  About half of the heavy elements in the Solar System were created by rapid
neutron capture, or r-process, nucleosynthesis. In the r-process, heavy
elements are built up via a sequence of neutron captures and beta decays in
which an intense neutron flux pushes material out towards the neutron drip
line. The nuclear network simulations used to test potential astrophysical
scenarios for the r-process therefore require nuclear physics data (masses,
beta decay lifetimes, neutron capture rates, fission probabilities) for
thousands of nuclei far from stability. Only a small fraction of this data has
been experimentally measured. Here we discuss recent sensitivity studies that
aim to determine the nuclei whose properties are most crucial for r-process
calculations.
