  From new detailed experimental data, we found that the Radial Distribution
Function (RDF) of inertial particles in turbulence grows explosively with
$r^{-6}$ scaling as the collision radius is approached. We corrected a theory
by Yavuz et al. (Phys. Rev. Lett. 120, 244504 (2018)) based on hydrodynamic
interactions between pairs of weakly inertial particles, and demonstrate that
even this corrected theory cannot explain the observed RDF behavior. We explore
several alternative mechanisms for the discrepancy that were not included in
the theory and show that none of them are likely the explanation, suggesting
new, yet to be identified physical mechanisms are at play.
