Prebiosignatures With The Habitable Worlds Observatory (HWO)

The Habitable Worlds Observatory (HWO) aims to characterize habitable exoplanets in search of signs of life. However, detectable life may be rare, either because abiogenesis is intrinsically contingent and unlikely, or because biospheres may efficiently recycle their products.

Here, we explore the potential of HWO to test theories of life in the universe even if detectable life is rare by searching for “prebiosignature gases”. Prebiosignatures gases are gases whose detection constrains theories of the evolution of prebiotic (habitable but uninhabited) planets, thereby testing theories of abiogenesis and guiding laboratory investigations of the origin of life.

We catalog 5 theories of prebiotic environments that are potentially testable by HWO, identify their observational tests, and rank them by perceived detection plausibility. The prebiosignature paradigm is novel and potentially compelling, but considerable work is required to mature it and assess its practical relevance for HWO, especially simulated spectral observation and retrieval studies.

However, consideration of the absorption properties of prebiosignature observables alone reveals that coverage at NUV wavelengths (200-400 nm) will be required to effectively realize a prebiosignature science case for HWO, supporting the argument for UV capabilities for HWO.

Prebiosignature atmospheric species and the wavelengths where they absorb or scatter (extinct) light. Wavelengths where species extinction exceeds 10−24 cm−2 molecule−1 and 10−18 cm−2 molecule−1 are indicated by dashed lines and solid lines, respectively. Species are grouped by the origin-of-life scenario they correspond to. The UV bandpass will be key to detecting prebiosignature gas species. Underlying extinction data are from Arney et al. (2016); Hu et al. (2013); Ranjan & Sasselov (2017); Keller-Rudek et al. (2013). Underlying extinction data are limited to what is available in the literature; it is possible that these species absorb at other wavelengths as well, but such absorption is not yet known. Figure motivated by Figure 2 of Rimmer et al. (2021). — astro-ph.IM

Sukrit Ranjan, Danica Adams, Michael Wong, Martin Schlecker, Nicholas Wogan, Jessica M. Weber

Comments: Science Case Development Document for the Habitable Worlds Observatory (https://outerspace.stsci.edu/display/HWOCOMMUNITYSCI/HWO+Community+Science+Case+Portal). Comments and endorsements welcomed via the link provided or at [email protected]. Comments/Endorsements received by August 15 will be incorporated into the published version (PASP conference proceedings)
Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM); Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:2507.00165 [astro-ph.IM] (or arXiv:2507.00165v1 [astro-ph.IM] for this version)
https://doi.org/10.48550/arXiv.2507.00165
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Submission history
From: Sukrit Ranjan
[v1] Mon, 30 Jun 2025 18:14:44 UTC (629 KB)
https://arxiv.org/abs/2507.00165

Astrobiology,