[meteorite-list] Fw: Re: Is 3He a reliable comet impact marker?

[E.P. Grondine]

Bonjour - 

With Albert's permission. Enjoy. 

Merci Beaucoup, 
E.P. Grondine
Man and Impact in the Americas
(Waiting for the IG's report on NASA's response to the Brown Ammendment.)

--- On Fri, 6/5/09, Albert Jambon 
> Date: Friday, June 5, 2009, 11:22 AM
Ed,

sorry but I tried when you first raised the question to
write a detailed answer but it was not delivered to the met list,
for reasons which I do not understand and had no time to inquire
further.
 
3He is not a marker of cometary material. It is not
specific to cometary material... and there is a debate going on about
the relationship between cometary material and carbonaceous
chondrites which could be the remant of extinct comets.

There is abundant literature about the abundance and
isotopic composition of He in all kinds of meteorites. Excess 3He
(relative to the terrestrial atmospheric reference) is the rule.

3He alone means little, what matters also is the 3He/4He
ratio. 
1) 3He is a cosmogenic isotope (but not only)
2) In the solar wind the 3He/4He ratio is about 100 times
that of the terrestrial atmosphere. Therefore the idea that 3He could
be mined from the lunar regolith.
3) 3He is found in all meteorites, at different levels
though, and trapped in a variety of components (carbonaceous matter is
one).
 
4) To make it simple (?)(which is probably not)
- we have primordial He (several components) trapped in the
pristine material of meteorites (or comets).
- we have He implanted from the solar wind (near the surface
of samples)
- we have cosmogenic 3He produced by nuclear reactions
(spallation) during the travel through space. This
component is more penetrative and decreases with depth.

The last two components vary with the duration of exposure
and usually dominate the budget. The first component varies
with the type of extraterrestrial matter.
 
Albert
> 
> 
> 
> 
> 
> 
> >Hello Albert - I worded my question poorly. Is that
> "No, no one
> >knows" or "No, 3He is not a reliable marker"? Ed --- On
> Thu, 6/4/09,
> >Albert Jambon <albert.jambon at upmc.fr>
> wrote: > From: Albert Jambon
> ><albert.jambon at upmc.fr>
> > Subject: Re: [meteorite-list] Is 3He a
> >reliable comet impact marker? > To: "E.P. Grondine"
> ><epgrondine at yahoo.com>
> > Date: Thursday, June 4, 2009, 10:52 AM >
> >No > > > > > >Hi all - > > >
> >Now that the shock has dissipated, I
> >ask again if > anyone knows if > >3He is a
> reliable cometary or
> >comet marker? > > > >E.P. Grondine >
> >Man and Impact in the
> >Americas > > > > > > >
> >______________________________________________ >
> >http://www.meteoritecentral.com >
> >Meteorite-list
> >mailing
> >list > >Meteorite-list at meteoritecentral.com
> > >http://six.pairlist.net/mailman/listinfo/meteorite-list
> > >
> >-- > Albert JAMBON > Laboratoire Magie  46-0
> 4eme étage, Case 110 >
> >Université P et M Curie > 4 place jussieu 75252
> Paris Cedex O5
> >France > Tel: 33 (0) 144 27 51 35 > FAX: 33 (0)
> 144 27 39 11 > >
> >Parcours de Planétologie d'Ile de France >
> >http://www.ipsl.jussieu.fr/formation/Planeto/Pageweb.html
> > > Site
> >du master SDUEE spécialité Géosciences, >
> Géomatériaux >
> >http://www.master.sduee.upmc.fr/M1/geo/geo_m1.htm >
> >
> 
> --
> Albert JAMBON
> Laboratoire Magie  46-0 4eme étage, Case 110
> Université P et M Curie
> 4 place jussieu 75252 Paris Cedex O5 France
> Tel: 33 (0) 144 27 51 35
> FAX: 33 (0) 144 27 39 11
> 
> Parcours de Planétologie d'Ile de France
> http://www.ipsl.jussieu.fr/formation/Planeto/Pageweb.html
> 
> Site du master SDUEE spécialité Géosciences,
> Géomatériaux
> http://www.master.sduee.upmc.fr/M1/geo/geo_m1.htm
> 
>