Europa

Europa is one of the many moons of Jupiter.

Its most interesting characteristic is that it has a thick ice layer covering a liquid water ocean very similar to our own.

The water is kept from freezing by the tidal pulls of Saturn, causing heat to vent from the ocean floor. This is very similar to deep-water heat vents on Earth, which are teeming with life.

The various temperature rangs from warm to freezing would allow any potential life to avoid the warm-blooded size barrier brought on by overheating. Size would only be limited by the supporting ecosystem.

Any potential life would also develop in complete darkness, leading to creatures very similar to our own deep-water organisms, like the anglerfish and viperfish.

In 1997, on Earth in the South Pacific Ocean, the U.S. National Oceanic and Atmospheric Administration (NOAA) detected an ultra-low frequency, extremely powerful underwater sound. This sound is colloquially called "Bloop". It source remains unknown, but the sound is comparable to that of sounds made by some marine animals. This has led most scientists to believe that whatever made the sound is an animal.

To make sound of this magnitude, the creature would have to be several times the size of a blue whale.

This sound was recorded in waters that are just a couple miles deep.

The ocean of Europa is believed to be 62 miles deep.