On Mon, 19 Nov 2007 22:39:10 -0800, johac
<jhachmann@remove.sbcglobal.net> wrote:

In article <4cv3k3lc6hgss19jrl8345ag4cgpua25nq@4ax.com>,
Michael Gray <mikegray@newsguy.com> wrote:

Evidence of Oldest Oxygen Discovered in Western Australia.

(Australiasian Science, Vol28, No 10)

"Evidence of atmospheric oxygen has been found in 2.5 billion-year old
rocks.
The rocks were formed 50-100 million years prior to the Great
Oxidation Event, in which the Earth's atmosphere first became rich in
oxygen.
The finding came as a complete shock to the NASA scientists who
discovered it.
Rocks that old are rare but can be found in the northern parts of
Western Australia, particularly when drilling 1 km into the Hammersley
Basin, as occurred in this case.
Previous studies have found an absence of oxygen in the atmosphere
prior to a sudden increase to levels similar to today.
"We seem to have captured a piece of time during which the amount of
oxygen was actually changing - caught in the act, as it were," says
A/Prof Ariel Anbar of Arizona University.
The team did not actually recover oxygen itself. Rather, they looked
for molybdenum, rhenium and uranium, as the quantities of these all
depend on oxygen present in the atmosphere when the rocks were formed.
The evidence casts light on a major debate regarding the early history
of life.
One theory holds that the Great Oxidation Event occurred when
ancestral plants first began photosynthesismg in large quantities.
The alternative theory is that mass production of oxygen had begun
some time before, but a surfeit of reactive chemicals in both the
atmosphere and
surface rocks quickly eliminated any oxygen released.
Only when these materials had been used up could the atmosphere become
rich in oxygen.
"Our findings strengthen the notion that organisms learned to produce
oxygen long before the Great Oxidation Event. and that the rise of
oxygen in the atmosphere ultimately was controlled by geological
processes," Anbar says.
"Studying the dynamics that gave rise to the presence of oxygen in the
Earth's atmosphere deepens our appreciation of the complex interaction
between biology and geochemistry," said Carl Pilcher, director of the
NASA Astrobiology Institute at NASA's Ames Research Center.
"Their results support the idea that our planet and the life on it
evolved together."
"

Nice article. I found this one a little while ago:

http://tinyurl.com/2fqnxs

It appears to cover the same ground. It links the appearance and
scrubbing of oxygen to volcanic activity.

Thanks.
I had not seen this report before.

I must say that I find this subject fascinating, partly for the same
reason that creationists are in raptures. It is all about what and how
we were started.

One of my sisters runs the huge station (ranch) that includes the Jack
Hills in W.A. where the worlds oldest rocks are to be found (tiny
zircons), and regularly cooks for the cadres of scientists who visit.
Imagine the terrain to be a combination of Death Valley & Mars.
The Western Australian geology appears to be conducive to accessible
preservation of somewhat aged rocks, to stretch understatement to
breaking point.

And, (as I have alluded to in other posts, in response to claims that
detection of free oxygen on extra-terrestrial planets is a sure sign
of life), we are often wrong.
Unlike the creationists who are always wrong.