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Serpentinization is a pervasive hydration process of ultramafic and mafic rock which releases significant amounts of diatomic hydrogen (H2) alongside characteristic secondary minerals and primary altered serpentine minerals. It occurs throughout Earth’s subsurface and marine realms, as well as across the continents in ophiolites and ultramafic intrusions, and is considered the foundation of a diverse chemolithoautotrophic microbiota in all of these environments. Serpentinization reactions optimally proceed at approx. 300 °C, but there is doubt as to this process’s efficacy at so-called ultra-low temperatures—<50 °C—specifically in terms of ability to support microbial life. This study presents a comprehensive incubation experiment of two methanogen strains—Methanobacterium oryzae strain FPi and a novel strain from the Chimaera Seeps, Türkiye—at 37 °C over ~100 days, in order to assess the aforementioned serpentinization efficacy. Headspace from experimental samples was analyzed by gas chromatography (GC) to determine partial pressures of methanogen metabolic gasses as a proxy of growth and serpentinization rates, while x-ray diffractometry (XRD) and energy-dispersive x-ray (EDX) microanalysis were used to directly gauge conversion of dunite powder in the samples into serpentinite. Results indicate not only a lack of growth in samples relying solely on serpentinization as H2 source, but also a null-percent conversion of dunite into serpentinite over this short timescale. Curiously, results also indicate a heretofore undocumented inhibitive relationship between both methanogen strains utilized and dunite. Thus, this work has important implications for constraining abiogenesis research, the search for extraterrestrial life, and criteria for serpentinization-sourced methane in climate modeling.