[X] My Assistant

[Bill Harris]

Yep, I keep hopping around on this and arm-waving. They might be devitrification byproducts, the probably aren't hematitic BlueBerries and they might even be something else. We won't know until we learn the mineralogy of this unit, and we won't learn that until The Big Paper comes out at LPSC.

I'm still leaning towards weathering and alteration byproducts on the pre-Endeavour land surface. This will certainly tell us much about Martian environmental conditions at that time.

"Zeolites" can have a very broad range of characteristics, much like the phyllosilicate family. I found a very interesting paper tonight on this subject:

Identification of hydrated silicate minerals on Mars using MRO-CRISM: Geologic context near Nili Fossae and implications for aqueous alteration

Bethany L. Ehlmann, John F. Mustard, Gregg A. Swayze, Roger N. Clark,
Janice L. Bishop, Francois Poulet, David J. Des Marais, Leah H. Roach,
Ralph E. Milliken, James J. Wray, Olivier Barnouin-Jha, and Scott L. Murchie

Received 23 January 2009; revised 8 May 2009; accepted 11 June 2009; published 23 October 2009

http://www.planetary.brown.edu/pdfs/3932.pdf

--Bill

[atomoid]

[attachment=28313:fibrous.jpg]
A higher resolution view of the fibrous example, (in parallel stereo).

Fascinating stuff... what really gets me in marsophile's stereo view its dramatically apparent how the veined ('fibrous') section protrudes from the rock almost like planes of a desert rose suggesting it crystalized inside of, or more likely is an erosion resistant remnant of an eroded spherule interior.

note that no other spherules (afaik) exhibit this, suggesting (to my non-geologist eye) the veining formed through mineralization of fractures.

an odd puzzle is the fractures seem to occur in only this small area, not across a larger section as would be expected from slumpage or dessication, unless they did exist but were erased from erosion and this is all thats left

[ronald]

Pancam Sol 3084:



left is L3-L5-L6 (bit screwed up colours ), middle the usual L2-L5-L7, left a try on combining L7-R1

One more - L3-L5-L6 this time:

[jamescanvin]

Whitewater Lake (used all 6 L filters for better colour and to reduce artefacts)

[ronald]

Sol 3085:

[xflare]

Get used to the view folks, we're going to be here a while.

http://www.jpl.nasa.gov/news/news.php?release=2012-306

One working hypothesis, out of several, is that the new-found spherules are also concretions but with a different composition. Others include that they may be accretionary lapilli formed in volcanic ash eruptions, impact spherules formed in impact events, or devitrification spherules resulting from formation of crystals from formerly melted material. There are other possibilities, too.


That's a subtle hint if I ever saw one.

[Bill Harris]

Ah so. Matijevic Hill is the "official" name of the location that I had informally called "Shoemaker Bench". This will prove to be a great stop.

--Bill

[Stu]

Whitewater Lake RAT hole...

[Tesheiner]

Looks soft as butter, isn't it?

[Stu]

I can't believe it's not butter...

[climber]

Looks soft as butter, isn't it?

This is important information I'd say! Soft as clay would be even nicer.

[elakdawalla]

I can't believe it's not butter...

Tesheiner just set 'em up for you to knock 'em down

The softness of these rocks is crazy. I've been imagining Opportunity's wheels crunching like boots on rock but I'll bet that when there's gravel underfoot it doesn't crunch so much as grind; gravel between your foot and the rock might gouge its way in. On a field trip to west Texas while I was in college I encountered a rock made of bentonite -- it was able to form cliffs in the desert but walk on it and your boots gouged right in. It was weird stuff. (Here's a neat photo essay about that rock.)

[Eutectic]

...a rock made of bentonite...

My college geology field class drove past a bentonite mine in Wyoming -- the stuff was scooped right out of the hillside into rail cars. Bentonite has many uses, including incorporation into candy bars, which in this case could lead to a whole new meaning for Mars Bars. Here's a little more about bentonite -- note the rock-water interaction:

http://www.rawell.co.uk/products_technical...s_bentonite.php
Bentonite is a natural inert clay that was formed from volcanic activity during the Cretaceous period approximately 100 million years ago. Long periods of repeated eruptions laid ash into the sea where it was chemically altered and consolidated into layers of clay. Over time the ground folded and lifted thrusting up the clay and silt to form the Black Hills and Big Horn mountains of Wyoming, USA. The term bentonite is generally applied to colloidal clay associated with the Cretaceous Benton shale found near Fort Benton. Bentonite mining first began in 1888.

The first recorded use of the mineral known as “the clay of a thousand uses” was for making cosmetics, it then became used as a foundry sand bond in the 1920s followed soon after as a drilling mud. The uses have continued to expand into the fields of bleaching clay, animal feeds, pharmaceuticals, colloidal fillers for paints and inks, ceramics and in the motor industry for spark plugs and catalytic converters.

[Bill Harris]

I wouldn't make too much of it being bentonite. I've seen kaolinite in east Alabama, chalk/marl in south Alabama, loess along the Missippi and bentonite in the Big Bend of Texas that all look similar. We can see/say that it is a soft, fine-grained, amorphous material of uncertain composition and origin.

Yeah, more arm-waving and hopping back-and-forth. Hot on the trail of a hypothesis...

--Bill

[elakdawalla]

I wasn't suggesting Opportunity's rock is made of bentonite; I was just musing on how different the soft rock seems from what one normally thinks of as "rock."