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Geomorphology of Gale Crater, Rock on!
serpens
post Jun 7 2017, 08:40 AM
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Julius, I think that Curiosity will need to get up close and personal with the clay bearing trough before they can assess how and when it was formed. In their brilliant Geological mapping and characterisation of Gale as a potential landing site, Anderson and Bell depicted the clay as a thin bedding plane with a segment exposed by the trough and that characterisation has carried forward. As I understand it the clay signature seems to indicate smectites. The overlying hydrated sulphates would likely have formed in an acidic environment and smectites are pretty good at consuming acidity with the end product being amorphous silica. So if the smectites had been exposed to the acidic waters during sulphate deposition, wouldn't hydrated silica and kaolinite have been detected, unless the clay had been covered by an impervious layer? An alternative is that the clay was formed following deposition of the sulphates as a function of erosion of the sulphate and formation of the fan. Could this clay be a localised deposit formed from pooled water that had leached Mg from the higher sulphate deposits? Both the hematite ridge and the clay trough are going to tell interesting stories.
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serpens
post Nov 9 2018, 12:14 AM
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QUOTE (HSchirmer @ Nov 8 2018, 05:06 PM
...Given the elevation of Gale crater, and recent northern-ocean papers, is there any way to differentiate whether Gale was lacrustine or perhaps an interior estuary?

All evidence to date implies lacustrine. Dichotomy elevation differences aside, the northern crater rim is heavily degraded compared to the northern rim and the area directly north of Gale is somewhat atypical compared to adjoining topography. it is possible that it was overtopped by lake water or by catastrophic events such as impact driven tsunami although there is no evidence of such. The rim is above the elevation assessed for proposed shorelines for the northern ocean(s).

Hmm, reminds me of the Newark Basin paradox- a 2-mile deep deposit of shallow water mudstone interbedded with fanglomerates and sandstones. (It is a paradox because with a 2-mile deep basin [~about the average depth of the Atlantic or Pacific] you'd expect to start with deep water sediments which get shallower as you fill in the basin over time. Instead, the Newark basin was shallow during the entire time that 2 miles of sediment were deposited.)

I thought the Newark basin was the result of a slow graben process? As the land sank the rate was matched by shallow lake deposition.
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HSchirmer
post Nov 9 2018, 12:57 AM
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QUOTE (serpens @ Nov 9 2018, 01:14 AM) *
The rim is above the elevation assessed for proposed shorelines for the northern ocean(s).


Curious about that, a recent paper suggested that early shorelines make sense, IF you remove the Tharsis bulge, and the corresponding antipodal bulge near Gale.



That puts the Arabia shorline (purple line) right around the elevation of Gale


QUOTE (serpens @ Nov 9 2018, 01:14 AM) *
I thought the Newark basin was the result of a slow graben process? As the land sank the rate was matched by shallow lake deposition.


Yep. Newark is a hanging wall/graben.
Which is interesting with the possible faulting/slumping of Gale's north crater wall.
But the twist for Newark - clays interbedded with fanglomerates and sand, might illuminate what happened at Gale.
If you have sediment from 2 sources, young rivers cutting into the hanging wall side, providing mineral rich fanglomerates; while flat rivers from the Martian interior providing weathered clay sediments.

Earlier papers discuss the hypothesis of an Elysium lake overtopping the north rim,
https://vdocuments.mx/hydrogeologic-evoluti...biological.html
but either way, the notch in the north crater rim would let north draining rivers flow into Elysium lake/Arabia sea during wet periods,
but would/should also result in shallow areas to the north draining fine clays back INTO Gale-

I'm thinking of the paradox that ~250 million years ago, US east coast rivers- Potomac, Susquehenna, Schuylkill and Delaware, initially drained NORTHWEST.
When the Atlantic ocean opened up, the rivers reversed course and began cutting back from the new ocean, causing the same valleys to drain SOUTHEAST.

I wonder if something similar applies to Peace Vallis, where the notch in the northern rim allowed drainage from the southern highlands into Elysium lake or Arabia sea,
but when those streams dried up, the notch allowed the lake and sea to drain back into Gale.

http://spaceref.com/mars/curiousmars-box-s...stinations.html
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serpens
post Nov 11 2018, 05:33 AM
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I suspect that this would represent the maximum fill with your suggested high ocean level, with the northern rim less degraded and above water level. Occasional tsunami drain back cutting the few possible channel like features but who knows. Certainly the mount would not exist at this time and the central uplift would be the sole feature within the lake. There is some evidence from tsunami features that the proposed first ocean was not iced over although the second, shallower ocean was.
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HSchirmer
post Nov 11 2018, 04:12 PM
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Theory - Gale Crater was a bay when the Arabia Ocean filled the northern lowlands of Mars.


