The lunar regolith contains gases that have been implanted in its grains by
the solar wind. These gases include nitrogen, and measurements of N-15/N-1
4 in lunar soils have revealed puzzling temporal variations. These variatio
ns have frustrated attempts to determine the value of N-15/N-14 in proto-so
lar nitrogen. A new measurement of this important isotope ratio on Jupiter
allows us to clarify the lunar problems and to establish relationships amon
g nitrogen reservoirs in the solar system and the galaxy.