The deep sea is one of humanity's last frontiers. For most of our history it has been a remote realm, invoking awe and terror as it lays shrouded in darkness. But here, where the light cannot reach, lies a strange, wonderful and breath-taking portal into Earth's past, teeming with scientific marvels and lessons for the future of life on this planet. In The Dark Frontier, marine microbiologist and expert deep-sea explorer Jeffrey Marlow plunges us into the unreachable realm and invites us into close-up encounters with its hidden brilliance. There are translucent shrimp that dance through sulfurous vents, crabs that stretch twelve feet from claw to claw and the eerie chalk-white towers of the 'Lost City'. Immersive and illuminating, Marlow's journeys heed warnings too: our reach is exceeding our grasp. We are irrevocably changing the deep sea before we even know it. This expansive book offers crucial and surprising insights into the birthplace of life on ancient Earth. It shows how life can thrive in even the most extreme conditions and expands our understanding of possibilities - and our responsibilities - on earth and beyond.