Prospects For Detecting Signs of Life On Exoplanets In The JWST Era
The search for signs of life in the Universe has entered a new phase with the advent of the James Webb Space Telescope (JWST). Detecting biosignature gases via exoplanet atmosphere transmission spectroscopy is in principle within JWST’s reach. We reflect on JWST’s early results in the context of the potential search for biological activity on exoplanets.
Wasp 39b transmission spectrum. The planet size (shown as amount of light blocked) changes with wavelengths, increasing where individual gases are strongly absorbing. Figure credit: NASA, ESA, CSA, STScI.
The results confront us with a complex reality. Established inverse methods to interpret observed spectra-already known to be highly averaged representations of intricate 3D atmospheric processes-can lead to disparate interpretations even with JWST’s quality of data.
Characterizing rocky or sub-Neptune-size exoplanets with JWST is an intricate task, and moves us away from the notion of finding a definitive “silver bullet” biosignature gas. Indeed, JWST results necessitate us to allow “parallel interpretations” that will perhaps not be resolved until the next generation of observatories.
Nonetheless, with a handful of habitable-zone planet atmospheres accessible given the anticipated noise floor, JWST may continue to contribute to this journey by designating a planet as biosignature gas candidate. To do this we will need to sufficiently refine our inverse methods and physical models for confidently quantifying specific gas abundances and constraining the atmosphere context. Looking ahead, future telescopes and innovative observational strategies will be essential for the reliable detection of biosignature gases.
Schematic of a biosignature gas evaluation framework for thousands of gases. The first “triage” step identifies gases with prominent, distinctive spectral features. The second “evaluation” step focuses on photochemistry, assessing a molecule’s atmospheric survival and whether biological production rates, compared to Earth’s biofluxes, are plausible. Credit: Seager and Zhan.
This “selfie” was created using a specialized pupil imaging lens inside of Webb’s Near Infrared Camera, or NIRCam, instrument, which was designed to take images of the primary mirror segments instead of images of the sky. This configuration is not used during scientific operations and is used strictly for engineering and alignment purposes. In this image, all of Webb’s 18 primary mirror segments are shown collecting light from the same star in unison. Larger image
Sara Seager, Luis Welbanks, Lucas Ellerbroek, William Bains, Janusz J. Petkowski
Comments: In press, paper accepted in PNAS on: 2025-01-29
Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Instrumentation and Methods for Astrophysics (astro-ph.IM)
Cite as: arXiv:2504.12946 [astro-ph.EP] (or arXiv:2504.12946v1 [astro-ph.EP] for this version)
https://doi.org/10.48550/arXiv.2504.12946
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Submission history
From: Janusz Petkowski
[v1] Thu, 17 Apr 2025 13:48:43 UTC (929 KB)
https://arxiv.org/abs/2504.12946
Astrobiology, Astronomy, Biosignatures,
