THE PATH of REDUCED NITROGEN TOWARD EARLY EARTH: The COSMIC TRAIL and ITS SOLAR SHORTCUTS

Large isotopic anomalies are found in meteoritic insoluble organic materials (IOMs) and, for nitrogen, show ¹⁵N-excesses up to δ¹⁵N ∼ 5000%. These ¹⁵N-enrichments are commonly ascribed to presolar origins, but the attribution seems contradicted by available data on N-isotopes' cosmic distribution. We report here that ¹⁵N hotspots in several IOMs are reduced by hydrothermal treatment and their loss correlates with ¹⁵N values of ammonia released upon treatment. Because released ammonia's ¹⁵N-enrichments also relate with meteorites' mineralogy, i.e., asteroidal processes, and no current models offer plausible explanations for the finding, we account for our data with a novel scenario whereby ¹⁵N-enriched ammonia produced in the solar nebula is incorporated by carbonaceous materials and delivered to early Earth by comets and meteorites. The proposal also implies that abundant reduced nitrogen, a required element in origins of life theories, could reach our nascent planet and other planetary systems affecting their habitability.