Deep-Sea Organisms Challenge the Idea That Life Needs Sunlight to Begin

Scientists have observed microbial life thriving in the deep-sea sediments of the Mariana Trench, challenging long-held assumptions about the necessity of sunlight and surface-derived nutrients for the origin of life.

An international team led by researchers from the Japan Agency for Marine-Earth Science and Technology (JAMSTEC) collected samples from depths exceeding 10,000 meters during expeditions in 2021 and 2022. Using advanced genomic techniques, they identified active microbial communities in the hadal zone, the ocean’s deepest region, where pressure exceeds 1,000 atmospheres and temperatures hover near freezing.

The findings, published in the journal Nature Communications, reveal that these microorganisms derive energy not from photosynthesis but from chemosynthesis, utilizing inorganic compounds such as hydrogen sulfide and methane released from hydrothermal vents and serpentinization processes. This metabolic pathway allows life to persist independently of surface ecosystems.

Dr. Takuro Nunoura, a senior scientist at JAMSTEC and lead author of the study, stated: “We found that the microbial communities in the trench sediments are not only surviving but are actively cycling carbon and nitrogen, indicating a self-sustaining ecosystem.” He added that the discovery expands the potential habitats for life on Earth and informs the search for extraterrestrial life in similar environments, such as the subsurface oceans of icy moons like Europa and Enceladus.

The research likewise examined the genetic adaptations enabling survival under extreme pressure, including specialized membrane lipids and enzyme structures that maintain functionality where conventional biomolecules would fail. Comparative analysis with shallow-water microbes showed significant evolutionary divergence, suggesting long-term isolation and adaptation to the hadal environment.

While the study confirms the presence of active life in the deepest oceanic trenches, it does not address how such life originated. Scientists note that whether these communities arose independently or descended from surface ancestors remains an open question requiring further investigation into the genetic and geochemical records of the deep ocean.