In the never-ending quest to discover that Earth is not a lone producer of life in the universe, scientists have found that the sixth largest moon of Saturn, Enceladus, holds the potential to sustain living organisms, much the same way that hydrothermal vents deep in the ocean sustain an ecosystem.
Space reports that a research team headed by Hunter Waite of the Southwest Research Institute (SwRI) in San Antonio has produced findings from the data sent back by the Cassini probe, when it made a dive through an Enceladus geyser plume back in October, 2015, that suggests that chemical reactions akin to those surrounding an oceanic hydrothermal vent may occur in the watery depths of the Saturn moon. An ecosystem like this is powered by chemical reaction rather than by reaction to sunlight — important because Saturn is so far from the sun and the ocean water of Enceladus is protected by a thick shell of surface ice. And it could mean that there is alien life in the oceans of the faraway moon.
The study, which was published in Science magazine on April 13, found that Enceladus has an abundance of molecular hydrogen, or H2. Carbon dioxide was also detected in the geyser plume.
Waite and his team concluded that the H2 was likely a product of reactions between hot water and rock in and around the core of Enceladus. The water is believed to be heated by what is known as “tidal heat,” a condition generated by Saturn’s immense gravitational pull as it twists and stretches the 313-mile-wide (504 kilometers) moon as it orbits the gas giant.
So where does the presence of H2 and carbon dioxide present as clues to alien life on Saturn’s sixth-largest satellite?
“Some of the most primitive metabolic pathways utilized by microbes in these environments involve the reduction of carbon dioxide (CO2) with H2 to form methane (CH4) by a process known as methanogenesis,” Jeffrey Seewald wrote in an accompanying piece in the same Science magazine. Seewald works out of the Marine Chemistry and Geochemistry Department at the Woods Hole Oceanographic Institution in Massachusetts.
Chris Glein of SwRI, a co-author of Enceladus plume study, told Space that the H2 levels detected in the geyser indicated that there was plenty of chemical energy potentially available in the moon’s ocean.
“It’s quite a bit larger than the minimum energy required to support methanogenesis,” he said.
Still, Glein issued a word of caution, noting that there is yet no actual evidence of the chemical reactions taking place under Enceladus’ icy shell.
“This is not a detection of life,” Glein told Space. “It increases the habitability, but I would never suggest that this makes Enceladus more or less likely to have life itself. I think the only way to answer that question is, we need data.”
Seewald echoed Glein’s caution, pointing out that there is a reason molecular hydrogen does not appear in abundance on Earth — microbes ingest it.
An abundance of H2 on Enceladus could just as easily point to an absence of life, hydrothermal vents or not.
Discovering life on Enceladus will undoubtedly take an accumulation of new data, just as Glein suggested. A mission to Enceladus, called ELF (Enceladus Life Finder), has been proposed. Said mission would launch a space probe, according to Spaceflight Now, that would pass through a geyser plume, or several plumes, numerous times to acquire data.
There are other plans for exploring the depths of watery worlds like Enceladus in the works as well. As an 2016 article at The Conversation revealed, missions including the use of submarines and ice-penetrating radar are being considered for the moons of Ganymede and Europa of Jupiter, and Enceladus and Titan of Saturn.
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