QUOTE
Certainly the mount would not exist at this time and the central uplift would be the sole feature within the lake.


Perhaps but if Gale was a beach environment, why wouldn\'t there be sand, and perhaps dunes?
If there was an ocean, then there had to be an atmosphere, and had to be wind, and had to be waves,
and had to be sand, and sand plus wind means dunes.

If there was a northerly wind, why wouldn\'t the central peak of Gale trap a static barchan style dune?
Is there a name for the barchan-dune looking half-crater north of the Gale notch?


QUOTE
I suspect that this would represent the maximum fill with your suggested high ocean level, with the northern rim less degraded and above water level.


A bit of digging finds that early plaotting of the "Arabia Sea" aka "Contact 1" goes right through Gale crater.

QUOTE (PALEOSHORELINES AND THE EVOLUTION OF THE LITHOSPHERE OF MARS)
https://eprints.ucm.es/33193/1/3-Marte%20SL.pdf]
Parker et al. (1989, 1993) also proposed an older, higher-standing Contact 1, later on
renamed Arabia shoreline (Clifford and Parker, 2001). This shoreline, which would be of
Noachian age (see Clifford and Parker, 2001), is roughly coincident with the Martian
dichotomy separating the lowlands from the highlands,


figure #2 from the paper is enlarged as the first image below

At the Arabia shoreline, Gale crater would have been a bay.
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HSchirmer
post Nov 11 2018, 05:27 PM
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QUOTE
I suspect that this would represent the maximum fill with your suggested high ocean level, with the northern rim less degraded and above water level.


Actually, "just overtopping" is the Arabia Ocean level, Meridiani would be higher, making Gale the entrance to an estuary.

QUOTE (Topographic evidence for lakes in Gale Crater)
https://www.lpi.usra.edu/meetings/lpsc2013/pdf/1844.pdf
Figure 1: Three lake levels at Gale:at - 2277 m spilling over the northern rim


The shorelines suggest 3 oceans, Deuteronilus, Arabia, and Meridiani.

A zoom in from the Paeloshorelines paper shows the various shorelines in black in the images attached below-

QUOTE
Figure 6. The Deuteronilus (yellow), Arabia (green) ... shorelines after Clifford and Parker (2001), represented on the Martian topography (scale in km). Also represented (black) are the contour of the a) -1.5 km, cool.gif -2.09 km, and c) -3.792 km elevation levels.


Three images below (which of course are out of order...) To judge the ocean height, look at Elysium.
Working left to right- Gale crater is due north of the left most yellow dot at the bottom center of the images.

At the Arabia shorline, (left image) Elysium is an island with wide flanks, and Gale is a circular bay.

At the lowest shoreline Deuteronilus, (middle image) Elisum is still attached to the continent, and Gale is a notch at the fall-line.

At hightest shoreline, Meridiani, (right image) Elysium is a small island, and Gale is the entrace to a large estuary including the lowlands to the east.

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HSchirmer
post Feb 2 2019, 03:17 PM
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Reaching way back to discussions about the thickness of sediment deposits in Gale-

QUOTE (serpens @ Dec 22 2016, 10:54 PM) *
It would be reasonable to expect that the water availability in the Gale lake would vary as would the amount of available sediment, particularly airfall.
But this very thin sheet of cracked material does seem to be an anomaly and difficult to reconcile to dessication. Chemcam should reveal something about the makeup of the sheet as it could be possible that these cracks formed sub aqueous in a thin, possibly localised layer of clay rich sediment.
Subsequent settling of underlying sediment causing the cracking would explain the variation in shape and size.


Well, now it looks like the Gale crater was NOT filled to the brim with sediment-
Thanks to some creative re-purposing of accelerometers and gyroscope to go gravity/density measurements-
'Mars Buggy' Curiosity Measures a Mountain's Gravity
The rocks aren't compressed in the way that would be expected if they were deeply buried-and-then-excavated.
A surface gravity traverse on Mars indicates low bedrock density at Gale crater

So, what process raised Mount Sharp? Nice summary of depositional models at
https://marsoweb.nas.nasa.gov/landingsites/...er_Gale_opt.pdf


Initial expectations mentioned possible contact with non-sedimentary basement-basalt.

