We develop a simple model to predict the radial distribution of planetesimal formation .
The model is based on the observed growth of dust to mm-sized particles , which drift radially , pile-up , and form planetesimals where the stopping time and dust-to-gas ratio intersect the allowed region for streaming instability-induced gravitational collapse .
Using an approximate analytic treatment , we first show that drifting particles define a track in metallicity–stopping time space whose only substantial dependence is on the disk ’ s angular momentum transport efficiency .
Prompt planetesimal formation is feasible for high particle accretion rates ( relative to the gas , \dot { M } _ { p } / \dot { M } \gtrsim 3 \times 10 ^ { -2 } for \alpha = 10 ^ { -2 } ) , that could only be sustained for a limited period of time .
If it is possible , it would lead to the deposition of a broad and massive belt of planetesimals with a sharp outer edge .
Including turbulent diffusion and vapor condensation processes numerically , we find that a modest enhancement of solids near the snow line occurs for cm-sized particles , but that this is largely immaterial for planetesimal formation .
We note that radial drift couples planetesimal formation across radii in the disk , and suggest that considerations of planetesimal formation favor a model in which the initial deposition of material for giant planet cores occurs well beyond the snow line .