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Iapetus - Black on white or white on black?
Ice and Gunk
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SFJCody
post Sep 14 2007, 07:40 AM
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Seems to be a lot of dispute on this subject... I think it's ice from the interior, but what does everyone else think?

Edit:

This world seems very complex so the question could perhaps be phrased as 'which of these options is most responsible for the Iapetan dichotomy?'
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Bill Harris
post Sep 16 2007, 10:41 AM
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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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JRehling
post Sep 17 2007, 05:22 AM
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QUOTE (Bill Harris @ Sep 16 2007, 03:41 AM) *
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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Posts in this topic
- SFJCody   Iapetus - Black on white or white on black?   Sep 14 2007, 07:40 AM
- - ngunn   I think the responses you offer are inadequate. Gl...   Sep 14 2007, 08:03 AM
- - ugordan   Where's the option "Black on White - blac...   Sep 14 2007, 08:04 AM
- - akuo   Is this a Michael Jackson song? Oh Iapetus, I wou...   Sep 14 2007, 08:15 AM
- - volcanopele   I would prefer a both option: white on black in so...   Sep 14 2007, 08:54 AM
|- - JRehling   QUOTE (volcanopele @ Sep 14 2007, 01:54 A...   Sep 14 2007, 04:15 PM
- - Juramike   (Objects collide) Object one: "Heeeey, you ...   Sep 14 2007, 03:41 PM
- - nprev   ...of course, in the Family Guy parody of this com...   Sep 14 2007, 04:00 PM
- - Michael Capobianco   I have to choose white on black on white - black e...   Sep 14 2007, 04:33 PM
- - lyford   The only thing that I can say is that after readin...   Sep 14 2007, 05:00 PM
- - MarcF   It was not a good idea to go to vacation far from ...   Sep 15 2007, 04:26 PM
- - tasp   I would pick transparent material everywhere, keye...   Sep 15 2007, 04:59 PM
|- - David   QUOTE (tasp @ Sep 15 2007, 04:59 PM) I wo...   Sep 15 2007, 08:34 PM
|- - ugordan   QUOTE (David @ Sep 15 2007, 09:34 PM) whe...   Sep 15 2007, 09:38 PM
|- - David   QUOTE (ugordan @ Sep 15 2007, 09:38 PM) C...   Sep 16 2007, 03:09 AM
- - tasp   Here is another 'negative' print of Iapetu...   Sep 16 2007, 04:00 AM
- - edstrick   I get an overwhelming impression that the white an...   Sep 16 2007, 05:23 AM
- - Bill Harris   You're right, Ed, this is all very mysterious....   Sep 16 2007, 10:41 AM
|- - JRehling   QUOTE (Bill Harris @ Sep 16 2007, 03:41 A...   Sep 17 2007, 05:22 AM
- - dvandorn   I agree, Bill -- the distribution of dark material...   Sep 16 2007, 02:37 PM
|- - David   QUOTE (dvandorn @ Sep 16 2007, 02:37 PM) ...   Sep 16 2007, 05:32 PM
|- - dvandorn   QUOTE (David @ Sep 16 2007, 12:32 PM) Wha...   Sep 17 2007, 04:48 PM
|- - nprev   QUOTE (dvandorn @ Sep 17 2007, 09:48 AM) ...   Sep 17 2007, 05:56 PM
- - tasp   I was wondering about those streamlined (not quite...   Sep 16 2007, 05:38 PM
|- - volcanopele   QUOTE (tasp @ Sep 16 2007, 10:38 AM) I wa...   Sep 17 2007, 05:18 AM
- - ilbasso   Seeing that old picture of Stevie Wonder made me t...   Sep 16 2007, 05:45 PM
- - tasp   I can't help but think in the initial flush of...   Sep 17 2007, 04:10 AM
|- - David   QUOTE (tasp @ Sep 17 2007, 04:10 AM) I ca...   Sep 17 2007, 06:10 AM
- - tasp   Hyperion.   Sep 17 2007, 01:53 PM
|- - David   QUOTE (tasp @ Sep 17 2007, 01:53 PM) Hype...   Sep 17 2007, 02:32 PM
|- - ngunn   QUOTE (David @ Sep 17 2007, 03:32 PM) no ...   Sep 17 2007, 04:00 PM
- - nprev   Like oDoug, I too noticed the apparent "dunin...   Sep 17 2007, 04:27 PM
|- - dvandorn   QUOTE (nprev @ Sep 17 2007, 11:27 AM) Lik...   Sep 17 2007, 04:59 PM
- - tasp   Here is some more 'ponding' to contemplate...   Sep 17 2007, 05:37 PM
- - tasp   And the comparison. {I suppose it would be nice...   Sep 17 2007, 05:39 PM
- - tasp   Crikey, there is something hinky going on tweenst ...   Sep 17 2007, 05:43 PM
- - tasp   We note earth's moon to have an orbit about ea...   Sep 17 2007, 06:08 PM
- - nprev   True, but Earth's Moon is thought to be an art...   Sep 17 2007, 06:12 PM
- - alan   There was a paper a couple of years ago linking Ti...   Sep 17 2007, 07:42 PM
- - edstrick   What can I say.. just look at this d__n stuff... A...   Sep 18 2007, 08:24 AM
|- - TheChemist   QUOTE (edstrick @ Sep 18 2007, 11:24 AM) ...   Sep 20 2007, 01:34 PM
|- - ugordan   QUOTE (TheChemist @ Sep 20 2007, 03:34 PM...   Sep 20 2007, 01:45 PM
- - dvandorn   OK -- I understand your conclusion, here. But I s...   Sep 18 2007, 01:46 PM
|- - The Messenger   QUOTE (dvandorn @ Sep 18 2007, 07:46 AM) ...   Sep 19 2007, 05:20 AM
|- - ugordan   QUOTE (dvandorn @ Sep 18 2007, 03:46 PM) ...   Sep 20 2007, 02:04 PM
- - TheChemist   Ugordan, I think that I see wide openings (holes) ...   Sep 20 2007, 02:00 PM
- - Bill Harris   RE: edstrick and the chemist, posts 40 & 42-- ...   Sep 20 2007, 04:26 PM
|- - David   QUOTE (Bill Harris @ Sep 20 2007, 04:26 P...   Sep 20 2007, 04:51 PM
|- - ustrax   Tilmann Denk's "vote" at spacEurope:...   Sep 24 2007, 04:35 PM
- - dvandorn   After seeing some of the contrast-enhanced images ...   Sep 24 2007, 04:59 PM
|- - JRehling   QUOTE (dvandorn @ Sep 24 2007, 09:59 AM) ...   Sep 24 2007, 08:03 PM
|- - David   QUOTE (JRehling @ Sep 24 2007, 08:03 PM) ...   Sep 24 2007, 09:24 PM
- - Bill Harris   My first, and continuing, impression of the dicho...   Sep 24 2007, 10:04 PM
- - David   QUOTE (Bill Harris @ Sep 24 2007, 10:04 P...   Sep 25 2007, 02:48 AM


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