Discovery of novel structures at 10.7 km depth in the Mariana Trench may reveal chemolithoautotrophic microbial communities

During an expedition in 2012 we recovered sediment, water, and biological samples from the inner slope of the Mariana Trench using a lander equipped with cameras, three twenty-liter Niskin bottles, a baited net trap, and a pressure calibrated depth sensor. Images and samples collected from the 10,677 m drop site reveal filamentous structures covering both talus and outcrop, which we cautiously identify as a microbial mat community. Analyses of retrieved sediments and images of the outcrop indicate that serpentinization of exposed ultramafic rock may be the source of the chemical energy needed to sustain this ecosystem. If true, this is the deepest known such community to be identified in Earth's ocean. •Images, video, and a small sample were retrieved from the Sirena Deep (10,677 m) within the Mariana Trench.•Geologic evidence reveals the site to have possible undergone serpentinization, past or present.•Filaments attached to the talus and potential outcrop may be of microbial origin.•This site may be the deepest known chemolithoautotrophic microbial mat community in our ocean. One Sentence Summary: We report on the discovery of novel structures at 10.7 km depth in the Mariana Trench that may be the result of microbial communities sustained through serpentinization.