We made significant progress in all main packages of the project, namely Theme 1 (The stardust voyage – from dying stars to the birth of our Sun), Theme 2 (The formation history of the solar system’s earliest solids) and Theme 3 (Building habitable worlds) described in appendix A of the grant agreement. The results were communicated in the form of 31 research articles published in peer-reviewed journals (as of July 1, 2022), including 7 papers in high-impact, multidisciplinary journals.
We identified and extracted several presolar silicate grains from various primitive chondrite meteorites for in-depth characterisation, including chemical and isotopic compositions as well as micro-structural investigations. Based on their oxygen isotope compositions, there grains are inferred formed in the outflows of asymptotic giant branch (AGB) stars and type II supernovae. We performed detailed chemical land micro-structural investigations by combining high-resolution scanning transmission electron microscopy (HR-STEM) imaging, spatially resolved electron energy-loss spectroscopy (SR-EELS), and spatially resolved energy-dispersive X-ray spectroscopy (EDS) on a subset of these grains. Our results show a broad range of microstructural and chemical compositions of presolar silicates, irrespective of their stellar sources. Both AGB and supernovae grains are reveal equilibrium and nonequilibrium formation conditions. This work points out the importance of coordinated isotopic, microstructural, and chemical studies of presolar silicates as a tool to investigate their origins.
We have made progress towards our understanding of the origin of the nucleosynthetic diversity of the Solar System. For example, we have showed that solids formed within only 10,000 to 20,000 years of the formation of the Sun record the entire spectrum of oxygen isotope heterogeneity observed in the Solar System. This observation requires that the oxygen isotope heterogeneity was inherited from the Sun’s parent molecular cloud as opposed to resulting from disk-related processes. In another contribution, we show that the core and rims of individual chondrules from pristine carbonaceous chondrites have distinct nucleosynthetic compositions, namely an inner and outer Solar System compositions, respectively. This observation requires significant radial mixing of inner and outer Solar System reservoirs during the disk lifetime. Moreover, in two contributions, we investigated the Nd nucleosynthetic composition of various Solar System reservoirs. This work shows that the divergent distribution of presolar dust as a function of physicochemical processing in the disk best explains the solar system isotope dichotomy as opposed to changes in the composition of the infall.
Finally, we have improved our understanding of the accretion history of the terrestrial planets and the origin of their volatiles. For example, we have discovered that Earth’s Fe isotope composition is akin to a rare type of primitive chondrites (CI) that represent the bulk Solar System composition. This result suggests a rapid accretion and differentiation of Earth during the ~5 Myr disk lifetime, when volatile-rich CI-like material is accreted to the proto-Sun via the disk. In another contribution, we analyzed ancient Martian meteorites to probe the formation history, geodynamics and potential habitability of Mars. Collectively, this work showed that Mars developed a first long-lived crust only 20 Myr after the birth of our Sun, and that water was present on the Martian surface shortly after. Mars may thus have been habitable before Earth, potentially making Mars the first harbour for life in the Solar System.
