Abstract. Data from the mass spectrometer on the Galileo Probe indicate an approximately uniform
enrichment (relative to hydrogen) of 3±1 times the solar value for Ar, Kr, Xe, C, S and N on Jupiter.
These data also reveal that 15N/14N = 2.3 ± 0.3 × 10−3 in Jupiter’s nitrogen, indicating that this
element reached the planet primarily in the form of N2 . The ensuing requirements on the nature
and total mass of the icy planetesimals needed to produce these results strongly suggest that a disk
instability in the solar nebula could not have produced this giant planet.