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Life in Ocean of Saturn’s Moon, Enceladus?

Life might be existing in the ocean of Saturn’s moon, Enceladus. Evidence of a form of chemical energy important for life to exist has been found, and the paper is published in the journal Science.

A graphic illustration of how water interacts with rocks on the ocean-bed of Saturn’s moon, Enceladus. Photo credits: NASA/JPL-Caltech/Southwest Research Institute.

Are we alone in the world? Could life exist out there, in our solar system? We might be nearer to an answer to this question, suggests new evidence obtained from NASA’s Cassini mission: a team of Cassini researchers have found a region on a moon of Saturn, Enceladus, that contains ingredients required for the occurrence of life.

Enceladus is the 6th largest moon of Saturn. Previous NASA missions have shown that it bears a subsurface ocean of liquid water at its southern pole. Now, it seems that this ocean might be harbouring some of the compounds necessary for living organisms. Hydrogen gas, originating from hydrothermal activity on the seafloor, was found entering into the subsurface ocean. The gas might be a potential chemical energy source (food) for life, according to Thomas Zurbuchen, associate administrator at the Science Mission Directorate of NASA.

How is hydrogen an indication of life? The scientists explain that the occurrence of the gas in the ocean implies that methanogenesis might be happening, a process whereby carbon dioxide is combined with hydrogen to release energy. Some microorganisms are known to obtain energy in this way. This reaction is said to be at the root of the tree of life on our planet.

Of course, life needs much more than just a source of energy: liquid water together with certain chemical compounds (carbon, hydrogen, nitrogen, oxygen, phosphorus, and sulphur) are also required. That’s where it gets interesting: Cassini has shown Enceladus to comprise all of these, to be exception of the latter two. However, the scientists believe that phosphorus and sulphur might be existing on the moon. The authors consider their discovery of a source of energy for life to be an important step forward.

“Confirmation that the chemical energy for life exists within the ocean of a small moon of Saturn is an important milestone in our search for habitable worlds beyond Earth,” says Linda Spilker, a Cassini project scientist.

The hydrogen was identified on Enceladus when the Cassini spacecraft dived into a gas plume on the moon back in 2015. Cassini also looked into the plume composition during its flybys. When the researchers analysed this data, they concluded that almost 98% of the plume gas is water, with 1% of hydrogen, and the rest being other molecules like carbon dioxide, methane, and ammonia.

“Although we can’t detect life, we’ve found that there’s a food source there for it. It would be like a candy store for microbes,” says lead author Hunter Waite.

Zurbuchen and his colleagues are not the only NASA scientists looking for evidence of extra-terrestrial life. Another paper published recently focuses on Jupiter’s moon, Europa, and its subsurface ocean. Commenting on the two studies, Zurbuchen says:-

“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.”

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