[meteorite-list] Radioactive meteorites

From: Matson, Robert <ROBERT.D.MATSON_at_meteoritecentral.com>
Date: Thu Apr 22 09:55:47 2004
Message-ID: <AF564D2B9D91D411B9FE00508BF1C8698E5912_at_US-Torrance.mail.saic.com>

Hi All,

On meteorite radioactivity, Piper piped up:

> In the articles which I looked at, none of the radioactive isotopes
> measured indicated an intensity of more than 100 dpm/kg (disintegrations
> per minute per kilogram of sample), and very low values of less than
> 10 dpm/kg were more typical of short-lived isotopes such as 28Mg and
> 57Ni. By comparison, the radioactivity of ordinary seawater is
> approximately 750 dpm/kg, attributable mainly to naturally occuring
> potassium-40.

Exactly. Even the freshest meteorite fall has radioactivity
comparable to or perhaps slightly lower than natural background level,
meaning a signal-to-noise ratio (SNR) of unity or less than unity.
To boost the SNR to the point that a Geiger counter would be of any
use, you'd have to put the sample and sensor inside a lead box to
shield the sensor from background noise. In any event, we're talking
orders of magnitude below human injury threshold.

> To give an idea how far these levels are from acutely dangerous levels:
> pure radium, which IS dangerously radioactive even for a brief exposure,
> has an activity of 2.22 million billion dpm/kg. Madame Curie would have
> undoubtedly lived longer if she had studied freshly fallen meteorites
> rather than radium.

Decades ago in my high school Physics class, a student asked the professor,
"How much radiation is a curie?" He answered, without a pause, "Enough to
kill an old lady!" --Rob
Received on Thu 17 Jan 2002 03:52:56 PM PST