On the Road Again - volume 3 - Page 3

sol 2029 ( Oct 8, 2009 ) MI closeup of Shelter Island meteorite:

with a location link.

Sure looks a lot like Block Island...

more to come.

How will they be able to detect a fusion crust? It looks pretty shiney in your image Hort.

Not sure about the relationship to BI. No apparent Widmanstatten pattern and are those inclusions?

The 'chinese' troll postings is yet another depressing indicator that the average IQ of the human race is, like oil, past peak.

sol 2029 ( Oct 8, 2009 ) MI 3D detail of Shelter Island:

Makes the old utube songs seem not so bad, so ill just, no I want.

Fred

> No apparent Widmanstatten pattern ...

How about here:

http://qt.exploratorium.edu/mars/opportunity/micro_imager/2009-10-09/1M308307005EFFA7CHP2956M2M1
.JPG

and here:

Also recall that it takes some etching to bring them out.

sol 2031 ( Oct 11, 2009 ) 3D of Shelter Island:

with links to several details.

Ok, a bowl of berries on the top and dark soil in and under the meteorite.

Which means what?

Was the meteorite once completely covered in berry-laden soil? ( lighter soil blew away and berries trapped in the bowl? )

Did the dark soil "recently" collect in the crevices in the "recentely uncovered bottom?

If the dark soil is coarser and heavier than the red dust then why was it blown into the crevices - but not the red dust?

I am missing something here.

Hort; I don't think you missed anything.
The loose berries are lag deposits wherever located and are a product of prolonged erosion.
The dark,heavier soil collected during a period of denser atmosphere and cant be removed by the current weaker winds and thin atmosphere thatnow only moves the red dust around .

Horton, Great Work, I especially love the 3D detail of the "inclusion" poking into the "berry bowl" on top of Shelter Island. Sheesh! What a complicated object this meteorite - indecipherable without the 3D, thanks. The "inclusion" seems to have been "weathered out" of the rest of the material but in some places the weathering has apparently followed the "inclusion" below the surface of the meteorite leaving it separated from the "matrix" by a narrow gap but still tucked in below the surrounding metal. Wierd, but I guess it makes sense if there were a more easily eroded rind of matrix surrounding the "inclusion". I think that this erosion of deep recesses is evidence that favors chemical erosion over wind erosion as the agent.

Staying with the same 3D pair: The shape that intrudes into the berry bowl on top of Shelter Island does seem to have somewhat affected the shape of the bowl. The pits in Shelter Island have various shapes. Several are near circular but others seem to be affected by lumpy variations in the metal. It is as if a circular pit results where the metal is uniform. The trick is to correctly interpret the interaction between the "inclusion" and the pit shape and arrive at a conclusion about how erosion works here.

There can't actually be any true inclusions if this is a nickel-iron meteorite. (The 3 little meteorites Santa Catarina, Santorini and Barberton are stony-irons and do have real inclusions.) I think that we have to account for the "inclusions" as Widmanstatten variations in the resistance of the metal to erosion.

This meteorite has the same problem as the last one. Despite being a very cool object it just doesn't tell us very much yet. There's not enough pieces of the puzzle in place to make anything definite out of these new ones.

The big pits undercutting Shelter Island are something new. They suggest that the meteorite has a definite top and bottom and has been in this one orientation for most of the period of pit formation.

3D "walk-around" animation of Shelter Island:

The south side has more cavities - again with dark soil underneath the meteorite.

Perhaps there is a "cave" system under the meteorite in which the wind sweeps bright dust away.

Sure would be nice to peek inside the cavern with the long pointy projection on the right.

