Colors Of Life In The Clouds: Biopigments Of Atmospheric Microorganisms As A New Signature To Detect Life On Planets Like Earth
When Carl Sagan and Ed Salpeter envisioned potential Sinkers, Floaters, and Hunters living in Jupiter’s clouds in 1976 (C. Sagan & E. E. Salpeter 1976), the nature of life in Earth’s atmosphere remained widely unknown.
Decades later, research has revealed a remarkable variety of microorganisms in our atmosphere. However, the spectral features of airborne microbes as biomarkers for detecting atmospheric life remained a mystery.
Here, we present the first reflectance spectra of biopigments of atmospheric microorganisms based on laboratory cultivars of seven microbial strains isolated from Earth’s atmosphere.
We show their distinct UV-resistant biosignatures and their impacts on models of diverse planetary scenarios, using Habitable Worlds Observatory (HWO) parameters. The reflectance of these biopigments from aerial bacteria creates the means to detect them on other Earth-like planets.
It provides a paradigm shift that moves the search for life beyond the surface of a planet to ecosystems in atmospheres and clouds.
Relative reflectance spectra of seven aerial microorganisms of wet (top frame) and dry (middle frame) measurements, and absolute reflectance (dashed lines for dry biota; solid lines for wet biota) with zoomed-in visible range wavelength panel on the right. Control (black lines in the bottom frame) refers to a filter with culture medium only, where wet control refers to fresh medium and dry control refers to dry medium. Biopigments show features between 400 and 600 nm (see Zoom), water absorption features at 1490 nm and 1900 nm are indicated by vertical blue bands. (Dataset available on Zenodo) — astro-ph.EP
Ligia F. Coelho, Lisa Kaltenegger, William Philpot, Adam J. Ellington, Noelle Bryan, Stephen Zinder, Brent C. Christner
Comments: Manuscript in revision, following peer review. 10 pages, 3 figures, 1 table
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:2509.25173 [astro-ph.EP] (or arXiv:2509.25173v1 [astro-ph.EP] for this version)
https://doi.org/10.48550/arXiv.2509.25173
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Submission history
From: Ligia Fonseca Coelho
[v1] Mon, 29 Sep 2025 17:58:46 UTC (2,954 KB)
https://arxiv.org/abs/2509.25173
Astrobiology
