I Late Water Flow on Mars

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BillTre

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Perhaps this thread would be better located in the Earth forum (where hydrologists might more likely see it), but it is Mars not Earth.

I recently read about a study on riverbeds (size, catchment size, meandering) on Mars that claimed large water flows in some riverbeds "late" in Mars history (post-dense atmosphere).
Here is the original publication in Science magazine (behind a paywall).
This was attributed to some kind of climate that would support lots of rain on particular places (or enough heat to melt snow and keep it liquid) after much of Mars's atmosphere (through which the water molecules to make the intense rain would have to flow) was lost to space.
Perhaps I am not understanding the article properly, but I don't see how such a thin atmosphere and convey enough water through to rain to achieve this.
The article's conclusion:
Unexpectedly, Mars river dimensions provide evidence for intense runoff production persisting late in the wet-to-dry transition, even as deep fluvial erosion became more spatially restricted, with more arid and/or shorter wet periods. The implication that up to 1 km of erosion late in Mars’ wet-to-dry transition was associated with high peak runoff production disfavors explanations for late-stage river-forming climates on Mars that require atmospheric pressure of >1 bar [e.g., (45)]. That is because of the difficulty of physically justifying the removal of a thick atmosphere after 3.4 Ga (2). If atmospheric pressure fell between the Noachian/Hesperian boundary and Late Hesperian/Early Amazonian, then the peak runoff yielded by strongly atmospheric pressure–dependent warming mechanisms should wane as well.
Explaining the high runoff production rates implied by our data makes the difficult problem of making liquid water on ~3 Ga Mars even more difficult (Fig. 4). Therefore, our results globalize and intensify the challenge set to climate modelers by Mars Science Laboratory rover results of explaining late-stage river-forming climates on Mars (14, 48).
An alternative source of liquid water to flow in riverbeds might be localized melting of the extensive permafrost known to exist on Mars.
It is not clear to me (in my lack of hydrological knowledge) if the article can distinguish between highly intermittent very large flows (like the outflows from Glacial Lake Missoula for example) and a more continuous, climate fed, seasonal flow of rivers.
It is also not clear to me if there have been large localized heat sources, at these times in later Mars history, to melt large areas of Mars permafrost (perhaps volcanoes or large meteor impacts).
I would be interested to her from people more knowledgeable about these things.
 
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Interesting.
I'm not entirely clear where you are heading when you say "I don't see how such a thin atmosphere [can]convey enough water through to rain to achieve this. "
As I read the article conclusion they are saying exactly the same thing: "our results globalize and intensify the challenge set to climate modelers by Mars Science Laboratory rover results of explaining late-stage river-forming climates on Mars."
They have presented a data set and an interpretation that conflicts with other "facts" about Mars. Ultimately, this is great news as it demands an explanation!

I shall take a read through Mars: A Warmer Wetter Planet J.S.KArgel ISBN:1-85233-568-8 (which has been sitting unread in my library for too long), top it up with some more recent research articles and post anything relevant I find.
 

BillTre

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I'm not entirely clear where you are heading when you say "I don't see how such a thin atmosphere [can]convey enough water through to rain to achieve this. "
What I mean is that with such a thin atmosphere how can such an atmosphere contain enough water vapor to support the extensive amount of rain to produce large river water flows.
 
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What I mean is that with such a thin atmosphere how can such an atmosphere contain enough water vapor to support the extensive amount of rain to produce large river water flows.
I get that Bill, but that is exactly what the researchers are also saying. There is a contradiction in the evidence or in the interpretation of the evidence.

Bakc to your first post: it should be possible, I think, as a matter of scale, to distinguish between catastropic flow events and seasonal flow variations.
 

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