So far in this series I have discussed the possibility of life existing on Mars or Jupiter. In this post I turn my focus to Saturn.

Best known for it's unique and spectacular planetary rings Saturn is the sixth planet from our Sun and is the second largest in our system, some 95 times larger than the Earth. The planet itself is not believed to be able to sustain life as we know it, due to it's poisonous and dense atmosphere, however Saturn has a record number of moons totalling 62! These range in size from 1 kilometer to massive Titan which is larger than Mercury.

Titan

Often described as a planet like moon, Titan is 50% bigger than our moon and is the second largest in our galaxy after Jupiter's Ganymede. It also holds the distinction of being the only known moon to have a dense atmosphere, comprised largely of nitrogen with additional components of methane and ethane - combining to make a very nitrogen rich smog. The atmosphere is twice as thick as it is on Earth.

Liquid methane lake on Titan

At -179.2C or -290.6F the surface temperature of Titan is much colder than here on Earth and despite there being a lack of evidence for the existence of water, there is speculation that life not as we know it could indeed exist in the chemically rich lakes of liquid methane. This life would have to be methane based and oxygen free. This hypothesis came into being in 2015, when chemical engineers in the US created a template explaining how life on Titan and other places in the universe could potentially exist. Experiments in the lab showed that membrane like structures could indeed be created, built from nitrogen, carbon, and hydrogen molecules - which are in abundance on Titan. Theoretically these membranes could eventually evolve in living cells and primitive organisms under the same conditions as are present on Saturn's largest moon.

Enceladus

In 2004 the space probe Cassini began weaving it's way through Saturn's rings and moons. When it aimed it's instruments towards Enceladus it was discovered that the although it was a frozen moon, giant geysers spewed out into space, most likely due to volcanic activity at it's core. In addition indications were that underneath Enceladus' icy shell it had a vast subsurface salt water ocean. The geysers are formed through water being pushed out through the ice in a network of cracks nicknamed tiger stripes. In 2015 Cassini flew through the plumes of what turned out to be gas and icy particles that make up Enceladus’ geysers, where it detected a great deal of molecular hydrogen. NASA scientists' best explanation for this is that hydrothermal reactions occur on Enceladus’ ocean floor, similar to hydrothermal vents back here on Earth.

Artist's impression of the interior of Enceladus

The chemical and thermal dynamics in hydrothermal vents make these environments extremely suitable for chemical evolution processes to take place. In April of this year scientists announced that molecular hydrogen in the plumes of Enceladus may be due to methanogenesis, a process that implies microbial life.

Hydrothermal vents on Earth

Liquid water is an energy source, and the right chemicals - carbon, hydrogen, nitrogen, oxygen, phosphorus and sulphur - are the main requirements for life as we know it. So far, apart from phosphorous and sulphur, scientists have discovered all of these ingredients on Enceladus.

If indeed microbial life does exist on Enceladus, could more complex lifeforms have evolved beneath it's icy shell?

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Do you think Enceladus is teeming with life beneath it's icy surface? Let me know in the comments below

In my next post in this series we will leave our neighbourhood and venture out of our galaxy in our hunt for ET

Part 1: Mars and Part 2: Jupiter

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Source 1, 2, 3, 4, 5, 6

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