[X] My Assistant

[elakdawalla]

Curiosity has put more than 400 meters on the odometer and tosol (sol 56) she bumped up to a sand drift that we now know (via Twitter) is named Rocknest and will be the site of the first sample grab. In last week's press briefing, John Grotzinger warned that we will be here for "what seems like a very long time," 2-3 weeks. They will have to run several samples through the SA-SPaH (Sample Acquisition, Processing and Handling subsystem, pronounced "Saw-spa") and in particular CHIMRA (Collection and Handling for In situ Martian Rock Analysis, pronounced "chimera") in order to "clean" it of any remaining Earthly contamination with good Mars dirt before they deliver the first sample to SAM or Chemin. So this seems like a good place to start a new thread.

As usual, discuss stuff that happened through sol 56 in the previous thread.

[elakdawalla]

To me it looks exactly like flour. Completely dry, yet cohesive -- that's the nature of very fine-grained material.

[ollopa]

To me it looks exactly like flour. Completely dry, yet cohesive -- that's the nature of very fine-grained material.

"109:23:38 Armstrong: I'm at the foot of the ladder. The LM footpads are only depressed in the surface about 1 or 2 inches, although the surface appears to be very, very fine grained, as you get close to it. It's almost like a powder. "

And I've always thought he then said: "Now and then it gets very fine", which I always took to mean total powder (not the garbled transcript on ALSJ), all of which speaks to how fine this stuff can really get. (Yes, I know Luna isn't Mars)

[dvandorn]

And I've always thought he then said: "Now and then it gets very fine", which I always took to mean total powder (not the garbled transcript on ALSJ), all of which speaks to how fine this stuff can really get. (Yes, I know Luna isn't Mars)

Actually, I've discussed this with Eric Jones who compiled the ALSJ, and I'm comfortable with his interpretation that this sentence was "The ground mass is, uh, very fine." This was one of the items on Neil's observation checklist pre-flight, to describe the ground mass, and there is even a recording of Neil during a simulation saying of the sand that had been set up around the ladder on the training unit that "the ground mass is sandy, like beach sand," which of course it was.

Yes, Mars is not Luna, and you get very different erosion processes on a planet that has even a thin atmosphere vs. a moon that has none. In general, there is much greater variation in grain sizes in Martian soils as opposed to lunar soils. On the Moon, you either have very fine dust or rocks from cobbles up to boulders. Because grains in the Martian soil were transported by water (a long time ago) and since by wind, you get much more well-sorted soil fines and a lot of very fine grains deposited by the global dust storms. Add to this the continual impact mixing, and, well Martian soils are far more complex than anything you'd ever find on Luna.

-the other Doug