The source of earth water has always been a hot topic in Earth Science and planetary science. Hydrogen isotope composition is the most important basis for tracing the source of earth water. The existing results show that the hydrogen isotopic compositions of celestial bodies in the solar system are quite different: the sun, Jupiter and Saturn have similar hydrogen isotopic compositions (δ D is about 0 -The hydrogen isotopic composition of earth like planets, chondrites and comets is significantly higher than that of the sun, such as the earth’s ocean water (δ d = 0 ‰), carbonaceous and ordinary chondrites (δ d = – 220-1600 ‰, except for type R), comets (δ d = – 300 ‰), 103p / Hartley 2). According to the hydrogen isotope composition, many studies have suggested that carbonaceous chondrites and comets are the main sources of earth water (Morbidelli et al. , 2000;Hartogh et al。 However, it can not explain the obvious difference of hydrogen isotope between earth water and carbonaceous chondrite and cometary water. In recent years, more and more high-precision isotopic analyses have shown that the O, Cr, Ti, CA isotopic compositions of enstatite chondrites (EC) are almost the same as those of the earth, and enstatite chondrites may be the main materials for building the earth. The enstatite chondrites (Fig. 1) are formed in a very reduced environment, in which Na and k elements can be produced in the form of sulfides. Therefore, it is generally believed that the enstatite chondrites were formed near the sun (Fig. 2). From the perspective of nebula evolution, it is impossible for hydrogen to combine with minerals in the form of hydroxyl or water molecules near the sun. However, it has been reported that water bearing minerals such as djerfisherite (Fuchs, 1966) can be found in enstatite chondrites. Recently, Dr. Laurette Piani of the University of Lorraine, France, has analyzed the water content and hydrogen isotope of 13 pieces of enstatite chondrites (type 3-6) with different thermal metamorphism, and also analyzed the aubrite, which is considered to be the product of the heated enstatite chondrite. The analysis results show that the whole rock water content of the enstatite chondrite is 0.08-0.54 wt%, while that of the enstatite achondrite is 0.3 ± 0.2 wt%, which is significantly lower than that of the water rich carbonaceous chondrite (7.2-9.1wt%). The hydrogen isotopic mean values (δ d = – 103 ± 3 ‰) of Eh3 and EH4 are lower than those of the earth’s oceanic water, and the hydrogen isotopic compositions of eh5, eh6 and aubrite are lower (δ d = – 127 ± 15 ‰) (Fig. 3). At the same time, the in-situ water content and H isotope analysis of glass components in Sahara 97096 pellets were carried out by ion probe. The results show that the water content is 2700-12300 ppm and the hydrogen isotope ratio is uniform (δ d = – 147 ± 16 ‰). Since there is no evidence of water alteration in Sahara 97096, it can be considered that the matrix of Sahara 97096 was not disturbed by water alteration and other events. < p > < p > the statistical results show that the matrix water content of the spherulites is about 13% of the whole rock water, and the organic matter water is only 7.7%. Where does the remaining 80% of the water come from? Is it from enstatite (a kind of low calcium pyroxene) which is the main component mineral? Previous studies have shown that the water content of pyroxene on Itokawa is 700-1000 ppm, and that of pyroxene in ordinary chondrite (OC) larkman nunatak 12036 is 600-1300 ppm (Jin and Bose, 2019). The water content of enstatite in aubrite can reach 5300 ppm. Combined with the model content of enstatite in EC (50 vol%), it is estimated that the water content of enstatite accounts for 15% (OC based) or 58% (based on aubrite) of whole rock water. The study suggests that the earth’s water can be supplied entirely by enstatite chondrites. (3) water content and hydrogen isotope composition of enstatite chondrites (Piani et al. , 2020)。 (A) In order to further confirm that the enstatite chondrite is the source of earth water, it is necessary to determine the hydrogen isotopic composition of the whole rock (represented by logarithm); (c) the water content of the matrix in the chondrite; (d) the hydrogen isotopic composition of the matrix in the chondrite < / P > < p > because the hydrogen isotopic composition of some water rich cm type carbonaceous chondrites also falls within the mantle, it is necessary to further confirm that the enstatite chondrite is the source of earth water In addition, it can be distinguished by isotope index. The hydrogen nitrogen isotopic composition is a very good indicator. The analysis results show that only the hydrogen nitrogen isotopic composition of enstatite chondrites is within the range of mantle rocks (Fig. 4). Therefore, it can be considered that enstatite chondrites not only provide water, but also are the main material for constructing the earth, which is consistent with the results of high-precision isotope analysis. Piani et al. Applied the analysis data to the theoretical model of earth formation, and found that the material similar to enstatite chondrite can contribute 3.4-23.1 times of the earth’s ocean water, and glass components and organic matter can contribute 3-4 times of ocean water, which is consistent with the estimation of mantle water content. Global Tech