I may have missed it, but was there any outcrop or exposure that looked like basement-rock basalt?
http://marsjournal.org/contents/2010/0004/...s_2010_0004.pdf

Anybody have a link to the most recent stratigraphic mapping?
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serpens
post Feb 4 2019, 05:53 AM
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The basal/basalt misinterpretation was explained, in fact done to death in pages 7 to 9 of this thread. Let's not resurrect it.

The accelerometer analysis by Lewis et al is innovative although I am not certain that their conclusion on the extent of overburden considers all the variables. I do not question their methodology or measurement results. However I do note that during the ascent of Mount Sharp the Murray formation has consisted primarily of mudstone with some sandstone lenses. Depositional muds have high porosity (up to 65- 70%) due to the nature of the particles and electrostatically bound water and compaction of such in Mars' low gravity takes significant overburden. Given the thickness of the mudstone significant pore fluids may have been retained, retarding compaction and retaining density indicative of shallower depth than was the case.
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atomoid
post Feb 5 2019, 10:04 PM
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As referenced in an article on sciencenews.org accelerometer-based gravity readings suggest:

"...the rock beneath Curiosity's wheels is less dense than its mineral composition led them to expect. It's "more like the density of soil than a fully cemented rock," Lewis says. That means the crater must never have completely filled with rock — the upper layers would have crushed the lower ones — and supports the windblown sands theory for how Mount Sharp formed...
...suggests there were two different periods of mountain-building in Gale Crater, one that laid down lake sediments and a drier one that built Mount Sharp's peak. Curiosity might find the transition point as it keeps climbing...
...measurements suggest that the rocks beneath Curiosity are riddled with holes. “But the rover doesn’t see any holes,” Kite says. Either the pores are too small for Curiosity to see, less than 10 micrometers wide, “or there’s something unusual about the rocks right at the surface where Curiosity is driving.”..."


Assuming an accelerometer measurement wouldn't be able to discriminate between holes/pores at surface vs subsurface... so seems simpler that the subsurface pore fluids desiccating could lead to mineral solidification of their environs preventing the sedimentary compaction due to pore collapse could help explain away some of the missing mass?
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serpens
post Feb 6 2019, 01:27 AM
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The hardness of the Jura and upper Pettegrove Point members combined with CRISM results indicate that they are well cemented with iron oxide, primarily hematite. This localised and comparatively shallow phenomena most likely occurred post lithification and the erosion resistant upper surface of the ridge is indeed different to the underlying Murray formation. Mudstone is a bit of an anomaly where compaction is concerned because the platy particles compact at surfaces rather than points, significantly reducing porosity. But this reduction means that the remaining pore water is retained despite increases in load, so bulk density is not necessarily an accurate yardstick to measure load (overburden).
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serpens
post Feb 9 2019, 04:08 AM
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Just in case anyone missed it, Emily provided an update on Curiosity's investigations including the intriguing Rock Hall drill initial results. http://www.planetary.org/blogs/emily-lakda...-2257-2312.html with a link to the LSPC abstract. https://www.hou.usra.edu/meetings/lpsc2019/pdf/1127.pdf
Sheer conjecture, but the decreasing phyllosilicates and increasing amorphous with elevation at VRR combined with the identification of akaganeite would seem to strengthen the case for volcanic outgassing providing precipitation, acid snow perhaps including dissolved HCl. Subsequent melting and interaction with groundwater would provide ferrous and chloride ions in acidic conditions.
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HSchirmer
post Mar 17 2019, 03:22 PM
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Curious if a new theory about the Pathfinder site might be relevant for Curiosity...

The Pathfinder landing site may have been shaped by water overflowing from Mar's northern ocean into a depression.

    The 1997 Mars Pathfinder Spacecraft Landing Site: Spillover Deposits from an Early Mars Inland Sea
    J. A. P. Rodriguez, V. R. Baker, T. Liu, M. Zarroca, B. Travis, T. Hui, G. Komatsu, D. C. Berman, R. Linares, M. V. Sykes, M. E. Banks & J. S. Kargel

    Scientific Reportsvolume 9, Article number: 4045 (2019)


    “Our paper shows a basin, with roughly the surface area of California, that separates most of the gigantic Martian channels from the Pathfinder landing site. Debris or lava flows would have filled the basin before reaching the Pathfinder landing site. The very existence of the basin requires cataclysmic floods as the channels’ primary formational mechanism” said Rodriguez.


