Discriminating organic carbon from endokarstic moonmilk-type deposits by LIBS. The case of a natural carbonated Martian analogue

• Published in: Talanta (Oxford) Vol. 271; p. 125639
• Main Authors: Delgado, T., García-Gómez, L., Fortes, F.J., Cabalín, L.M., Liñán, C., Vadillo, I., Jiménez-Gavilán, P., Ojeda, L., Laserna, J.J.
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01.05.2024
• Subjects: Biosignatures; Karstic caves; LIBS; Molecular emission; Moonmilk deposits; Biosignatures; LIBS; Molecular emission; Moonmilk deposits; Karstic caves
• ISSN: 0039-9140; 1873-3573
• DOI: 10.1016/j.talanta.2024.125639

Moonmilk-type deposits exemplify carbonated Martian analogues existing in the subsurface of Earth, an endokarstic speleothem with a possible biochemical origin composed principally by carbonates, mainly huntite and dolomite. In this work, samples of moonmilk located in Nerja Cave (southern Spain) have been studied by LIBS with the aim of identifying carbon of biogenic origin by establishing a relationship between a molecular emission indicator, CN signal, and the organic carbon content. The characterization of this kind of carbonate deposit with a multiple mineralogical composition has been completed using scanning electron microscopy (SEM), energy dispersive X-ray (EDX) and X-ray diffraction techniques for qualitative and semi-quantitative analysis. The information attained from LIBS regarding energy thresholds and time-resolved kinetics of CN emissions provides useful insight into the identification of different molecular emitters, namely organic and inorganic CN, depending on the laser irradiance and time settings conditions. These promising results are of application in the search and identification of biosignatures in upcoming planetary missions with astrobiological purposes. [Display omitted] •Analysis of natural moonmilk speleothems by LIBS.•Ability of LIBS to detect molecular emission in karstic environments.•Correlation between optical CN emission and organic carbon content in carbonate rocks.•Differentiation of organic carbon and inorganic carbon by time-resolved LIBS.•Application in the identification of biosignatures in upcoming astrobiological missions.