Inside-out planet formation – VII. Astrochemical models of protoplanetary discs and implications for planetary compositions

• DOI: 10.1093/mnras/stac2650
• Publication Date: 2022-09-23T03:57:56Z
• Authors: Arturo Cevallos Soto; Jonathan C Tan; Xiao Hu; Chia-Jung Hsu; Catherine Walsh
• Keywords: Gas giant

Inside-Out Planet Formation (IOPF) proposes that the abundant systems of close-in Super-Earths and Mini-Neptunes form in situ at pressure maximum associated with Dead Zone Inner Boundary (DZIB). We present a model physical chemical evolution protoplanetary disk midplanes follows gas advection, radial drift pebbles gas-grain chemistry to predict abundances from 300~au down DZIB near 0.2 au. consider typical properties relevant for IOPF, i.e., accretion rates 1E-9 < dM/dt / (Msun/yr) 1E-8 viscosity parameter alpha = 1E-4, evolve fiducial duration t 1E5 years. For outer, cool regions, we find C up 90% O nuclei start locked CO O2 ice, which keeps CO2 H2O one order magnitude lower. Radial icy is influential, gas-phase volatiles enhanced two orders ice-lines, while outer becomes depleted dust. Disks decreasing gradually cool, draws icelines closer star. At <~1 au, advective models yield water-rich C/O ratios <~ 0.1, may be inherited by atmospheres planets forming here via IOPF. planetary interiors built pebble accretion, IOPF predicts volatile-poor compositions. However, advectively-enhanced volatile mass fractions ~10% can occur water ice line.