Scientists have long been fascinated by life in extreme environments. Understanding how organisms thrive in the most inhospitable conditions on Earth offers invaluable insights into life’s resilience and evolutionary potential. The subsurface—the realm beneath the ocean floor and within terrestrial caves—represents a vast and largely unexplored frontier in the search for the limits of life.  A surprising diversity of life persists here, especially archaea, ancient single-celled organisms. This project focuses on the extremophilic archaea that thrive in Brazil’s deep seafloor and caves. By recovering and analyzing their DNA, we aim to unravel their unique adaptations and evolutionary history, including the emergence of eukaryotes and new adaptations to survive in extreme conditions. Perhaps this could help us search for life on the oceanic worlds of our solar system.