Three Forks Depot Analogues in Mars Analogue Sample Library – Representativity Assessment via Raman and LIBS Spectroscopy

NASA-ESA Mars Analogue Sample Library (ASL) officially opened in 2024 at the Natural History Museum of Oslo. ASL aims to provide the scientific community with samples analogous to those sampled by Mars 2020 Perseverance in Jezero Crater during the Crater Floor and Delta Front campaigns.  The goal is to prepare for operations and research relating to Mars, particularly on the eventually returned samples of Mars Sample Return[1], as well as outreach activities.

To assess analogue fidelity [2,3] tests are needed: among others, extensive mineralogical, petrological, chemical and mechanical characterization. Furthermore, in order to facilitate the comparison between the martian samples and the terrestrial analogues, characterization of the analogues via in-situ techniques used onboard Mars2020 is necessary. This study aims to analyze the ASL analogues with Raman Spectroscopy and Laser Induced Breakdown Spectroscopy (LIBS).  Raman spectroscopy, in particular, has been a crucial tool in the detection of many minerals on Mars [4], while LIBS gives a first order indication of the sample geochemistry.

ASL includes five sites with two representative samples of Jezero crater floor, one regolith analogue, and two samples aiming to represent the delta sediments [5,6, https://www.mn.uio.no/geo/english/research/projects/msr-asl-analogue-sample-library/msr-asl/]. 

Olivine cumulates from the Isle of Rum (Scotland) share similarities with cumulates found in Séítah formation and corresponding Robine, Malay, Salette and Coulettes samples. Aphyric (HMA) and phyric (HMP) holocrystalline basalts from Hart Mountain (HM), Oregon, USA, are the selected analogues for Máaz formation (samples Montdenier, Montagnac, Ha'ahóni, Atsá). Basaltic lithic sand from Lambahraun (Iceland) is intended to emulate Martian regolith (samples Atmo Mountain and Crosswind Lake). Finally, sandstones were sampled at Salton Sea and Ridge Basin (California) in order to represent the Delta Front Skinner Ridge, Wildcat Ridge and Amalik formations (samples Hazeltop, Bearwallow, Skyland, Swift Run, Shuyak and Mageik).

 

SimulCam, the heavy-duty laboratory emulator supporting SuperCam science [7], has been used to collect coaligned, time-resolved Raman and LIBS analyses from ~3-5 cm bulk samples. For each sample, 5–10 spots have been analyzed at 2m distance to disclose the mineralogical and geochemical complexity of the materials. Additionally, thin sections have been prepared for EDX mapping to provide laboratory ground-truth for observations made by Raman and LIBS. These measurements complement the baseline laboratory characterisation, which includes X-ray diffraction, X-ray fluorescence, and measurements of calcium carbonate content, particle size distribution and shape.

 

In Rum, olivine is abundant, as in Séítah, evidenced by Raman spectrometry (Fig. 1): the distinct olivine doublet peak correlates with the Raman spectrum acquired by SuperCam on Dourbes. Furthemore, the olivines appear to chemically match estimations of the forsterite% for Séítah samples Salette and Coulettes [8], but look partially serpentinized, whereas no serpentine was detected in Séítah. Carbonates, widespread in Séítah, appear as up to 10% in Rum. Rum is a good textural analogue to Séítah, with olivine grains of the same size (1-3 mm) and similar poikilitic texture.

As a representative case study, spectroscopic analyses of Rum performed by SimulCam revealed elemental and molecular compositions similar to those of targets investigated by SuperCam at Séítah. In this context, the combined interpretation of LIBS and Raman features could be employed to develop and test methods for quantifying fayalite–forsterite ratios in olivines, a key focus of the ongoing work by the SuperCam science team.

Figure 1: Séítah Raman spectra at Dourbes abrasion patch in Brac outcrop (top), and Simulcam spectra of Rum (bottom), indicating the presence of the typical olivine doublet peaks (shaded area).

 

Basalts from Hart Mountain (Máaz analogues), are composed of plagioclase and pyroxene. Texturally, HMA samples are representative of the samples Montdenier and Montagnac. HMP presents a larger porphyric texture, though the plagioclase crystals are one order of magnitude too large compared to Ha'ahóni and Atsá.

Lambahraun sand is composed of basaltic grains close in size and composition to what has been observed in Crosswind Lake and Atmo Mountain. In particular, one of the aims of sampling a megaripple was to sample the <150 micron size range [9] to characterize the global regolith of Mars. Such small particles appear to constitute >20% of Lambahraun samples, making it a good engineering analogue. It is well-sorted, rather coincident with the moderately to well-sorted martian samples. Their grain shape is consistent both in sphericity and roundness.

The sandstones analogous to Delta Front rocks contain carbonate and/or sulfate cement in varying amounts, but their clastic material is predominantly quartz and feldspars, unlike basaltic grains on Mars. Texturally, Ridge Basin can be analogous to the well-sorted material of Shuyak and Mageik, as well as the carbonate-rich laminations of Skyland and Swift Run. Salton Sea appears richer in sulfates, while still containing carbonates, making its cement analogous to Bearwallow and Hazeltop cores.

 

ASL analogues are extensively tested to evaluate their relevance to mission science preparations. While laboratory analyses provide ground-truth characterization of the analogue material, evaluation of the analogues with SimulCam allows more direct comparison with data collected in situ on Mars. Furthermore, such results combined with extensive ongoing characterization of analogues via laboratory techniques can support interpretation of martian formations, as the results highlight capabilities and limitations of the Perseverance instruments in detecting and characterizing mineralogical and geochemical details of encountered rocks.

Disclaimer: The decision to implement Mars Sample Return will not be finalized until NASA’s completion of the National Environmental Policy Act (NEPA) process. This document is being made available for informational purposes only.

Acknowledgments: Curation of Mars ASL is financed by ESA and NoSA (PRODEX) project.

References: [1] Tait. K. et al. (2022) Astrobiology 22(S1), S-57 [2] Foucher F. et al. (2021) Planetary and Space Science, 197, 105162. [3] Thorpe M. T. et al. (2025) LPI Contributions, Abstract #2109. [4] Lopez-Reyes, G. et al. (2025) Authorea Preprints, ESS Open Archive [5]Thiessen F. et al. (2024) LPI Contributions 3036, Abstract #6173. [6] Thiessen F. et al. (2025) EPSC-DPS2025-953 [7] Manrique J. et al (2024) Advances in Space Research, 74(8), 3855-3876 [8] Beyssac O. et al (2023) Journal of Geophysical Research: Planets 128 (7), e2022JE007638 [9] Hausrath E. M. et al. (2025) Journal of Geophysical Research: Planets, 130(2), e2023JE008046.