tokens: the significance of the migration of the giant planets was recognized, JFCs and Oort cloud comets (OCCs) were thought to have formed in distinct regions, where JFCs formed beyond Neptune and OCCs formed between giant planets ( Dones et al. 2004 ). Except for P/SW3, we see little if any systematic difference between JFCs and OCCs, even when freshly exposed interior materials were measured. In terms of chemical composition, surveys of cometary volatiles have also shown no systematic difference between JFCs and OCCs, but that significant variations are present within each group ( Mumma Charnley 2011 ; A’Hearn et al. 2012 ). As growing observational evidence reveals that JFCs and OCCs formed within the same broad region, dynamical simulations, in the framework of planetary migration, also suggest that the Oort cloud and scattered disk are derived from a common parent population, i.e., the primordial trans-Neptunian disk ( Brasser Morbidelli 2013 ). Recent measurements of HDO/H 2 O in 67P ( Altwegg et al. 2015 ) by the ROSINA mass spectrometer on board the Rosetta spacecraft, also suggest that JFCs and OCCs formed in largely overlapping regions where the giant planets are today ( A’Hearn 2017 ). However, the proportions of comets formed at different heliocentric distances are not yet clear ( Dones et al. 2015 ). Füri Marty (2015) studied the distribution of N isotopes in the solar system and found that it follows a rough trend with increased 15 N abundances at larger radial distances from the Sun. Nitriles detected in cometary comae so far are consistently enriched in 15 N by a factor of ~3 relative to the protosolar nebula and a factor of 1.8 relative to the terrestrial planets ( Füri Marty 2015 ). The significant enrichment in 15 N is unlikely to be due to primordial nucleosynthetic heterogeneities, but rather a result of isotope fractionation processes during the formation of the solar system ( Füri Marty 2015 ). Possible processes include ion-molecule reactions in the interstellar medium under cold temperature with sufficient density ( Charnley Rodgers 2002 ) or photodissociation of N 2 by UV light from the proto-Sun or nearby stars ( Muskatel et al. 2011 ). Unlike nitrogen, the available carbon isotope ratios of comets, including the newly derived 12 C/ 13 C ratio of ER61, are consistent with the solar system abundance ratio of 90 ± 10 ( Wyckoff et al. 2000 ). The in situ measurements of the CO 2 isotopologs in the coma of 67P/Churyumov-Gerasimenko, taken by the Double Focusing Mass Spectrometer (DFMS) of the ROSINA, find that 12 C/ 13 C = 84 ± 4 ( Hässig et al. 2017 ). The DFMS measurements show a slight enrichment in 13 C in terms of the 12 C/ 13 C ratio compared to an average 12 C/ 13 C ratio of 91.0 ± 3.6 ( Manfroid et al. 2009 ; Bockelée-Morvan et al. 2015 ). However, given the large uncertainties of other ground-based observations, this difference seen in the DFMS measurements of 67P is not statistically significant. Our observations
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