How Hot is Too Hot for Earth-Style Life?

Posted on Sept. 15, 2016

Prof. Tina Treude will board the ship mid October to measure the activity of microorganisms (sulfate reduction and methanogenesis) in sediments recovered from deep drilling to study their upper temperature limits. She will be using radioisotope techniques (feed radioactive sulfate and bicarbonate to the microbes) to determine how fast they convert these substances into hydrogen sulfide and methane, respectively. This is a neat technique to track the activity of microorganisms in natural settings. Sulfate reduction and methanogenesis are classical microbial metabolisms that we expect to find in the deep subsurface. Both processes can be involved in the degradation of organic matter or chemosynthesis. It is, however, unknown if they persist in the deep subsurface at high temperatures (up to 120-140 °C). The drill site in the Nankai Trough is the ideal place to test the natural upper temperature limit of sulfate reduction and methanogenesis. Prof. Treude hopes to learn a lot from these studies about limits of life (present and past) on Earth and in potential extraterrestrial habitats.