[meteorite-list] Earth's Surface Transformed by Three MassiveAsteroid Imp...

[MexicoDoug at aol.com]

Hola Tracy, since moon rocks are up to 3.8 or  4.0 billion years old or maybe 
someone can correct that upward, the theory it is  commonly "over 4 billion 
years ago".  I don't know if more precision is  available, but the crust would 
have formed after the collision so we are looking  at after Earth formation, 
say 4.4 billion years ago, to before Moon crust  formation 4.0 billion years.  
Averaging it out for no particular reason  give 4.2 billion years ago for the 
Moon coalescence - plenty before  3.2 billion years, though who knows about 
"over 3.2 billion years" referenced in  the news-short, at first glance...
Saludos, Doug

Tracy L.  wrote:
>Someone please refresh my memory -- about how long ago was the  theorized 
>impact that tore loose the Moon from the proto-Earth?   This sounds like it 
>happened after the Moon had coalesced enough to be a  single solid.

>Tracy Latimer

>From: Ron Baalke  <baalke at zagami.jpl.nasa.gov>
>To:  meteorite-list at meteoritecentral.com (Meteorite Mailing List)
>Subject:  [meteorite-list] Earth's Surface Transformed by Three 
>MassiveAsteroid  Impacts 3.2 Billion Years Ago
>Date: Fri, 5 Aug 2005 11:47:36 -0700  (PDT)
>
>
>http://info.anu.edu.au/mac/Media/Media_Releases/_2005/_August/_050805glikson.
asp
>
>Earth's  surface transformed by massive asteroids
>Australian National University  media release
>August 5, 2005
>
>A cluster of at least three  asteroids between 20 and 50 kilometres
>across colliding with Earth over  3.2 billion years ago caused a massive
>change in the structure and  composition of the earth's surface,
>according to new research by ANU  earth  scientists.
>


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