content long 26-September-2018 09:17:14

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16-18 years old: Ice plumes at the south pole of Enceladus

 Author: Daniel Marcus Corazzi

Does life exist beyond Earth? This is one of the most fundamental questions we can ask. I believe that pointing Cassini’s cameras back at one of Saturn’s moons, Enceladus, would provide us with one of the best opportunities to date to answer this question. Life requires water, heat, organic material and long-term stability. By studying Enceladus further we will be able to discover if it has all these crucial components, and thus determine whether it could harbour life.

In 2005, interest grew in Enceladus when Cassini detected interference in Saturn’s gravitational field. One explanation for this was that Enceladus could be larger than it appeared, which suggested the possibility of an atmosphere surrounding the moon, as well as something residing beneath its icy surface.

At the time scientists were also looking for an explanation for Saturn’s E-Ring, which is composed of small, icy particles, because it appeared that the material in this ring was replaced frequently. On Cassini’s third fly-by, which was much closer than pervious visits, 4 “tiger stripes” along the South Pole were photographed. In addition, jets ejecting icy particles and vapour from beneath the surface were observed. On a later fly-by, the material was analysed, and was found to contain about 1% salt, slightly less than the oceans on Earth. The only way to achieve these high concentrations is to have a large body of water, one of the necessities for life, under the icy surface. A large ocean of this type would also mean the conditions under the surface are stable, which is another requirement for life to exist.

The jets also contained silica particles, which can be produced through interactions of rock with water in warm conditions. It was then suggested that there may be hydrothermal vents on the ocean floor, meaning heat is also present on Enceladus. Since life exists on hydrothermal vents on Earth, it is possible that the same thing could be replicated on Enceladus. Organic hydrocarbons have also been detected in the jets.

If Cassini were to return to Enceladus, it would be able to further analyse the material ejected from the geysers to try and detect other organic molecules. It would also be able to attempt to detect Hydrogen, a key element that can be harnessed by small organisms. If Hydrogen is present on this moon, it is possible that organisms could use it as a source of energy; they would produce methane as a result of this process. Hydrogen has not been detected so far, however turning Cassini’s attention back to Enceladus would mean we would be able to search for it, along with other signs that life could exist on this moon.

Although the other targets are highly interesting, I think Enceladus is the best choice because it provides the best chance of discovering life beyond Earth. In my view this is one of the most important pursuits in science today, and therefore Enceladus would be the best target for Cassini.


Last Update: 19 May 2017

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