"Carla Schneider" wrote in message
...
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.
There are no sand dunes like at gusev crater, because the spheres
prevent them from forming - is this possible ?
Could there be an other reason as density that prevents these spheres from
beeing
burrowed below the dust, maybe some electrostatic effect ?
If the spheres were very light the wind would blow them to dunes, if they
were heavy they would be buried below the dust, and there is a lot of dust
falling down if you wait long enough...

Actually, if there is a little soil movement activity, or if the spheres
are moderately dense, the movement of sand could be enough to keep them on
top. Try placing various sized objects in a container and shaking it- the
smallest objects will sift to the bottom and the larger ones will rise to
the top. These spheres could be going through a similar process, keeping
them on the upper layer of regolith.
I am of the idea that the spheres are from one of three possible
origins:
a) an impact in mud and the thin air and low gravity allow them to
solidify and fall back to the ground. The spheres might have been heated in
this sort of event, hardening them.
b) accretion from some geological process, perhaps through the presence
of water.
c) biological activity.

If a) is true, then you would expect that these spheres might be very
old, when it was more likely that water was extant on the surface. But,
permafrost theories also say that there might be occasional torrents when
impacts or other events release the water bound up in permafrost.
If b) is true, you might expect a broader range of sizes, although some
type of sorting process might also be at work. However, the look at the
layering of the rocks and the fact that spheres are embedded throughout
seems to indicate that they were present before the rock layer were formed.
If true, and if the rock is sedimentary (as it appears to be) then it leads
you to think that the spheres are resistant to the action of water and from
an earlier period.
Of course, some suggest that the spheres might have formed inside the
rock, but my gut feeling (not very scientific!) is that this should lead to
various concentrations of these spheres through the rock, not the sparse
concentration we see. In other words, some clusters of the spheres should
occur if they were formed in the rock.
If c) is true, then we have found what we are after. I notice that many
of the spheres have odd characteristics, such as "tapered" ends, or small
depressions. Could these be traces of some structure that an original
organism had?
Another possibility is that some outcrop of mineral had crumbled and
rolled downstream in the past, wearing away and producing smooth "pebbles".
Note that this can also produce a sorting mechanism, as the movement of
water and the mass and size of the stones could select out the ones in a
narrow range of cross sections and masses. If true, we could expect to find
other areas with lots of spheres of different diameter- larger or smaller
overall.
Note that I do include the effects of water in most of my ideas. Well,
enough rambling.

Cheers!

Chip Shults