"Doug..." wrote in message
...
In article ,
says...

snip

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 they're ancient I wouldn't expect the spheres to show a diversity
of condition, some badly broken, some very pristine. The Spirit
site looks ancient, this just doesn't to me.



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.


Isn't soil on earth built by repetitive biological cycles? Wouldn't
we expect to see fossilized examples of the biology that built the
soil in the bedrock, sedimentary bedrock?



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?


When I look at this pic I can't help thinking we're seeing an
entire life cycle. Smudges of formation, mature forms and
broken forms.

http://marsrovers.jpl.nasa.gov/galle...P2953M2M1.HTML



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.



I really wish the rover would take a spin outside the crater to get
some good images of the surrounding field.



Cheers!

I think maybe there are some clues from the overhead imagery to the
formation of the units we're seeing on the ground. What those clues
mean, I'm not sure... *smile*... but there are clues.

I've looked at the enhanced version of the last DIMES images many times,
and I get the impression that something flowed across the flat plain,
from south to north. There are several features that look like very low
flow fronts -- they're roughly lobate and have subtle surficial
distortions that would indicate the bottom-to-top flow in reference to
the image.

These flow features don't look like the standard fluidized ejecta you
see around Martian craters. They look a *lot* lower, less relief. And
there's no conveniently-located craters (especially of the right size)
in the context views I've seen to have created such a pattern due to
ejecta.

So, there seem to be landform cues for very thin material flow across
the region. It certainly doesn't look like aeolian dust movement, it
looks like ground material flow. Now, whether this represents extremely
thin, runny magma or flooding by water or some other fluid. that's a
mystery, at present. But it ought to be taken into consideration when
trying to analyze the origin of the surficial materials...



I live along the Florida everglades, it's a 40 mile wide river of grass
following the flow of mostly underground water. I can't help but think
the soil, spheres and smooth flowing terrain around Opportunity is a result
of underground water or ice.


Jonathan

s





Doug