Published: Thu, April 20, 2017
Research | By Jennifer Evans

Possible life in the Enceladus ocean: Saturn

Possible life in the Enceladus ocean: Saturn

Discovering conditions that would allow life on Enceladus was one of the final achievements of the Cassini space probe, a joint mission between NASA, the European Space Agency and the Italian space agency, Agenzia Spaziale Italiana, which was launched in 1997. "These results demonstrate the interconnected nature of NASA's science missions that are getting us closer to answering whether we are indeed alone or not".

"The abundance of H2, along with previously observed carbonate species, suggests a state of chemical disequilibria in the Enceladus ocean that represents a chemical energy source capable of supporting life", Jeffrey Seewald, a researcher at the Woods Hole Oceanographic Institution in MA who was not involved in the study, wrote in an accompanying "Perspectives" piece published alongside the new paper. Scientists determined the gas in the plume almost 98 percent water, about 1 percent of which is hydrogen, with the rest being a mixture of carbon dioxide, methane and ammonia. The white icy moons close to the ring plane are, from left, Enceladus, Dione and Mimas. In fact, some moons may contain subsurface oceans with a larger total volume of water than Earth has.

Scientists on NASA's Cassini mission conjecture that this is how water interacts with rock at the bottom of the ocean of Saturn's icy moon Enceladus, producing hydrogen gas (H2).

The detection of molecular hydrogen occurred in October 2015 during Cassini's last pass through Enceladus' plumes, when it skimmed 30 miles (49 km) above the moon's southern pole taking samples. Hydrogen and carbon dioxide in the water could bolster a metabolic procedure called "methanogenesis".

It was lucky Cassini was even able to determine this much - the Ion and Neutral Mass Spectrometer (INMS) instrument used for this analysis was included to sample the atmosphere of Titan.

Life as we know it requires liquid water, and until recently that seemed to be in short supply outside of Earth.

"We're moving towards Enceladus's ocean being habitable, but we're not making any claims at this point about it being inhabited", lead author Hunter Waite of the Southwest Research Institute (SwRI) in San Antonio, Texas told Reuters.

And now, with the recent discovery, NASA confirms that there are hydrothermal vents in the oceans on Enceladus, which is important, because on Earth, hydrothermal vents are found deep, deep in the sea and offer food and warmth to weird sea creatures of the abyss. Plumes have also been observed by the Hubble Space Telescope (HST) erupting through the solid ice surface of Europa's ocean. These images bolster evidence that the Europa plumes could be a real phenomenon, flaring up intermittently in the same region on the moon's surface.

Astronomers had, in the past few years, added Enceladus to that list, with these plumes evidence that there is something beneath the moon's icy crust. Researchers speculate that, like Enceladus, this could be evidence of water erupting from the moon's interior.

"The relatively high hydrogen abundance in the plume signals thermodynamic disequilibrium that favors the formation of methane from Carbon dioxide in Enceladus' ocean".

Two years ago, Cassini discovered tiny particles of silica, a material which is dissolved from rocks.

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