Cape York - The "Lakelands", Starting sol 2703 Options

[djellison]

That is what I initially thought but decided that the surface looked "too glassy" to be deeply weathered. I imagine that the actual criteria for hardness of the rock would be Oppy's RAT engineering telemetry, such as the current draw or the grind time of the operation, and not amount of cuttings.

--Bill

They have indeed done just that - infer hardness based on RAT performance. If you remember back in the early days - a berry was picked up mid-grind as a spike, and later caused the RAT to stall.

[Jam Butty]

Tribulation L257
sols 2718 & 20

[CosmicRocker]

Does that mean it is not basaltic?

While fresh basalt is a pretty hard rock, the softness doesn't rule out basalt. If basalt is weathered or altered, especially in the presence of water, it can become quite soft. I think the light color of this rock pretty much eliminates it from having an overall basaltic composition, though the dark, angular rock fragments embedded in the breccia could very well be basalt. The minerals of basalt are very dark in color.

The dark blocks of a different breccia lying on top of the nearby hill look very much like basalt. The geology here is fascinating. I can't wait for Opportunity to explore more of Cape York and send back more pictures.

That is what I initially thought but decided that the surface looked "too glassy" to be deeply weathered. I imagine that the actual criteria for hardness of the rock would be Oppy's RAT engineering telemetry, such as the current draw or the grind time of the operation, and not amount of cuttings. ...

Bill: You are right about the RAT telemetry being the ultimate measure of the rock hardness, but it will be a while before that data will be available...and I won't know how to interpret it when the data is released. My comment on the rock's softness was based solely on depth of the grind. We know that the remaining life of the RAT is a resource the team is trying to conserve for the most important scientific targets, so I would be surprised if they instructed the rover to grind away on this first target without limits. To me, it looks like other soft rocks they have ground into.

[CosmicRocker]

Tribulation L257
sols 2718 & 20

I really appreciate that you post important information like the sol and the filters used in your images. Some people often neglect to provide that information, and that makes it difficult for others to follow up.

[Bill Harris]

For sure. The surface we are looking at is the product of 3 bln years of deposition, weathering and erosion and each rock fragment tells a story. Some of these rocks are ejectite'd impactites.

There are going to be many profound papers generated from the data at this site.

I'm sure that they know precisely what the "hardness" of the rock is from the engineering data, which we in the p'nut gallery are not privy to. Just as they have an idea what mineral is represently by every "RGB color" we see in the Pancams. Even with seriously degraded IDD parts, geologists have made do with scratch plates, acid bottles and rock hammers and calibrated "TLAR"eyeballs for decades for mineral identification.

The first thing they are doing on Sol-2722 ("today") is making a FHazcam assessment of the RAT teeth("frhaz_RAT_bit_check_subframe") and getting ready to do chemistry ("front_haz_idd_apxs_doc").

Having snagged the post-grind Pancams of Salisbury1 from the 0:35 Data Express and done my preliminary oooh-ing and ahhh-ing, I'm hitting the sack again... yawnn

--Bill

[Fran Ontanaya]

the dark, angular rock fragments embedded in the breccia could very well be basalt. The minerals of basalt are very dark in color.

Could they be obsidian in a perlite matrix?

[Bill Harris]

Couldn't get my beauty rest, I ended up working on the new images. Note the implication of different mineralogy-- the RAT cuttings are purplish or gray, instead of the usual ochre or blue.







--Bill

[mhoward]

Here's an attempt at a color flicker pair. L257, R21(synthesized green), animated GIF, anaglyph

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[djellison]

All that different to earlier grindings?

http://marsrovers.jpl.nasa.gov/gallery/pre...1-B041R1_br.jpg

[Bill Harris]

Good example. This is the first RAT done in Eagle Crater on Sol-36.

More difference than 21km and 2+ Billion years...

--Bill

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[Phil Stooke]

It would be interesting to compile a sequence of images showing the RAT holes at different dates - right now we are getting that small circle inside the larger one, which was not seen in the first hole. When did it start looking like that?

Phil

[centsworth_II]

... right now we are getting that small circle inside the larger one, which was not seen in the first hole....

My guess is, that's what happens when the two grinding wheels are not rotated around each other.

"Two grinding wheels rotate at high speeds. These wheels also rotate around each other at a much slower speed so that the two grinding wheels sweep the entire cutting area."
http://marsrover.nasa.gov/mission/spacecraft_instru_rat.html

[M@!]

It may be a result of the damage to the RAT brush. At the very least it's not new. I see similar circle-within-a-circle patterns in this RAT hole from Sol 2513.

[Bill Harris]

The circle-within-a-circle is how the RAT operates. The carbide cutters are on an arm that moves around in a cyclical motion. You can see how it works in the images at the Athena site (the link to the "Honeywell Robotics" RAT site is dead):

http://athena.cornell.edu/the_mission/ins_rat.html

After the grind is done the brush is supposed to clear away the cuttings but the brush is kaflooey...


You can get an idea of how well it works from this animation:

http://images.spaceref.com/news/2004/rover.armspin.mov


--Bill

[Phil Stooke]

Interesting responses! But that's why it would be interesting to collect RAT images throughout the mission to see how the holes have varied in appearance. Anyone? (I don't have time right now)

Phil