let's clean up this stinkhole !! </div>

jaxtraw · Sep 12, 2007

The problem I can see here is your timing. You need a chemical reaction that conveniently maximises in perfect synch with the period of Iapetus' orbit (i.e. 20 days, precisely 1/4 of the orbital period). That's serendipity that I think would raise eyebrows among chemists considering the hypothesis. The blackening seems to be perfectly symmetrical around the dead centre of Iapetus' leading hemisphere. Scientists don't like coincidences so far as I can tell <img src="/images/icons/smile.gif" />

tdamskov · Sep 12, 2007

Those cratered crests are perplexing at first glance. But I think the explanation must be that the mountains are heaps of extremely fine particles. With no moisture to glue the particles together they will flow easily if disturbed by a nearby impact, particularly on the slopes. Such particle flows would be almost indistinguishable from liquid flows. Although the mountains are 10-20 km's high the pressure caused by 0.02 G's and resulting friction on the deeper layers is relatively light (comparable to 2-400 meter dunes on Earth!). I suspect the profile of the mountains may have been steeper with an almost flat top (still visible in some places). - almost like a sinusoid hump. One will notice that the remaining flat parts of the mountains are riddled with small craters. With time, impacts on the sides of the mountains have caused repeated flows outwards, picking at the top of the "hump" from both sides and sharpening it into a triangular ridge. Impacts on the top of the ridge will tend to stay as there is no material above to slide into it and the crater edges further down will sag slightly. A similar effect can be seen on dunes on Earth: if you walk on the crest, you will find it rather solid and most of the footprints will stay there, but footprints on steeper sides are immediately dragged down and filled by material sliding down from above, causing soft, stretched dimples instead of sharp footprints. I would say that this evidence points strongly towards deposition as source of the Voyager Mountains.

anthmartian · Sep 12, 2007

tdamskov : You may be onto something there. We talk about coincidence. The two major features that nobody can explain about this moon, could as you say be married together. That is my favourite theory so far, it is neat and tidy. But it does suggest the darker substance from the Voyagers being the new covering material, covering the white. Which i have already said i have doubts about. ( call me devils advocate ). However white on top of dark, which i have presented photographic evidence for, could be just local to certain places. Overall the trend could be dark on white. I have searched and found an old article on Iapetus i read some time ago, which states that the dark terrain is surfaced by carbonaceous molecules, according to measurements made with Earth-based telescopes? but i say old article, published in 2000, a life time away considering what has come after it was written. That is beyond my knowledge, so i can't comment on that. <div class="Discussion_UserSignature"> "Traveling through hyperspace ain't like dusting crops, boy! Without precise calculations we could fly right through a star, or bounce too close to a supernova and that'd end your trip real quick, wouldn't it?"Han Solo - 1977 - A long time ago in a galaxy far far away.... Click Here And jump over to my site. </div>

jaxtraw · Sep 12, 2007

They look for all the world like "piles of sand" to me too. Yes, I know that's "ice sand" <img src="/images/icons/smile.gif" /> Tdamskov's post echoes my humble amateur view. They look like heaps of deposits, not extruded mountains. If the dark material is carbonaceous, that suggests to me that a carbonaceous body broke up, formed a ring, that gradually collaped onto the surface?

jaxtraw · Sep 12, 2007

Could the picture be slightly more complicated? The carbonaceous material formed the mountains and coated the entire moon- then that was subsequently coated by white stuff?

jaxtraw · Sep 12, 2007

http://anthmartian.googlepages.com/iapetus010september2007et3-enhanced-.jpg/iapetus010september2007et3-enhanced--full.jpg Looking at this picture, particularly that large crater on the right (just above half way up the pic) I see a lot of slumped, loose material on its left, which has slumped downslope. Naively, they surely look like rubble piles.

anthmartian · Sep 12, 2007

here's a link to that article. http://www.solarviews.com/cap/sat/iapetus5.htm One interesting bit caught my eye. "The dark material is made of organic substances, probably including poisonous cyano compounds such as frozen hydrogen cyanide polymers. Though we know a little about the dark terrain's chemical nature, we do not understand its origin." <div class="Discussion_UserSignature"> "Traveling through hyperspace ain't like dusting crops, boy! Without precise calculations we could fly right through a star, or bounce too close to a supernova and that'd end your trip real quick, wouldn't it?"Han Solo - 1977 - A long time ago in a galaxy far far away.... Click Here And jump over to my site. </div>

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