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List of evidence for water on Mars
serpens
post Aug 27 2016, 03:14 AM
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Well Spirit at Tyrone demonstrated that a thin layer of regolith can provide for a relative humidity gradient protecting hydrated salts. If the regolith is breached then the atmosphere acts as a desiccant. This could explain the appearance and then disappearance of limited amounts of hydrated salts in RSL and would not contradict this latest measurement. Or is could be something else. I suspect it will be a long time before there is consensus on RSL.
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Julius
post Aug 29 2016, 08:12 PM
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A study published discussing inverted river channels in Arabia terra as a sign of a warm and wet climate on early Mars talks about ancient river channels flowing from topographic highs to lower regions from south to the lower northern regions. My question is where would meridiani planum fit along this topographic gradient? The rocks stu died by opportunity rover were mainly sulphate rocks suggestive of acidic water alteration . The inverted channels discussed seem to originate on early mars where water would be expected to form different rock types from those observed by opportunity! Maybe I am getting the ages wrong. Correct me if I am wrong.
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serpens
post May 9 2019, 12:48 AM
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The linked Planetary Society blog article provides an interesting read on the faint young sun paradox with respect to long lived surface water on early Mars and puts to bed some of the hypothetical explanations. However the article did miss the hypothesis that the solar system transiting through interstellar dust clouds could have the effect of significantly increasing the sun's output through the capture of molecular hydrogen. That hypothesis has always made a lot of sense to me.

http://www.planetary.org/blogs/guest-blogs...le-paradox.html
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HSchirmer
post Jun 19 2019, 05:05 PM
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QUOTE (serpens @ May 9 2019, 01:48 AM) *
The linked Planetary Society blog article provides an interesting read on the faint young sun paradox with respect to long lived surface water on early Mars and puts to bed some of the hypothetical explanations. However the article did miss the hypothesis that the solar system transiting through interstellar dust clouds could have the effect of significantly increasing the sun's output through the capture of molecular hydrogen. That hypothesis has always made a lot of sense to me.

http://www.planetary.org/blogs/guest-blogs...le-paradox.html


I saw two recent papers/references that seem relevant, or at least interesting.

FIRST, was a paper on the 11/22 year solar cycle and Jupiter (yes, related to the barycenter theory) which looked at
the 11.07 year cycle of solar atmospheric tides that results from Venus-Earth-Jupiter orbital resonances.



So, let's consider that Theory #1 the "solar cycle / planetary barycenter theory" might be correct
well,
let's consider that Theory #2 "Nice-Model" might be correct as well.

In that case, the early Sun had 4 gas giants between ~5 AU and ~17 AU.
Resonances would have driven massive solar dynamo effects.

Basically, if you have 4 gas giants on circular orbits within ~17 AU, you have tides stirring the Sun and stoking the fire.

SECOND is a combination of idea, the mention of lunar GRAIL data that the lunar surface is roughly 15% void space for the first few kilometers, and a review that the breccia and impact melt under Gale crater could be 17 km deep (for comparision, the Marianas Trench on earth is ~11 km deep) with an initial void space of 3,600 cubic kilometers.
This suggests that there is plenty of "space" for liquid water to exist in the Martian subsurface.
That implies that the real trick about water on the surface of Mars is keeping it from draining back down into the regolith.

Perhaps we only see Martian rivers when they run across compacted sediments or permafrost, otherwise, the water quickly soaks into the sand and gravel.

Flip the thinking to view rivers on the surface of Mars more like the meltwater channels on the top of a glacier, as soon as they encounter a lens of clean sand or a crack, they are gone.

https://phys.org/news/2018-01-glacial-mouli...ered-rapid.html

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marsbug
post Feb 21 2020, 05:56 PM
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I don't know if this has been mentioned before, but the story is on several news outlets, so it seems appropriate to post the original paper here: Crocus melting on Mars:
https://iopscience.iop.org/article/10.3847/1538-4357/ab612f


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serpens
post Feb 24 2020, 06:35 AM
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Here is the complete abstract from the LPSC 2020 Marsbug.

https://www.hou.usra.edu/meetings/lpsc2020/pdf/1792.pdf

I believe the last sentence in the abstract is germane. There simply isn't sufficient precipitable water vapor in the atmospheric column to create meaningful brine.
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HSchirmer
post Feb 24 2020, 02:17 PM
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QUOTE (marsbug @ Feb 21 2020, 05:56 PM) *
I don't know if this has been mentioned before, but the story is on several news outlets, so it seems appropriate to post the original paper here: Crocus melting on Mars:
https://iopscience.iop.org/article/10.3847/1538-4357/ab612f


I also thought this was quite interesting- but for a slightly different reason-

If a boulder can generate the necessary shadows from positive curved geometry,
wouldn't the negative geometry of a crater have a similar effect?

Also, a crater would seem to have an advantage of access to absorbed/adsorbed subsurface moisture.
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atomoid
post Feb 25 2020, 09:49 PM
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You're right we don't hear much on this anymore. I recall that being part of initial speculation when the first gullies were discovered by MGS some 20 years ago. i got a sense that the cold-trap model didnt hold up but nevertheless i still like to armchair-speculate such processes may remain relevant at certain points in Mars' climate intervals to accelerate erosion in applicable places and contribute to such formations.
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marsbug
post Feb 27 2020, 02:11 PM
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Just generally, from my physics background, layman's understanding of Martian weather and geology, and following forums and threads like this one, it has always seemed like there's no insurmountable barrier to small amount of transient liquid water forming on present day Mars, when the right conditions come together. But really solid evidence of it seems to be elusive, so perhaps, like me, people are waiting for something really direct and unarguable.


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