Protosolar nitrogen

We have derived a value of N-15/N-14 = (2.3 +/- 0.3) x 10(-3) in the Jovian atmosphere using data from the Galileo Probe Mass Spectrometer. Adopting t his as the average value for nitrogen in the solar nebula leads to a consis tent interpretation of other measurements of nitrogen isotopes in the solar system, once nuclear evolution in the Galaxy and ion-molecule reactions in the interstellar medium are taken into account. The result confirms the as sumption that atmospheric nitrogen on Earth was not delivered as N-2 but th at N-2 was the dominant form of nitrogen in the solar nebula.