Planetesimals may form from the gravitational collapse of dense particle clumps initiated by the streaming instability .
We use simulations of aerodynamically coupled gas-particle mixtures to investigate whether the properties of planetesimals formed in this way depend upon the sizes of the particles that participate in the instability .
Based on three high resolution simulations that span a range of dimensionless stopping time 6 \times 10 ^ { -3 } \leq \tau \leq 2 no statistically significant differences in the initial planetesimal mass function are found .
The mass functions are fit by a power-law , { d } N / { d } M _ { p } \propto M _ { p } ^ { - p } , with p = 1.5 - 1.7 and errors of \Delta p \approx 0.1 .
Comparing the particle density fields prior to collapse , we find that the high wavenumber power spectra are similarly indistinguishable , though the large-scale geometry of structures induced via the streaming instability is significantly different between all three cases .
We interpret the results as evidence for a near-universal slope to the mass function , arising from the small-scale structure of streaming-induced turbulence .