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The Key to Unlocking Exoplanet Biosignatures: a UK-led IR Spectrograph for the Habitable Worlds Observatory Coronagraph

Beth Biller, Dan Dicken, Olivier Absil, Raziye Artan, Jo Barstow, Jayne Birkby, Christophe Dumas, Sasha Hinkley, Tad Komacek, Katherine Morris, Lorenzo Pino, Sarah Rugheimer, Colin Snodgrass, Stephen Todd, Vinooja Thurairethinam, Amaury Triaud

Abstract

The detection of life on rocky exoplanets in the habitable zones of nearby stars would be a paradigm-shifting advance, and it is one of the greatest scientific challenges of our time. There is no single spectral feature that is an unambiguous sign of life on a given exoplanet. Instead, the current state-of-the-art approach involves detecting multiple molecular atmospheric features that should not exist together in equilibrium, e.g. simultaneous detection of O$_2$ and CH$_4$. Spectra across a wide wavelength (0.3-1.7 $μ$m) range are necessary to cover multiple spectral features per molecule of interest and to contextualise the suite of molecular features detected. While the US will lead the optical arm of the Habitable Worlds Observatory (HWO) coronagraph, a UK-led contribution of a near-infrared Integral Field Spectrograph (IFS) for the infrared arm will ensure UK leadership in the flagship scientific goal of HWO - to search for signatures of life on potentially habitable exoplanets.

The Key to Unlocking Exoplanet Biosignatures: a UK-led IR Spectrograph for the Habitable Worlds Observatory Coronagraph

Abstract

The detection of life on rocky exoplanets in the habitable zones of nearby stars would be a paradigm-shifting advance, and it is one of the greatest scientific challenges of our time. There is no single spectral feature that is an unambiguous sign of life on a given exoplanet. Instead, the current state-of-the-art approach involves detecting multiple molecular atmospheric features that should not exist together in equilibrium, e.g. simultaneous detection of O and CH. Spectra across a wide wavelength (0.3-1.7 m) range are necessary to cover multiple spectral features per molecule of interest and to contextualise the suite of molecular features detected. While the US will lead the optical arm of the Habitable Worlds Observatory (HWO) coronagraph, a UK-led contribution of a near-infrared Integral Field Spectrograph (IFS) for the infrared arm will ensure UK leadership in the flagship scientific goal of HWO - to search for signatures of life on potentially habitable exoplanets.
Paper Structure (9 sections, 2 figures)

This paper contains 9 sections, 2 figures.

Table of Contents

  1. Executive Summary
  2. Scientific Motivation & Objectives
  3. The Importance of NIR Coverage
  4. Beyond Habitable Rocky Worlds -- Broader Science Impacts
  5. Strategic Context
  6. Proposed Approach and Technical Solution
  7. UK Leadership and Capability
  8. Partnership Opportunities
  9. Conclusion

Figures (2)

  • Figure 1: Figure 1: Earth's spectrum over time (right panel), reproduced from Krissansen-Totton2025. The biosignature gases present change dramatically from epoch to epoch (left panel), producing significantly different spectra. The simultaneous detection of O$_2$ at $<$0.8 $\mu$m with H$_2$O, CH$_4$, and CO$_2$ at $>$0.8 $\mu$m demonstrates the presence of life in the modern Earth spectrum shown in the bottom right panel, but for habitable planets without much evidence of oxygenic biosignatures (e.g. Proterozoic and Archean Earth), coverage beyond 0.8 $\mu$m will be key to capture H$_2$O, and CH$_4$ features.
  • Figure 2: Figure 2: An online survey of the UK exoplanet community shows overwhelming consensus: the highest scientific priority for HWO is detecting biosignatures on rocky exoplanets in the habitable zones of Sun-like stars. More details on this survey available here: http://www.exocommunity.uk/networks/HWO/HWO.html.