To do that, they developed a model for a hypothetical methanogen, whose thermal and energetic niche was modelled after known strains from Earth. The team looked at Enceladus' plume composition as the end result of several hypothetical chemical and physical processes in the moon's interior.įirst, the researchers assessed what hydrothermal production of dihydrogen would best fit Cassini's observations, and whether this production could provide enough 'food' to sustain a population of Earth-like microbes that produce methane. Most of the production is due to microorganisms that use hydrothermally produced dihydrogen as a source of energy, and produce methane from carbon dioxide during methanogenesis. Methane, a powerful greenhouse gas, can be produced through hydrothermal activity on Earth, but at a slow rate.
On Earth, hydrothermal activity occurs when cold seawater seeps into the ocean floor, circulates through underlying rock and passes a heat source, like a magma chamber, before spewing out into the water again through hydrothermal vents. This artist's impression depicts NASA's Cassini spacecraft flying through a plume of presumed water erupting from the surface of Saturn's moon Enceladus Therefore, Ferriere and colleagues constructed mathematical models to calculate the probability that different processes, including biological methanogenesis, might explain the data on the plumes emanating from Enceladus, captured by Cassini.ĭata is consistent either with microbial hydrothermal vent activity, or with processes that don't involve life forms but are different from the ones known to occur on Earth, they conclude. 'Searching for such microbes, known as methanogens, at Enceladus' seafloor would require extremely challenging deep-dive missions that are not in sight for several decades.' 'We wanted to know, could Earthlike microbes that "eat" the dihydrogen and produce methane explain the surprisingly large amount of methane detected by Cassini?' said study author Professor Regis Ferriere at the University of Arizona. The amount of methane found in the plumes was particularly unexpected, according to the authors, from the University of Arizona and Paris Sciences & Lettres University. When flying through the plumes during its nearly 20-year mission, Cassini detected a relatively high concentration of certain molecules usually associated with hydrothermal vents on the bottom of Earth's oceans – dihydrogen and carbon dioxide, as well as methane.
Giant water plumes erupt from Enceladus, indicative of a vast ocean that is believed to be sandwiched between the moon's rocky core and its icy shell. It's one of few locations in the Solar System with liquid water, along with Earth and Jupiter's moon Europa, making it a target of interest for astrobiologists.
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