Re: Supernova Explosion May Have Caused Mammoth Extinction (Forwarded)

In article <yle_e.1151$l03.260518@xxxxxxxxxxxxxxxxxxxxx>,
Andrew Yee <ayee@xxxxxxxxxxxxxxxxxxxxxx> wrote:

> Lawrence Berkeley National Laboratory
>
> Contact:
> Dan Krotz, 510-486-4019
>
> September 23, 2005
>
> Supernova Explosion May Have Caused Mammoth Extinction
>
> BERKELEY, CA -- A distant supernova that exploded 41,000 years ago may
> have led to the extinction of the mammoth, according to research
> conducted by nuclear scientist Richard Firestone of the U.S. Department
> of Energy's Lawrence Berkeley National Laboratory (Berkeley Lab).

--snip--

> Firestone and West also uncovered evidence of an even earlier event that
> blasted parts of the Earth with iron-rich grains. Three mammoth tusks
> found in Alaska and Siberia, which were carbon-dated to be about 34,000
> years old, are pitted with slightly radioactive, iron-rich impact sites
> caused by high-velocity grains. Because tusks are composed of dentine,
> which is a very hard material, these craters aren't easily formed. In
> fact, tests with shotgun pellets traveling 1,000 kilometers per hour
> produced no penetration in the tusks. Much higher energies are needed:
> x-ray analysis determined that the impact depths are consistent with
> grains traveling at speeds approaching 10,000 kilometers per second.

So, just how did those near-microscopic grains make it through the
atmosphere and still manage to be moving at such a speed when they got
down to the bottom where the mammoths were? Why didn't they burn up like
all madern-day particles do?

Isaac
.