* Astronomy

The Enshi meteorite fell on Dec. 26, 1974, in the Enshi County , Hubei Provence, China (109°51'20"E,30°34'40"N). The total mass recovered is about 9.57kg. The Enshi meteorite is an ordinary chondrite, classified as belonging to group H5. The K Ar and Ar Ar geochronology indicates that the K Ar gas-retention age is 4 503±91Ma, 40 Ar/ 39 Ar plateau age, total gases Ar Ar age and isochron age are 4 518±8Ma, 4 515±23Ma and 4505±16Ma, respectively. The result of ages shows that the parent body of Enshi meteorite has not suffered collisional event probably.A correlation diagram from gases release above 1000°C gives a primordial trapped 40 Ar/ 36 Ar ratio, 0.89±0.44, using York formula. From the plot of derived K/Ca ratios, it is concluded that the high temperature release of trapped Ar is from Ca rich phases with low K/Ca ratios, almost certainly the bronzite. The ratio, 0.89±0.44, is possible that the source component of 40 Ar/ 36 Ar of the earth's atmosphere and the trapped Ar originated in the solar wind.
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