Iapetus - Black on white or white on black? |
Iapetus - Black on white or white on black? |
Sep 16 2007, 04:00 AM
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#16
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Member Group: Members Posts: 903 Joined: 30-January 05 Member No.: 162 |
Here is another 'negative' print of Iapetus.
I am still thinking we are seeing a material not unlike silver nitrate applied to the Iapetan surface and 'developed' by exposure to sunlight. The 'silver nitrate' analog is 'applied' as a gaseous efflux to Iapetus as it moves around the far side of Saturn, and dissipates to the void in ~40 days, with some 'ponding' in very low spots persisting longer. The efflux may not persist as a gas in the Iapetan environment, it may absorb on to the surface materials, but it still manages to dissipate in less than 1 Iapetan day. The material is sensitive to local heating effects, and local here can apparently be a matter of meters. Note in the negative print the shadow like aspect of the dark areas. The difficulty we are having in interpreting these images (regarding the black on white or white on black discussion) is perhaps due to the 'negative' visual characteristic of the actual appearance of the Cassini Regio 'crud'. Negative prints help visualize the effects of insolation on this 'silver nitrate' analog. |
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Sep 16 2007, 05:23 AM
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#17
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Senior Member Group: Members Posts: 1870 Joined: 20-February 05 Member No.: 174 |
I get an overwhelming impression that the white and black materials are both granular (at the optically visible surface -- I can't tell about 10 cm down), mobile, and SELF-SEGREGATE, sorting each other out.
Almost nowhere do I see what look like diffuse dustings of black onto white, and the dustings of white on black, like small crater ejecta in black terrains, clearly are rapidly destroyed, presumably by sublimation of the white ice. Near the equator in light terrain, dark material lies flat in depressions, down to surface pits and irregularities of unresolved sizes. Off the equator a ways, the material forms round splotches in smallish craters that are lopsided, sitting on the sun-facing floor of the crater, but not up on the adjacent wall. In bigger, flat-floored craters, it's on the floor against the sun-facing wall. Well away from the equator, I get the overwhelming impression that the splotches have actively climbed the wall! Landslides of ice may disturb the splotches, but I get the impression that the mass of granular dark material has actively crept into a maximally sun-facing position, even against gravity. HOW this might happen, I can only vaguely arm-wave. A few beers too many might help! Thermal expansion-and-contraction of the dark granules relative to white ones might be a method of driving a creep process, together with thermal sublimation of ice at the contact with a coherent splotch of dark. Numerical theoy and physical modelling of processes might give a clue. |
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Sep 16 2007, 10:41 AM
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#18
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Senior Member Group: Members Posts: 2998 Joined: 30-October 04 Member No.: 105 |
You're right, Ed, this is all very mysterious. The answer may be billions of 5cm-tall Monoliths, or something odder.
Seriously: one thing I've noticed from the closest images. We've seen a few small, recent craters with white ejecta rays in the dark regions. But I haven't seen the opposite: dark, fresh craters on the light-toned regions. This leads me to suspect that the black is a thin dusting over the white, whereas the white is a thicker layer. I'm looking closely at the white-black-white contacts in the hi-res images for puzzle-pieces... --Bill -------------------- |
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Sep 16 2007, 02:37 PM
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#19
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Senior Member Group: Members Posts: 3419 Joined: 9-February 04 From: Minneapolis, MN, USA Member No.: 15 |
I agree, Bill -- the distribution of dark materials just screams to me that it overlies the brighter, cleaner ice surfaces.
I also still believe I can see evidence of dark material piling up in craters, filling and/or deforming the "downwind" sides of some craters, and exhibiting some dune-like striations. I've been really busy and haven't had enough time to annotate images to point out what I think I'm seeing -- but I am certain that I'm seeing it. To me, it all adds up to dark material covering light material, thickly in some places and more thinly in others. -the other Doug -------------------- “The trouble ain't that there is too many fools, but that the lightning ain't distributed right.” -Mark Twain
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Sep 16 2007, 05:32 PM
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#20
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Member Group: Members Posts: 809 Joined: 11-March 04 Member No.: 56 |
filling and/or deforming the "downwind" sides of some craters, and exhibiting some dune-like striations. What do you literally mean by this? Obviously, there is no wind on Iapetus (hence your "quotes") and there can likewise be no dunes. So what process do you think is in fact occurring? |
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Sep 16 2007, 05:38 PM
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#21
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Member Group: Members Posts: 903 Joined: 30-January 05 Member No.: 162 |
I was wondering about those streamlined (not quite actually) lumps in some of those pictures.
