= Planetesimals =
=== Early Differentiaton and Consequences for Planets ===
=== QB603.O74 P55 2017 PSUlib ===

|| ξ       || accretion efficiency, (MF-M1)/M2 ≤ 1           ||
|| SSC     || Similar Sized Collision,  R1 ~ R2, vrel ~ vesc ||
|| HRC     || Hit and Run Collision,  ξ ~ 0                  ||
|| NLB     || Next largest contributor bodies                ||
|| GMC     || graze-and-merge collions, ξ → 1                ||
|| SFD     || size frequency distribution dn ~ R^^(-α) dR    ||
|| γ       || Normalized projectile mass ( M2/(M1+M2)        ||
|| θ       || Impact angle asin(b/R1+R2)                     ||
|| b       || impact parameter, closest radial distance      ||

This is mostly about the formation of planets from planetesimals,

 .p11 Walsh 2011 Vesta and Ceres (remaining oligarchs) are the last of hundreds >99% ejected by resonant scattering.
 .p11 we know of metallic cores from small satellites, most core compositions unknown
 .p11 planetesmals > 100-200 km immune to impact disruption
 .p22 iron droplets can rain out on a Stokes timescale ~ R η / g r^^2 Δ ρ  η matrix viscosity in poises

 .p40 Fig 3.1 Estimated values of present dayt asteroid belt from Bottke et al (2005b) "Linking ... " Icarus 179, 63-94
  . cumulative log-log plot, vaguely straight lines

|| populations  || 1m count || max size 1 body || count exp || volume exp ||
|| NEA          ||    2e10  ||    20 km        ||       2.4 ||        0.8 ||
|| main         ||    1e13  ||   600 km        ||      2.25 ||       0.75 ||

 .p71 Enstatite meteorites: E-type, 2% of falls, rare, 200 known, parent body Psyche, reduced, metal or sulphide not oxide, MgSiO₂