Exploring Terrestrial Lava Tubes as Martian Analogs (I): Multi‐Analytical Study of Mineralization Processes in Cueva del Vidrio, La Palma (Canary Islands)

Abstract The study of terrestrial lava tubes is essential for understanding geological processes occurring during volcanic activity on other planetary bodies, such as Mars. These processes lead to the formation of minerals analogous to those found on other planets. Volcanic eruptions are often associated with hydrothermal activity and gas emissions (e.g., CO 2 , SO 2 , H 2 S, HCl, H 2 O, H 2 ) through fumaroles, which can simulate Martian atmospheric conditions. These gases and fluids interact with the host rock, leading to mineral alteration and the formation of secondary minerals. This study analyzes the Cueva del Vidrio lava tube on La Palma (Canary Islands, Spain), formed during the 1949 San Juan eruption. Although its materials exhibit low alteration due to their relatively recent origin, the 2021 Tajogaite eruption introduced new gas emissions, groundwater interactions, and surface runoff, thereby promoting the formation of alteration crusts and coatings. The methodology combined minimally invasive techniques, such as X‐ray diffraction, and non‐destructive techniques, including X‐ray fluorescence (μEDXRF) and Raman spectroscopy. In order to facilitate the interpretation of the results, runoff waters were analyzed by ion chromatography. The results highlight the presence of carbonates, sulfates, and iron oxides, notably hematite, which likely formed from silicate weathering, particularly olivine alteration, leading to iron depletion and magnesium enrichment. Additionally, amorphous silica was identified, likely formed through reactions involving sulfate and carbonate precipitation, which leached silicon from silicate‐rich host rocks. Similar processes have been described on Mars, where opal is considered a key mineral for astrobiological investigations due to its potential for preserving biosignatures.