Given that Gale may have been close to the shoreline



and a Martian ocean would have waves capable of sediment transport,

    https://gsa.confex.com/gsa/2017AM/webprogra...aper303500.html
    WIND, WAVES, AND SHORELINE DEVELOPMENT ON MARS
    Our results indicate that winds ranging from 5-35 m/s blowing across fetch distances from 10 – 100 km would have generated breaking wave velocities ranging from about 1 – 4 m/s. These velocities, in turn, would have been capable of transporting basalt boulders up to about 50 cm.


Could Gale basin have occasionally been filled from the ocean side?

    CuriousMars: Box Shaped Martian Features and Deep Water Lake Deposits Offer New Rover Destinations
    By Craig Covault



I'm curious, has anybody modeled whether an asteroid or comet impact into an early Mars ocean would generate a Tsunami?

We see many references to sudden "mega floods" carving channels along the Martian coastlines, which are often attributed to impacts melting ices and releasing melt waters. What sort of water movement would an ocean impact generate?
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HSchirmer
post Mar 17 2019, 08:45 PM
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QUOTE (serpens @ Dec 2 2012, 01:27 AM) *
nprev. I'm with you in that Mount Sharp probably has a central uplift core, but the bulk of the mountain is sedimentary. Have a look at a couple of the complex Lunar craters such as Maunder to get an idea of the relative size of a pretty much pristine central uplift.

The puzzle (and I deliberately avoid the word mystery) is why the sediment ended up as a central mound. I have difficulty accepting the explanation that the crater was overfilled to the height of (or greater than) Mt Sharp and then excavated, despite the credentials and credibility of the proposers. That hypothesis requires that the sediment that must have covered the rest of the crater and the surrounding area was totally removed while that on Mount Sharp was significantly more resistant. I'm backing a shallow crater lake for the phyllosilicates and a vortexing effect for the remainder. I don't have the smarts to model something so complex so take the last as being accompanied by wild guestures from the depths of an armchair.


Yep, quoting from quite a while back, but I thought that given recent papers about a possible Mars- groundwater-level, and about possible "slush-tsunami" it was appropriate to go back to early questions about Gale Crater.


Gale, crater combines two (perhaps three) interesting elements: a deep depression AND equatorial location AND (maybe) proximity to the Northern ocean (shoreline within reach of Tsunami waves expected from asteroid and comet strikes.)

- Gale's equatorial location is roughly analagous to an East African rift valley lake on Earth, Lake Turkana, that generates it's own wind due to the thermal inertia of the water versus the land.
- Gale seems to be deep enough to tie into any local, regional and planetary groundwater level, and it's depth and warnth would allow liquids over a long, long time.
- Gale's location near a possible shoreline might tie-in with a Northern ocean Tsunami theory.


Lake Turkana- https://en.wikipedia.org/wiki/Lake_Turkana
"On-shore and off-shore winds can be extremely strong, as the lake warms and cools more slowly than the land. Sudden, violent storms are frequent."


Mount Sharp-
We known that equatorial lakes in deserts can create their own microclimate and strong local wind patterns- during the day winds blow from the lake onto the shore, at night the wind reverses and blows from the shore onto the lake


Lake Turkana Wind Power Station- https://en.wikipedia.org/wiki/Lake_Turkana_...d_Power_Station
The Lake Turkana Wind Farm Project - M. Burlando, F. Durante; DEWI GmbH, Branch in Italy, Genoa, ItalyL. Claveri; DEWI GmbH, Oldenburg
https://www.dewi.de/dewi_res/fileadmin/pdf/...gazin_37/02.pdf
"A semi­permanent low pressure cell centered over Lake Victoria forces the main air­streams of both the monsoons, which are roughly parallel to the coastline over eastern Kenya, to flow zonally westward over north­western Kenya. This thermally­induced synoptic­scale deflection interacts with the orography of Eastern Africa to generate some con­vergence zones over the Ethiopian and Kenyan highlands. Just in between the Ethiopian and Kenyan highlands, the Turkana­Marsabit Corridor occurs, which is one of the windiest among these convergence zones. "


