geology of Gale Crater and Mount Sharp Options

[David Palmer]

The idea that the Lower Formation of Mt. Sharp is of lacustrine origin (lakebed sediments) has rather fallen out of favor recently, but I just finished my essay on Mars, "An Interpretation of the Geology of Gale Crater & Mount Sharp, with Implications for the History & Habitability of Mars," which I have spent over one year researching and writing, and the primary thrust of this paper is to offer a fresh defense of the lacustrine model, incorporating some fairly original ideas on my part. I'm not a professional scientist, but this is a labor of love that springs from a near-lifelong interest in Mars (since I was a young boy in the 1960s). And I'm trying to publicize it prior to Curiosity reaching Mt. Sharp, as that will be a test of my theories, and I'm hoping to get some recognition if I'm right. So here's the link for all interested readers: http://galecratergeology1.tumblr.com/post/...le-crater-mount

[serpens]

I have a little difficulty with some of the assumptions on which you base your last post David. Taking your numbered points:

(1) Endeavour crater currently reflects the required topography so it is possible that so could Gale at the time the channels were formed.

(2) To my eyes the channel is not pristine and the filled remnant wends towards the top right of the image, disappearing under the (Aeolian?) sediment without narrowing.

(3) The extent of lithification of the various levels of mount Sharp can only be assessed if Curiosity gets up close and personal. But I submit that can assume that the lower (dark) beds will have been saturated (Curiosity's findings, the presence of boxwork and clays and the channels/delta deposits). The overlaying light (Aeolian) deposits evident in the layers above this level would almost certainly have much reduced cementation. So there would seem to be a reasonable probability of a significant difference in erosional vulnerability, particularly in light of the increasingly gentle environment of the past few billion years.

Painstaking analysis of Curiosity's findings by the resident experts will narrow the field but as I mentioned previously, there will probably be a number of hypotheses as to the formation of Gale alive and well at the end of the mission. Consider how long it took to get a handle on Opportunity's small area of Meridiani. Anyway, as you are aware I threw the "overland-flow hypothesis" as you termed it in purely to point out that there are alternatives to an extremely high pressure aquifer to explain the Mount Sharp channel features. But it is merely wild arm waving from the depth of an armchair and not worth argument.

[David Palmer]

Reply to Serpens:

Actually, I WANT "argumentation" over my hypotheses....my model needs to be roundly criticized, it needs to go through the wringer....its not just there to sit and look pretty.....and I figure that by this time next year, it will have been proven right or wrong. It's put forth as a serious scientific hypothesis, which means it is something that needs to be tested....Emily (elakdawalla) doesn't seem to understand exactly what I am trying to accomplish here....just because I am an amateur scientist, and this is a hobby of mine, doesn't mean I also can't be attempting serious science, and attempting to get the notice of professional planetary scientists. And sure, I'm going out on a limb by presenting my ideas, but there's a void to be filled, because no one else has a coherent, all-encompassing model to present. And although Gerald wishes to wait till there is more data in, I figure that the prize is to be had by the person who jumps into the fray and is the first to come up with a model that holds water (no pun intended), even before the so called "experts."

I'm having to get back to work now, but later today I'll make specific replies (concerning geology) to you and Gerald.

Dave

[mcaplinger]

...I figure that by this time next year, it will have been proven right or wrong... the prize is to be had by the person who jumps into the fray and is the first to come up with a model that holds water (no pun intended), even before the so called "experts."

What is the test for your hypothesis that you expect to be resolved in a year?

BTW, referring to the scientific community as "so-called experts" is a sure way to have your work dismissed.

[David Palmer]

What is the test for your hypothesis that you expect to be resolved in a year?

1. Particle size distribution, minerology, and bedding characteristics of the Lower Formation should all indicate lacustrine, not aeolian, deposition,
2. The channel fill of what I am referring to as the "Northern Channel" should show a very young cosmic-ray exposure age (several million years),
3. The minerology and isotopic ratios of the channel fill should reflect a groundwater origin, rather than surface precipitation (I am expecting a high salt content....and a bias towards heavy isotopes in the bound water, as compared with atmospheric moisture or frost or snow).

[Gerald]

3. ...I am expecting a a bias towards heavy isotopes in the bound water...

Didn't you actually mean a bias towards light isotopes? That's what I would expect for an old aquifier.

Item 1 could be explained by lakes, ruling out Kite's simplified purely aeolean model, although not the concept;
item 2 could have been caused by rapid recent erosion.
Item 3 appears to be more specific to your main hypothesis of an ancient aquifier, although there may be some ambiguity with a hypothesis of an early formation of the channel filling material, or just old buried ice as kind of a local aquifier.

In which way is the test specific to the (high-pressure) artesian spring hypothesis? Or which additional tests could provide unambiguous evidence?

[David Palmer]

Reply to Gerald:

No, I did mean what I said, that groundwater would be enriched in heavy hydrogen and oxygen isotopes, relative to atmospheric precipitation (and thus any residual bound water in minerals and sediments that interacted with this ground water, such as ones eroded and transported by spring water, would show such an enrichment).

Any atmospheric precipitation will be biased towards light isotopes, because lighter molecules are slightly more apt to evaporate. This effect becomes significant in some environments on Earth....in the polar regions, deuterium concentrations in snow can be 40% lower than in sea water. And the same is true for groundwater vs. atmospheric moisture....groundwater will have a relative over-abundance of heavy isotopes, compared with water that has evaporated and subsequently precipitated.

For example, see http://www.whoi.edu/cms/files/kcasciotti/2...t1996_14124.pdf

You are quite right in saying that a lacustrine origin for the Lower Formation would not prove my hypothesis....but it is a necessary condition for that hypothesis to be valid (a necessary but not sufficient condition, to use terminology from logic).

The first condition lays the groundwork for the possibility of my hypothesis being right, but the later two conditions are more directly a test of it (low cosmic ray exposure age, and chemistry and isotopic ratios characteristic of groundwater involvement).

You state that a low cosmic ray exposure age could also be the result of rapid erosion (of very ancient materials), and not signify recent deposition. However, my point is that IF rapid erosion of a relatively thin formation is occurring (several hundred feet thick, in the case of the channel fill), that observation suggests that the strata in question is fairly young (I am claiming less that 100 million years old), because given such a rapid erosion rate, any such thin (surface) deposit would otherwise be long gone. The only alternative would be that a (now vanished) overlying stratum was protecting the channel fill until recent geologic times, but this would seem an unlikely coincidence, especially considering that (per the law of superposition) the channel fill is one of the most recent deposits in the Gale/Mt. Sharp complex (it overlies the mound-skirting unit, which in turn embays the Peace Vallis fan deposits).

So it can be seen that my "artesian hydrant" hypothesis is a scientific hypothesis in the truest sense of the word, with very specific, quantitative, field-testable predictions (another of which, unfortunately, may have to wait till the distant future to be tested....namely my prediction that there will be underground conduits in Mt. Sharp, to be mapped out by high-definition ground-penetrating radar or seismic studies).

Dave