4:00 PM - 4:15 PM
[PCG20-09] Evolution of dust size distribution and isotopic composition in the protosolar nebula with a planetary gap
It is important to understand the evolution from dust particles to planetesimals, which is the first step of planet formation. Recent meteorites analyses show that the isotopic composition of non-carbonaceous chondrites is different from the one of carbonaceous chondrites. This implies that there is a region where dust particles are non-carbonaceous isotopic composition and a region where dust particles are a carbonaceous composition, respectively.
It is widely believed that these two distinct regions are caused by an early giant planet in the protosolar nebula. Because the planet and the nebula interact gravitationally, the giant planet creates a gas gap in the nebula. The gap structure is expected to suppress the inflow of dust aggregates from the outer region to the inner region, achieving two isotopically different regions. However, the suppression of the dust inflow depends on the size of the dust aggregates. In particular, small dust particles produced by the collisional fragmentation of dust aggregates can pass through the gap due to turbulent diffusion. However, it is still unclear how the turbulent diffusion of the small dust particles affects the isotopic composition at the two planetesimal forming regions.
The purpose of this study is to investigate the effect of the dust size distribution on the isotopic compositions at the planetesimal forming regions inside and outside the planetary gap. To this end, we construct a model to simulate the evolution of dust size distribution and isotopic composition (54Cr/52Cr) due to dust advection, diffusion, growth, and fragmentation. Assuming the solar nebula with a planetary gap and heterogeneous isotopic composition, we examine the evolution of the isotopic composition at the planetesimal formation region inside and outside the planetary gap.
We found that the size of the dust aggregates which pass through the gap is determined by the ratio of the turbulent strength to the Stokes number which is a dimensionless parameter representing the strength of gas drag. This is consistent with previous studies. We found that the evolutions of the isotopic composition inside and outside the gap depend on the Stokes number and the turbulent strength. If the dust particles pass through the gap inefficiently, the isotopic composition at the inner region is constant over the dust drift timescale. We also found that the isotopic composition at the outer region reflects the isotopic composition of dust aggregates from the disk’s outer edge if the dust particles pass through the gap efficiently. We will compare the simulation results with actual data and discuss the early stages of solar system formation.
It is widely believed that these two distinct regions are caused by an early giant planet in the protosolar nebula. Because the planet and the nebula interact gravitationally, the giant planet creates a gas gap in the nebula. The gap structure is expected to suppress the inflow of dust aggregates from the outer region to the inner region, achieving two isotopically different regions. However, the suppression of the dust inflow depends on the size of the dust aggregates. In particular, small dust particles produced by the collisional fragmentation of dust aggregates can pass through the gap due to turbulent diffusion. However, it is still unclear how the turbulent diffusion of the small dust particles affects the isotopic composition at the two planetesimal forming regions.
The purpose of this study is to investigate the effect of the dust size distribution on the isotopic compositions at the planetesimal forming regions inside and outside the planetary gap. To this end, we construct a model to simulate the evolution of dust size distribution and isotopic composition (54Cr/52Cr) due to dust advection, diffusion, growth, and fragmentation. Assuming the solar nebula with a planetary gap and heterogeneous isotopic composition, we examine the evolution of the isotopic composition at the planetesimal formation region inside and outside the planetary gap.
We found that the size of the dust aggregates which pass through the gap is determined by the ratio of the turbulent strength to the Stokes number which is a dimensionless parameter representing the strength of gas drag. This is consistent with previous studies. We found that the evolutions of the isotopic composition inside and outside the gap depend on the Stokes number and the turbulent strength. If the dust particles pass through the gap inefficiently, the isotopic composition at the inner region is constant over the dust drift timescale. We also found that the isotopic composition at the outer region reflects the isotopic composition of dust aggregates from the disk’s outer edge if the dust particles pass through the gap efficiently. We will compare the simulation results with actual data and discuss the early stages of solar system formation.