REMELT – Refractory Material from Early Times

来自行星体的陨石的同位素组成揭示了太阳内部的非碳质天体(NC)和太阳外部的碳质天体(CC)之间的根本二分法。这种二分法的起源和过程是未知的，也是宇宙化学领域正在进行的辩论的主题。申请者最近的研究表明，存在一种未知的晚期形成的物质，这种物质只存在于内太阳系。为了了解太阳盘的早期演化，有必要了解这种物质在整个北冰洋地区是如何分布的，其中包括普通(调查中)、顽辉石(调查中)和鲁木鲁蒂(本项目)球粒陨石。申请人在以前的工作中已经证明，这种大规模的二分法在富铝球粒陨石中也是可见的，因为普通球粒陨石(NC区)的富铝球粒陨石不同于CaI和AoAs(形成于早期太阳星云的第一种物质)，也不同于来自CO球粒陨石(CC区)的富铝球粒陨石的50Ti同位素组成。这就得出了这样的结论：内太阳系中存在一种未知的耐火材料(可能是唯一的)，它在氧同位素组成上与已知的CaIs和AoAs相似，但在钛同位素组成上与它们明显不同。这种耐火材料在NC和CC区之间的独特分布很难用X-WIND或圆盘-WIND模型解释，因为没有过剩50Ti的耐火材料也必须存在于CC区。但是，粘性膨胀盘的新模型已经预测了北冰洋地区具有不同同位素组成的耐火材料，它们的形成可能发生在数十万年后，形成了一种较晚形成的耐火材料，富含16O，没有过剩的50Ti。后来两个圆盘区域之间的混合被一个大物体(很可能是木星)阻止了。根据这一模型，太阳系内部的同位素不一定是均匀的，最新的研究显示，有证据表明，地球、火星和小行星灶神星似乎存在与日心距离相关的同位素异常。由于太阳系内的三个主要球粒陨石群(顽辉岩、普通球粒陨石和鲁木鲁提球粒陨石)也聚集在离太阳不同的距离上，这些不同的球粒陨石群中的富铝球粒陨石也应该显示出与日心距离相关的同位素变化。在这种情况下，鲁穆鲁提球粒陨石发挥了关键作用，因为据推测，它们与早期太阳的距离最远。为了得出关于太阳系内部存在一种未知的晚期形成物质的假设的最终结论，需要研究Rumuruti球粒陨石中的各种富铝天体，以了解早期太阳盘的演化。

The isotopic composition of meteorites stemming from planetary bodies reveals a fundamental dichotomy between inner solar non-carbonaceous (NC) and outer solar carbonaceous (CC) objects. The origin of and processes responsible for this dichotomy are unknown and the subject of ongoing debate in the field of cosmochemistry. Recent studies by the applicant have indicated the existence of an unknown late formed material that was exclusively present in the inner solar system. In order to understand the early evolution of the solar disk, it is necessary to understand how this material was distributed in the whole NC region, which includes the ordinary (investigated), enstatite (under investigation) and Rumuruti (this project) chondrites. In previous works, the applicant already demonstrated that this large-scale dichotomy is also visible in Al-rich chondrules, as Al-rich chondrules from ordinary chondrites (NC region) differ from CAIs and AOAs (first material that was formed in the early solar nebula) and also Al-rich chondrules from CO chondrites (CC region) in their 50Ti isotopic composition. This led to the conclusion that an unknown refractory material was (maybe exclusively) present in the inner solar system, which resembles known CAIs and AOAs in its O-isotopic composition, but clearly differs from them in its Ti-isotopic composition. This unique distribution of refractory material between the NC and CC region is difficult to explain with the X-wind or disk-wind model as the refractory material without an excess in 50Ti would also have to be present in the CC region. But, the new model of a viscous expanding disk already predicts refractory material with a different isotopic composition in the NC region and it is possible that their formation occurred over hundreds of thousand years, creating a late formed refractory material enriched in 16O and without an excess in 50Ti. A later mixing between the two disk-regions was then prevented by a large object (likely Jupiter). According to this model, the inner solar system was not necessarily isotopically homogeneous and first current studies revealed evidences that Earth, Mars and the Asteroid Vesta seem to have isotopic anomalies correlated with their heliocentric distance. As the three main chondritic groups of the inner solar system (enstatite, ordinary, and Rumuruti) were also accreted in different distances to Sun, the Al-rich chondrules from these distinct groups should also show isotopic variations in correlation with their heliocentric distance. In this context, Rumuruti chondrites play a key-role as it is assumed that they accreted with the greatest distance to the early Sun. In order to draw a final conclusion about the hypothesis of the existence of an unknown late formed material that was exclusively present in the inner solar system, various Al-rich objects from Rumuruti chondrites need to be investigated in order to understand the evolution the early solar disk.