[meteorite-list] Mars Rover On NPR News Today

[Sterling K. Webb]

Hi,

    NPR radio just did (4:20 pm CDST, 5:20 pm EDST) a nice story about
the Rover "escape," interviews with Dr. Squyres, lots of intelligent
questions and comments, about five or six minutes long.
    They asked a lot of questions about the "strange" sand and its
characteristics.  What that came down to was "slippery," vastly more
slippery than any of  the simulated materials that were tested on
Earth.  There is a lot of curiosity about what this stuff is and why its
coefficient of friction is so incredibly low.
    Sand is not slippery. However fine and fluid, it is gritty.  Try
pouring sand into the moving parts of a machine; it will not work as a
lubricant.  Quite the opposite.  Rock dust or rock flour is not
slippery.  Most rocks are not slippery in any sense.
    The only mineral surface (that I could think of, not being a deep
thinker about rocks) that could be considered "slippery" are the planar
surfaces of a variety of perfect crystals (which makes no sense for
something that looks like sand) and one other:  glass.
    An impact glass layer consisting entirely of micro-spheroids, say,
roughly the size of sand grains or pehaps slightly smaller, would be
very slippery stuff indeed, especially if their surfaces were not
abraded nor grossly weathered nor de-vitrified and their shapes
reasonably regular spheroids.
    Imagine a fluid of miniature very smooth glass ball bearings,
Assuming the load was not sufficient to shatter the individual
spheroids, I think it's a good candidate for the "slippery" mystery.
    The nearest analog on Earth would be a fresh layer of
micro-tektites, such as are found, although very degraded, in ocean
sediments, but Mars seems to preserve minerals well (like that olivine).

    Good idea? Bad idea? Jeers? Cheers? Opines?


Sterling K. Webb
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Ron Baalke wrote:

> Opportunity's next task is to examine the site to provide a
> better understanding of what makes that ripple different from
> the dozens of similar ones the rover easily crossed..
>
> "The first thing we're going to do is simply take a hard look
> at the stuff we were stuck in," said Dr. Steve Squyres of
> Cornell University, Ithaca, N.Y. He is the principal
> investigator for the Mars rovers' science instruments.