Rather than mention them with a question as to what everyone else thought they were, I was hoping for inspiration to strike and then I would post the question and the answer. {I'm not at that juncture yet . . . . } |
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Sep 16 2007, 05:45 PM
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#22
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Member Group: Members Posts: 753 Joined: 23-October 04 From: Greensboro, NC USA Member No.: 103 |
Seeing that old picture of Stevie Wonder made me think that you should add the "Michael Jackson" option to the vote - "Formerly black, now white, androgynous"
-------------------- Jonathan Ward
Manning the LCC at http://www.apollolaunchcontrol.com |
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Sep 17 2007, 04:10 AM
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#23
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Member Group: Members Posts: 903 Joined: 30-January 05 Member No.: 162 |
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Sep 17 2007, 05:18 AM
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#24
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Senior Member Group: Moderator Posts: 3233 Joined: 11-February 04 From: Tucson, AZ Member No.: 23 |
I was wondering about those streamlined (not quite actually) lumps in some of those pictures. Rather than mention them with a question as to what everyone else thought they were, I was hoping for inspiration to strike and then I would post the question and the answer. You noticed those too Why can't they be streamlined? Keep in mind, that stream-lined forms indicate the presence of fluid flowing over a surface. The fluid could be a liquid-filled stream, an atmosphere, or dust "flowing" out from a nearby impact. -------------------- &@^^!% Jim! I'm a geologist, not a physicist!
The Gish Bar Times - A Blog all about Jupiter's Moon Io |
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Sep 17 2007, 05:22 AM
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#25
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Senior Member Group: Members Posts: 2530 Joined: 20-April 05 Member No.: 321 |
Seriously: one thing I've noticed from the closest images. We've seen a few small, recent craters with white ejecta rays in the dark regions. But I haven't seen the opposite: dark, fresh craters on the light-toned regions. This leads me to suspect that the black is a thin dusting over the white, whereas the white is a thicker layer. I think this is absolutely correct. But the truth may be a little more complex. Most icy moons have a surface somewhat darker than ice. Impacts tend to surface whiter ice underneath. But the surface isn't dark, just "dingy". I suppose that Iapetus's native regolith was like that -- similar to what we see on Rhea. The places where dark has spread, the top surface layer has lost its ice, leaving only the dark stuff behind. This could be, and is almost bound to be, quite thin. If the ice that sublimated away from dark stuff has settled onto the original dingy surface in non-black areas, then we have at least three layers: fresh ice deep in the crust, a dingy regolith, and a fresh white coating of frost. So an impact in the white areas would surface a tiny bit of dingy material, but far more white ice. |
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Sep 17 2007, 06:10 AM
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#26
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Member Group: Members Posts: 809 Joined: 11-March 04 Member No.: 56 |
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Sep 17 2007, 01:53 PM
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#27
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Member Group: Members Posts: 903 Joined: 30-January 05 Member No.: 162 |
Hyperion.
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Sep 17 2007, 02:32 PM
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#28
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Member Group: Members Posts: 809 Joined: 11-March 04 Member No.: 56 |
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Sep 17 2007, 04:00 PM
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#29
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Senior Member Group: Members Posts: 3516 Joined: 4-November 05 From: North Wales Member No.: 542 |
no sharp boundaries between light and dark, for one thing. I shouldn't be surprised if they turned out to be quite different phenomena. I agree, but it is possible that Hyperion shows some sublimation but little if any deposition due to it's lower gravity. Maybe it requires both competing processes to produce the sharp boundaries. |
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Sep 17 2007, 04:27 PM
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#30
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Merciless Robot Group: Admin Posts: 8783 Joined: 8-December 05 From: Los Angeles Member No.: 602 |
Like oDoug, I too noticed the apparent "duning" of dark material in some places; unlike him, didn't have the guts to mention it!
If this impression is true, then what the hell?! All I can think of is long-term outgassing that almost has to be recent & very local to the "dunes". Really want to see what the magnetometer read during this flyby; if anything's being emitted at all, that's the only shot we seemingly have of detecting it...(and, no, if any of this is really happening I have no feasible mechanism(s) to explain it...) -------------------- A few will take this knowledge and use this power of a dream realized as a force for change, an impetus for further discovery to make less ancient dreams real.
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