Grinding Wheel Profile

This graphic dubbed by engineers as the "Grinding Wheel Profile" is the detective's tool used by the Opportunity team to help them understand one of the processes that formed the interior of a rock called "McKittrick." Scientists are looking for clues as to how layers, grains and minerals helped create this rock, and the engineers who built the rock abrasion tool (RAT) wanted to ensure that their instrument's handiwork did not get confused with natural processes.

In the original microscopic image underlaying the graphics, engineers and scientists noticed "layers" or "scratches" on the spherical object nicknamed "blueberry" in the lower right part of the image. The designers of the rock abrasion tool noticed that the arc length and width of the scratches were similar to the shape and size of the rock abrasion tool's grinding wheel, which is made out of a pad of diamond teeth.

The scrapes on the bottom right blueberry appear to be caused by the fact that the berry got dislodged slightly and its surface was scraped with the grinding pad. In this image, the largest yellow circle is the overall diameter of the hole ground by the rock abrasion tool and the largest yellow rectangular shape is the area of the grinding wheel bit. The smaller yellow semi-circle is the path that the center of the grinding tool follows. The orange arrow arcing around the solid yellow circle (center of grinding tool) indicates the direction that the grinding tool spins around its own center at 3,000 revolutions per minute. The tool simultaneously spins in an orbit around the center of the hole, indicated by the larger orange arrow to the left.

The grinding tool is 22 millimeters (0.9 inches) in length and the actual grinding surface, which consists of the diamond pad, is 1.5 millimeters (0.06 inches) in length, indicated by the two smaller rectangles. You can see that the smaller bottom rectangle fits exactly the width of the scrape marks.

The grooves on the blueberry are also the same as the curvature of the arced pathway in which the grinding tool spins.

By overlaying appropriately scaled representations of the rock abrasion tool schematics, the evidence reveals a strong indication that the scrapes on the blueberry were induced by the tool, rather than caused by some natural geologic process.

The two rectangular boxes in the lower left and upper middle parts of this image are "drop outs," where the data packets inadvertently did not make it back to Earth during the initial communications relay via the Deep Space Network antennas. The missing data packets should be resent to Earth within the next few days. Just above each of the black "drop out" rectangles is another rectangular area filled with a cluster of smaller rectangles in different shades of gray, which are image compression artifacts.

The rock abrasion tools on both Mars Exploration Rovers were supplied by Honeybee Robotics, New York, N.Y.

Image credit: NASA/JPL/Cornell/US Geological Survey

Strange orange lines on Mars.
Maybe paintings of old Marssians. Any Idea?

Did the Oportunity rover grind deep enough to grind out the surface bumps of the rock in the above image ( as Spirit did to Adirondack ) or is this rock very porous/soft and doesn't lend itself to forming a nice smooth surface when abraided? The blueberries appear to be dense/hard and polish to a nice flat surface.

Well, yeah, the surface bumps are gone. I'm quite sure the diamond grinder removed everything above -- what was it? -- 0.16 inch, save the loose dust and grit it left behind. I imagine the material is rife with voids, with a compostion of small particles cemented together, and the apparent "chicken footprints" going relatively deep into the rock. Maybe the cementing is weak enough, too, to make some particles get torn out instead of ground down, so the result is very little truly flat surface.

I don't think this rock would make very good kitchen countertops -- not that I'd turn down a set if NASA offered.

Oh, I meant to mention a clue to the weak cementing: that scratched spherule apparently rotated within its socket. That's really a quite a bit of surface area and I think a paste of flour and water might even have held that spherule in place better than whatever cements this Martian rock.

This bedrock appears to be more like dried mud when compared to the hardness of the blueberries.
I'm surprised at the cohesiveness of the dust. Since the grinding site itself is probably not level and lacking in moisture, I would think that gravity and wind should have carried most of the excavated material away.
Has anyone heard anymore about what the spectroscopic readings have revealed about minerology of the blueberries and bedrock? I think the blueberries contain the iron and the soft bedrock is made of salt, mud, and a mixture and calcium containing minerals ( think dried lake bottom ).

