Periodic Reporting for period 3 - DEEPTIME (Probing the history of matter in deep time)
Reporting period: 2023-01-01 to 2024-06-30
The solar system represents the archetype for the formation of rocky planets and habitable worlds. A full understanding of its formation and earliest evolution is thus one of the most fundamental goals in natural sciences. The only tangible record of the formative stages of the solar system comes from ancient meteorites and their components, some of which date back to the birth of our Sun. The main objective of this proposal is to investigate the timescales and processes leading to the formation of the solar system, including the delivery of volatile elements to the accretion regions of rocky planets, by combining absolute ages, isotopic and trace element compositions as well as atomic and structural analysis of meteorites and their components. We identify nucleosynthetic fingerprinting as a tool allowing us to probe the history of solids parental to our solar system across cosmic times, namely from their parent stars in the Galaxy through their modification and incorporation into disk objects, including asteroidal bodies and planets. Our data will be obtained using state-of-the-art instruments including mass spectrometers (MC-ICPMS, TIMS, SIMS), atom probe and transmission electron microscopy. These data will allow us to: (1) provide formation timescales for presolar grains and their parent stars as well as understand how these grains may control the solar system’s nucleosynthetic variability, (2) track the formation timescales of disk reservoirs and the mass fluxes between and within these regions (3) better our understanding of the timing and flux of volatile elements to the inner protoplanetary disk as well as the timescales and mechanisms of primordial crust formation on rocky planets. The novel questions outlined in this proposal, including high-risk high-gain ventures, can only now be tackled using pioneering methods and approaches developed by the PI’s group and collaborators. Thus, we are in a unique position to make step-change discoveries.
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.
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.
We have made progress beyond the state of the art for a number of research initiatives during the first part of the grant period. This is based on the development of new analytical tools as well as the initiation of multidisciplinary ventures. For example, we have developed new techniques for high precision measurement of the iron isotope composition of planetary materials. The application of this new technique on various types of meteorites has demonstrated that Earth's mantle has a Fe isotope composition that is akin to a rare type of primitive meteorite, which impacts our understanding of the accretion history of Earth. Moreover, we have developed theoretical models of planet formation to provide context for the new isotope measurements generated to date, using a multidisciplinary approach. We expect to continue the development of new techniques for high precision measurements of novel nucleosynthetic tracers in the future and their application in understanding the origin of inner Solar System volatiles during the remaining part of grant period.