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首页> 外文期刊>The Astrophysical Journal. Letters >Identification of AN~(84)Sr-Depleted carrier in primitive meteorites and implications for thermal processing in the solar protoplanetary DISK
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Identification of AN~(84)Sr-Depleted carrier in primitive meteorites and implications for thermal processing in the solar protoplanetary DISK

机译：原始陨石中AN〜（84）Sr耗尽的载流子的鉴定及其对太阳原行星盘中热处理的影响

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The existence of correlated nucleosynthetic heterogeneities in solar system reservoirs is now well demonstrated for numerous nuclides. However, it has proven difficult to discriminate between the two disparate processes that can explain such correlated variability: incomplete mixing of presolar material or secondary processing of a well-mixed disk. Using stepwise acid-leaching of the Ivuna CI-chondrite, we show that unlike other nuclides such as ~(54)Cr and ~(50)Ti, Sr-isotope variability is the result of a carrier depleted in ~(84)Sr. The carrier is most likely presolar SiC, which is known to have both high Sr-concentrations relative to solar abundances and extremely depleted ~(84)Sr compositions. Thus, variability in ~(84)Sr in meteorites and their components can be attributed to varying contributions from presolar SiC. The observed ~(84)Sr excesses in calcium-aluminum refractory inclusions (CAIs) suggest their formation from an SiC-free gaseous reservoir, whereas the ~(84)Sr depletions present in differentiated meteorites require their formation from material with an increased concentration of SiC relative to CI chondrites. The presence of a positive correlation between ~(84)Sr and ~(54)Cr, despite being hosted in carriers of negative and positive anomalies, respectively, is not compatible with incomplete mixing of presolar material but instead suggests that the solar system's nucleosynthetic heterogeneity reflects selective thermal processing of dust. Based on vaporization experiments of SiC under nebular conditions, the lack of SiC material in the CAI-forming gas inferred from our data requires that the duration of thermal processing of dust resulting in the vaporization of CAI precursors was extremely short-lived, possibly lasting only hours to days.
机译：现在已经为许多核素很好地证明了太阳系储层中相关的核合成异质性的存在。但是，事实证明很难区分这两个可以解释这种相关变异性的不同过程：前太阳能材料的不完全混合或充分混合的圆盘的二次加工。使用Ivuna CI球粒晶体的逐步酸浸法，我们显示出与其他核素（如〜（54）Cr和〜（50）Ti）不同，Sr同位素变异性是〜（84）Sr耗尽的载流子的结果。载体极有可能是前体SiC，已知它既具有相对于太阳丰度的高Sr浓度，又具有极贫的〜（84）Sr组成。因此，陨石中〜（84）Sr及其组分的变异性可归因于前太阳系SiC的不同贡献。钙铝难熔夹杂物（CAI）中观察到的〜（84）Sr过量表明它们是从无SiC气态储层中形成的，而在分化的陨石中存在的〜（84）Sr贫化则需要从浓度增加的材料中形成。 SiC相对于CI球粒陨石。 〜（84）Sr和〜（54）Cr之间存在正相关，尽管分别存在于负和正异常的载体中，但与前太阳系物质的不完全混合不相容，而是表明太阳系的核合成异质性反映了粉尘的选择性热处理。根据星状条件下SiC的汽化实验，从我们的数据推断，CAI形成气体中SiC材料的缺乏要求粉尘热处理导致CAI前体汽化的持续时间非常短，可能仅持续小时到几天。

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