Geomorphology of Gale Crater, Rock on! Options

[ngunn]

My favourite LPSC abstract (so far, I'm still reading) : http://www.google.co.uk/url?sa=t&rct=j...d2k&cad=rja

[jmknapp]

In lieu of movement towards Mt. Sharp, here's an attempt at what a scene might look like from an aerial view when the rover gets there (anaglyph):



That's reprojected from a HiRISE image, using the digital terrain model on the HiRISE site. The location is in the large outflow channel that Curiosity may go up to get to the "non-conformity" boundary (at the upper left half of the image), looking kinda like lava flows.

[Fran Ontanaya]

Can this inconclusive blue green spotty pattern on CRISM where Curiosity has found carbonates be extrapolated to what is seen higher on Mount Sharp, past the blue and magenta sulfates (as seen here: http://www.planetary.org/multimedia/space-...le-crater.html)? It would be something if under the dust it was all phylosillicates, except for a sulfates apron.

[serpens]

Suffering from a mild case of cabin fever from being stuck inside due to dreadful weather I thought I would resurrect this thread to throw out a few ideas on the dating of Gale. pdf attachment for brevity of post.

Attached File(s)

 gale_age.pdf ( 358.09K ) Number of downloads: 981

 

[Gerald]

Re 3: Reliably tracking back the orbits of the planets of our solar system more than about 0.5 billion years isn't currently feasible, afaik. Adding the excentricity of Mars' orbit, I don't see convincing evidence for the implicite assumption, that the Martian orbit has been 3.7 billion years ago where it is today.
So, I'd think that there is sufficient space to play with resonances and close encounters with other planets, which may or may not still be present in our solar system. Some planets/planetesimals might have been ejected from the solar system, swallowed by the Sun or the gas giants, or fused to today's planets.
Over long time scales close encounters with other stars might have disturbed the orbits of our planets, too.
The faint sun hypothesis is a hypothesis, and despite theoretical evidence, data are lacking. The activity of stars can vary.
And radiogenic heat has generally been considerably higher in the young solar system than today; so we get the Martian interior as a source of heat.
There is of course still quite some uncertainty about the composition and density of the early Martian atmosphere, as well as of its albedo.
Hence I agree, that an early warm Mars is a mystery, but not because there is a lack of possible solutions, but because there are too many solutions.

Therefore I'd take it as valid to assume surface temperatures as inferred from geology, no matter for which particular physical reason.

[Don1]

@Gerald: I recently came across another very interesting possible explanation for the faint young sun paradox. In his "Lectures on physics", Feynman discussed the possibility that the gravitational constant G had changed over time. It turns out that the luminosity of the Sun is strongly affected by changes in G, with the luminosity proportional to G to the sixth power. Feynman points out that this would have made the ancient earth far too warm. However Feynman wrote that in 1962, which was a few years before the faint young sun paradox was identified. It turns out that a warmer earth is just what we need.

I did some digging around on the internet and it appears the current observational constraints on G can't rule out the possibility of G changing by enough to solve the faint young Sun paradox. So the idea that G has always been constant is really an assumption.

[Don1]

From the GSA meeting abstracts:

"LONG-LIVED DEEP LAKES IN EARLY MARS: SEDIMENTOLOGICAL EVIDENCE FROM THE CURIOSITY ROVER AT GALE CRATER"

"... the Striated and the Murray formations represent a subaqueous fan in a large lake, estimated to be 1 - 3 km deep. Fining-upward layers of the Striated formation are coarse-grained turbidites deposited on the proximal part of the fan by sediments delivered by floods through the northern rim of the crater. The Murray formation formed on the distal part of the fan and extended into the center of the lake in waters so deep that bottom sediments were unaffected by wave actions, lake-level fluctuations, and storm activities....."

"The rhythmic nature of layering indicates a regulated flow of flood waters into the lake, possibly controlled by changes in climate. The most likely forcing mechanism was variations in obliquity. Floods occurred during hothouse periods when the Martian climate was warmer than Present. The lake became saline at least to gypsum saturation during subsequent cold and/or dry climate of icehouse intervals and precipitated sulfate-rich nodules in the Murray formation. "

My comment: This was a deep lake. Other abstracts indicate that it likely lasted for millions of years.

"TESTING A MECHANICAL MODEL OF FRACTURE FORMATION BY COMPACTION-RELATED BURIAL IN GALE CRATER, MARS; IMPLICATIONS FOR THE ORIGIN OF AEOLIS MONS"
"These results imply that formation of these fractures [in the Murray and Stimson rocks] requires at least one significant burial event in the evolution of Mt. Sharp, providing key insight into the geologic history of Gale crater. "

My comment: After the lake dried up, sand dunes formed which later became the Stimson formation. Then the crater filled in and the pressure fractured the rocks.

"DIAGENESIS ALONG FRACTURES IN AN EOLIAN SANDSTONE, GALE CRATER, MARS"
" The mineralogy and geochemistry of the altered sandstone suggest a complicated history with several (many?) episodes of aqueous alteration under a variety of environmental conditions (e.g., acidic, alkaline). "

My comment: More water flowed through the fractures and altered the rocks.

