Abstract_EANA2026-112

Abstract EANA2026-112

Degradation of lipid biosignatures from iron-oxidizing bacteria under simulated Martian radiation

Anaïs Roussel (1), Mariano Battistuzzi (1), Andrew Alberini (1,2), Francesco Renzi (1,2), Sole Biancalani (1,3,4,5), Cristina García Florentino (1), Giovanni Poggiali (1), Teresa Fornaro (1), John R. Brucato (1)

(1) INAF - Astrophysical Observatory of Arcetri, Florence, Italy (2) Department of Physics and Astronomy, University of Florence, Sesto Fiorentino, Italy (3) Department of Physics, University of Trento, Povo, Italy (4) Italian Space Agency (ASI), Rome, Italy (5) Department of Earth Sciences, University of Florence, Florence, Italy

Unprecedented efforts from both the European and American space agencies are underway to find traces of ancient life on Mars (i.e., biosignatures). These include the current NASA Curiosity and Perseverance rover missions and the future ESA/NASA Rosalind Franklin mission, launching in 2028. However, the Martian surface is an extremely hostile environment, bathed in solar and galactic cosmic radiation (GCRs), so understanding how biosignatures degrade under radiation is crucial to increase our chances of detecting them on Mars. Despite Rosalind Franklin’s capability to drill and collect samples down to two meters [1], models and experimental studies predict these materials to still receive a significant dose of GCRs over hundreds of millions of years [2]. We propose to study for the first time the impact of ionizing radiation on lipid biosignatures from iron-oxidizing bacteria.

Iron-oxidizing bacteria have been described as a promising target for Martian astrobiology [3], due to the availability of Fe²⁺ on early Mars, their independence from sunlight (allowing them to develop protected from the hostile surface), and their potential for long-term preservation. The metabolism of the bacteria results in an iron oxide crust around them, leading to their death but potentially preserving remnant biosignatures over geological timescales. However, it is still unknown how GCRs degrade molecular biosignatures in iron oxide matrices.

On Earth, membrane lipids are the most resilient molecular biosignatures over geological timescales [4,5]. We will characterize the degradation of a range of membrane lipids (free fatty acids, phospholipids, and hopanoids) under gamma radiation, to mimic GCRs on the Martian surface. Additionally, we will investigate the impact of two iron oxide matrices to mimic the bacterial crust and its dehydration over time (goethite and hematite). Interestingly, goethite contains structural water, which under ionizing radiation could produce oxidizing radicals and enhance biosignature degradation.

To measure the degradation rates and formation of byproducts, we will use laboratory high-resolution instruments (solvent extraction-HPLC-MS), as well as mission analog instruments for the Perseverance rover (Raman spectroscopy for SHERLOC, FTIR for SuperCam) and the Rosalind Franklin rover (LDI-MS for MOMA). The results will be directly relevant to the mission teams, informing the selection of sampling sites and the interpretation of mission results, and ultimately improving our chances of finding Martian biosignatures.

[1] Vago et al., 2015, Sol. Syst. Res.

[2] Pavlov et al., 2022, Astrobiology

[3] Price et al., 2018, Front. Microbiol.

[4] Brocks and Summons, 2003, Treatise on Geochemistry

[5] Finkel et al., 2023, Astrobiology