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AlexBlackwell
Iron Meteorites as the Not-So-Distant Cousins of Earth

--- Numerical simulations suggest that some iron meteorites are fragments of the long lost precursor material that formed the Earth and other terrestrial planets.

Written by William F. Bottke (Southwest Research Institute, Boulder, CO) and Linda M. V. Martel (Hawai'i Institute of Geophysics and Planetology)
posted July 28, 2006

Alex's Note: Is it me or is this release a week early?
The Messenger
There are some cool simulations in the article, and a demonstrated plausibility that iron rich meteors come from within, rather than from without. But I always raise a red flag when a theory is modified to accomidate a discrepancy between what is observed and what was expected. Sometimes, the best answer is that the basic theory, in this case the theory of planetary formation, is flawed.
Richard Trigaux
I read the article, and also followed some links, especially about datation of the meteorites.

It is really impressive thant in analysing a tiny sand grain, we are able to date events which happened before the formation of Earth!


The forming solar system was really an alien world, with a sun which was very different of what we know: pulsing, flaring (perhaps from a strong magnetic field). Also the accretion disk was probably not so calm that we can imagine, it had its storms and whirls, not just like the eternally still Saturn ring. Perhaps violent movements from near the sun were able to mix large parts of the accretion disk.

Also the presence of AL26 made solid bodies very different of what we know today. Bodies in the hundred kilometres range were able to melt, differenciate, and have volcanism. Perhaps bodies like Enceladus could be liquid (although this likely did not happened, as it formed much later, when Al 26 was nearby extinct).

Anyway it is clear that rocky chondrites never melt, even if the size of the parent bodies was in the hundred kms or more.


I agree with Messenger, and we should wait a bit before the hypothesis becomes a "know fact". But sometimes too, discrepencies between observation and theories can be explained with adding some bits of new facts like here.
PhilCo126
On the subject of meteorites:

The annual October-month Orionids meteor shower, named after their radiant, which occurs in the constellation of the hunter “Orion” produced a spectacular example with an amazing afterglow:
Orionids peak around October 21st. Typically the peak is 10-15 meteors an hour:

http://www.spaceweather.com/meteors/orioni...qq6is3ef43t8vi5

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