¹F. Alberquilla (>10)
Journal of Geophysical Research: Planets, 131, e2026JE009742 Open Source Link to Article [DOI: 10.1029/2026JE009742]
¹University of the Basque Country (EHU), Leioa, Spain
Published by arrangement with John Wiley & Sons

Volcanic tubes provide stable environments where unique mineralogical assemblages can form and be preserved, making them valuable terrestrial analogs for Martian studies. This work investigates tree-like structures within two lava tubes on La Palma Island (Canary Islands, Spain) through a comprehensive geochemical and mineralogical characterization. Samples were analyzed using X-ray diffraction (XRD), micro Energy Dispersive X-Ray fluorescence (µ-EDXRF), Raman microscopy, Scanning Electron Microscopy Energy-Dispersive X-ray Spectroscopy (SEM-EDX), Short-Wave infrared (SWIR) hyperspectral imaging, and multivariate analysis Principal Component Analysis and Multivariate Curve Resolution-Alternating Least Squares (PCA and MCR-ALS) to identify primary mineral phases and assess potential organic matter preservation. The results reveal that these structures are predominantly composed of hydrated silica (opal-A), with secondary phyllosilicates, carbonates, sulfates, and iron oxides. Organic signatures were identified as spectral features consistent with microbial pigments such as β-carotene within the opal matrix, suggesting the potential encapsulation and preservation during silica precipitation. Hyperspectral analyses revealed spectral features consistent with the presence of opal-A, calcite, and nontronite, highlighting complex mineral associations. The comparison with CRISM observations from Jezero Crater revealed similarities in mineral assemblages and suggests that comparable alteration pathways may have affected basaltic substrates, with hydrated silica formation followed by carbonate precipitation under evolving fluid conditions. These findings underscore the relevance of terrestrial lava tubes as analogs for Martian volcanic environments and emphasize the potential of hydrated silica deposits to preserve biosignatures in extraterrestrial contexts.