Stable Isotope Geochemistry

ClaytonEAR-0126185原始太阳系物质的氧同位素组成已被证明是非常强大的化学过程示踪剂，涉及到小到球粒到大到行星的天体的形成。同位素组成用于确定潜水陨石群的成因联系，如SNC(火星)陨石和Hed(钠辉石、真榴石、闪长岩)群。从储层成因、蚀变条件和水岩比等方面对碳质球粒陨石中的低温水作用进行了研究。尽管我们对“反常”效应的最终来源缺乏共识，但所有这些都是可能的。一种新的方法，结合了光化学和恒星吸积的X风模型，有可能提供一致的氧同位素演化图像，以及对内太阳系化学演化的新解释。此外，我们计划使用碳质陨石中有机分子的氧同位素组成来确定有多少有机化学发生在母行星内部，以及有多少发生在太阳星云或星际空间中。这些都是关于生物前有机分子起源的基本问题。

ClaytonEAR-0126185Oxygen isotopic compositions of primitive Solar System materials have proved to be very powerful tracers of chemical process involved in formation of objects as small as chondrules to as large as planets. Isotopic compositions serve to determine genetic associations of divers meteoritic groups, such as the SNC (martian) meteorites and the HED (howardite, eucrite, diogenite) groups. Low-temperature aqueous processes in carbonaceous chondrites have been studied in terms of reservoir origins, alteration conditions and water/rock ratios. All this has been possible even though we lacked consensus on the ultimate origin of the "anomalous" effects. A novel approach, combining photochemistry and the X-wind model of stellar accretions, has the possibility of providing a consistent picture of oxygen isotopic evolution, along with a novel interpretation of the chemical evolution of the inner Solar System. In addition, we plan to use oxygen isotopic compositions of organic molecules in carbonaceous meteorites to determine how much of the organic chemistry occurred within the parent asteroid, and how much occurred earlier, in the Solar Nebula or in interstellar space. These are fundamental questions for the origin of pre-biotic organic molecules.