{
  "abstract": "Comets preserve volatile material from the early stages of planetary-system formation. The discovery of the interstellar comet 3I/ATLAS enables a direct comparison between a comet formed around another star and comets in the Solar System. We characterise the coma composition of 3I/ATLAS across perihelion using homogeneous high-resolution near-UV and optical spectroscopy with UVES on the ESO Very Large Telescope, from August 2025 (r$_h$=3.14 au) pre-perihelion to February 2026 (r$_h$=4.34 au) post-perihelion. From flux-calibrated spectra, we measured OH, NH, CN, C$_3$, CH and C$_2$ emissions, derived production rates, examined abundance ratios and heliocentric-distance trends, constrained NH$_2$, and compared OH-based water production with estimates from forbidden oxygen lines. Gas production rates show broadly symmetric pre- and post-perihelion behaviour, with steeper heliocentric-distance dependences than typically observed in Solar System comets. NH and NH$_2$ are strongly depleted, indicating a severe deficiency of ammonia-related volatiles. The C$_2$/CN ratio indicates carbon-chain depletion and evolves with heliocentric distance, consistent with coma-driven effects such as hyperactivity rather than intrinsic compositional changes. Water production from forbidden oxygen lines exceeds OH-based estimates except near perihelion, suggesting varying contributions from H$_2$O and CO$_2$ to coma chemistry. Relative abundance correlations place 3I/ATLAS outside the canonical Solar System comet cluster and closest to strongly carbon-chain depleted comets, including G-Z-type comets, while showing strong depletion of NH- and C$_3$-bearing species relative to CN. 3I/ATLAS therefore extends the known diversity of cometary compositions, demonstrating that volatile reservoirs in other planetary systems can differ substantially from those sampled by Solar System comets.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": null,
  "arxiv": "2609.26577",
  "author_total": 12,
  "authors": [
    {
      "name": "K. Aravind"
    },
    {
      "name": "E. Jehin"
    },
    {
      "name": "C. Opitom"
    },
    {
      "name": "J. Manfroid"
    },
    {
      "name": "D. Hutsemékers"
    },
    {
      "name": "D. Bodewits"
    },
    {
      "name": "M. Bannister"
    },
    {
      "name": "R. C. Dorsey"
    },
    {
      "name": "L. Ferellec"
    },
    {
      "name": "H. Kawakita"
    },
    {
      "name": "M. Lippi"
    },
    {
      "name": "C. Snodgrass"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/83teeztn7eceb.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2609.26577",
  "fulltext_url": null,
  "id": "83teeztn7eceb",
  "issns": [],
  "landing_url": "https://arxiv.org/abs/2609.26577",
  "language": null,
  "licence": "LicenseRef-arXiv-nonexclusive-1.0",
  "licence_label": "arXiv licence",
  "licence_source": "article",
  "licence_url": "http://arxiv.org/licenses/nonexclusive-distrib/1.0/",
  "metadata_licence": "CC0-1.0",
  "native_subjects": [
    [
      "arxiv",
      "astro-ph.EP"
    ]
  ],
  "openalex": null,
  "pdf_url": "https://arxiv.org/pdf/2609.26577",
  "pmcid": null,
  "pmid": null,
  "published": "2026-09-22",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/83teeztn7eceb.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:23:39Z",
      "native_id": "2609.26577",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2609.26577"
    }
  ],
  "subjects": [
    {
      "field": "astronomy",
      "origin": "arxiv:astro-ph.EP",
      "subfield": "planetary"
    }
  ],
  "title": "High-resolution optical spectroscopy reveals the distinctive volatile composition of the interstellar comet 3I/ATLAS",
  "title_text": "High-resolution optical spectroscopy reveals the distinctive volatile composition of the interstellar comet 3I/ATLAS",
  "type": "preprint",
  "updated_at": "2026-10-30T12:23:39Z",
  "url": "https://research.draconitic.com/paper/83teeztn7eceb",
  "venue": "arXiv",
  "versions": []
}