Before descending from orbit in September 2017, Cassini examined the plume of grains of ice and water vapor that erupted from cracks in Enceladus’s icy surface and discovered molecular hydrogen, a potential food source for microbes. A new article, published in the journal Icarus planetary science, explores other potential energy sources.
“The discovery of molecular hydrogen (H2) in the plume has shown that there is free energy in the ocean of Enceladus,” explains lead author Christine Ray. – On Earth, aerobic or oxygen-breathing creatures consume energy from organic matter. Namely glucose and oxygen to create carbon dioxide and water.”
Previous research has found increasing evidence of hydrothermal vents and chemical imbalances at Enceladus, indicating livable conditions in the underground ocean.
Scientists wondered if other types of metabolic pathways could provide energy sources in the ocean of Enceladus. Since this would require a different set of oxidants not yet found in the Enceladus plume, the researchers performed chemical simulations.
For example, the authors examined how ionizing radiation from space can create oxidants O2 and H2O2 and how abiotic geochemistry in the ocean and rocky core helps support metabolic processes. The team looked at whether these oxidants could build up over time.
“We compared our free energy estimates with ecosystems on Earth and determined that, overall, our values for aerobic and anaerobic metabolism meet or exceed the minimum requirements,” concludes Ray. “The results show that oxidant production and oxidation chemistry can contribute to the maintenance of eventual life and a metabolically diverse microbial community on Enceladus.” Metabolic processes could support a potentially diverse microbial community in the ocean of liquid water under the icy facade of this moon of Saturn.
The findings of the article are also of great importance for the next generation of researchers.
A spacecraft of the future could fly through the Enceladus plume to test this article’s predictions about the abundance of oxidized compounds in the ocean.