Evidence for Surprising Heavy Nitrogen Isotopic Enrichment in Comet 46P/Wirtanen’s Hydrogen Cyanide
Abstract 46P/Wirtanen is a Jupiter-family comet, probably originating from the solar system’s Kuiper Belt, that now resides on a 5.4 yr elliptical orbit. During its 2018 apparition, comet 46P passed unusually close to the Earth (within 0.08 au), presenting an outstanding opportunity for close-up observations of its inner coma. Here we present observations of HCN, H 13 CN, and HC 15 N emission from 46P using the Atacama Compact Array. The data were analyzed using the SUBLIME non-LTE radiative transfer code to derive 12 C/ 13 C and 14 N/ 15 N ratios. The HCN/H 13 CN ratio is found to be consistent with a lack of significant 13 C fractionation, whereas the HCN/HC 15 N ratio of 68 ± 27 (using our most conservative 1 σ uncertainties), indicates a strong enhancement in 15 N compared with the solar and terrestrial values. The observed 14 N/ 15 N ratio is also significantly lower than the values of ∼140 found in previous comets, implying a strong 15 N enrichment in 46P’s HCN. This indicates that the nitrogen in Jupiter-family comets could reach larger isotopic enrichments than previously thought, with implications for the diversity of 14 N/ 15 N ratios imprinted into icy bodies at the birth of the solar system.
Authors
- Anthony J. Remijan (ORCID: https://orcid.org/0000-0001-9479-9287)
- Nathan X. Roth (ORCID: https://orcid.org/0000-0002-6006-9574)
- Stefanie N. Milam (ORCID: https://orcid.org/0000-0001-7694-4129)
- N. Biver (ORCID: https://orcid.org/0000-0003-2414-5370)
- Steven B. Charnley (ORCID: https://orcid.org/0000-0001-6752-5109)
- B. P. Bonev (ORCID: https://orcid.org/0000-0002-6391-4817)
- Chunhua Qi (ORCID: https://orcid.org/0000-0001-8642-1786)
- Martin Cordiner (ORCID: https://orcid.org/0000-0001-8233-2436)
- D. Bockelée–Morvan (ORCID: https://orcid.org/0000-0002-8130-0974)
- J. Boissier (ORCID: https://orcid.org/0000-0002-1545-2136)
- K. Darnell (ORCID: https://orcid.org/0000-0002-5377-7740)
- J. Crovisier
Institutions
- Institut de Radioastronomie Millimétrique (FR)
- Laboratoire d’études spatiales et d’instrumentation en astrophysique (FR)
- Deleted Institution
Publication Details
- Journal
- The Planetary Science Journal
- Published
- 2024-10-01
- DOI
- https://doi.org/10.3847/psj/ad7829
- Citations
- 2
- Primary Topic
- Astro and Planetary Science
- Type
- article
- Field-Weighted Citation Impact
- 0.66
Funders
- National Science Foundation
- National Aeronautics and Space Administration
- National Radio Astronomy Observatory
- National Science Council
- Korea Astronomy and Space Science Institute
- National Astronomical Observatory of Japan
- National Science and Technology Council
- National Institutes of Natural Sciences
- Planetary Science Division