Mars - miscellaneous anomalies

Historic planetary instability and catastrophe. Evidence for electrical scarring on planets and moons. Electrical events in today's solar system. Electric Earth.

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Re: Recreating "Martian dendritic ridges" here on Earth?

Unread post by David Talbott » Wed Nov 27, 2013 11:06 am

A further thought for those interested in the electrostatics of granular flow. I've followed the recent work of Dr. Troy Shinbrot, in the Dept of Biomedical Engineering at Rutgers University. See his interesting discussion of electric charging and the patterns created in flowing grains:
http://sol.rutgers.edu/~shinbrot/Web2009/index.html

I cited a portion of this work in "The Lighting-Scarred Planet Mars." See the 18:22 in the segment posted on YouTube:
https://www.youtube.com/watch?v=U-qrnsh83f4

Other issues with respect to dendritic ridges are discussed in this video clip as well. To me, all of the questions arising from the observation of granular flow must have something to tell us about dendritic ridge formation on Mars, though there is clearly more to it as well.

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Re: Recreating "Martian dendritic ridges" here on Earth?

Unread post by Max Photon » Wed Nov 27, 2013 11:10 am

To be clear, I was aware that the prize is for an electrical demonstration.

I just like to use the word "money." :mrgreen:


For all you lovers of the dynamics of grains, may I highly recommend The Self-Made Tapestry: Pattern Formation in Nature by Phillip Ball. The chapter on grains is, well, like the entire book: awesome!

(It might be my favorite book.)


Btw, to those with slower internet connection: my apologies if the link in the opening post is slow to load. A number of photos have to download, and it may take awhile. (I did a rather poor job of file size management.) Please be patient; I tried to provide high quality photos. (Remember, you can click on them to enlarge even further.)
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Angles of repose that exceed modern angles

Unread post by Max Photon » Wed Nov 27, 2013 6:17 pm

More interesting information on angles of repose...

Angles of repose that exceed modern angles

Mann, C. John; Kanagy, Sherman P., II
Geology, vol. 18, Issue 4, p.358

ABSTRACT

Angles of repose for naturally occurring materials are known to be a function of, among other geologic parameters, the acceleration of gravity and cohesion between particles. Thus, steeper angles[*] may have been recorded in ancient sediments because Earth's acceleration of gravity was less than now. Published data suggest that eolian and aqueous sediments have documented these changes. Previously, angles of repose steeper than modern angles were attributed to structural steepening and soft-sediment deformation. More detailed study is required to separate the contribution that each of many factors may have had in specific cases of ancient angles of deposition.


[*] Max's note:

The abstract is a bit vague. In a previous post in this thread, Static and dynamic angles of repose under reduced gravity, it was shown that for g = 0.38 x (g earth) -- that is, for g on Mars --

the STATIC angle of repose for, say, sand, increases by about 5 degrees,

while the DYNAMIC angle of repose decreases by about 10 degrees.
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Angle of repose in reduced gravity explains much

Unread post by Max Photon » Thu Nov 28, 2013 7:37 am

Ummm... is it just me, or is this thread fascinating? :geek:

From the above posts about angle of repose in reduced gravity, we can expect that, on Mars for example (with 38% of Earth's g):

-- Loosely consolidated material at its angle of repose, when undercut, will flow in a manner leaving steeper scarps (with dendritic ridges), and flatter avalanche run-out fields than would be seen on Earth.


This would be even more pronounced on, say, Comet Tempel 1, with its very low g; any disturbance of a slip face would result in a very steep scarp, and an avalanche run-out field so flat you might not notice it.

Is this what happened to the copper probe impact crater that "filled back in"? ... unstable crater walls flowed, and, with the very low dynamic angle of repose, did not freeze until the crater had substantially healed itself?

Is this why the comet has mesas (and unexpectedly sharp relief in general)? ... Slumps leave steep scarps and flat avalanche run-out fields, giving a "mesa look."

Remember, the notion that angle of repose is gravity-dependent is new. NASA, and Wal Thornhill et. al., did not have this information when commenting on Comet Tempel 1 in the past. Revisions must be made to incorporate this new finding.


I've just been informed I'm not fascinating, so it must be this thread.
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Re: Recreating "Martian dendritic ridges" here on Earth?

Unread post by Sparky » Thu Nov 28, 2013 8:33 am

This would be even more pronounced on, say, Comet Tempel 1, with its very low g; any disturbance of a slip face would result in a very steep scarp, and an avalanche run-out field so flat you might not notice it.

Is this what happened to the copper probe impact crater that "filled back in"? ... unstable crater walls flowed, and, with the very low dynamic angle of repose, did not freeze until the crater had substantially healed itself?
Can't agree with that line of logic. You might want to look at what standard model predicted. ;)
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Unread post by Max Photon » Thu Nov 28, 2013 8:41 am

Sparky, are you assuming Comet Tempel 1 is rock-hard rock, and as such there was no impact crater?

Are there not data pointing to a density less than rock, but greater than an ice/dust conglomerate? Is this not at least consistent with loosely consolidated material -- loosely consolidated material that can flow?

Please elaborate.
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Re: Recreating "Martian dendritic ridges" here on Earth?

Unread post by Sparky » Thu Nov 28, 2013 9:30 am

:? hint ;) ...think gravity... :? ;)
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Re: Recreating "Martian dendritic ridges" here on Earth?

Unread post by Max Photon » Thu Nov 28, 2013 9:37 am

Not the most elaborate elaboration I've ever seen. :D

Come on Sparky, your name isn't Spartan ... out with it. :mrgreen:
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Re: Recreating "Martian dendritic ridges" here on Earth?

