Speaker: Tim Lichtenberg (University of Oxford)
Title: Bifurcation of planetary building blocks during Solar System formation
Abstract:
The origin of the Solar System shapes our understanding of the physical and chemical processes that drive planetary formation and early evolution. Geochemical analyses of meteoritic materials and astronomical observations of circumstellar disks provide evidence for a fragmented planet formation process, which is recorded in the Solar System as two spatially and temporally separated reservoirs that accreted to form the inner, volatile-depleted and outer, volatile-rich planetary populations. The origin of this dichotomy is unknown. In this talk I will discuss our recent work that investigated how the evolution of the solar protoplanetary disk influenced the timing of protoplanet formation and their internal evolution. Migration of the water snow line during the Class I and Class II stage can generate two distinct bursts of planetesimal formation that sample different source regions of interstellar materials. We find that these reservoirs evolved in divergent geophysical modes and developed distinct volatile contents, consistent with constraints from planetary accretion chronology and volatile composition, thermochemistry of extraterrestrial materials, and the mass divergence of inner and outer Solar System. Our simulations suggest that the compositional fractionation and isotopic dichotomy of the Solar System observed today was initiated by the interplay between disk dynamics, heterogeneous accretion, and internal evolution of forming protoplanets. I will conclude by outlining the paths to test this new accretion framework for the early Solar System and how it links our own planetary system to the distribution of exoplanets with Earth-like bulk compositions.