On the Road Again - volume 4 - Page 5

Hort,
The 'white' dust is typical of ground-up rock material, if the minerals are silicates. More subtle shades result depending on how much iron and magnesium is present (pyroxenes and amphiboles), becoming more pale green. Feldspars and quartz give whiter dust.

The surface of Marquette that Peck Bay is on appears to me to be a fracture plane or joint that has undergone "weathering" or alteration. The possibility is that it has undegone alteration from hydrothermal fluids-- this would ties in to the idea that this is a buried crustal gabbro that has been exposed to groundwater and is undergoing serpentization. The appearance of the ground-and-brushed section suggests this. I'm not a hard-rock IG-MET-PET type, so I'm awaiting to hear what experts have to say...

--Bill

Yes, let's hope we can free Spirit. Winter is getting closer every sol and the little lady does not have enough tilt to make it safe. We are working on it and you should know all the incredible effort that's done to make this happen. We have lots of fight left so chin and sleeves up !!!
Have a great day all - Nathalie

By the way, a showel would help too...Nath

From Opportunity update sols 2111-2117:

The alpha particle X-ray spectrometer (APXS) measurements of Peck Bay 2 were significantly different than the pre-grind measurements. Based on these results, Opportunity is spending another week at Marquette Island for more observations of Peck Bay 2.

So the APXS results are confirming that the crust of marquette is significantly different than the rock interior.

The rock is described as "very hard"

Hort--

And that compositional difference would further suggest the alteration zone along a fracture. Depends on what the compositional changes are-- whether it is added to or taken away from. Frequently hydrothermal fluids deposit material-- a quartz- or calcite-filled healed fracture is the classic example. We'll see how the APXS numbers turn out, but thus far this duck does not have chicken feets.

Forgot to mention earlier-- those PanCams that show the fracture(s) on Marquette were from Sols 2087 & 2089.

--Bill

sol 2119 ( Jan 9, 2010 ) daytime meteor over Meridiani???:

See image comments for reasons why I think this is a meteor and not a CCD cosmic ray strike.

2087 and 2089 views of the fracture running through the Peck Bay RAT area. The fracture is visible in the lower bottom area of the MIs - especially in the colorized MI panorama animation.

It is also curious that most of the, er, curious short linear features not parallel to the frature are near the fracture.

Do a Google Image search on "serpentinized gabbro thin section" for some interesting images.

Let me see if I can get this image to work...

Good find on the bolide.

--Bill

Ah, serpentine can be short, linear features.

Thanks Bill for the image link.

I was mightally annoyed that the sol 2117 pancam images taken of the brushed RAT hole were a full frame highly compressed image rather than a 1/4 frame lossless image of just the hole. And the time of day was not exactly the same so the shadows are "wrong" too.

As a result the colorized MI does not have much spatial or color resolution. I prepared a 4X sub-image of the RAT hole to illustrate the point, but thought it would be useless griping to post it.

Sometimes - hell, most of the time - I just "don't get" what the mission planners are doing.

The olivine and pyroxene in gabbro (or a periodotite or a mafic rock) are altered in the presence of water to a serpentine (or properly, the serpentinite family of minerals), which has the form of long, thin fibers. Asbestos is an example of the class of mineral.

I'm puzzled by the L1 PanCam panorama we got today. Rover equivalent to twiddling thumbs?

--Bill

Here is the colorized Extended Depth of Field ( EDF ) MI panorama of the brushed RAT grind. I have processed it to bring out detail on the grind surface.

The L1 images posted today were part of a full 360 pan taken on sol 2111 ( Jan 1, 2010 ).

Usually the pan is 1/2 reduced size, but because this is an important site, full frame images were done. I posted parts of the panorama earlier and will do the whole thing when all the data is posted.

I am still curious about this whole "serpentinization" process.

Why does the reaction proceed in such a way as to create fibrous material???

Perhaps the fibers are filled tunnels dug into the rock by microbes in the surrounding water looking for a good meal???

Perhaps many ( if not all ) of the short fibers we see are serpents from Mars Garden of Eden.

( Sorry, sorry. I just had to make the pun. )

er, I realized I made a processing mistake when I colorized the RAT grind MI pancam, so I redid it. ( I colorized the MI with a pancam false color image and then white balanced rather than colorize the MI with an already white balanced pancam image. )

Here is a colorized MI of the grind made from the sharpened average of the 4 best focused images after translation registration. Er, it's a little green - maybe it really is?

"Why does the reaction proceed in such a way as to create fibrous material???"

That is the way it is. Seriously. The reaction byproduct of olivine + water is a mineral with a fibrous crystal structure. It just happens that way. I'm sure that a geochemist could look at the crystal or molecular structure of an olivine and a serpentine mineral and figure why the reaction with water gives that byproduct.

I take it on faith.

Not terribly surprised that the revised RAT colorization is a biy greenish. The olivine group of minerals (and the alteration products) are characteristically yellowish-greenish.

Here ia a nice diagram of the alteration processes:

--Bill

The fibrous coating on MI looks similar to Chrysotile or "white asbestos," which is a serpentine mineral. Apparently the crystals can form as follow tubes or cylinders, which tend to become filled by other materials.

There is an interesting article in the current Scientific American magazine about the putative nanobacteria
, which suggests that crystals as a primitive replicating system may have been involved in the origin of life.

Er, what?:

I would be interested in a soil guy's take on this animation.

I have no explantion for what happened between 13:05:12 and 13:06:34.

This sort of massive change to the SOD has been seen before - but I could never convince myself that something the rover did did not trigger the response.

I will await other's rsponses before I spout.

Hort

Yes it has happened before. I'll check my images to see if I can find the instance where they made an image of a ratted hole, then returned after about 2 days to reimage it. The hole was now full of "gunk" as NASA referred to it. The explanation was that wind movements in the interim period had somehow filled the hole with that gunk. I was not convinced but everyone else on the blog accepted the NASA explanation. I thought as I think now that wind had nothing or very little to do with it and that perhaps absoption / release of moisture by the SODs was the key.

This one is very similar.

Winston

Here's the gif of an oppy image of a rat hole between sol 546 and 549

http://www.smugmug.com/gallery/705090_JEQRs#153425717_6BC8M-O-LB

http://www.smugmug.com/gallery/705090_JEQRs#153425717_6BC8M-O-LB

Winston

Winston; This stuff had to be initially quite hot created by the grinding action.

As you point out, couldn't the physical changes be the result of expansion caused by absorption of moisture as it cooled?

I am curious about what happens at night near the surface of Mars.

All the motion seems to be more or less in the same direction (towards top left). Wouldn't expansion caused by absorption of moisture tend to be in all directions? The directionality seems to support wind as the cause. Or gravity if the movement was in a downward direction (which I don't think is the case here).