[X] My Assistant

[Guest_RGClark_*]

Last year I made a plea for Spirit to examine the dark material in Bonneville crater:

From: rgregorycl...@yahoo.com (Robert Clark)
Date: 20 Mar 2004 05:50:12 -0800
Subject: Mystery material in the Bonneville crater on Mars.
Newsgroups: sci.astro, alt.sci.planetary, sci.geo.geology, sci.geo.mineralogy
http://groups.google.com/group/sci.geo.geo...21ac267d592d633

Spirit was not commanded to enter the crater for fear of it being trapped by the craters steep slopes.
However, Edstrick noted that the dark sands in El Dorado resembles the dark material in Bonneville:

Non color calibrated image.

(Note: in uncalibrated images this material appears blue, but without calibration data all that can be said is that it is darker than the surrounding terrain.)

Then we may have another chance for determinining the make up of this dark material. I argue that this material may resolve one of the key questions on the mineralogy of Mars: what is the make up of the wide spread dark material seen on Mars, termed Surface Type 2 rock by Mars Global Surveyor scientists.
As I discuss in the sci.astro post, two explanations have been offered: one that it is andesitic rock, the other that it is liquid water altered basalt. Both the andesitic and weathered basalt explanations have important implications for the geologic past of Mars - the andesitic, suggesting tectonic plates may have operated on Mars, and the weathered basalt, suggesting liquid water oceans may have occurred on Mars.



Bob Clark

[djellison]

I'm not a geologist, but I'll put my $5 on Olivine rich basaltic sand

Doug

[ustrax]

I'm not a geologist, but I'll put my $5 on Olivine rich basaltic sand

Doug

Yes, I'm on the olivine party too...

http://www.unmannedspaceflight.com/index.p...indpost&p=33497

http://www.unmannedspaceflight.com/index.p...indpost&p=33816

Could be...:

http://web.utk.edu/~tdunn/green_olivine_sand.jpg

From here:

http://web.utk.edu/~tdunn/hawaii.htm

Is it possible that the true colour of the sand might be nearer this, greener?
(mhoward, I've used one of your images...):

http://img.photobucket.com/albums/v352/ustrax/greener.jpg

[ustrax]

'And we got solid Mini-TES, APXS and Moessbauer data that tell us that the sands of El Dorado are composed of a very clean, olivine-rich basalt.'

[ustrax]

'Pretty Green Mineral -- Pretty Dry Mars?'

http://www.psrd.hawaii.edu/Nov03/olivine.html

[Guest_RGClark_*]

'Pretty Green Mineral -- Pretty Dry Mars?'

http://www.psrd.hawaii.edu/Nov03/olivine.html

But then there is this:

How was the green sand beach on the Big Island, Hawaii formed? Do you know if there is another green sand beach? do all volcanoes form olivine crystals?
http://volcano.und.edu/vwdocs/frequent_que...estion1428.html

"green sand beach" - Google Image Search
http://images.google.com/images?q=%22green+sand+beach%22



Bob Clark

[ustrax]

I had already mention that green sand beach here:

http://www.unmannedspaceflight.com/index.p...indpost&p=34285

But I really liked reading the article you've linked us too...
http://volcano.und.edu/vwdocs/frequent_que...estion1428.html
So...Where's the cone?...And the water?

Is it possible that the entire inner basin area was a tuff ring?
Hello Mr. Home 'Mafic' (not 'felsic'...) Plate...

http://www.geology.sdsu.edu/how_volcanoes_...fring_page.html

[Guest_RGClark_*]

I had already mention that green sand beach here:

http://www.unmannedspaceflight.com/index.p...indpost&p=34285

But I really liked reading the article you've linked us too...
http://volcano.und.edu/vwdocs/frequent_que...estion1428.html
So...Where's the cone?...And the water?

Is it possible that the entire inner basin area was a tuff ring?
Hello Mr. Home 'Mafic' (not 'felsic'...) Plate...

http://www.geology.sdsu.edu/how_volcanoes_...fring_page.html

I had earlier suggested Home Plate might be a maar.
If the flat area is indeed a maar then perhaps the nearby cones are tuff cones which like maars are created through volcanic/water interaction:

HYDROVOLCANIC ERUPTIONS
http://www.geology.sdsu.edu/how_volcanoes_...rovolcanic.html


Tuff Cone - Maar Volcano.
http://geology.about.com/library/bl/images/bltuffcone.htm


Bob Clark

[Guest_RGClark_*]

I had earlier suggested Home Plate might be a maar.
If the flat area is indeed a maar then perhaps the nearby cones are tuff cones which like maars are created through volcanic/water interaction:

HYDROVOLCANIC ERUPTIONS
http://www.geology.sdsu.edu/how_volcanoes_...rovolcanic.html
Tuff Cone - Maar Volcano.
http://geology.about.com/library/bl/images/bltuffcone.htm
    Bob Clark

There is a link to a microscope image of the Green Beach sand here:

Beach Sand from Green Sand Beach, Mahana Bay, Hawaii.
http://www.gly.uga.edu/railsback/sands/sand286.html


Bob Clark