AGE OF METEORITES BY ISOTOPIC MEASUREMENT
The results of radioactive age determinations on meteorites by various methods are summarized. The significance of these figures for the history of meteoritic matter is discussed. It is pointed out that indications for the presence of nomnal gases in meteorites are found by several investigators. The significance of measurements on these gases, especially on their isotopic composition, is outlined. Special interest is given to the cosmic ray produeed isotopes of gases, and the possibilities of obtaining radiation ages for meteorites are discussed. The only method used so far, which in principle gives precise radiation ages, consists in the measuremeet of the helium-3/hydrogen-3 ratio. For the Norton County achondrite this method has given a radiation age of 260 million years, compared with an A/K age of 4400 million years. The influence of shorttime variations of the cosmic ray fiux on the helium3/hydrogen-3 age is discussed. The secular changes of the cosmic ray intensity may be investigated by the comparison of cosmic ray produced K/sup 40/ and for instance Ar/sup 38/ in iron meteorites. Argon contents of stone meteorites can be used to estimate radiation ages with sufficient precision in order to draw conclusions about the meaning of these ages. It is derived that the Ar/sup 38/ contents imply radiation ages of chondrites of the order of 40 million years and of some achondrites of 10 to 20 million years. It is shown that these radiation ages are determining the moment of the creation of the meteorite by the break-up of a larger body. (auth)
- Research Organization:
- Physikalisches Institut der Universitat Bern
- NSA Number:
- NSA-12-011477
- OSTI ID:
- 4303395
- Journal Information:
- Chimia (Switz.), Journal Name: Chimia (Switz.) Vol. Vol: 11
- Country of Publication:
- Country unknown/Code not available
- Language:
- English
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