SETI & Technosignatures

The Challenge of Detecting Remote Spectroscopic Signatures From Radionuclides

By Keith Cowing

Status Report

astro-ph.EP

December 1, 2024

Filed under astro-ph.EP, astronomy, atmosphere, exoplanet, imaging, radionuclides, SETI, spectrsocopy, Technosignatures

The Challenge of Detecting Remote Spectroscopic Signatures From Radionuclides — Assessment of the detectability of HI at an enriched abundance (400 ppm versus at most 10 ppt). The top panel shows the emitted radiation of the Earth seen at quadrature with the atmosphere (blue), without the atmosphere (gray), and with exclusively 400 ppm of HI in the atmosphere to indicate the positions of the HI spectral features (orange). The bottom panel shows 1-transmittance, which guides the reader through the different absorption features seen in the top panel. HI is indicated in dark orange. The right panels show the same quantities, but focused on the 4 to 5 µm region which is analysed here. — astro-ph.EP

The characterization of exoplanetary atmospheres through transit spectra is becoming increasingly feasible, and technology for direct detection remains ongoing.

The possibility of detecting spectral features could enable quantitative constraints on atmospheric composition or even serve as a potential biosignature, with the sensitivity of the instrument and observation time as key limiting factors.

This paper discusses the possibility that future remote observations could detect the presence of radioactive elements in the atmospheres of exoplanets. Such radionuclides could arise from cosmogenic or geologic sources, as well as from industrial sources, all of which occur on Earth. The detection of radionuclides in an exoplanetary atmosphere could reveal important properties about the planet’s geology or space environment, and potentially could serve as a technosignature.

However, many radionuclides, including those from industrial sources, attach to aerosol or other particles that cannot be remotely characterized. Limited experimental and theoretical spectral data exist for long-lived radionuclides, but the sensitivity required to detect the spectral features of some known radionuclides would be at least several orders of magnitude greater than required to detect the spectral features of molecular oxygen.

Present-day remote spectroscopic observing mission concepts at ultraviolet to mid-infrared wavelengths are not sensitive to discern the presence of radionuclides in exoplanetary atmospheres. Interplanetary fly-by or probe missions may be more likely to provide such data in the future.

Jacob Haqq-Misra, Vincent Kofman, Ravi K. Kopparapu

Comments: Accepted for publication in the Astrophysical Journal
Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Instrumentation and Methods for Astrophysics (astro-ph.IM)
Cite as: arXiv:2408.04467 [astro-ph.EP] (or arXiv:2408.04467v1 [astro-ph.EP] for this version)
https://doi.org/10.48550/arXiv.2408.04467
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Journal reference: ApJ (2024) 973: 161
Related DOI:
https://doi.org/10.3847/1538-4357/ad6d5f
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Submission history
From: Jacob Haqq-Misra
[v1] Thu, 8 Aug 2024 13:55:16 UTC (100 KB)
https://arxiv.org/abs/2408.04467
Astrobiology,

Keith Cowing

Explorers Club Fellow, ex-NASA Space Station Payload manager/space biologist, Away Teams, Journalist, Lapsed climber, Synaesthete, Na’Vi-Jedi-Freman-Buddhist-mix, ASL, Devon Island and Everest Base Camp veteran, (he/him) 🖖🏻

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