🚀 go-pugleaf

In article <C1E8C9.66y@well.sf.ca.us> Tom Van Flandern,
metares@well.sf.ca.us writes:

>     That's an interesting question, and I have some speculations about
>that myself, based on the synthesis of evidence for the explosion
>hypothesis in my coming book.  There are clues, such as the heavy neutron
>flux exposure, shock, partial melting, charring, and isotopic anomalies
>found in meteorites.  Meteorite evidence (especially from chondrules)
>strongly suggests an unspecified high-energy event, definitely not pre-
>solar system.  That's why the standard model calls for a nearby supernova
>event; but they can't quite get the details to work out.  I think the
>relatively enormous implied abundance of Al-26 is one of the chief clues
>about what really happened -- unless, of course, that hypothetical
>supernova contained at least a solar-mass worth of Al-26.

I have always subsumed collision into explosion when discussing this
problem. One expects that, given the heterogeneity of the asteroids (seen
by spectroscopy) and of the meteorites known, the asteroids and
meteoroids originated in a large, differentiated body - a planet. Richard
Shumacher's question got me thinking about explosion mechanisms, and I've
got a really wild one to cast out for potshots. Suppose that a small
planet differentiated gravitationally. What element(s) would be found at
the center? Siderophiles would make up the largest single phase, but they
are not the densest of metals. I don't know if uranium is a siderophile,
but if it isn't, it is denser than iron, and it could very conceivably
wind up at the center. A spontaneous chain reaction was once sustained in
an ore body in Africa, in an epoch when U235 was sufficiently abundant to
do it.

  * Perhaps a fission bomb could "happen" for a small enough planet. *

Well, there it is. Start throwing rocks at it.

Leigh