contamination spatiale

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L'uranium contamine l'espace autour de la Terre. Amitiés. Bernard Blanc.

 

Source:

<A HREF= " http://ens.lycos.com/ens/feb2001/2001L-02-01-09.html " >

http://ens.lycos.com/ens/feb2001/2001L-02-01-09.html</A>

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URANIUM CONTAMINATES SPACE AROUND EARTH

 

SAN LUIS OBISPO, California, February 1, 2001 (ENS) - Minute particles

of

uranium are orbiting the Earth, say scientists from California

Polytechnic

State University.

 

The researchers, led by Roger Grismore, came across the uranium almost

by

accident. In June 1991, a small space blanket made in California was

placed

over a glass instrument on the outside of the Russian space station Mir.

 

The blanket, which consists of ten thin layers of aluminium and

polyester,

protected the instrument from solar radiation and showers of tiny

meteorites.

The blanket was removed in August 1995, returned to Earth and kept in a

clean

room for 16 months before Grismore and his team looked at it.

 

They analyzed gamma radiation given off by the blanket, revealing

energies

characteristic of two radioactive isotopes, lead 214 and bismuth 214 -

both

decay products of uranium 238. To check that the blanket had not been

contaminated in storage, the researchers also analyzed a similar blanket

that

had stayed back on Earth. It emitted less than a tenth as much

radiation.

 

" That is the thrill of science - seeing something that no one has seen

before, " said Grismore.

 

The scientists have three possible scenarios for the source of the

uranium.

It could have come from nuclear weapons tested in space in the 1960s, or

from

uranium powered satellites that have burnt up on reentry into the

atmosphere.

 

Or, an exploding supernova could have blasted the uranium into our solar

system many thousands of years ago. More data is needed to establish the

true

origin, the scientists say.

 

The study is published in the " Journal of Environmental Radioactivity, "

volume 53, and in the February issue of the British magazine " New

Scientist. "