Unread post by starbiter » Thu Nov 28, 2013 10:07 am

Hi Max,

On Earth there might be other factors at play. One would be moisture. The dunes in Great Sand Dunes National Park are very wet below 1'. The top foot is very dry. The dune You photographed might have been damp below a certain level.

Dry sand wastes at 35 degrees. Damp sand can maintain a 45 degree angle. Wet sand slumps. This might be a factor.

Also, there appeared to be ripples on the surface above the ridge in Your images. These ripples could be repeated all the way down. The dendritic ridges aren't perfectly symmetrical, and neither are the ripples.

http://www.panoramio.com/photo/53577792

This process might compact the sand, causing diminished wasting. Or not. As Dave Talbott stated earlier, static electricity could also be a factor.

Temple 1 seems to be electrically active. This might produce molten dust in the electrically active areas. The copper impactor might have created even more heat than normal.

Lots of options to consider.

Mars is a wild card. It might be easier to study sand dunes on Earth. It's warmer.

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Re: Recreating "Martian dendritic ridges" here on Earth?

Unread post by Max Photon » Thu Nov 28, 2013 11:36 am

Michael, you made a number of good points.

As I remember it, the sand was dry -- as dry as sand can get at Ocean Beach, San Francisco, which is going to almost always have a relatively high humidity. Plus, fog can dampen the top layer.

The top layer on the windward side of the dune had an ever-so-delicate "crust" -- sand that was slightly more cohesive, maybe about 1/4 inch (6-7 mm) thick. You can see it on the top lip of the slip faces.

I appreciate your point that the dune is not symmetric internally.

Also, and this might be relevant from an electrical perspective, the sand has a certain amount of hematite. I have experimented at Ocean Beach with a magnet; it doesn't take too long to have the thing "furry" with hematite.

I wonder if the flowing sand, both as the dune forms, and as the slip face fails, creates electrical effects that ultimately help electrostatically stabilize some of the higher, sharper edges on the dendritic ridges?


As for Mars? Ah yes, as you said, if only it had road cuts. (God bless road cuts.)
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Re: Recreating "Martian dendritic ridges" here on Earth?

Unread post by Sparky » Thu Nov 28, 2013 5:37 pm

Not the most elaborate elaboration I've ever seen.
Since you are much smarter than I am, I thought a hint is all you needed.... :D

What is the gravity on a asteroid that size.? Escape velocity? Energy of impact ? Standard model expectation? Observed impact! Observed residual effect of ejected matter? Follow the evidence. :D
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Re: Recreating "Martian dendritic ridges" here on Earth?

Unread post by Max Photon » Fri Nov 29, 2013 6:47 am

Much smarter? "Max Photon" is just a reaction-formation to being rather dim. Sparky, ever heard of little brain complex? :mrgreen:


Okay, I may have strayed a bit with respect to Comet Tempel 1.

We were discussing observed dendritic ridges on a terrestrial sand dune slip face that was undercut.

Then I brought up that relatively recent findings show that the static and dynamic angles of repose vary with g.

Now surely this new information must be incorporated into any models of the terrains of this planet, other planets, asteroids, and comets.

The notion is that with reduced g, the static angle increases, and the dynamic angle decreases.*

It was established by experiment that with g(Mars) = 0.38g(Earth), the former increases by about 5 degrees, while the latter decreases by about 10 degrees. (Result: failures produce steeper scarps and flatter avalanche run-out fields.)

* Sparky, I believe your basic point is that this change in angles of repose under reduced g does not continue without limit. That is, under the super low g of Comet Tempel 1, other factors, the main one being a low escape velocity, become significant.

I concede without resistance. I was merely putting forth a speculative idea that, if the angle of repose trend did continue with lower g, and if Comet Tempel 1 has loosely consolidated material that can flow, then the combination might explain the surprising observed terrain, and its changes over time.


In the end we are left with an interesting question:

What does mass wasting look like in an extremely low g environment?
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Re: Recreating "Martian dendritic ridges" here on Earth?

Unread post by Sparky » Fri Nov 29, 2013 7:55 am

Now surely this new information must be incorporated into any models of the terrains of this planet, other planets, asteroids, and comets.
Yes, it should be considered.. :?
What does mass wasting look like in an extremely low g environment?
It depends upon cause doesn't it? For myself, If it looks electrical, or electrical artifacts are nearby, I don't try to shoehorn in other possibilities. :? :D
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Re: Recreating "Martian dendritic ridges" here on Earth?

Unread post by Max Photon » Fri Nov 29, 2013 8:11 am

Sparky, I hardly see mass wasting effects and electrical effects as mutually exclusive.

If electricity in whatever form -- devastating strikes; nibbling arcs; electrostatic levitation; etc., -- disturbs material, will there not be mass wasting (i.e., stuff adjusting) after the electrical event, possibly eons after?

And as such, isn't is critical to know about mass wasting effects under extremely low g?

So maybe it's time to bust out that shoehorn! :D
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Re: Recreating "Martian dendritic ridges" here on Earth?

Unread post by starbiter » Fri Nov 29, 2013 8:23 am

A question Max. Do You think the dune You photographed was new, created during a recent windy storm? Or was it added to? If it was newly created it might have been dry all the way through, if the windy condition was completely dry. If only the top was new, or it rained during the storm, it might have been damp on the interior. That would add a new wrinkle. That would probably not be a factor on Mars, but who really knows?

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