Mind The Gap - Identifying traces of first-generation bodies in the inner solar system

• Applicant: Dr. Samuel Ebert
• Subject Area: Mineralogy, Petrology and Geochemistry ; Geology
• Term: since 2026
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 576422787

In order to understand how the inner planets of our solar system, including the Earth, formed, we must be able to reconstruct the exact sequence of the formation of the first planetesimals into larger objects at the beginning of our solar system. However, there are some unanswered questions and even a gap of ~2 million years in the development of the first planetesimals, which we cannot fill satisfactorily with the current state of knowledge. One starting point are small objects such as calcium-aluminum-rich inclusions (CAIs), which are the first objects to form near our early sun, marking the datable beginning of our solar system. Subsequently, they were distributed throughout the solar system and incorporated in varying amounts in the different chondritic parent bodies, the so-called chondrites. The reconstruction of the mechanisms of this enrichment of CAIs in the respective chondritic groups helps to understand how matter basically moved and was distributed in the early solar system. In this model, there is currently still the so-called "CAI-storage-problem", which the proposed project should help to solve. This problem arises from the observation that CAIs were found in all chondrites of the inner solar system - although they could no longer have been present in the inner solar system at the time when the first chondritic bodies formed. This is due to their small size, which allowed them to move relatively "fast" (~1AU/1Ma) into the Sun in the early phase of the solar system, while the inner chondritic bodies aggregated only after ~2 Ma. One approach to solving the "CAI-storage-problem" in the inner solar system would be so-called "first-generation-bodies" (FGBs). These are chondritic parent bodies that formed before the final parent bodies, which would have allowed them to store CAIs. Over time, these FGBs were destroyed again by impacts and thus released their material for the formation of the later chondritic mother bodies. During my preliminary investigations I discovered a chondrite that contains with 0.14 vol% the highest amount of CAIs of all inner chondrites measured so far (~0.009 vol%). Based on Mn-Cr measurements of fayalites, I was able to determine an approximate formation age of 1.0-1.5 Ma. This would make it the oldest chondrite discovered so far and a potential FGB. With this single sample, however, the data situation is not sufficient for a definitive answer to the question of whether FGBs exist and whether they could serve as a storage for CAIs. The proposed project aims to identify further chondrites of this type in order to solve the "CAI-storage-problem" and close the glaring temporal gap in the existing explanations for the evolutionary processes in the early inner solar system.

• DFG Programme: Research Grants