"Timothy Demko" wrote

The interpretation of the bedrock as a volcanic ash, even an altered
ash, has not yet been supported. In fact, the presence of cross beds:


http://www.jpl.nasa.gov/mer2004/rove...s/image-1.html

suggests that even if it is an ash, it's been transported by some sort
of traction currents and is not a simple air fall.

Cross beds I take it simply means that the layers are not always
parallel--they diverge and converge sometimes? If so, how about this photo
of the effect of "volcanic bombs":
http://www.geo.hunter.cuny.edu/~cwang/impacts.jpg Wouldn't the layers in
that photo be a simple air fall?

It's interesting that last week Squyres said there were three main theories
for the origin of the spherules: lapilli, solidified volcanic material, or
concretions. He said the lapilli idea was "fading fast" on the logic that
they look to be of a different material than the matrix. There has not been
a word in the press conferences since about any progress along those lines.

However, an interview with Ronald Greeley, Ph.D., Regents Prof. of Geology,
Arizona State University Dept. of Geological Sciences, and one of the 7
Chairs of the Science Operations Working Group (SOWG) for Spirit and
Opportunity, Tempe, Arizona this Wednesday was a bit surprising. When asked
about the spherules, Prof. Greeley said:

"The general consensus seems to be centering around two possibilities:

"First, that they are what are called 'accretionary lapillae' * that is a
volcanic feature that forms in certain kinds of eruptions in which material
is added to a small nucleus like a little dust grain and these form these
spherule masses."

"Secondly, they could be some kind of precipitate * perhaps from water. In
additional findings, there are some minerals that have been identified in
the infrared that would suggest the presence of water since they form in
water. In particular, if this is a volcanic terrain that we are looking at,
the presence of these minerals might suggest this was a hydrothermal area."

What--lapilli are fading back in and the other two theories (magma &
concretions) are gone, to be replaced with "some kind of precipitate"?

Continuing:

IS THERE ANYTHING FROM ANY OF THE SPECTROMETERS OR ALPHA X-RAY THAT INDICATE
WHAT THE SPHERULES ARE MADE OUT OF?

"We can't measure the spherules individually * they are too small. We have
to get the chemical and mineralogical signatures for the whole mass and then
try to deduce what would be the composition of the spherules."

SO TODAY AS WE SPEAK ON FEBRUARY 11, IS IT STILL UNKNOWN WHAT THE SPHERULES
ARE MADE OUT OF?

"Yes * that's a work in progress."

....

AND ALL THIS IS ADDING UP TO A QUESTION ABOUT WHETHER THE PLACE WHERE
OPPORTUNITY CAME DOWN ORIGINALLY MIGHT HAVE BEEN HOT MAGMA COMING UP TO THE
SURFACE IN SOME KIND OF VOLCANIC ACTIVITY? OR AT LEAST HOT SPRINGS?

"Yes. The evidence is sort of pointing towards the presence of a hot
environment * hot for some reason and that's under debate right now.
Volcanic activity, magma close to the surface, is one possibility."

....

THE BIGGEST SURPRISE RIGHT NOW HAS BEEN THE HIGH AMOUNT OF SULFUR IN THE
BEDROCK?

"That was a surprise, yes. The measurements that have been made there
suggest there is a very high percentage of sulfur present in the material
and that there are these spherules that have been seen and reported earlier,
those are still very curious features."

"Such a high percentage of sulfur (in the bedrock) is unusual and this is
what leads some folks to consider the volcanic origin (at the Martian
bedrock), or at least volcanic processes to be involved. There are some
minerals that have been identified in the infrared that would suggest the
presence of water since they form in water. In particular, if this is a
volcanic terrain that we are looking at, the presence of these minerals
might suggest this was a hydrothermal area and sulfur is a component of such
environments."

SO THE BEDROCK MIGHT BE, IF WE WERE COMPARING IT TO THE EARTH, MIGHT HAVE
HAD AN ORIGIN SIMILAR TO SAY YELLOWSTONE NATIONAL PARK?

"Yes, to some parts of Yellowstone, that's right."

http://www.earthfiles.com/news/news....tegory=Science

Joe