Biosignatures & Paleobiology

Directional Aspects Of Vegetation Linear And Circular Polarization Biosignatures

By Keith Cowing
July 18, 2022
Filed under
Directional Aspects Of Vegetation Linear And Circular Polarization Biosignatures
The average polarization spectra Q/I (A,& D) U/I (B & E) and V /I (C & F) of 27 leaves of different species averaged over azimuth. In the upper panels, the colors represent the different phase angles and the shaded areas denote the standard error.

Homochirality is a generic and unique property of all biochemical life and is considered a universal and agnostic biosignature.

Upon interaction with unpolarized light, homochirality induces fractional circular polarization in the light that is scattered from it, which can be sensed remotely.

As such, it can be a prime candidate biosignature in the context of future life-detection missions and observatories. The linear polarizance of vegetation is also sometimes envisaged as a biosignature, although it does not share the molecular origin as circular polarization. It is known that the linear polarization of surfaces is strongly dependent on the phase angle. The relation between the phase angle and circular polarization stemming from macromolecular assemblies, such as in vegetation, however, remained unclear.

We demonstrate in this study using the average of 27 different species that the circular polarization phase angle dependency of vegetation induces relatively small changes in spectral shape and mostly affects the signal magnitude. With these results we underline the use of circular spectropolarimetry as a promising agnostic biosignature complementary to the use of linear spectropolarimetry and scalar reflectance.

C.H. Lucas Patty, Antoine Pommerol, Jonas G. Kühn, Brice-Olivier Demory, Nicolas Thomas

Comments: 37 pages, 12 figures
Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Biological Physics (; Biomolecules (q-bio.BM)
Cite as: arXiv:2207.08125 [astro-ph.EP] (or arXiv:2207.08125v1 [astro-ph.EP] for this version)
Submission history
From: Lucas Patty
[v1] Sun, 17 Jul 2022 09:50:31 UTC (8,833 KB)

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) 🖖🏻