Search of intersteller media and the evolution to planetary matters.

原始陨石中的星际介质是澄清太阳系前历史的唯一线索。星际物质与太阳物质的区别仅在于元素的同位素比。我们对原始陨石中单个微粒的同位素比、结构、形状和晶体结构进行了现场测量。为构建星际物质向行星物质演化的新情景，发展了一种新的基于二次离子质谱的微尺度氧同位素分析方法。对来自阿连德陨石的富含钙铝的包裹体（CAI）进行了分析，发现其中含有具有极端氧同位素组成的黄长石晶体（相对于地球上的氧-16而言，-5%的氧-16富集）。矿物间氧同位素的变化（黄长石、尖晶石和方铅矿）表明CAI的结晶是从富含氧-16的物质开始的，这些物质可能是太阳星云中的液滴，而与周围贫氧-16的星云气体的氧同位素交换则通过CAI的结晶过程进行。在随后的太阳星云再加热事件中也发生了额外的氧同位素交换。从CAI形成时期到球粒形成时期，富含160的尘埃和缺乏160的气体一直在太阳星云中共存。原太阳附近的星际介质经过热处理后发射到外太阳系。因此，太阳星云的成分在沿着径向上呈不均匀分布，各行星的成分和同位素比值特征在太阳系演化的前100万年就已获得。

Interstellar media in primitive meteorites are only clue to clarify presolar history. The difference between interstellar media and solar matters is only isotope ratio of elements. We have made in-situ measurements of isotope ratios, textures, shapes and crystal structures for individual fine particles in primitive meteorites. The goal of in this study is construction of new scenario for material evolution from interstellar media to planetary matters.A novel micro-scale analysis for oxygen isotope ratios has been developed by secondary ion mass spectrometry. A calcium-aluminum-rich inclusion (CAI) from the Allende meteorite was analyzed and found to contain melilite crystals with extreme oxygen-isotope compositions (-5 percent oxygen-16 enrichment relative to terrestrial oxygen-16). The oxygen isotopic variation measured among the minerals (melilite, spinel, and fassaite) indicates that crystallization of the CAI started from oxygen-16-rich materials that were probably liquid droplets in the solar nebula, and oxygen isotope exchange with the surrounding oxygen-16-poor nebular gas progressed through the crystallization of the CAI.Additional oxygen isotope exchange also occurred during subsequent reheating events in the solar nebula. The 160-rich dust and 160-poor gas continued together in the solar nebula from the CAI-forming period until the chondrule-forming period.A possible scenario for new evidence would be an active protosun with bipolar out-flow. Interstellar media near the protosun has been processed thermally and then launched into outer solar system. Therefore, composition of solar nebulae distributed heterogeneously along radial direction, The characteristics of composition and isotope ratio of each planet have been achieved in the first million years of solar system evolution.