PCA-based modeling of SuperCam LIBS data for comparing geological composition across Martian formations

The Perseverance rover landed in Jezero Crater in February 2021 as part of the Mars 2020 mission, with objectives that include geological characterization of the landing site, detection of potential biosignatures, and collection of samples for future return to Earth [1,2]. To achieve these goals, the SuperCam instrument has been extensively used, integrating Laser-Induced Breakdown Spectroscopy (LIBS) among other spectroscopic and imaging techniques to investigate the elemental, geochemical, and mineralogical composition of the Martian surface [3]. The reliability of LIBS measurements is ensured by an onboard calibration system comprising multiple reference targets [4].

Since the rover began its traverse on Mars, its scientific exploration has been organized into a series of Scientific Campaigns analyzing distinct geological units within Jezero Crater. The first campaign, the Crater Floor Campaign, focused on the Máaz, Artuby, Content, and Séítah formations. It was followed by the Rapid Traverse Campaign, whose primary objective was to reach the Delta region, resulting in limited scientific measurements. The third campaign, the Delta Front Campaign, and the fourth, the Delta Top Campaign, provided detailed investigations of the deltaic deposits. Subsequently, the Margin Unit Campaign distinguished between the Western and Eastern Margin Unit formations, with a focus on carbonate-bearing lithologies. The most recent phase corresponds to the Crater Rim Campaign, which is currently ongoing and targets the rim structures of Jezero Crater.

In this study, LIBS data collected by the SuperCam instrument during the first five scientific campaigns (until Sol 1280) were analyzed using Principal Component Analysis (PCA), to develop a model that can serve as a basis for comparing and predicting the composition of new targets from other geological formations investigated by the rover.

The full LIBS spectra measured by the Perseverance rover from the Máaz, Artuby, Content, Séítah, Delta Front, Delta Top, Eastern Margin Unit, and Western Margin Unit regions were used. Only targets measured on rocks or floats were selected, while those acquired on regolith or heavily dust-covered rocks were excluded to avoid misinterpretations, since regolith material can be transported across different regions of Mars by wind activity. For each target, the median LIBS spectrum was computed, followed by Norm-2 normalization and mean-centering. The PCA model was then developed using the PLS_Toolbox (Eigenvector Research, WA, USA) working under Matlab environment (The Mathworks, MA, USA).

The resulting PCA was robust and effectively captured compositional differences among the geological formations. The PCA results reveal clear geochemical differences among the Martian formations. Séítah is characterized by higher Mg contents and local olivine enrichment, while Máaz is enriched in Si, Fe, Al, and alkali elements, consistent with a feldspar- and pyroxene-rich composition. Artuby shows intermediate compositions between Séítah and Máaz formations and Content has a similar composition than Máaz. In contrast, Delta Front, Delta Top, Eastern Margin Unit and Western Margin Unit exhibit more homogeneous signatures dominated by Fe- and Mg-rich phases.

In conclusion, PCA based solely on LIBS spectra provides a rapid and robust framework for comparing and interpreting the mineralogical composition of new targets, enabling their integration into existing compositional models even when other SuperCam datasets are unavailable or incomplete. Furthermore, this approach facilitates the comparison of geological compositions across different formations within a consistent multivariate framework. 

 

References

[1] Mars 2020: Perseverance Rover, (n.d.). https://science.nasa.gov/mission/mars-2020-perseverance/  (accessed April 27, 2026).

[2] K.A. Farley, K.H. Williford, K.M. Stack, R. Bhartia, A. Chen, M. de la Torre, K. Hand, Y. Goreva, C.D.K. Herd, R. Hueso, Y. Liu, J.N. Maki, G. Martinez, R.C. Moeller, A. Nelessen, C.E. Newman, D. Nunes, A. Ponce, N. Spanovich, P.A. Willis, L.W. Beegle, J.F. Bell, A.J. Brown, S.-E. Hamran, J.A. Hurowitz, S. Maurice, D.A. Paige, J.A. Rodriguez-Manfredi, M. Schulte, R.C. Wiens, Mars 2020 Mission Overview, Space Sci Rev 216 (2020) 142. https://doi.org/10.1007/s11214-020-00762-y.

[3] S. Maurice et al., The SuperCam Instrument Suite on the Mars 2020 Rover: Science Objectives and Mast-Unit Description, Space Sci Rev 217 (2021) 47. https://doi.org/10.1007/s11214-021-00807-w.

[4] A. Cousin, V. Sautter, C. Fabre, G. Dromart, G. Montagnac, C. Drouet, P.Y. Meslin, O. Gasnault, O. Beyssac, S. Bernard, E. Cloutis, O. Forni, P. Beck, T. Fouchet, J.R. Johnson, J. Lasue, A.M. Ollila, P. De Parseval, S. Gouy, B. Caron, J.M. Madariaga, G. Arana, M.B. Madsen, J. Laserna, J. Moros, J.A. Manrique, G. Lopez-Reyes, F. Rull, S. Maurice, R.C. Wiens, SuperCam calibration targets on board the perseverance rover: Fabrication and quantitative characterization, Spectrochim Acta Part B At Spectrosc 188 (2022) 106341. https://doi.org/10.1016/J.SAB.2021.106341.   

Acknowledgements

We are grateful to the many engineers and scientists who have supported the Perseverance mission. We acknowledge the support of Spanish Agency for Research (AEI), NASA’s Mars Exploration Program, CNES, CNRS and other supporting organizations. SuperCam data are archived in the PDS. This work is supported by the 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 (through the Spanish Ministry of Science and Innovation, MCIN, and the European Regional Development Fund, FEDER, MCIN/AEI/10.13039/501100011033/FEDER,UE), the Strategic Project “Study of Alteration Processes in Terrestrial and Planetary Materials” (Grant No. UPV/EHU PES21/88), funded by the UPV/EHU, and the Italian Space Agency (ASI) through the ASI/INAF agreement no. 2025-12-HH.0.