(meteorobs) Meteorite pix

[Matt Mundorf]

Wow!  Great explanation.  I appreciate you detailing the meteor
radioactivity to me.

 

 

-----Original Message-----



From: meteorobs-bounces at meteorobs.org
[mailto:meteorobs-bounces at meteorobs.org] On Behalf Of mexicodoug at aim.com
Sent: Wednesday, December 03, 2008 10:45 PM
To: marco.langbroek at wanadoo.nl; meteorobs at meteorobs.org
Subject: Re: (meteorobs) Meteorite pix

 

Matt Mundorf schreef:

 

"Hmmm.  Is the radioactivity generally because of the obsorbed radiation

that is emitted from a number of sources in space or that the material

in the meteor itself is radioactive?"

 

Marco explained:

It are shortlived isotopes formed in the meteorite by cosmic radiation 

while it

was in space.

 

Hello,

 

Right, Marco.  Keeping in mind that "cosmic radiation" is a misnomer or 

confusing term at best.  More conventionally the so-called cosmic RAYS 

are ions and particles, mostly protons, accelerated to 'a non-trivial 

fraction of, to nearly the speed of, light". It is their collision with 

the meteorite that has enough energy to alter certain atomic nuclei and 

leaving them unstable enough to decay which is the source of 

radioactivity.

 

However, Cosmic RAYS is also a misnomer, since it is a relatively 

random background of solar and extrasolar PARTICLES AND not a ray, 

radiation or from a radiant.  So you could call them femto-meteors 

(micro-meteorites is already spoken for) when they collide with Earth 

or meteoroids, even though the former are not orbiting the Sun.

 

The high energy of the particle collision with meteoroids in space 

generates new isotopes in the rinds of the meteoriods, some of which 

are rather short lived - easier to meaure ages with precision.  

Meteoriticists like to study the isotope ratios for in fresh meteorites 

as this provides at least two types of information.  Once on Earth, 

they are mostly shielded by cosmic ray particles by the earth's 

magnetic field and atmospheric collisions.

 

1) How long the meteoroid has been circulating in space - cosmic rays 

typially don't make it more than a meter or so through mass, so, 

assuming the meteoroid was ejected from a deep crater somewhere, rather 

than being a primordil bolder, the cosmic ray exposure by comparing 

isotope ratios can indicate how long ago the ejection event(s) did (or 

didn't) originate.

2) Similar information by putting together a puzzle to form a gradient 

and estimate the size of the original meteoriod before it ablated.  But 

this is a softer science requiring many assumptions.

 

My two centavos as I understand it,

Best wishes and Good Health,

Doug

 

 

 

-----

Dr Marco (183294) Langbroek

Dutch Meteor Society (DMS)

 

e-mail: marco at langbroek.org

http://www.dmsweb.org

http://www.marcolangbroek.nl

-----

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