On the Road Again - Again - Page 12

sol 1978 ( Aug 17, 2009 ) L256 7x2 study of cobble fields and ripples:

"This means something!" he exclaimed to his mashed potatos.

sol 1979 ( Aug 18, 2009 ) 2x2 MI montage of dodad on the edge of Siah's Swamp:

The "neck" of the hammer is about 100 microns thin and about 1.5 mm long.

This is not the most interesting critter in the swamp.

3D detail of the hammer neck:

I see NOTHING! I know NOTHING!

Thanks Horton, It looks to me like the doodads are the leftovers of pit formation. The projections are shaped like they are made up of the curved partial rims of old pits that have since grown and merged to form Siah's Swamp. It seems that once the active part of the pit has eroded "away from" (below?) a particular bit of metal that bit is "stranded" never to be eroded again unless its attachment to the meteorite is cut by erosion somewhere the process is still active. This argues against an erosion process that acts on the whole meteorite. The process must be LIMITED to the pits or the delicate projections could not form. This makes Block Island's submersion in ground water, soil or ice during erosion less likely, as the strict localization of the chemistry in pits is less likely with burial of the whole rock.

I think that the current surface conditions may well be eroding Block Island.

sol 1975 infrared / visible 3D of Siah's Swamp on Block Island:

Look's like after the APXS study of the darkish blobs on the top of Siah's Swamp Oppy will be on the move today.

Here is the "next drive direction" ( NW ):

Thanks for the comments Kye.

I tend to agree that weathering rather than chemical erosion shaped the dodads. Notice that several "hammers" in the "swamp" have broken away and are laying in the dark soil.

The circular "rinds" might be "bubbles" of slightly different minerals in the original magma that formed the parent body.

The APXS results on the darkish blobs should be quite interesting.

Horton, I think that the weathering of Block Island has been chemical. It takes place wherever the meteorite acquires a layer of dust or soil. The oxidation of iron in igneous rocks (and meteorites) should be a common process on Mars because there is strong oxidant in the soil and traces of moisture. Perhaps the oxidation is greatly accelerated by shallow burial. I'm a big believer in the slogan "The present is the key to the past." (Charles Lyell). This idea sometimes seems to have been abandoned by many of those studying Mars, who tend to think that almost everything that has ever happened on Mars could not happen under present conditions. I think that the chemical erosion of Block Island is still underway wherever the pits have trapped dust. The same is probably true of Gong Gong:

It is a very simple theory.

Kye's idea that Siah's Swamp is, if you will, a fractal extrapolation of pits is an interesting one. I can visualize sand-blasting (or perhaps dust-blasting) causing an effect like this. But if the meteorite has been sitting on the surface for 3 billion years, I would have expected such a process to have eroded it away completely.

I am wondering if the small "berries" in the pits could also be the product of erosion. Say, do the hematite berries contain a small amount of nickel as well as the hematite?

Er, if the meteorite erosion were iron oxidation, wouldn't the surface of the meteorite be rusted - and therefore mostly red or yellow or black?

The red and yellow on the meteorite seems mostly the ubiquitous fine Matrian dust. The black soil in Siah's swamp seems to be the dark dust ( Hematite and Magnetite?) found between the dunes.

I posted the infrared / visible 3D to hint at the chemical makeup of the stuff in the swamp.

Notice the white / red and yellow ( Infrared / Visible ( I/V ) ) pockets of dust on the surface.

The dust free surface is mostly yellow / blue ( I/V ) but Siah's Swamp seems mostly blue / red or blue / blue ( I/V )

Warning: the lower right corner in the Infrared is synthesized. I will redo when all the data is posted.

Sol 1961 ( Jul 31, 2009 ) R0 6x1 pan of dunes near Block Island:

with links to sol 1980 L256 montages of dunes. Even the "big guns" would not stitch the Pancam pans.

Much to my surprise Oppy just bumped a few cm to a new position on sol 1981 ( today ).

Looks like more study of the swamp is planned.

Kye. "The present is the key to the past." (Charles Lyell). This idea sometimes seems to have been abandoned by many of those studying Mars Yes true. And also by modern geologists studying Earth.
http://en.wikipedia.org/wiki/Uniformitarianism_(science).

I prefer Ager's quote The present may not be a long enough key to penetrate the deep lock of the past This is particularly relevant to Mars given the significant erosion evident planetwide that could not be a product of the current environment. The very fact that Block Island is intact is an indication that there was significantly more atmosphere to provide braking when it landed.

