Biomarkers of Puga Hot Spring, Ladakh, India: Tracing plausible Prebiotic Pathways and Biogenic Metabolites

The search to unravel the origins of life on Earth pivots on recognizing environments capable of synthesizing and preserving prebiotic organic molecules (chemical precursors to biological systems). Prebiotic chemistry plays a crucial role in understanding the origin of life on Earth, and terrestrial hydrothermal systems may offer the suitable environment for its emergence. In this study, we investigated the travertine deposit of the Puga hot spring in Ladakh, India- a site that not only mimics early Earth environments but also shares similarities with the hydrothermal conditions proposed for early and modern-day Mars. The Puga hot spring is situated in extreme cold location settings of Ladakh, India which is characterized by near-neutral to alkaline waters, enriched in boron, and exhibiting rapid calcium carbonate precipitation. Such features are conducive to capturing and preserving organic molecules that serve as molecular fossils of prebiotic processes. We employed gas chromatography-tandem mass spectrometry (GC-MS/MS) for the first time to analyse sample scraped from both the inner and outer surfaces of the travertine deposit of Puga hot spring. Key compounds identified include traces of β-alanine derivatives (amino propanoic acid), pyran-2-thione, TMS-derivatized formamide, cyclooctasulphur (S₈), and hexadecenoic methyl ester (fatty acid). These findings suggest that both biogenic and abiotic mechanisms may contribute to the synthesis and preservation of these molecules. We hypothesised reaction pathways for molecules identified, which supports possibility of the dynamic interplay between high-temperature geothermal fluids and rapid cooling in a high UV, low-pressure environment facilitating the formation of complex prebiotic molecules. The detection of these compounds in the Puga travertine not only supports the hypothesis that hot spring environments could have been frameworks of early life on Earth but also highlights their potential as analogues for extraterrestrial settings. Current study highlights the pivotal role of hydrothermal systems in chemical evolution associated with origin of life. Our findings provide substantial support for the hypothesis of a natural "prebiotic soup" like conditions in Puga hot-spring, Ladakh, India, revealing that cold environmental conditions may possibly work in synergy with hot spring conditions, playing a crucial role in effectively preserving organic moieties within calcic matrices.