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Re: (meteorobs) Iridium from Impacts vs Volcanism
wayne>>Meanwhile, look at asteroids, comets, and the meteoroids that result.
If
they are smaller bodies, they do not heat up enough to differentiate, so
these metals are spread throughout the material. And, as we see from iron
meteorites, at least some objects that are the source, became large enough
to create an iron core, which was liberated when the object(s) were smashed
to smithereens. These would of course have the highest concentrations of
such metals.<<
I've read somewhere that iron meteorites don't need to originate from a
parent body that was large enough to differentiate and have an iron core.
I've believe it indicated something to the effect that during the solar
nebular phase there was some strong magnetic fields at certain distances from
the primordial sun. These magnetic fields interacted with the small
planetismals and created a sort of electric current that generated heat to
cause melting and differentiating. Planetismals located where the most
electrial current is generated was subject to the most heating. Planetismals
a little further from this area doesn't generate as much heat and ends up
with less heating and differentiation. At least this is how I visualize it...
Something similar to what is happening to Jupiters moon Io now....except it
is a little bigger object.
wayne>>30 years ago, when we were striving to reach the moon, only a young
geologist named
Eugene Shoemaker believed the craters there were from impacts...almost
everyone else though they were volcanic. <<
Really? 30 years ago I didn't get this impression? I thought it was common
belief then that most craters were from impacts with some volcanic activity
here and there? I recall seeing a series of very amazing photograph from a
lunar orbiting probe taken back in the mid 60's. I believe it was in Time
magazine and I think I still have it stored away somewhere? Anyhow in the
photograph, the caption of one of the photos was describing volcanic cinder
cones. Knowing what I know today and recalling the images, I still think they
are cinder cones or something similar and volcanic.
GeoZay
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