Iodine solar abundance

The Zag meteorite fell in the western Sahara of Morocco in August 1998. This meteorite was unusual in that it contained small crystals of halite (table salt), which experts believe formed by the evaporation of brine (salt water). It is one of the few indications that liquid water, which is essential for the development of life, may have existed in the early solar system. The halite crystals in the meteorite had a remarkably high abundance of 128Xe, a decay product of a short-lived iodine isotope that has long been absent from the solar system. Scientists believe that the iodine existed when the halite crystals formed. The xenon formed when this iodine decayed. For this reason, the Zag meteorite is believed to be one of the oldest artifacts in the solar system. In this lab, you will use potassium-argon radiochemical dating to estimate the age of the Zag meteorite and the solar system. 

Swindle TD, Podosek FA (1988) Iodine-Xenon dating. In Meteorites and the Early Solar System. Kerridge JF and Matthews MS (eds) University of Arizona Press, Tucson, p 1114-1146 Tang M, Lewis RS, Anders E (1988) Isotopic anomalies of Ne, Xe, and C in meteorites. I. Separation of carriers by density and chemical resistance. Geochim Cosmochim Acta 52 1221-1234 Tera F, Eugster O, Burnett DS, Wasserburg GJ (1970) Comparative study of Li, Na, K, Rb, Cs, Ca, Sr and Ba abundances in achondrites and in Apollo 11 lunar samples. Geochim Cosmochim Acta Suppl 1 1637-1657... 

In all, iodine has 33 isotopes, of which 16 are radioactive. The one of interest is iodine-129 with a half-life of 15.7 x 10 years. Common iodine is iodine-127. Xenon is an inert gas present in the atmosphere in minute amounts of around 0.006 ppm. It has 36 isotopes, of which the one of interest is xenon-129 produced by iodine-129 via decay. This has an abundance in the naturally occurring element of 26.4 atom %. The I/Xe system could be a potentially precise geochronometer, especially of events in the solar system. 

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