Evolved Extraterrestrial Materials

Evolved extraterrestrial materials are generally igneous rocks, which according to their thermal history can be discnssed analogonsly to terrestrial samples. To this category belong planetary bodies, differentiated asteroids, and achondritic meteorites. 

The Moon is now nbiqnitonsly viewed as the prodnct of a collision between the early Earth and a Mars-size protoplanet. To test whether the impactor has introduced isotopic heterogeneity as a conseqnence of collision, Wiechert et al. (2001) have searched for small isotope variations by measnring high-precision and 

The most notable feature of the sulfur isotope geochemistry of lunar rocks is the uniformity of 8 S-values and their proximity to the Canyon Diablo standard. The range of published 8 S-values is between -2 to +2.5%o. However, as noted by Des Marais (1983), the actual range is likely to be considerably narrower than 4.5%o due to systematic discrepancies either between laboratories or between analytical procedures. The very small variation in sulfur isotope composition supports the idea that the very low oxygen fugacities on the Moon prevent the formation of SO2 or sulfates, thus eliminate exchange reactions between oxidized and reduced sulfur species. 

SNC-meteorites have an average 8 0-value of 4.3%c, which is distinctly lower than the 5.5%c value for the Earth-Moon system (Clayton and Mayeda 1996 Franchi 

As is the case for hydrogen, carbon isotope signatures in Martian meteorites present evidence for different carbon reservoirs. Wright et al. (1990) and Ro-manek et al. (1994) distingnished three carbon compounds one component released 

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