Most Fascinating Clue To Liquid Water!, Eberswalde Crater Delta Options

[SigurRosFan]

Fossil Delta in Eberswalde Crater

http://www.msss.com/mars_images/moc/2005/0...alde/index.html

--- The Eberswalde delta provides the first clear, "smoking gun" evidence that some valleys on Mars experienced on going, persistent flow of a liquid with the physical properties of water over an extended period of time, as do rivers on Earth. In addition, because the delta today is lithified -- that is, hardened to form rock -- it provided the first unambiguous evidence that some martian sedimentary rocks were deposited in a liquid (presumably, water) environment.

The presence of meandering channels, a cut-off meander, and crisscrossing channels at different elevations (one above the other), provided the clear geologic evidence for these interpretations. ---

Imho: This lithified delta is the greatest and most fascinating clue to liquid water!

Forget Ares Vallis mouth, drainage channels, recently formed gullies, Gusev ...

[Guest_Richard Trigaux_*]

I have already see these images somewhere, in an image book of Mars.


The strangest here is not that extensive water flow formed a delta, but that this delta was further eroded on a great thinkness. Such an erosion process is common on Mars, where we can see many other example of inverted geology layers, especially in ancient craters. But what is this process? Wind? Dust devils? Yes dust devils would be able to dig so deeply and send all the dust into the higher atmosphere. But after this dust must fall somewhere. And it cannot do otherwise than fo fall evenly onto the whole Mars surface, which is contradictory with the previous process. (Oppy an spirit sites were free of any thick layer of dust). So all this dust must be trapped somewhere in a way or another. Where and how? in the polar caps? In higher latitudes where dust devils cannot form?

[Bob Shaw]

The important point is that these criss-crossing channels show evidence of *persistent* waterflow, not just the catastrophic floods of the sort that gave us the Washington Scablands here on Earth. All sorts of mechanisms give us flowing water on Mars *briefly* (even today) but few allow real river-system development. The just-released close-ups really do nail the whole thing down!

[SigurRosFan]

--- After the sediments were deposited to form the delta, the material was further buried by other materials -- probably sediments -- that are no longer present. The entire package of material, now buried, became cemented and hardened to form rock. Later, erosive processes such as wind stripped away the overlying rock, re-exposing the delta. Now preserved essentially as a fossil, the former floors of channels in the delta became inverted, to form ridges, by erosion.

Channels can be inverted by erosion on both Earth and Mars. Usually this happens when the channel floor, or the material filling the channel, is harder to erode than the surrounding material into which the channel was cut. In some cases, the channels on Earth and Mars have been filled by lava to make them more resistant to erosion. In the case of Eberswalde, there are no lava flows; instead, the channel floors may have been rendered resistant to erosion either by being better-cemented than the surrounding material, or composed of coarser-grained sediment (e.g., sand and gravel as opposed to silt), or both. ---

In the following illustration I tried to summarize the upper abstract. Is it a correct rendering of the content?

My sketch:

[ElkGroveDan]

In the following illustration I tried to summarize the upper abstract. Is it a correct rendering of the content?

Yes except that the shapes of the channels would not be inverted as is the case in your drawing.

[Ames]

"cut-off meander" - would that be an Oxbow lake?

http://en.wikipedia.org/wiki/Oxbow_lake

[Bob Shaw]

"cut-off meander" - would that be an Oxbow lake?

http://en.wikipedia.org/wiki/Oxbow_lake

If it had a standing body of water in it, yes - to my mind Oxbow Lakes are a sub-set of cut-off meanders. Of course, then you get empty Oxbow Lakes...

[Guest_Richard Trigaux_*]

"cut-off meander" - would that be an Oxbow lake?

http://en.wikipedia.org/wiki/Oxbow_lake

Oh, the border was fossilized.

[SigurRosFan]

Another inverted Feature.

Inverted Valley - http://www.msss.com/mars_images/moc/2005/12/15/

[SigurRosFan]

More ...

- http://www.msss.com/mars_images/moc/2006/04/13/ (Inverted Channels)