  Galactic cosmic rays undergo complex nuclear interactions with nuclei within
planetary bodies that have little to no atmosphere. Radiation transport
simulations are a key tool used in understanding the neutron and gamma-ray
albedo coming from these interactions and tracing these signals back to
geochemical composition of the target. We study the validity of the code Geant4
for simulating such interactions by comparing simulation results to data from
the Apollo 17 Lunar Neutron Probe Experiment. Different assumptions regarding
the physics are explored to demonstrate how these impact the Geant4 simulation
results. In general, all of the Geant4 results over-predict the data, however,
certain physics lists perform better than others. In addition, we show that
results from the radiation transport code MCNP6 are similar to those obtained
using Geant4.
