[meteorite-list] Neutron and Proton productioninhyper-velocityimpacts

From: Sterling K. Webb <sterling_k_webb_at_meteoritecentral.com>
Date: Fri, 28 Dec 2007 21:46:05 -0600
Message-ID: <0a9101c849cd$579f2530$b64fe146_at_ATARIENGINE>

Hi, EP, Chris, Doug, Darren, and
Anyone still dipping into the Mammoth Stewpot,

    Doug, I don't believe EP is claiming for a minute
that radiation killed any critters, much less extincted
a species, only that digressions in the isotope record
seem to correlate with extinctions and impacts. He
proposes that neutron generation in impacts may be
the connecting mechanism. I proposed that supernovae
dust infall may explain the isotope digressions. Firestone
first proposed a great neutron exposure over a continental
area would explain them, an event that allows for multiple
explanations. Anything that un-protects the Earth from
the solar wind and cosmic rays would explain it. Now
Firestone finds evidences of impact. Oddly, the impact
theory explains features that the great neutron flux theory
couldn't, but unexplains things it could! The extinctions
are sort of a by-issue as they are minor, disputed and
not clear-cut in their timing. It's a mess. Until the pieces
all "fall into place," as we say. Right now, they're still
bouncing.

    You mention the notable absence of still-radioactive
craters as an indicator that impacts do not produce any
neutrons. Well, nobody's talking about that many neutrons
in the first place. Firestone is talking about tiny ppm
geochemically detectable traces, not craters that glow
in the dark. I don't think that anybody is proposing an
extinction mechanism more energetic than a climatic
disturbance. The glaciations were strong environmental
stressors, creating a harsh environment. Another stressor on
top of that might have extinctive effects. Even if (and I don't
believe this for a minute) there were slightly "hot" craters,
induced unstable isotopes are mostly short-lived. We have
no fresh giant craters to check (that being the only place you
could test the theory of neutron production by impact). If
there were traces of neutron production in impact, it too
would be only detectable in ppm geochemical tests.

    If EP is suggesting that impacts generate enough
neutrons to increase the C14 in the Earth's atmosphere,
he be far from the first to do so. I've heard it batted
about for fifty years with no conclusive answer. There
have been articles in "Nature" proposing mechanisms and
all the usual arguments, for decades. It's not a new idea,
nor an "extreme" one, just a hard-to-prove one (or a
wrong one).

    The neutrons which transform N14 to C14 are the
lowest energy neutrons of all: thermal neutrons (meaning
that their speed is determined by the temperature, like
molecules of a gas, less than half an electron-volt likely).
The pace of thermal neutrons is so slow and leisurely
that you could easily win a race with one. Even I could.

    These lazy neutrons have no trouble creating C14
for just that reason; they just sneak up on the nitrogen
atoms and grab'em! The Earth's atmosphere makes a
fine trap to slow fast neutrons down to the slow pace
that creates C14. They start out fast because it takes
far more energy to produce them than they have as
thermal neutrons. Then, the fast neutrons have to bounce
their way off lots of atoms until they slow down enough
to get one!

    Neutrons can be produced by natural decay and by
interactions with photons, with electrons, with protons.
The energies required vary with the target, as every
element is different in this regard. Knowledge in the
this area is incomplete and an "accidental" neutron
generator is sometimes created by mistake, like the
maker of industrial x-ray machinery who discovered
that his dense tungsten shielding stopped off-axis
x-rays just fine -- by converting them into immense
doses of neutrons! (Recall time.)

    If anybody thinks we have C14 all neatly understood,
read this discussion of C14 levels in coal (where there
shouldn't be ANY):
http://www.talkorigins.org/faqs/c14.html

    All the models of large impacts (I stress the "large"
part) show the production of plasma at 30,000 K up
to 50,000 K. and in reasonably large amounts. Plasmas
at these energies produce energetic electrons, energetic
photons, and energetic ions, all of which can produce
plentiful neutrons.

    The key question is HOW MUCH? and the answer is:
we don't know. As I pointed out in a Mammoth Stew issue
on 12-21, Libby calculated that Tunguska's small C14
increase, if it was from Tunguska, was only about 15%
of what a nuclear explosion of the same force would have
generated. That's a respectable performance but not a
world-beater. I doubt anybody has calculated the neutron
flux of a variety of impact types (if even possible) and
I'm sure not going to try.

    However, everybody's overlooking the obvious: that the
impactor brings it's own Carbon 14 to the party. There
are a plentitude of carbon-rich potential impactors: C-type
asteroids, D-type, and more, cometary chunks, and so
forth. Big impacts would vaporize within the atmosphere
many millions of tons of material, with many 100,000 tons
of carbon. A mere 5000 tons of Carbon 14 would double
the C14 content of the Earth's atmosphere, so you see
it doesn't take an impossible amount. But this possibility
is also "vagued up" by the fact that we don't know the C14
abundance in such objects.

    Even tiny micrometeorites, the pellets and dust that
make "ordinary" meteors, showers and erratics, largely
from cometary sources and relatively carbon-rich, would
have carbon 14 enriched exteriors from space exposure to
energetic radiation and that carbon 14 will get oxidized
directly into the atmosphere when they burn up.

