Carla Schneider wrote:
Ron wrote:

[...]

The plan for sol 20, which will end at 8:20 p.m. Friday, PST, is to
do a "touch and go," meaning Opportunity will touch the soil with its
instrument arm around the outpost area Charlie, then stow the arm and
drive. It will head for an area of soil that the rover's miniature
thermal emission spectrometer indicates is rich in hematite. Over the
following few sols, engineers intend to use one of Opportunity's wheels
to spin into the soil and "trench" a shallow hole so scientists can check
what's below the surface early next week. Knowing more about the hematite
distribution on Mars may help scientists characterize the past environment
and determine whether that environment provided favorable conditions for
life.


Any guesses what they will find in the trench ?
I bet they will not find a lot of hematite below the surface,
because it is concentrated in the spheres and the spheres are only
lying on the top.

The spheres are not only lying on the top -- they are the main
constituent of many of the thin layers. Most of the microscopic
images show layers of small, tighly packed (though not clear how
firmly cemented) spherules. Some, it looks to me like mostly the
somewhat larger ones, are weathering out. It looks to me like
most of the outcrop -- at least the one they have imaged most
closely -- is made of the spheres plus matrix of much more
fine-grained material, which (presumably) when it weathers turns
into the fine sand in which the loose spheres lie.




--
_____________________________________
Richard I. Gibson, Gibson Consulting
Gravity-Magnetic-Geologic Interpretations
http://www.gravmag.com

Education Director, World Museum of Mining
http://www.miningmuseum.org

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