  We use data from the Lunar Prospector Neutron Spectrometer to make the second
space-based measurement of the free neutron lifetime finding $\tau_n=887 \pm
14_\text{stat}{\:^{+7}_{-3\:\text{syst}}}$ s, which is within 1$\sigma$ of the
accepted value. This measurement expands the range of planetary bodies where
the neutron lifetime has been quantified from space, and by extending the
modeling to account for non-uniform elemental composition, we mitigated a
significant source of systematic uncertainty on the previous space-based
lifetime measurement. This modeling moves space-based neutron lifetime
measurement towards the ultimate goal of reducing the magnitude of the
systematics on a future space-measurement to the level of those seen in
laboratory-based experiments.
