Heavy p-process nuclides in early solar system materials

早期太阳系材料中的重 p 过程核素

• 批准号: 146763062
• 负责人: Professor Dr. Carsten Münker
• 金额: --
• 依托单位: Institut für Geologie und Mineralogie
• 依托单位国家: 德国
• 项目类别: Priority Programmes
• 财政年份: 2010
• 资助国家: 德国
• 起止时间: 2009-12-31 至 2018-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/146763062?language=en
• 关键词: Heavy; process; nuclides; early; solar

Within our solar system, the isotope inventory of all elements heavier than Fe is mostly made up of nucleosynthetic r- and s-process isotopes. These isotopes are the most abundant ones, and they exhibit fairly uniform isotope compositions in early solar system materials. Our proposal focuses on the so-called heavy p-process isotopes that are among the rarest stable isotopes in the solar system which reflects their specific stellar formation conditions in supernovae. It can therefore be expected that their abundances may vary significantly, but their low abundances have hitherto made sufficiently precise measurements impossible. We now have developed for the first time analytical protocols that permit sufficiently precise abundance measurements of heavy p-process isotopes at the epsilon-level. During the first funding phase, we focused on 180W and started to develop analytical protocols for 174Hf and 180Ta. Measurements of 180W abundances in magmatic iron meteorites, some of the oldest solar system materials, revealed large excesses of 180W that were initially explained as reflecting different degrees of isotopic homogenisation in the early solar system. However, our measurements of 174Hf in chondrites and young differentiated meteorites did not show such heterogeneities. We could subesequently show that the 180W excesses are to a large extent explained by alpha decay of 184Os. In the final phase of the project we will continue to develop analytical protocols that allow combined measurements of p-process 168Yb, 162Er-164Er, 180Ta and 190Pt on the same sample split. These data will complement existing data for the heavy p-process isotopes 180W and 174Hf, thus permitting to evaluate nucleosynthetic models for p-process isotopes and models arguing for the injection of supernova material into the nascent solar system. A particular focus will be on acid leachates and residues of unequilibrated chondrites, in order to identify potential carrier phases of anomalous p-process isotope signatures.

在我们的太阳系中，所有比Fe更重的元素的同位素清单主要由核合成R-和S过程中的同位素组成。这些同位素是最丰富的同位素，它们在早期太阳系材料中表现出相当均匀的同位素组成。我们的建议着重于所谓的重型P过程，这些同位素是太阳系中最稀有的稳定同位素之一，该同位素反映了它们在超新星中特定的恒星形成条件。因此，可以预料的是，它们的丰度可能会有很大差异，但是迄今为止，它们的丰度低，使得不可能进行足够精确的测量。现在，我们首次开发了分析方案，这些方案允许对Epsilon级的重型P过程进行足够精确的丰度测量。在第一个融资阶段，我们专注于180W，并开始为174HF和180TA制定分析方案。岩浆铁陨石中180W丰度的测量是一些最古老的太阳系材料，显示出大量过量的180W，最初被解释为在早期太阳系中反映了不同程度的同位素均质化。但是，我们在软骨和年轻分化的陨石中对174小时的测量并未显示出这种异质性。我们可以屈服地表明，180W的过度在很大程度上是由184os的α衰变所解释的。在该项目的最后阶段，我们将继续开发分析方案，这些方案允许在同一样本分开的P-Process 168YB，162ER-164ER，180TA和190PT的合并测量。这些数据将补充180W和174HF的重型P过程的现有数据，从而允许评估核合成模型的核合成模型，并主张将超新星材料注入新生的太阳系中。特定的重点将放在酸渗水和未平衡的软骨的残基上，以鉴定异常的P过程同位素特征的潜在载体阶段。