Mid-ocean ridges are dotted with seafloor hot springs feeding a 'deep hot biosphere' of ancient microbes, likely the first lifeforms on Earth. Indeed, the ocean is considered the 'cradle of life' because of the potential for organic molecules to spontaneously form in hot springs - a process we do not fully understand. Increasing evidence for diverse organic molecules in these fluids suggests they form by multiple diverse pathways. These include purely chemical "abiotic" transformations of volcanic carbon dioxide to simple organic molecules (from which life may have emerged), but also thermal decomposition of marine biological matter or microbes already present in the crust - perhaps signifying life's presence beneath the seafloor.
The global mid-ocean ridge is dotted with deep-sea hot springs fueling a 'deep biosphere' of ancient microorganisms, likely the first to emerge on Earth. The ocean is thus considered the 'cradle of life', yet the nexus of this thinking - the potential for dissolved organic molecules to spontaneously form in these hot spring fluids - is a process we do not fully understand. Emerging evidence of diverse organic molecules in hot, reducing fluids emanating from these aquifers suggests they form by multiple pathways, including non-biological CO2 reduction (generating abiotic molecules from which life can emerge), and thermal breakdown of crustal microbial carbon or dissolved organic matter (DOM) - perhaps signifying life's presence beneath the seafloor. Both abiotic synthesis of origin-of-life relevant molecules, and pyrolysis of pre-existing organic matter are poorly studied phenomena at conditions of deep-sea hot springs, leaving huge gaps in our understanding of carbon transformation in ocean crust fluids. Understanding hydrothermal production of the small organic molecules now detectable is critical for assessing energy sources for biotech-relevant microbes, and a potential hydrothermal origin of life on Earth and other ocean worlds in our Solar System (e.g. Enceladus). HyPOD will rigorously examine generation of diverse hydrocarbons, sulfur-, nitrogen- and oxygen-rich organic molecules from multiple carbon sources (CO2, microbial carbon, DOM, sedimentary kerogen) in hot springs, using state-of-the-art high temperature-pressure experiments and theoretical models to illuminate the diversity, differences & isotope signatures of organic products formed. Validating these findings through organic analyses from real hot spring fluids as part of HyPOD will transform our understanding of carbon cycling in volcanic ocean crust, revealing the high-temperature fate of microbial deep biosphere carbon, and the prebiotic hydrothermal organic ingredients for the origin of life.