"MINERALOGY OF MUDSTONE AT GALE CRATER, MARS: EVIDENCE FOR DYNAMIC LACUSTRINE ENVIRONMENTS"

" At the time of writing, CheMin has analyzed 14 samples, seven of which were drilled from lacustrine deposits. The mineralogy from CheMin, combined with in-situ geochemical measurements and sedimentological observations, suggest an evolution in the lake waters through time, including changes in pH and salinity and transitions between oxic and anoxic conditions. "

My comment: The mention of "oxic conditions" is interesting. Anoxic conditions are not surprising on a planet with a CO2 atmosphere. However, what produced the oxic conditions? Where did the oxygen come from?

[serpens]

Re your comment on "TESTING A MECHANICAL MODEL.....". The Stimson Murray interface is an erosional unconformity covered by an fragile aeolian dune deposit that does not seem to demonstrate any significant compaction or lithification. Rather than being an early construct buried by crater infill the Stimson deposit was potentially laid down following the erosion of the crater infill with a large contribution from landslips from a degrading Mount Sharp. In other words the Murray formation is an erosional endstate for the mudrock (mudstone/siltstone because it is hard to tell the difference) lacustrine Murray formation and the easily eroded sandstone of the Stimpson is a late feature (in Mount Sharp erosional terms) .

[Gerald]

In his "Lectures on physics", Feynman discussed the possibility that the gravitational constant G had changed over time.... So the idea that G has always been constant is really an assumption.

Although G isn't known very accurately, varying G over (space)time would challenge present cosmological models, including the Einstein field equations. Missions like EUKLID might eventually narrow down according constraints.
Feynman hadn't access to astronomical and astrometrical data as we have today. I don't think, that with contemporary knowledge Feynman would have suggested to assume G as variable within our observable universe (might be except very close to the Big Bang).

I'm sure, that the faint young sun paradox will turn out to be soluble within established standard physics.

[MOD: Agreed, and a reminder to all to review rule 1.9 as well as to stay on topic.]

[Don1]

@serpens....Yes, I was wondering about that when I wrote the post. I thought Stimson was supposed to be young, but the abstract didn't read that way. I went back this morning and took another look at it, and the authors do seem to be arguing that the cracking in Stimson was produced by burial in the same way that the cracking in Murray was produced. It seems to me that that would only be possible if Stimson is old.

The authors by the way are Watkins, Grotzinger and Avouac at Caltech.

"TESTING A MECHANICAL MODEL OF FRACTURE FORMATION BY COMPACTION-RELATED BURIAL IN GALE CRATER, MARS; IMPLICATIONS FOR THE ORIGIN OF AEOLIS MONS"
" Large fractures which exhibit complex banding structures with distinct chemical trends (e.g. halos) are primarily found in the Stimson formation, but do extend into the Murray formation in one location. Smaller, sulfate-filled fractures are most prevalent in the Murray but are also associated with haloed fractures in the Stimson."

[serpens]

The Watkins, Grotzinger and Avouac paper in no way precludes the probability that the Stimpson was laid down subsequent to a significant burial and then exhumation of the crater. The extension of minor fractures into the Stimpson with limited examples of larger fractures can be readily explained through reactivation.
A possible scenario would be that the initial fractures in the Murray formation occurred as a kilometres thick overburden was removed through erosion and pore water was released. Subsequent deposition of the Stimpson material would have provided a compression force on the Murray formation, albeit at a comparatively minor level. The catastrophic channel outflow events, combined with a surge in volcanic activity would have provided sufficient acidic water through groundwater recharge and limited precipitation to replenish pore water to a degree, as well as (poorly) lithify the Stimpson. Subsequent erosion of the Stimpson would have caused a change in pore pressure in the underlying Murray sequence which could cause the pre-existing fractures to propagate up into the overlying Stimpson rock. This propagation could be assisted by pore water at the fracture tip causing chemical weakening of the overlying rock. Fracture propagation would have been restricted by the limited availability of acidic pore water due to the minor compression unloading.

[MarkG]

In reading this, please keep in mind the profound ancient-ness of these landforms.

[tty]

"The mention of "oxic conditions" is interesting. Anoxic conditions are not surprising on a planet with a CO2 atmosphere. However, what produced the oxic conditions? Where did the oxygen come from?"


There is actually an abiotic mechanism for producing appreciable amounts of oxygen photochemically in a cold glacial/interglacial environment. UV light will produce small quantities of hydrogen peroxide which will be stable enough at low temperatures to be stored in ice. When an interglacial arrives and the ice melts the hydrogen peroxide decomposes into water and oxygen.

[serpens]

Probably photodissociation of CO2 and H2O. This recent release by JPL provides some substantiation.
http://www.jpl.nasa.gov/news/news.php?feature=6544

[tty]

Yes. The process has actually been rather extensively discussed in the literature in connection with Archaean/Proterozoic glaciations ("Snowball Earth") since there is evidence for oxic conditions immediately after the glaciations. And hydrogen peroxide is actually found in measurable amounts in snow in Antarctica. Incidentally the quantity deposited increases in early summer when ozone is low.

http://rstb.royalsocietypublishing.org/content/363/1504/2755

http://www.pnas.org/content/103/50/18896

https://www.academia.edu/15042568/Productio..._photosynthesis

http://web.gps.caltech.edu/~jkirschvink/pd...iewAndModel.pdf