How deep in the ocean does life exist?

A: Life often finds a way to survive even in extreme conditions. For example, in 1960, when Don Walsh and Jacques Piccard explored the bottom of the Challenger Deep in the Mariana Trench, they spotted a small fish at a depth of 8.1 km.

On July 30, researchers exploring the Kuril-Kamchatka and Aleutian trenches discovered the deepest known communities of life powered by chemosynthesis, where organisms get energy from chemicals like methane and hydrogen sulphide instead of sunlight. These ecosystems were found between depths of 5.8 and 9.5 km and stretched over 2,500 km along the ocean floor.

The communities, dominated by worms called siboglinids and clams, thrived where chemical-rich fluids rose through geological faults. These fluids were created by microbes breaking down organic matter, producing methane that may form gas hydrates in the high-pressure conditions.

Per the researchers, the finding suggests these ecosystems may be more widespread than previously believed and highlights a potential new role for deep-sea microbes in the earth’s carbon cycle: storing methane underground instead of letting it escape into the ocean or atmosphere.