At first glance it may be confusing as to what is happening in this photograph but upon further inspection it resembles a geyser. It is in fact a plume, spewing out water from the south pole of Enceladus, a moon orbiting Saturn. The Cassini spacecraft took this photo in part of its ‘grand finale’ before it finishes its mission and is controlled to crash into Saturn.
It isn’t the first photograph taken of these water plumes but that doesn’t make it any less exciting. Wherever we find water on Earth, we find life. This may be the case on Enceladus too. Water is essential for the chemical reactions that sustain life so when we look for life beyond Earth; we look where there is water. A source of energy is also required to fuel life and this may come from deep sea vents shooting out hot sulfide gases that would be poisonous for humans but tasty to microbes. These microbes could in turn support larger, more complex organisms.
The source of the water comes from below the surface of Enceladus in its South Pole. While it is commonly referred to as a subsurface ocean, perhaps a better name for the pool of water on Enceladus is subsurface great lake. This is because it is only present in the south pole of the icy moon. The tidal pull of Saturn is responsible for keeping the water in liquid form. The plumes form when water is heated by the core of Enceladus and forced through fissures referred to as ‘tiger stripes.’
In the image above, Enceladus is being illuminated by light reflecting off of Saturn. A small portion on left side of the moon is being light up by the sun. This can make the image slightly deceiving.
In its final months, the Cassini spacecraft will make three more flybys of Enceladus. On October 14, it will fly over the north pole of the moon. Then on October 28, it will actually pass through the plumes. It is possible that these maneuvers may inspire a future spacecraft that could detect microbes that are thrown into space by plumes. Finally, on December 19, it will pass over the South Pole. After this, Cassini will conclude its mission by exploring the rings of Saturn before it crashes.