    There's no bigger headache than trying to find ALL the
pathways on a carbon cycle diagram of any natural process,
and trying to do for one isotope of carbon is nightmarish.
The unstable isotope is decaying constantly from its total
of 5000 tons in the atmosphere, dropping about one ton
per year. It's being replenished by that roughly that same
amount every year, from cosmic rays (mostly), the solar
wind (some), by the modulation of cosmic rays by the
magnetosphere as modulated by the solar wind (again),
and dozens of other very minor pathways... we think.
Living things selectively reject it, releasing it into the
atmosphere; it may be brought in with meteoroids; it
may infall with comet dust, the list goes on and on...

    Meanwhile, much (most?) of what we think we know
about large impacts is theoretical musing. It might well be
totally correct musing (I think so; it hangs together; we all
love a good synthesis), but it's brain gas just the same. So
is the theory of gravity, but I can see it work a thousand
times a day. I can't see a big impact that often, not even
once a lifetime. No observations. And no guarantee of
completeness. Give me a fresh crater and 50 geochemists
any day...


Sterling K. Webb
-----------------------------------------------------------------------
----- Original Message -----
From: "mexicodoug" <mexicodoug at aol.com>
To: <meteorite-list at meteoritecentral.com>
Sent: Friday, December 28, 2007 2:09 PM
Subject: Re: [meteorite-list] Neutron and Proton
productioninhyper-velocityimpacts


Hi Ed, Chris,

I also posted a reply to this along the lines Chris did, but it didn't show
up. Ed, I am gathering from Chris' conclusions from your post that you've
mixed up visible light with gamma rays as sources of neutrons because they
are both radiation?

Best wishes,
Doug

my original below:
Hi Ed,

I am trying to understand what you mean to say. Please bear with me and
tell me what I'm missing:

The energy of the photons we see in visible light, whether from meteors or a
night light or Sunlight on the porch is the same (per discrete photon) we
see.

There is no upper limit for the energy content of a "photon", and any finite
proces has an energy associated with it. In other words, a generic 'photon'
can release anything requiring any energy, and anything releasing energy
releases "photons", so I can't follow what you mean by "It turns out photons
can...". In fact saying a "photon" can do something is just like saying a
certain energy can do something -nothing new here, if it weren't true,
nuclear fusion and fission, two observable processes would be impossible- as
all processes have an associated energy, including warming my hot chocolate
to 80 C with infrared "photons".

The energy is proportional to the inverse of the wavelength of the "photon".
So it is simple arithmetic to calculate the wavelength of a "photon" capable
of atomic fission - which is what you are discussing (more specifically
deuterium fission)...which is the same photon energy than is released on
deuterium fusion.

Although the incredible Hulk is green, the photon of green light (wavelength
nearly measurable at = 0.00055 millimeters), the most average light, has ten
thousand times less energy per "photon" than gamma "photons". Gamma
radiation in the neighborhood of the spectrum you are discussing, in fact,
is a result of nuclear fission explosions, and has a wavelength shorter than
any distance between atoms (no surprise since it is the amount of energy
that interacts with atomic nuclei).

Until one can mathematically derive or experimentally determine whether such
energy present in gamma 'photons' (and energenitic gamma photons at that)
can be generated and applied to a little deuterium atom somehow, from all
these impacts on Earth, the status of the theory is the same as the status
of
the Hulk comic character! I am the first to respect a thought experiment:
But what scientific experiment could you propose (or has one already been
done?) to follow through?

On the other hand, if all of the big impact sites are creating all of these
radiation byproducts, the least of which is 14-C, would likely create
radioactive waste dumps at every major impact event site - a measureable
quantity. Has this been seen at Canon Diablo? An observation of that would
support your theories. I don't believe any radioactivity has been deduced
from any of the impact sites, and this is a subject very interesting to look
for by the best military satellites of the most enthused nations.

I suppose a new extinction theory can be - the radiation released from
ground zero and into the atmosphere was extremely short lived, intense and
conveniently left no trace detected yet, but clearly could be responsible
for the great dyings in geological history for suceptible creatures.

Just need a little clarification,
Thanks, Doug

> ----- Original Message -----
> From: "E.P. Grondine" <epgrondine at yahoo.com>
> To: <meteorite-list at meteoritecentral.com>
> Sent: Friday, December 28, 2007 11:08 AM
> Subject: [meteorite-list] Neutron and Proton production in
> hyper-velocityimpacts
>
>
>> Hi all -
>>
>> Over the last several days, I've cited several C14
>> spikes associated with hyper-velocity impacts.
>>
>> It turns out that photons can release neutrons and
>> protons from a nucleus:
>>
>> http://galileo.phys.virginia.edu/classes/252/Nuclear_Notes/nuclear_notes.html
>>
>> To give you idea of the energies involved, we've all
>> watched the photons given off by meteors traveling at
>> cosmic speeds. If I remember right, those photons come
>> from excited electrons - as does the electrophorenic
>> sound discussed so many times here on the list over
>> the years.
>
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Received on Fri 28 Dec 2007 10:46:05 PM PST