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Geomorphology of Gale Crater, Rock on!
Julius
post Dec 29 2016, 07:52 AM
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Simply brilliant stuff!
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Greg Malone
post Dec 29 2016, 06:34 PM
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To add to the mix of ideas about dessicated mudcracks is the notion of syneresis, believed to have possibly been active at some sites investigated in Gale -- where differential salinity in interstitial water causes lower salinity water (I believe) to migrate out of the muds being replaced by denser higher salinity water, creating cracks that are somewhat similar to dessication cracks... all the while the entire environment being saturated with subsurface water... i.e. not a 'drying out' or dessication.

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Greg Malone
post Dec 29 2016, 06:42 PM
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QUOTE (Gladstoner @ Dec 21 2016, 11:38 PM) *
Stony-iron meteorite?


I've since noticed a couple of other features that, to the eye, appear possibly similar to the mentioned 'meteorite', in the same general location. Clearly not enough info to really know what we're seeing here, but still fun to muse on.


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HSchirmer
post Dec 29 2016, 10:53 PM
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QUOTE
We have to climb around another hundred metres of Murray formation mudstone
and sixty metres or more above that to the hematite ridge.


Good point. There are still hundreds of meters of strata to climb.
My point was that it takes a long time, (eh 3-30 million years?) and a huge amount of water
to transport the sediment that is eventually compressed to become those 100 meters of mudtone and 60 meters of hematite.

So, we should see orbital and processional effects (roughly 100k and 1.25 million years) in the lake levels,
as the lake in Gale goes from overflowing to a "dead sea", and goes from a salt lake to playa.

Yes, I guessed about 3-30 million years for 160 km of rock strata. So, gale crater is sedimentary basin.
The gale basin (90-100 miles) is close to the size of the well studied Newark basin (90-100 miles) on Earth.
We can calculate that the Newark rift basins filled in with about one meter of rock per 20k years under
Triassic Earth conditions (dry and hot, not too far from Mar's dry but cool..)
So, rough estimate, the optimal wet Martian climate at gale would be, at best, comparable to Earth's dry Triassic climate and take 3 million to fill 160 meters, but leave a 10x range, erosion during a wet period on Mars would still take ten times longer than erosion during a dry age on Earth, which gives 30 My.

What we see on Earth is that celestial mechanics creates 20ky patterns and 404ky patterns, and other effects create patterns within the patterns of climate that create wet / dry swings.
Same for Mars, but it seems that Mars has 100 thousand year and 1.25 million year patterns

QUOTE
Nicolas Steno\'s principle of lateral continuity holds that this strata would have originally covered Curiosity\'s current position,
requiring significant water influence over a long period of time.


The lake in Gale crater may have been there for 10 thousand years, or 10 million years.
On Mars, is that a long time, or is that a short time?

Mars seems to have a 1.25 Million year climate cycle, built out of smaller ~100k year cycles.
http://www2.physics.ox.ac.uk/sites/default...3_pdf_93344.pdf

You'd expect wet to dry climate to be a direct progression, like a piano scale exercise. Down the scale.
That is not what happens.
Climate happens in the moment; it is patterns within patterns, within patterns, within patterns-
Mars rotates each day, Mars revolves each year, Mars' poles shift each age,
and Mars' orbit bends to the will of the other planets sailing and circumnavigate the celestial ocean.
Mars' climate is not playing scales, it is playing Bach, patterns within patterns within patterns.

Goethe once said "Architecture is solidified music”
I think it's safe to say that geology is solidified climate...

