  Understanding the origin of life-essential volatiles like N in the Solar
System and beyond is critical to evaluate the potential habitability of rocky
planets. Whether the inner Solar System planets accreted these volatiles from
their inception or had an exogenous delivery from the outer Solar System is,
however, not well understood. Using previously published data of
nucleosynthetic anomalies of Ni, Mo, W and Ru in iron meteorites along with
their 15N-14N ratios, here we show that the earliest formed protoplanets in the
inner and outer protoplanetary disk accreted isotopically distinct N. While the
Sun and Jupiter captured N from nebular gas, concomitantly growing protoplanets
in the inner and outer disk possibly sourced their N from organics and/or dust
- with each reservoir having a different N isotopic composition. A distinct N
isotopic signature of the inner Solar System protoplanets coupled with their
rapid accretion suggests that non-nebular, isotopically processed N was
ubiquitous in their growth zone at 0-0.3 Myr after the formation of CAIs.
Because 15N-14N ratio of the bulk silicate Earth falls between that of inner
and outer Solar System reservoirs, we infer that N in the present-day rocky
planets represents a mixture of both inner and outer Solar System material.
