Subglacial water on Mars |
Subglacial water on Mars |
Aug 3 2020, 07:01 PM
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#1
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Senior Member Group: Members Posts: 3516 Joined: 4-November 05 From: North Wales Member No.: 542 |
This topic has been discussed here over a spread of time and in various threads but not recently, I think. This article might be a good way to kick off some more discussion from a present day perspective if anyone's interested:
https://www.sciencedaily.com/releases/2020/...00803120154.htm |
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Aug 7 2020, 01:48 AM
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#2
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Senior Member Group: Members Posts: 1053 Joined: 17-February 09 Member No.: 4605 |
That is another interesting hypothesis on the formation of drainage networks on Mars but as with all such it should be considered hypothetical rather than definitive. In fact the abstract in Nature states that the study modelling revealed that valley formation involved fluvial, groundwater sapping, glacial and sub glacial erosion with fluvial and subglacial the predominant mechanisms. This is a different picture to that cast by the Science Daily article.
I would make a few observations. In the main the distribution of valley networks does not match the distribution of evidence of glacial activity. The valley networks are distributed in the equatorial and mid latitude range. In the Southern highlands the glacial remnants are generally south of the valley networks and above the equator are to the further north, primarily along the dichotomy (Deuteronius, Prontonilus and Nilosyrtis Mensae). Interestingly, to the South of the Tharsis rise the valley networks are closer to the pole with glacial remnants to their North, closer to the equator, supporting the idea that the development of the Tharsis rise caused tectonic dislocation. Another point is that the dating of the drainage networks indicates that they were formed over a span of some 200 million years at the boundary between the Noachian and Hesperian periods, pretty much when Curiosity's ground truth has confirmed a warmer wet environment. As with Nick Hoffman's white Mars hypothesis and dburt's impact gardening hypothesis, concepts that look compelling from analysis of orbital data are revealed erroneous with analysis on the ground. |
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Aug 8 2020, 04:06 AM
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#3
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Member Group: Members Posts: 384 Joined: 4-January 07 Member No.: 1555 |
...As with Nick Hoffman's white Mars hypothesis and dburt's impact gardening hypothesis, concepts that look compelling from analysis of orbital data are revealed erroneous with analysis on the ground... I'd be curious about where you came up with the unusual term "impact gardening hypothesis," insmuch as I've never heard it used before. Nick Hoffman (on his web site about 20 years ago), based on available orbital data, and my coworkers and I about 15 years ago, based entirely on later rover "analysis on the ground," to use your term, independently came up with the hypothesis that many of the layered rocks seen by the orbiters and later by the three rovers on Mars could have been deposited by impactoclastic density currents (could be IDC deposits, in other words), analogous to the well-understood PDC deposits deposited by pyroclastic density currents on Earth (and also "base surge" deposits deposited around nuclear blast sites on Earth). In other words, they could be distal layered blast beds, resulting from large blasts on a planet with an atmosphere and abundant subsurface volatiles (unlike the Moon). Therefore, to what compelling "analyses on the ground" are you specifically referring? BTW, I gave a talk on this subject earlier today at a scientific meeting on impact cratering where "cold weather" (mainly on Mars) vs. "warm weather" (on Earth) glaciation was also discussed. I don't recall if you ever participated, but the subject of impact sedimentation was excessively discussed on this web site about 15 years ago, when my coworkers and I first proposed it, and it was never refuted, despite your possible recollections. I see no need to repeat this discussion now, despite the considerable additional supporting data available, and I'm sure the site moderators would agree. Best wishes. dburt |
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