  Granular gases are fascinating non-equilibrium systems with interesting
features such as spontaneous clustering and non-Gaussian velocity
distributions. Mixtures of different components represent a much more natural
composition than monodisperse ensembles, but attracted comparably little
attention so far. We present the first experimental observation and
characterization of a mixture of rod-like particles with different sizes and
masses in microgravity. Kinetic energy decay rates during granular cooling and
collision rates were determined and Haff's law for homogeneous granular cooling
was confirmed. Thereby, energy equipartition between the mixture components and
between individual degrees of freedom is violated. Heavier particles keep a
slightly higher average kinetic energy than lighter ones. Experimental results
are supported by numerical simulations.
