  Merging neutron stars produce "kilonovae"---electromagnetic transients
powered by the decay of unstable nuclei synthesized via rapid neutron capture
(the r-process) in material that is gravitationally unbound during inspiral and
coalescence. Kilonova emission, if accurately interpreted, can be used to
characterize the masses and compositions of merger-driven outflows, helping to
resolve a long-standing debate about the origins of r-process material in the
Universe. We explore how the uncertain properties of nuclei involved in the
r-process complicate the inference of outflow properties from kilonova
observations. Using r-process simulations, we show how nuclear physics
uncertainties impact predictions of radioactive heating and element synthesis.
For a set of models that span a large range in both predicted heating and final
abundances, we carry out detailed numerical calculations of decay product
thermalization and radiation transport in a kilonova ejecta with a fixed mass
and density profile. The light curves associated with our models exhibit great
diversity in their luminosities, with peak brightness varying by more than an
order of magnitude. We also find variability in the shape of the kilonova light
curves and their color, which in some cases runs counter to the expectation
that increasing levels of lanthanide and/or actinide enrichment will be
correlated with longer, dimmer, redder emission.
