The team behind the Cassini mission have made another fascinating discovery, and announced it today. They seem to have discovered a large lake of warm water on the surface of the moon Enceladus.

Enceladus is one of the moons of Saturn, and is actually relatively small being only the sixth largest of the moons. It was first discovered by Herschel in 1789, but due to its size and distance it was not well studied until the 1980s. Then the two Voyager probes passed close enough to photograph and examine Enceladus, and it was found to be about 300 miles in diameter and composed of a variety of terrains. Some parts of the moon were old rock, but other parts seem to be large oceans or lakes. 

Interest in this tiny moon increased in 2005 when the Cassini probe made several close fly-bys and discovered that the southern polar region also had plumes rising from it that contained a significant amount of water. This would indicate liquid water on the surface (or just below it) which would be ideal conditions for the development of aquatic life.

Now Cassini has provided more information, and it is even more interesting. Using very precise measurements of the probes motion around the moon and the effects of gravity, and complicated geophysical models of possible compositions of Enceladus, researchers have shown that there is a strong probability that the south pole contains a lake about the size of Lake Superior or perhaps slightly larger. It is about 10km deep, and is most likely warm salt water buried beneath an ice layer. 

And so Enceladus is now known to contain several of the key ingredients for life. It has a source of thermal energy to keep it warm enough, it receives solar energy as well, and now we know that it contains a large liquid water ocean or salt lake. Those factors together make it perhaps the best candidate for extraterrestrial life in our solar system. 

Perhaps in the near future we will be able to definitively prove the existence of alien life, and right here in our own solar system.