{
  "abstract": "Reflected-light spectra of Earth-sized exoplanets promise to probe habitability and biosignatures, but interpreting atmospheric oxygen can be challenging because $O_2$ can arise from both biological and abiotic processes. In addition, reflected-light retrievals exhibit degeneracies among atmospheric composition, clouds, surface reflectance, and gravity. We use the Bayesian retrieval framework ExoReL$^\\Re$, leveraging recent model developments that incorporate (i) $O_2$-$O_2$ collision-induced absorption (CIA), which produces the $O_4$ bands, and (ii) a wavelength-dependent (step-function) surface albedo parameterization. Focusing on a modern Earth analog, we compare retrievals with and without $O_2$-$O_2$ CIA using spectra within 0.25-1.8 $μ$m, and perform signal-to-noise ratio (SNR) sweeps for two observing configurations motivated by the Habitable Worlds Observatory: a resolved-visible case ($R_{VIS}=140$) and a broadband-visible case (three broad bins). Omitting $O_2$-$O_2$ CIA allows the retrieval to fit the spectrum with an incorrect $O_2$-dominated atmosphere. Including $O_2$-$O_2$ CIA leverages the $O_4$ bands to break this degeneracy and recover the correct $N_2$-dominated, $O_2$-rich solution without requiring a tight mass prior. Adopting a robustness criterion of $\\ge95\\%$ posterior mass in the $N_2$-dominated region, both configurations require SNR $\\gtrsim20$ at 0.75 $μ$m (SNR $\\approx14$ near the 1.27 $μ$m $O_4$ band for $R_{NIR}=70$) to identify the correct dominant gas, with higher cloud fraction increasing this threshold. Reducing near-IR coverage to 1.4 $μ$m prevents recovery of the correct $N_2$-dominated solution across the explored SNR range, and instead favors a spurious $O_2$-dominated, $CO_2$-rich atmosphere. These results support near-IR coverage to $\\sim1.7$ $μ$m and SNR $\\gtrsim20$ at 0.75 $μ$m for robust oxygen interpretation on Earth-like planets.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": null,
  "arxiv": "2610.42035",
  "author_total": 3,
  "authors": [
    {
      "name": "Nick Burri"
    },
    {
      "name": "Mario Damiano"
    },
    {
      "name": "Renyu Hu"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/98g70ss60ycxc.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2610.42035",
  "fulltext_url": null,
  "id": "98g70ss60ycxc",
  "issns": [],
  "landing_url": "https://arxiv.org/abs/2610.42035",
  "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"
    ],
    [
      "arxiv",
      "astro-ph.IM"
    ]
  ],
  "openalex": null,
  "pdf_url": "https://arxiv.org/pdf/2610.42035",
  "pmcid": null,
  "pmid": null,
  "published": "2026-10-30",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/98g70ss60ycxc.ris",
  "sources": [
    {
      "first_seen": "2026-11-02T12:21:15Z",
      "native_id": "2610.42035",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2610.42035"
    }
  ],
  "subjects": [
    {
      "field": "astronomy",
      "origin": "arxiv:astro-ph.IM",
      "subfield": "instrumentation-methods"
    },
    {
      "field": "astronomy",
      "origin": "arxiv:astro-ph.EP",
      "subfield": "planetary"
    }
  ],
  "title": "Distinguishing N$_2$-Dominated from O$_2$-Dominated Atmospheres on Terrestrial Exoplanets with Reflected-Light Spectroscopy",
  "title_text": "Distinguishing N_2-Dominated from O_2-Dominated Atmospheres on Terrestrial Exoplanets with Reflected-Light Spectroscopy",
  "type": "preprint",
  "updated_at": "2026-11-04T15:20:51Z",
  "url": "https://research.draconitic.com/paper/98g70ss60ycxc",
  "venue": "arXiv",
  "versions": []
}