Homochiral biomolecules such as amino acids, sugars, and lipids are fundamental to life, yet how their selective handedness emerged abiologically is still unclear. Abiotic l-enrichments of amino acids recurrently detected in carbonaceous chondrites—meteorites rich in organic carbon—suggest that the origin of life’s homochirality may be linked to processes that occurred in space [1]. Among the possible mechanisms, stellar ultraviolet circularly polarized light (UV CPL) has been recognized as a promising candidate for triggering symmetry breaking in interstellar environments [2].

In this context, I will present our recent work on the asymmetric interaction of UV CPL with prebiotically relevant chiral molecules [3,4]. To understand how chiral asymmetry may be induced, amplified, or preserved, we investigate the electronic circular dichroism (CD) and anisotropy spectra of chiral complex organic molecules in both gas and condensed phases using the AU-CD beamline at the ASTRID2 synchrotron, supported by time-dependent density functional theory calculations. These measurements allow us to disentangle the intrinsic chiroptical response of isolated molecules from environment-induced effects arising from solvation, hydrogen bonding, and conformer redistribution within water-rich matrices. They also provide quantitative predictions of monochromatic and broadband UV CPL-induced enantiomeric enrichments, which we validate through asymmetric photolysis experiments using synchrotron radiation and in-house UV-tunable circularly polarized laser sources [4]. By combining gas-phase chiroptical spectroscopy, condensed-phase studies, quantum chemical simulations, and asymmetric photochemistry, this work provides a molecular framework for assessing how stellar UV CPL may generate chiral imbalances under astrophysical conditions. Together with experiments on the formation of chiral organic molecules in cosmic ice analogues [5] and the analysis of meteorites and asteroid-return samples [6], these results contribute to a broader understanding of the earliest stages of molecular asymmetry in space. Future work will further extend this approach to probe the role of amorphous water in interstellar ice analogues, bridging intrinsic molecular properties with astrochemical processes that may have shaped the pathways leading to biological homochirality.

Fig. 1 Did stellar circular polarization selectively enrich one enantiomer over the other in interstellar chiral molecules?

[1]  D. P. Glavin, A. S. Burton, J. E. Elsila, J. C. Aponte, J. P. Dworkin, The Search for Chiral Asymmetry as a Potential Biosignature in our Solar System. Chem. Rev. 120, 4660 (2020).
[2]  A. Garcia, et al., The astrophysical formation of asymmetric molecules and the emergence of a chiral bias. Life 9, 29 (2019).
[3]  A. Garcia, et al., Chiroptical activity of gas phase propylene oxide predicting the handedness of interstellar circular polarization in the presolar nebulae. Sci. Adv. 8, eadd4614 (2022).
[4]  J. Bocková, N. C. Jones, J. Topin, S. V. Hoffmann, C. Meinert. Uncovering the chiral bias of meteoritic isovaline through asymmetric photochemistry. Nat. Commun. 14, 3381 (2023).
[5]  C. Zhang, et al. Ionizing radiation exposure on Arrokoth shapes a sugar world. PNAS 121, e2320215121 (2024).
[6]  V. Leyva, M. Robert, R. Pepino, J. Bocková, C. Meinert. Abiotic sugar enantiomers in the CI carbonaceous chondrite Orgueil. Nat. Commun. 17, 2060 (2026).

Acknowledgement
European Research Council under the European Union’s Horizon 2020 research and innovation programme [grant agreement 804144] and the Simone and Cino Del Duca Foundation - Institut de France.