  In this study we explore the nucleosynthesis in the dynamic ejecta of compact
binary mergers. We are particularly interested in the question how sensitive
the resulting abundance patterns are to the parameters of the merging system.
Therefore, we systematically investigate combinations of neutron star masses in
the range from 1.0 to 2.0 \Msun and, for completeness, we compare the results
with those from two simulations of a neutron star black hole merger. The ejecta
masses vary by a factor of five for the studied systems, but all amounts are
(within the uncertainties of the merger rates) compatible with being a major
source of cosmic r-process. The ejecta undergo a robust r-process
nucleosynthesis which produces all the elements from the second to the third
peak in close-to-solar ratios. Most strikingly, this r-process is extremely
robust, all 23 investigated binary systems yield practically identical
abundance patterns. This is mainly the result of the ejecta being extremely
neutron rich (\ye $\approx0.04$) and the r-process path meandering along the
neutron drip line so that the abundances are determined entirely by nuclear
rather than by astrophysical properties. This robustness together with the ease
with which both the second and third peak are reproduced make compact binary
mergers the prime candidate for the source of the observed unique heavy
r-process component.