Horton, Loved the 3D animated walk-around of Shelter Island. There seems to be a slightly raised pile of material surrounding the meteorite that is densely covered in spherules. As mann asks back in reply 30, "Why so many berries around these meteorites?" Maybe some of the missing metal from Shelter Island has gone to produce the hematite for the surrounding "proliferation" of spherules. Of course there are many possible explanations as usual. The comparisons that need be made are with the other meteorites and with spherule distributions adjacent to protruding blocks that are not meteorites. I've put a little time into this already: Block Island seems to have had some effect on surrounding spherule distributions but not as clearly as Shelter Island. The spherule distributions around Heat Shield Rock are confounded by a ripple that meets the rock. Of the three, Shelter Island is most heavily eroded and has the most obvious surrounding ring of spherules. I'd better have a look at the three stony-irons next.

I've not yet found another example of a rock at Meridiani surrounded by a "perimeter berm" or "circumferential ripple" like Shelter Island has. It seems to me that I may have seen this before and I'll keep an eye open for it, but for now one of Shelter Islands unique attributes might be that it is surrounded by a linear mound.

WOW!!!
That is one of the coolest 3D animations on Mars that I have ever observed! Your method could be refined into 3D video and maybe already has but no one can bring recent images into such quality as quickly and professionally as you have done here!
Thanks Horton!
I'll have to look at it again to check berries, etc.
I was amazed at how you aligned the 3D images through the rotation so quickly, WoW!

Kye. That is a very well reasoned and thought provoking post at reply 49. Could the inclusions be troilite - Reichenbach lamellae? From Hortonheardawho's painstaking processing it would seem that the inclusions only occur on the upper part of the meteorite. If so it would be reasonable to surmise that only the bottom part has been subjected to water and consequent preferential chemical erosion.

serpens, re your 54, troilite seems like a pretty good fit for the inclusions from the bit of reading I've done. It is an iron sulphide mineral that occurs in most iron meteorites, sometimes as discrete plate-shaped nodules. These are called inclusions in references I found, so I stand corrected - nickel-iron meteorites do sometimes have inclusions. Iron sulphide and nickel-iron metal could be very different in resistance to chemical erosion. Are you suggesting that the troilite nodules in the bottom half of Shelter Island have all been corroded away?

Kye. If the bottom part of the meteorite was immersed in groundwater, then this would have interacted with the FeS to form a dilute sulphuric acid. This plus the probably acidic groundwater could have caused preferential erosion of other immersed meteorite constituents. Both BI and SI seem to have less 'wear' in the upper portions. If this is a strewn field from an atmospheric breakup then the weathering should be consistent across the fragments. Makes a look at the third candidate off the starboard bow very tempting.

But this is all arm waving on my part. Still, I do think these meteorites will have opened another window on the early Meridiani environment.

sol 2032 ( Oct 11, 2009 ) L234567R1234 of "Shelter Island" meteorite:

Very interesting.

There are many kinds of inclusions in meteorites that might be subject to erosion on Mars. Some nickel-irons are known to have significant graphite (carbon) blobs....which would dissolve in dilute sulphuric acid.

The berry richness around the meteorites may have to do with abundances of Carbon, Iron, and Sulphur. Much like the biological and concretions on Earth. There are many inorganic ways to form concretions on Earth, I wonder how many inorganic concretions take place without carbon?

Do we know that Shelter island meteorite is a Stony Meteorite? If it's a Stony with inclusions like that.....it almost looks like a basalt, like basalts from Earth and Earth's moon....maybe one of Mars moons?

Some of the vugs or holes/voids in the iron-nickle meteorites on Mars might be due to the graphite inclusions having been burned away during entry in the atmosphere.....And having been weathered away from exposure to the martian atmosphere while sitting on the surface.

Certainly, any iron-nickel meteorites with graphite inclusions that were immersed in ground water for eons and then re-imerged onto the surface would show even more profound signs of chemical alteration.

I'm not convinced yet that these meteorites have been buried very deeply below the surface.

rpage. I'm not sure but doesn't there seem to be a silvery platish inclusion center left. or is that just a reflection. My thought was schreibersite.

Hey, Meteorite with graphite inclusions and sulphuric acid. Exfoliated graphite. The Martian's beat us to the punch by a few billion years. (My tongue is firmly in cheek).