Figure 7.

The same as for figure 6 but for N isotopes. The N isotopic compositions of individual comets are generally very consistent but the uncertainties can be large, so they have been averaged (table 2), except for the JFC outlier comet 73P. Titan's atmospheric N isotopic composition is thought to reflect that of the NH₃ it accreted [95]. The chondrite compositions (carbonaceous in blue, ordinary in red) are for bulk meteorites. However, amino acids and other N-bearing soluble organic compounds (blue double arrow) probably formed from HCN/NH₃ and exhibit a similar range of isotopic compositions to the bulk meteorites (see the text for details).