Supporting the Search for Organics on Mars Through Mission-Analog Spectroscopic Characterization of Terrestrial Analogs and Martian Meteorites

 

Introduction

Mars is one of the primary targets of astrobiological exploration, due to the presence of liquid water on its surface during its early stages and the existence of sedimentary environments that may have hosted and preserved biosignatures [1]. One of the main aims of the current and future missions, including NASA Mars 2020 Perseverance and ESA ExoMars Rosalind Franklin rovers, is to detect such biosignatures using advanced spectroscopic instruments operating across multiple spatial scales [2][3]. To fully exploit these datasets, it is essential to establish a robust interpretive framework based on the characterization of analogous terrestrial samples and Martian meteorites. Within this framework, terrestrial analog environments, such as Proterozoic clay-rich mudstones from the ~1 Ga El Mreiti Group (Mauritania), allow for the study of well-preserved biosignatures formed under sedimentary and diagenetic conditions comparable to those hypothesized for early Mars [4]. At the same time, Martian meteorites offer direct evidence of Martian geochemical evolution and the alteration of organic matter, albeit modified by secondary processes such as thermal and shock alteration during ejection from Mars and entry in Earth Atmosphere [5]. The combined study of terrestrial analogs and Martian meteorites is therefore essential for defining the pathways of biosignature preservation and assessing their detectability in Martian contexts. Another key aspect is the use of techniques that closely mimic those employed in current and future Mars missions. By applying spectroscopic methods relevant to these missions to complex natural samples, it becomes possible to assess detection limits, spectral ambiguities, and the influence of mineral matrices on the expression of biosignatures, thereby providing direct support for the interpretation of in situ data.

 

Methods

A multi-scale spectroscopic approach was implemented using techniques analog to those deployed on Mars 2020 and ExoMars rovers. Bulk mineralogical and compositional information was obtained through Fourier Transform Infrared (FTIR) spectroscopy in reflectance mode, enabling the identification of dominant mineral phases and broad organic functional groups. Micro-scale heterogeneity was investigated using a Hyperion 1000 micro-FTIR system, allowing the spatial mapping of mineral–organic associations. Visible and Deep Ultraviolet (DUV) Raman spectroscopy and fluorescence analyses were employed to probe the molecular structure and distribution of organic compounds, in a mineral matrix, with particular sensitivity to aromatic and conjugated systems such as kerogens and macromolecular carbons (MMC). This integrated methodology enables a systematic evaluation of biosignature detectability across analog and extraterrestrial materials.

 

Results

The results presented in this study provide a framework for understanding the spectroscopic expression of biosignatures in complex natural materials. Indeed, the investigation of terrestrial analog samples and Martian meteorites yields key insights into how biosignatures may be preserved, modified, and detected under realistic geological conditions. In particular, this work highlights the importance of multi-scale characterization in resolving mineral–organic associations, demonstrating how biosignatures may manifest differently depending on spatial resolution and analytical technique. The datasets contribute to defining practical detection limits for mission-relevant instruments, suggesting which spectroscopic approaches are best suited for identifying specific classes of organic compounds and their mineralogical context. Furthermore, the results provide constraints on the expected spectral signatures of biosignatures in Martian environments, offering guidance on how such signals may appear – or be obscured – within natural, heterogeneous matrices. Overall, this study establishes a foundation for both current and future analyses of Martian datasets, contributing to the development of more robust biosignature detection strategies and improving the reliability of interpretations derived from in situ and returned sample investigations.

 

References: [1] Vago J.L. et al. (2017), Astrobiology 17, 471–510; [2] Farley K.A. et al. (2020), Space Sci Rev 216, 142; [3] Vago J. et al. (2015), Solar System Research 49, 518–528; [4] Beghin J. et al. (2017), Precambrian Research 299, 1–14; [5] Steele A. et al. (2016), Meteorit Planet Sci 51, 2203–2225.

Acknowledgements: This research is supported by the Italian Space Agency (ASI) through the ASI/INAF agreement no. 2025-12-HH.0 and PAMMAT project “Alteration processes in Mars and Moon meteorites, and Terrestrial Analogues at different environments: Mars2020, Rosalind Franklin and Returned Samples from Mars and Moon” (Grant No. PID2022-142750OB-I00), funded by the Spanish Agency for Research MCIN/AEI/10.13039/501100011033/FEDER-UE.