Iapetus: Black and white? White and black? (APOD 14 Sep 07)

[craterchains]

Sure looks like some one lost their gases to space and it froze to it's surface me thinks.

http://antwrp.gsfc.nasa.gov/apod/ap070914.html

[NoelC]

Rather a snowy dirtball methinks.

-Noel

[13 Rabbit]

[Case]

Why is it that we see better perspective that way? Is it that the light source 'should' come from above?

[brianlj]

So I'm looking at today's APOD and I'm remembering how they can't quite work out how/why Iapetus got it's dark blanket (because it's not quite in the same plane as the (past or present) orbit etc) and I'm thinking to myself...

"Doesn't that look as though Iapetus was a dark moon which has been coated with white material?"

And then I look closer and I see that the dark edges of the missing 'holes' aren't quite crisp. On the SW edges, there's a degree of feathering. Y'don't suppose that could that be blown 'snow'?

Or am I right out in left field?

[BMAONE23]

I guess perspective has much to say about interpretation.

I see it as a snow white moon which had some impact, perhaps from a very large loose-packed (powdery) carbonatious chondrite, on the leading edge causing the blackness with the momentun carying the black material into the trailing edges of the existing white craters at the transition zone.

[thebobgy]

[quote="brianlj"]"Doesn't that look as though Iapetus was a dark moon which has been coated with white material?"

I tend to agree brianlj, the link http://www.planetary.org/news/2007/0906 ... nYang.html tells that their effort to view recent impact craters on the dark side was null but, if it is a dark moon with a white coating then the dark spots would indicate the recent craters, which it does. As to why the edges are not well defined it could be as you suggest; a white powdery substance such as snow. Good call!

thebobgy

[kbowersjr]

The black areas are tar pits.

[JohnD]

I can't see how this black material can be from secondary impacts, bma.
While in the centreof the image, the blackness is to one side of a larger crater, as if drifted, it is dead centre of others to top left of inverted image, and dotted around the interior of the large uppermost crater. Don't look like drifting to me.

How hot is Iapetus? Could its leading side have condensed a white substance from Saturn orbit onto a surface that is near enough to its sublimation point to be evaporated inside craters, more likely to receive heat from the interior, and other scattered points where heat escapes?

John

[brianlj]

I guess perspective has much to say about interpretation.

Indeed. To get round this illusion, it's often advantageous to rotate the image by 180 deg and see what that looks like. Let's have a look...

Okay, to me, that still looks like a dark moon which has an overlay of white material.

Look at the feathering of white bleeding into the dark of the top centre large black patch. There's no process that I know of which can deposit black onto a surface with a clean edge at one side and then tail out to produce a fading of the layer -- and then end with a clean edge! If the black were being deposited on the white at that feathering point, you'd get runnels and channels, just like you do on Mars.

Plus... how come the black deposits have either (a) landed so neatly onto the tops of the white mounds? Or, if you reverse the perspective, how come the black deposits have (b) landed exactly in the bottoms of the craters and not so much as left not so much as a grey smudge anywhere else?

[JohnD]

brian,
Perhaps you would like to consider the thesis in the post immediately before yours?
John

[brianlj]

brian,
Perhaps you would like to consider the thesis in the post immediately before yours?
John

Yes, that's one possibility: a bit like when the first snows of winter fall overnight onto a previously warm landscape and, as the morning sun rises, it warms the snow just sufficiently so that that heat combined with the heat from below produces pockets of revealed land.

Very like what I see in this picture, in fact.

[craterchains]

Is it black on white? or, , , white on black?

[NoelC]

Imagine yourself standing at the edge of one of these light to dark transitions. For example, standing on the "snow" looking at a place where molten black tar has soaked the snow from underneath. Out toward the black plain in front of you it almost appears to shimmer as the sun heats it... You look back and your footprints are filling with the black stuff...

Then in a few seconds you freeze to death, of course.

But it will have been a hell of a sight.

-Noel

[BMAONE23]

i think this latest apod http://antwrp.gsfc.nasa.gov/apod/ap070919.html says a lot about weather this moon is white with black dust or not. Considering the appearance of the impact on the black hills that exposed white surface.

[craterchains]

I think this thread says it all, , , grins , ,

http://asterisk.apod.com/vie ... hp?t=12792

[The Heavens Declare]

Can someone tell me what was meant by the term "organic" in the Sept 14th APOD? Clearly, we're not talking about a substance produced by living organisms. So, what kind of "organic" molecule/substance is being refered to?

[geckzilla]

It just means carbon compounds. If they meant some kind of substance from a living organism it'd probably be the top headline in the news for weeks.

[The Heavens Declare]

Thanks Geckzilla.

[Galactic Groove]

Considering all the dark spots are at the peaks of the white hills/mountains, what about volcanic activity being the cause. Whether it be actual volcanic activity (lava) or just the heat coming from below having some effect to the surface as it heats it up? Those 2 cases would clearly leave a defined border between the 2 colors we're seeing.

Also, anything "dark" in color against a large, white background will appear black so perhaps the camera simply didn't resolve the image correctly?

[geckzilla]

Groove, those are actually craters, not hills. I made another observation about the location of the dark material here:
http://asterisk.apod.com/vie ... 8429#88429

But it got lost and forgotten in the clutter after we started talking about aliens, or something.