5:15 PM - 6:30 PM
[MGI22-P04] Tandem Planetary Formation Theory
Keywords:Planetary Formation, Accretion Disk, Magneto-Rotational Instability
Planetesimals are formed through gravitational instability at the two distinct sites, outer and inner MRI fronts (the boundaries between the MRI suppressed region (MSR) and the outer and inner turbulent regions), because of the radial concentration of the solid particles. At the outer MRI front, icy particles grow through low-velocity collisions into porous aggregates with low densities. They eventually undergo gravitational instability to form icy planetesimals. On the other hand, rocky particles accumulate at the inner MRI front, since their drift velocities turn outward due to the local maximum in gas pressure. They undergo gravitational instability in a sub-disk of pebbles to form rocky planetesimals at the inner MRI front.
The tandem regime is consistent with the ABEL model, in which the Earth was initially formed as a completely volatile-free planet. The water and other volatile elements came later through the accretion of icy particles by the occasional scatterings in the outer regions.