If you look at the before and after - it apears that the structure (Cemented channels) that the blueberries sit in is harder then the surrounding sediment - that is why it sticks out - so it is harder than what ever is eroding it - however it also appears softer than surrounding rock when the rat tool works it. The blueberry itself seems to be the almost same hardness as the rock(to the RAT). All this is very contradictory. Heck - it is another planet - maybe no earthly analogue. I've been thinking oolites, maganese nodules, heck go for broke - fossilized Martian mud truffles.

Spectroscopy on blueberries:

I thought I heard in the Thursday press conference, in response to an early question, that there was a trough/peak (I wasn't listening hard) at mumble-hundred nm that had them thinking (I listened harder) of kinds of iron oxides. But, they were not committing, just speculating.

Slope of RAT'd hole:

The rock McKittrick didn't exactly present a vertical face for grinding. You can see the hole the RAT made, between Opportunity's front wheels, in this picture:

[link]

You can see the planned RAT, and get an idea of the rock's shallow slope, in the 3D modeling image:

[link]

It doesn't look like gravity would remove much of the ground rock dust.

Here is a Stereo (Crossed eye) view of the area ratted on Opportunity sol 30.

The images have been rotated clockwise 90 to emphasize the very slight stereo separation between the two images. The sun is in the upper left in this view.

I can't relate any feature in this image to the ratted area! Are we sure this is the pre-rat area?

Interesting pictures of the RAT are at:

[link]

It will give you an idea of what those crazy orange arrows mean in the lead article in this thread.

hello dear marswhiz posters;
I have a question regarding the origin and distribution of the spheres. A biological origin of them ist rather unlikely, origin from mineral concretions would seem strange to me, since the spheres seem quite well rounded and of same size (should show a variety of shapes and sizes in this case). So it seems most likely, that they formed from sprayed molten lava or rocks while an impact and dropped into the mud, sand dunes or whatever turned into these layered rocks.

But, help me:
Is there evidence of a horizontal distribution of the spheres. Volcanoes and Impact events should differ strongly in intensity over time. So there should be layers with lots of spheres and in between layers without spheres, representing quiet times of sedimentation. But my impression, correct me, is that the spheres are distributed in quite statistical fashion through the layers of the outcrop. Besides, glass beads should not live long, at least under "earth" conditions, the glassy matrix should easily be subject to recrystalisation processes and turn into dust.
So all theories i heard of seem unsatisfiyng.

besides, what the heck shall be theses chicken footprints be? voids? eroded crystals, that were growing across the layers? rifts in shrinking, drying mud? Sth, involving a process of frozing an thawing?

I would be glad, if you might help me out here, thak you!!

I hope the link I have pasted into the URL form box will take you to the colored El Capitan picture.

It looks as though the spherules are present to some degree through all the layers visible. Same layers contain more, and others less. If meteor impacts were the source of the spherules, meteors would have to impact and create some spherules, these spherules would have to be burried by some method, more meteors would impact, more burial, etc. etc. The apparent vertical distribution seen, would imply a very long and steady rate of impacts and burial.

On the other hand, sedimentation over a relative brief period and later concretion could explain the vertical spherule distribution. But sedimentation and concretion processes require the presence of some kind of liquid.

I have no likely explaination for the 'chicken tracks'. Could they result from freezing and thawing of mud? Worm trails? I have heard that in the Arctic, salt water will start to form ice crystals with the salt being concentrated into unfrozen brine. If the temperature continues to drop, the ice crystals will continue to freeze more water from the brine and thus concentrate the brine further. If this is true, maybe the voids are 'fossil'remains of water ice crystals that have sublimated over the eons into the cold, dry Martian atmosphere.

By the way, according to msnbc.com, Nasa is supposed the have a 'VERY IMPORTANT' news conference tuesday regarding Mars findings.

I can't wait!