Consider the diagram below, each section is an octave on a piano....
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serpens
post Dec 31 2016, 02:06 AM
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Basically a closed system I expect. One needs to pull back a bit to see the big picture. Aeolis Serpens to the NE of Gale is an inverted river complex over 500 kilometres long that spans a period somewhere between 1 to 20 million years with evidence of varying water and sediment supply and occasional desiccation. It would have terminated at the northern ocean and this would imply a shoreline to the north of Gale. Groundwater at Gale could reasonable be expected to reflect the level of the Northern ocean, creating a lake, while impact tsunami could also have overflowed the northern crater wall.
The problem is that empirical data from the rovers and orbiters prove an early warm wet Mars with a complex hydrological cycle spanning millions of years. No model of plausible environments can explain this. But Curiosity has a long way to climb and hopefully more clues will be found to help complete the jigsaw.
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dburt
post Dec 31 2016, 04:24 AM
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QUOTE (serpens @ Dec 30 2016, 07:06 PM) *
... empirical data from the rovers and orbiters prove an early warm wet Mars with a complex hydrological cycle spanning millions of years ...

Umm. The conflict with plausible environments may be more apparent than real. I remind you here that it is important not to confuse actual data with interpretations based on that data. Furthermore, much of the martian "data" (e.g., the detection of clay minerals) is itself based on interpretations of analytical or spectroscopic data. And the mere detection of clays gives no indication of how or when the clay minerals formed. Another example would be the imaging of channels or fans interpreted to have been formed exclusively by flowing water. Such interpretations, in some cases, prove nothing other than the bias of the observer. In science, multiple working hypotheses should dominate, although in practice they rarely do. A new year's resolution for Mars, perhaps.
DBurt
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HSchirmer
post Dec 31 2016, 02:33 PM
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QUOTE (serpens @ Dec 31 2016, 02:06 AM) *
Basically a closed system I expect.
...
Groundwater at Gale could reasonable be expected to reflect the level of the Northern ocean, creating a lake, while impact tsunami could also have overflowed the northern crater wall.
...
The problem is that empirical data from the rovers and orbiters prove an early warm wet Mars with a complex hydrological cycle spanning millions of years.


Good summary,
I've cleaned up my prior post a bit, but basically-
Laying down 90 miles of mudstone outcrop takes millions of years' worth of water.
Celestial mechanics suggests that Mars dries up every 1.25 million years,
when there is no water, erosion just halts and waits for a wet epoch to return.

Hmm, interesting point about tsunami, I hadn't thought of the possibility before...
The central mound in gale crater might be tidal wave debris.


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HSchirmer
post Dec 31 2016, 02:50 PM
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QUOTE (fredk @ Dec 31 2016, 03:00 AM) *
Wind action while we sat from 1526-52:
[attachment=40595:1526_52_flb_crop1.gif]
I like the advancing mini ripples.


Neat, was that a drill dump?

Thinking of drills, we've seen that rocks react strangely to vibration...

And there's actually a paper about erosion by vibration....

Seismicity and the strange rubbing boulders of the Atacama Desert, northern Chile
http://geology.gsapubs.org/content/40/9/851.abstract
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HSchirmer
post Jan 2 2017, 01:49 PM
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QUOTE (serpens @ Dec 31 2016, 03:06 AM) *
Basically a closed system I expect. One needs to pull back a bit to see the big picture. Aeolis Serpens to the NE of Gale is an inverted river complex over 500 kilometres long that spans a period somewhere between 1 to 20 million years with evidence of varying water and sediment supply and occasional desiccation. It would have terminated at the northern ocean and this would imply a shoreline to the north of Gale. Groundwater at Gale could reasonable be expected to reflect the level of the Northern ocean, creating a lake, while impact tsunami could also have overflowed the northern crater wall.
The problem is that empirical data from the rovers and orbiters prove an early warm wet Mars with a complex hydrological cycle spanning millions of years. No model of plausible environments can explain this. But Curiosity has a long way to climb and hopefully more clues will be found to help complete the jigsaw.


Since the discussion has been clipped out -



A new paper about the morphology of gale, compared to other high peaked craters....

GALE CRATER MORPHOLOGY COMPARED TO OTHER HIGH CENTAL PEAK CRATERS ON
MARS.
http://www.hou.usra.edu/meetings/lpsc2016/pdf/2822.pdf


Should also note that the central mound at Gale appears to be within the elevation (global -4087m to -3191) which has been suggested to be within the reach of norther ocean tidal waves.
http://www.nature.com/articles/srep25106

Interesting to think of a martian sea, not stirred by tides, but stirred by impact events.
http://www.lpl.arizona.edu/~shane/publicat...icarus_2013.pdf

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HSchirmer
post Jan 3 2017, 02:40 PM
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QUOTE (Greg Malone @ Dec 29 2016, 06:34 PM) *
To add to the mix of ideas about dessicated mudcracks
... i.e. not a 'drying out' or dessication.