I wonder if crater lake microclimates might help explain Mount Sharp and other "tall mound" craters.
Theory is, during the day, the rocks around the lake warm up, that warm air rises and that draws cool dry air down onto the crater lake and peak. This creates a cool microclimate at the central peak, and a cool moist microclimate around the crater lake. The moist climate around the lake shore should accellerate weathering.
During the night, relatively warm moist air rises from the lake, that rising air kicks up wind that carries dust from the surrounding area onto the central peak. Dust should stick to any snow or moist soil on the central peak. Any extra dust or very fine dust is carried by rising moist air, the dust nucleates snow, snow falls on the central peak. When the snow eventually melts, it leaves behind the dust.
Repeat for aeons, and you should get a net transfer of dust from the surrounding shoreline onto a snow capped central peak.





Depth is important for two reasons - first it appears that the crater would be deep enough to tap into local and regional groundwater networks. It's ALSO deep enough and warm enough that it would have been one of the last places where liquid water was stable as the Martian atmosphere thinned out. If Mars had an atmospheric cycle of freeze-deflate and thaw-inflate then Gale would conversely be one of the first areas to "thaw out".

Equatorial location is important becase this means Gale crater one of the best places on Mars for insolation, heat, and therefore evaporation of liquid water.

Coastline is interesting because this puts Gale within possible reach of Tsunami or slushie-Tsunami effects.

    Tsunami waves extensively resurfaced the shorelines of an early Martian ocean
    J. Alexis P. Rodriguez, Alberto G. Fairén, Kenneth L. Tanaka, Mario Zarroca, Rogelio Linares, Thomas Platz, Goro Komatsu, Hideaki Miyamoto, Jeffrey S. Kargel, Jianguo Yan, Virginia Gulick, Kana Higuchi, Victor R. Baker & Natalie Glines
    Scientific Reports volume 6, Article number: 25106 (2016)
    https://www.nature.com/articles/srep25106
    "The simulations also show that bolide impacts causing craters ~30 km in diameter would have generated tsunami waves with typical onshore heights of ~50 m and local variations from ~10 m to as much as ~120 m..."


Interesting twist - if an impact occurs during a warm to mild conditiions, a 150-360 foot tall Tsunami hits the shore, waves of water flow in, then flow out. If Mars is cold to cryogenic, you get an "ice surge" https://www.youtube.com/watch?v=OgMBQFf64JM which his basically a one-time long-run-out glacier. In between temperatures, and you might get a Tsunami where liquid water flows inland and then freezes in place.


So, perhaps we have a good Earth analog for Gale?


https://www.spectator.co.uk/2018/03/to-thos...place-on-earth/]To those with a taste for desolation, Lake Turkana may be the most beautiful place on Earth
A postcard from Kenya
Matthew Parris[/url]
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serpens
post Jun 7 2019, 06:33 AM
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HSchirmer, could I perhaps suggest that you may like to post images as thumbnails, it would make your posts easier to read.

It is now clear that Vera Rubin Ridge was laid down as part of the Murray formation and the erosion resistance is a product of post deposition diagenetic/alteration episodes. The comparative hematite, phyllosilicate, amorphous and opal CT proportions with elevation combined with the identification of akaganeite is indicative of low pH fluids infiltrating from above. The likely formation candidates from the options proposed to date are a springline during the Mount Sharpe erosion process or a much earlier, low energy stream after the lake dried.

It is pretty clear that clay rich Glen Torridon is not associated with the Murray formation, is possibly cemented with clay and does not seem to have undergone significant compaction. I retain the belief that this formed following the erosion of the Murray formation on both sides of the resistant ridge, and is potentially a function of the formation of the fan. Basalt buffered water and sediment originating in upper Mount Sharp pooling in the hollow between ridge and mount. In the absence of tidal influences the rhythmic laminations or “bundling” could well reflect a shallow lake with annual ice cover. During winter dust collects on the ice and on thawing settles to form the thin laminations. During summer ice on the mount melts and a thicker layer of sediment is deposited.

Or it could be something completely different which the experts, having actual data to work with will advise in due course.
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HSchirmer
post Jun 9 2019, 10:14 PM
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Already received that admonition from a Mod.

Curious,


QUOTE (serpens)
The comparative hematite, phyllosilicate, amorphous and opal CT proportions with elevation combined with the identification of akaganeite is indicative of low pH fluids infiltrating from above.


Why a preference for low pH from ABOVE, rather than BELOW?
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