[meteorite-list] Another news piece on Holocene Start impacts

From: Sterling K. Webb <sterling_k_webb_at_meteoritecentral.com>
Date: Tue, 25 Sep 2007 19:14:48 -0500
Message-ID: <155201c7ffd2$40f23a60$a025e146_at_ATARIENGINE>

Hi,

    The problem is that nobody thinks comets
were recently formed. Instead, they are seen as
preserving an ancient primordial composition,
from long enough ago that supernova isotopes
would have long decayed away, no matter how
long-lived.

    A dust density high enough to coat comets
with enough of these isotopes to matter would
require an incredibly dense glob beyond anything
possible. No, dust is basically sneaky.

    In the long history of arguing about comets
and the likelihood of them being perturbed into
the inner solar system, few if any of those who
propose mechanisms have mentioned the dark
globules of dust, because the largest of them,
the Giant Molecular Clouds, can mass 1,000,000
solar masses, and the little globs I'm talking about
could easily mass 0.01 to 1.0 solar masses and be
thousands of AU wide.

    Think that would perturb a few comets? Many
of them have orbital velocities at distance of mere
centimeters per second. Dust drag alone could
change their orbits. Dust could be the most likely
perturbing mechanism; we don't know.

    Just like the Dustbowl days of the Depression,
the solar system has "dust storms." In fact, we're
having one right now:
http://www.space.com/scienceastronomy/dust_storm_030814.html

    Observations of dust globs are virtually impossible
(they're dark). All we can say about dust between the
stars is a) it's there, and b) it's lumpy in its distribution.
Lumpy means there will be globs.

    There is no 10Be in the Sun; it's not a supernova.
A very small number of the 2000 isotopes are only
produced in supernovae -- nothing else can do it. Such
isotopes are called "cosmogenic," meaning they're
not local boys, not from the Earth, not from the present
solar system.

    They are these: 41Ca, 36Cl, 26Al, 60Fe, and 10Be.
Radioactive, they decay away quickly. 10Be can be
formed by cosmic rays in theory. Takes a lot, though.

    If you find ANY of these isotopes lying around,
you can be sure they are recent, that they are from a
supernova, and if I were you, I would take a quick
look over my shoulder, so to speak.

    The particles are very tiny, would remain suspended
in the upper atmosphere for decades or maybe longer,
and reflect a measurable percentage of light away. Expect
a 5 to 7 degree C. drop for every 1% of sunlight lost.
(And of course, there's argument about the relationship
between sunlight and Earth temperature, too. Maybe only
3 deg. So, lose 10% of your light, drop 30 degrees? Not
a happy notion.)


Sterling K. Webb
-------------------------------------------------------------------
----- Original Message -----
From: "E.P. Grondine" <epgrondine at yahoo.com>
To: <meteorite-list at meteoritecentral.com>
Sent: Tuesday, September 25, 2007 5:40 PM
Subject: Re: [meteorite-list] Another news piece on Holocene Start impacts


Hi Sterling -

As always, thoughtful comment.

My first guess - Your supernova elements (10Be etc.)
were likely incorporated into the comet.

My next guess - specifically, Comet Encke.

My next guess - Comet Encke fractioned while
performing a plane change near the Sun shortly before
10,900 BCE.

An alternativve guess - perhaps that 10Be was produced
by impact of a comet fragment with our Sun. I seem to
remember a link of 10Be with ozone, but since my
stroke...
Received on Tue 25 Sep 2007 08:14:48 PM PDT