The isotopic composition of solar nitrogen and the heterogeneity of the solar system

The isotopic composition of solar nitrogen is a long standing issue that received recently new impetus. The analysis of nitrogen isotopes in lunar samples and in Jupiter show that solar nitrogen is depleted in $15N$ by 30% relative to terrestrial. The systematic enrichment of $15N$ in terrestrial planets and bulk meteorites requires the contribution of $15N$-rich compounds to the total nitrogen in planetary materials. Most of these compounds are possibly of an interstellar origin that never equilibrated with the $15N$-depleted protosolar nebula $N2.$