The 41/2 Steps of Terrestrial Planet Formation in the Solar System.
Step 0.5: Once the the disk forms the dust
................ settles to a the mid-plane.
Step I: A miracle occurs, Planetesimal Formation (i.e. 1-10km objects form)
- Standard two-body accretion forms planetesimals.(Weidenschilling, Cuzzi)
- How do you get two rocks to stick?
- Gravitational instability (Goldreich & Ward).
- As dust layer settles, dust disk becomes unstable planetesimals.
- But, dust will orbit faster than gas turbulence
- If the dust/gas was ~3X solar, this would still work. (Sekiya)
- Youdin & Shu accomplish this with aerodynamic drift.
- Turbulence could trigger a radial instability in the dust layer
increase in local dust density
GI (Goodman & Pindor)
- Particle-Trapping in Eddies (Cuzzi et al.; Barranco & Marcus; Johansen et al.[Combines (2) and (3)])
- Eddies are generated in in Solar Nebula (scales and reasons differ between papers).
- Particles settle due to gas drag
high density, low velocities