Most Fascinating Clue To Liquid Water!, Eberswalde Crater Delta |
Most Fascinating Clue To Liquid Water!, Eberswalde Crater Delta |
Sep 21 2005, 07:20 PM
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Member Group: Members Posts: 531 Joined: 24-August 05 Member No.: 471 |
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 ... -------------------- - blue_scape / Nico -
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Sep 23 2005, 11:05 PM
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Member Group: Members Posts: 531 Joined: 24-August 05 Member No.: 471 |
--- 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: -------------------- - blue_scape / Nico -
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