But why can't this be a combination of chemical weathering (acidic groundwater) preferentially eroding Fe and leaving holes and Ni rich filagree, with eolian abrasion refining the process. I guess we have a fundamental disagreement on this as under your surge theory BI cannot be old or it would have been buried under multiple surge layers, and I cannot see the miniscule chemical weathering you propose causing this amount of erosion in a short timescale.

Hortonheardawho. Post 225 coloured x eye is superb. What were the filters in the visible?

Regarding reply #228 where Horton said rust.

Stainless steel contains nickel, and this meteorite also contains nickel, as I understand. With a very low amount of oxygen this may prevent this meteorite not to rust?

And/or the pits may have been formed by rust and eroded because lesser nickel-amount?

--Armchair observer Mizar.

Of course it should been "prevent this meteorite to rust"...

Mizar, yes thats what i thought first after reading them wondering why there is no rust but shining metal surfaces. Sandblasting is a common procedure to get rid of unwanted metal coatings like >rust The rust protection of nickle bearing iron as of stainless steel is worth a thought as well

Mizar, yes thats what i thought first after reading them wondering why there is no rust but shining metal surfaces. Sandblasting is a common procedure to get rid of unwanted metal coatings like rust or old paint (on earth). We all know that sandblasting is the most common and liked explanation for erosional effects on Mars so why should it spare rust coatings on a meteorite???
The rust protection of nickle bearing iron as of stainless steel is worth a thought as well

sorry doublepost (first try cut out text)

> Of course it should been "prevent this meteorite to rust"...

Actually, it should be "prevent this meteorite from rusting."

OK. I take that to my mind.I hope that typo didn't mess up my reply #231 for US readers.

MPJ, thanks, good explanation.

serpens, re your 230, Yes, the present is not always the key to the past, but given that we are starting geological inquiry all over again on a new planet, Lyell's slogan should describe one important approach to the investigation. If we understood current processes better this would help us to know when they might explain what we find and when radically different past processes are a necessary part of the explanation. Sorry, but I see a lot of lazy-mindedness that leaps to the introduction of past Earth-like conditions at the drop of a spherule. The analysis of the Phoenix results was a welcome relief from this tendency, and I think that over time the balance will shift and the Mars we know will be called upon to explain more of past developments.

You write,"This is particularly relevant to Mars given the significant erosion evident planetwide that could not be a product of the current environment." I see that there has been very little erosion on Mars over the last 4 billion years because huge ancient craters are still present. I see a landscape dominated by impact and volcanism because there is so little erosion by gradual processes, almost ruling out a significant period of erosion under Earth-like conditions since the craters formed. (The persistence of the craters also makes it very likely that the sediments created by all that crater ejecta are still in-place where they came to rest.)

You wrote "The very fact that Block Island is intact is an indication that there was significantly more atmosphere to provide braking when it landed." I don't know how or when Block Island landed. Is there any reason to think that it arrived as a single piece close to its present size or could this be a fragment (or remnant) of a larger impactor? The absence of any crater suggests that Block Island has had a history at least a little more complicated than a solitary meteorite that landed at the present location. It could date from any time in Mars's history. I'm not sold on the idea that it is ancient. Just being on top is enough to suggest that it is not ancient at this location but because we know so little about current erosion nothing can be ruled out.

sol 1975 ( Aug 14, 2009 ) infrared view of Siah's Swamp:

The JPEGies are very annoying but some very interesting mineral differences are visible.

Come on JPL, release your own version.

It's really simple:

After a translation alignment of the R2..R7 filters, create a false color image using the color map ( R, G, B ) = ( max ( R5,R6,R7), R4, min ( R2, R3 )); Then do a square root transform on the Saturation channel; Then white balance the image to the dark soil in the swamp; Then tweak the contrast and brightness to bring out the full aroma of the herbs and spices. Serve while still warm.

sol 1979 ( Aug 18, 2009 ) 3D colorized detail spots on the "dodad":

The 3D is rotated 90 degrees right so "up" is to the right.

These little dark specks seem to be "stuck" on a vertical surface.

"Fridge magnets"??

Re my 237, Maybe the best reason to study the current processes is that the ancient history of a site would often be much easier to understand if the more recent history is known. If we had any idea how quickly the plains are eroding we could maybe use this to constrain the history of Block Island, but absent this knowledge, Block Island might have rested here for anywhere from thousands to billions of years. If we knew the processes that have moved the loose spherules maybe we could say if there is any significance to there present distributions, including elevated above the plain in Siah's Swamp. There are so few knowns on any scale of time. Any certain knowledge is valuable, but as Mark Twain said,"Its not what you know that gets you into trouble, its what you think you know that just aint so."