Detecting fundamental chiral biosignatures in the ultraviolet polarization spectrum

Published

April 25, 2026

Author(s)

William Sparks, Thomas Germer, Frank Robb, Kevin Hand, Michael Bramble, George Cooper, Hiroshi Imanaka

Abstract

Chiral molecules are ubiquitous and necessary for life as we know it. Chirality is commonly defined as molecules composed of two non-superimposable mirror images (enantiomers). In extant life, biopolymers, including nucleic acids (DNA, RNA) are homochiral; their sugar constituents (deoxyribose, ribose) each consist of only one of their enantiomers. This "homochirality" is apparently a necessary feature for all terrestrial organisms and is thought to be generic to any biochemical life, and therefore may represent a pure, agnostic biosignature. The ultraviolet (UV) circular polarization spectrum offers a practical method for detecting chirality for generic biomass and hence can be a powerful tool for detecting such biosignatures in an extraterrestrial setting. In preparation for possible in situ measurements on other Solar System bodies we have demonstrated distinctive UV chiral signatures from astrobiology mission-relevant chemoautotrophic microbes when measured with transmission spectroscopy. Polarization and spectral absorption features are strongly evident at wavelengths expected for protein secondary structures and other chiral molecules, even though the microbial samples are not expected to have survived the study environment. When measured with reflection spectropolarimetry, which would be required for a remote sensing observation, we obtained only null results. Following 10 keV electron irradiation in the Minos chamber at JPL's Ocean Worlds Laboratory equivalent to exposure of approximately one month on the Europa surface in a region where the radiation is most intense, the chiral signatures persisted to a degree depending on sample thickness and composition. A null control measurement of the reflectance circular polarization of a Murchison meteorite sample was also carried out.

Citation

Astrobiology

Volume

26

Issue

5

Pub Type

Journals

Download Paper

https://doi.org/10.1177/15311074261444204

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Keywords

astrobiology, biosignature, chirality, circular dichroism, handedness, life detection, polarization, reflectance, ultraviolet

Citation

Sparks, W. , Germer, T. , Robb, F. , Hand, K. , Bramble, M. , Cooper, G. and Imanaka, H. (2026), Detecting fundamental chiral biosignatures in the ultraviolet polarization spectrum, Astrobiology, [online], https://doi.org/10.1177/15311074261444204, https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=960445 (Accessed September 3, 2026)

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