Good call on the syneresis folds and cracks.
Just noticed, we have what appear to be iron concretions in Mars Gale crater images...
Looks fairly similar to copper concretions in Earth Newark basin...
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Julius
post Jan 12 2017, 09:41 PM
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Sulphates on Earth require oxygen to form either by volcanic eruptions or the action of sulphate reducing bacteria. Deposits of iron pyrite have been attributed to rising levels of atmospheric oxygen. Varying sulphur isotopes have been regarded as biosignitures.

What do findings of sulphates, gypsum, manganese oxide and haematite on Mars tell us about climatic condition's with regard to atmospheric and water oxygen levels? Is Curiosity rover equipped to measure isotope ratios?
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serpens
post Jan 13 2017, 11:14 PM
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SAM has the capability to conduct isotopic analysis of the lighter elements. You have a few misconceptions in that sulphate reducing bacteria uses sulphates as an energy source, producing sulphides. Iron pyrite forms in a reducing, not a oxidising environment and on Mars probably formed through melt separation during magma crystallisation.
With respect to your question on what rover and orbital findings indicate about previous environments, these have been the subject of a huge number of erudite papers and articles by acknowledged experts in their fields and address the dramatically different environments encountered by the landers and rovers. A good search engine and some careful culling to separate the grain from the chaff will provide you with your answers and attempting to paraphrase these would take up immense space and justifiably draw the wrath of the overworked moderators.
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dburt
post Jan 14 2017, 12:02 AM
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Julius, I agree with what Serpens said, but to try to save you a bit of trouble, let me summarize (with some trepidation) what you are likely to find in an exhaustive literature search. In short, sulfates don't tell you a great deal about environments. Yes, they are oxygen-bearing, but so are virtually all the other minerals that make up planetary crusts, such as silicates and carbonates. Sulfates require a tad more oxygen than most, to avoid forming sulfides instead, but not much more. There are igneous and hydrothermal sulfates as well as sulfides, so sulfates are not unique to a particular environment (at least on Earth). Some elements (e.g., calcium) form sulfates more easily than others (e.g., iron), but you didn't ask about that.

Manganese oxides and hematite on the surface of Mars probably don't tell you a great deal either, because the surface of Mars is believed to be locally far more oxidizing than the inside, owing to the influence of solar ultraviolet light, not from an oxygen-rich atmosphere (as on Earth). It doesn't take a great deal of oxygen to form either type of oxide. Finding manganese or iron oxides inside a rock can tell you that it or its ingredients were formerly exposed to sunlight at the paleo-surface, and presumably to some moisture (to assist their growth), but nothing more.

I won't address sulfur isotopes, because there is no data and they are not my area of expertise.
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Julius
post Jun 7 2017, 02:41 AM
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The consensus up to now seems to have been that sulphate minerals tend to rest on top of more ancient clay minerals and has been interpreted as reflecting a climatic change on Mars from neutral water environment to a time when the planets water turned acidic indicating a drier environment. The finding of jarosite at Pahrump hills and lack of clay minerals sandwiched if you like between abundant clay containing Yellowknife bay rocks and abundant clays found in Murray buttes would seem to contradict this . Any thoughts about this?
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Gerald
post Jun 7 2017, 06:38 AM
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My first thought about the silica enrichment has been a process connected to the hematite enrichment at Vera Rubin ridge, kind of leaching and precipitation cycle. But there are lots of gaps, of course, and those two layers could have formed independently. I don't see an immediate connection to the overlying sulfate layer thus far.
One may also conclude, that we are going to learn more about the details of Martian history, but our understanding of the long-term geological structure doesn't need to be challenged.
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