REMELT – Refractory Material from Early Times

• Applicant: Dr. Samuel Ebert
• Subject Area: Mineralogy, Petrology and Geochemistry
• Term: since 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 463342295

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.

• DFG Programme: Research Grants