OCEAN WORLDS
Microbes Thrive in Laboratory Replica of Saturn Moon's Hidden Sea
Researchers report that a methane-producing organism grew in conditions meant to mimic the alkaline ocean beneath the ice of Enceladus.
MUNICH, GERMANY — An international team of scientists reports that it has grown a microorganism in a laboratory environment designed to resemble the subsurface ocean of Enceladus, the icy moon of Saturn, according to The Debrief. The findings were published in Science Advances.
The researchers hail from Ludwig Maximilian University of Munich, the Woods Hole Oceanographic Institution, the University of Regensburg and Freie Universität Berlin. They placed Methanothermococcus okinawensis, a methane-producing microbe found in Earth's deep-sea hydrothermal environments, into a low-oxygen chamber filled with a highly alkaline, salt-rich solution meant to echo the moon's chemistry.
Enceladus is described as a frozen world whose ice shell is estimated to average 12 to 16 miles thick, covering a global ocean kept liquid by gravitational interactions with Saturn and activity in its rocky interior. Scientists believe that ocean is extremely alkaline and contains little oxygen, and it had been thought that the scarcity of carbon dioxide would starve such organisms.
According to the report, the microbes struggled in conventional laboratory media at a pH of 10 or 11. When the team recreated aspects of the moon's water-rock chemistry, however, reactions in the system produced hydrogen that the organisms could use to make methane and grow. The organism also appears to have managed by scavenging tiny amounts of carbon dioxide.
Lead author Dr. Vanessa Helmbrecht is quoted as saying the experiments show the moon's geochemistry could be even more favorable to microbes than previously thought. Co-author Professor William Orsi cautioned that the study does not prove life exists on Enceladus, though he said it strengthens the case for missions to retrieve samples from the moon's plumes.
The article notes that the European Space Agency has been studying a future mission to Enceladus, and that NASA has considered concepts focused on its habitability. The paper is titled "Enceladus-like Geochemistry Fuels Methanogenesis Under Extreme CO2 Limitation."