• Corpus ID: 232092559

Cold traps of hypervolatiles in the protosolar nebula at the origin of comet C/2016 R2 (PanSTARRS)'s peculiar composition

@inproceedings{Mousis2021ColdTO,
  title={Cold traps of hypervolatiles in the protosolar nebula at the origin of comet C/2016 R2 (PanSTARRS)'s peculiar composition},
  author={Olivier Mousis and Artyom Aguichine and Alexis Bouquet and Jonathan I. Lunine and Gr{\'e}goire Danger and Kathleen E. Mandt and Adrienn Luspay-Kuti},
  year={2021}
}

• O. Mousis, A. Aguichine, +4 authors A. Luspay-Kuti
• Published 2 March 2021
• Physics, Geology

Recent observations of the long period comet C/2016 R2 (PanSTARRS) indicate an unusually high N2/CO abundance ratio, typically larger than ∼0.05, and at least 2–3 times higher than the one measured in 67P/Churyumov-Gerasimenko. Another striking compositional feature of this comet is its heavy depletion in H2O (H2O/CO ∼0.32%), compared to other comets. Here, we investigate the formation circumstances of a generic comet whose composition reproduces these two key features. We first envisage the possibility that this comet agglomerated from clathrates, but we find that such a scenario does not explain the observed low water abundance. We then alternatively investigate the possibility that the building blocks of the comet C/2016 R2 (PanSTARRS) agglomerated from grains and pebbles made of pure condensates via the use of a disk model describing the radial transport of volatiles. We show that N2/CO ratios reproducing the value estimated in this comet can be found in grains condensed in the vicinity of the CO and N2 icelines. Moreover, high CO/H2O ratios (> 100 times the initial gas phase value) can be found in grains condensed in the vicinity of the CO iceline. If the building blocks of a comet assembled from such grains, they should present N2/CO and CO/H2O ratios consistent with the measurements made in comet C/2016 R2 (PanSTARRS)’s coma. Our scenario indicates that comet C/2016 R2 (PanSTARRS) formed in a colder environment than the other comets that share more usual compositions. Our model also explains the unusual composition of the interstellar comet 2l/Borisov. Subject headings: astrobiology – comets: general – comets: individual (C/2016 R2 (PanSTARRS)) – methods: numerical – solid state: volatile