Large enantiomeric excesses in primitive meteorites and the diverse effects of water in cosmochemical evolution
Large enantiomeric excesses in primitive meteorites and the diverse effects of water in cosmochemical evolution
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DOI：
10.1073/pnas.1204865109
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发表时间：
2012-07-24
影响因子：
11.1
通讯作者：
Lauretta, Dante S.
中科院分区：
文献类型：
--
作者：
Pizzarello, Sandra;Schrader, Devin L.;Lauretta, Dante S.
碳质陨石是小行星的陨石碎片，避免了较大行星的地质再处理，并允许实验室探测早期太阳星云材料。其中，在南极洲发现的Renazzo型（CR）陨石看起来非常原始，并以丰富的有机物质和水溶性分子（如氨基酸和氨）而闻名。我们提出了一个全面的分析的有机组成的CR陨石不同的岩相分类和比较化合物的丰度和分布，因为它们可能涉及到小行星的水处理和伴随的矿物相的演变。我们发现，几个CR化合物，如氨基酸和糖醇是完全代表在石头没有或最小的水暴露表明形成，如果太阳能，母体过程之前。最原始的CR也显示了高达60%的对映体过量（ee），比以往任何时候都大得多。然而，水性改变似乎会影响CR可溶性有机组成和丰度，特别是一些非对映体氨基酸可能会通过其ee的外消旋化来衡量其程度。
Carbonaceous chondrites are meteoritic fragments of asteroids that avoided the geological reprocessing of larger planets and allow laboratory probing of early solar-nebula materials. Among these, Renazzo-type (CR) chondrites found in Antarctica appear remarkably pristine and are distinguished by abundant organic materials and water-soluble molecules such as amino acids and ammonia. We present a comprehensive analysis of the organic composition of selected CR meteorites of different petrographic classification and compare compounds' abundance and distribution as they may relate to asteroidal aqueous processing and concomitant evolution of the mineral phases. We found that several CR compounds such as amino acids and sugar alcohols are fully represented in stones with no or minimal water exposure indicating a formation that, if solar, preceded parent body processes. The most pristine CRs also revealed natal enantiomeric excesses (ee) of up to 60%, much larger than ever recorded. However, aqueous alteration appears to affect CR soluble organic composition and abundances, in particular some diastereomeric amino acids may gauge its extent by the consequent racemization of their ee.