  The mechanical properties of granular materials change significantly in the
presence of a wetting liquid which creates capillary bridges between the
particles. Here we demonstrate, using X-ray tomographies of dry and wet sphere
packings, that this change in mechanical properties is not accompanied by
structural differences between the packings. We characterize the latter by the
average numbers of contacts of each sphere $\langle Z\rangle$ and the shape
isotropy $\langle \beta_0^{2,0} \rangle$ of the Voronoi cells of the particles.
Additionally, we show that the number of liquid bridges per sphere $\langle
B\rangle$ is approximately equal to $\langle Z\rangle + 2$, independent of the
volume fraction of the packing. These findings will be helpful in guiding the
development of both particle-based models and continuum mechanical descriptions
of wet granular matter.
