One of Saturn's moons, Enceladus, is barely 300 miles in diameter which means if you could drive a car along its circumference it would take roughly six hours at 50 miles an hour to drive all the way around it. It is covered in ice that scientists believe is around 19 to 25 miles thick.
What is so interesting about Enceladus is the recent discovery of an ocean beneath that thick layer of ice. The ocean might be regional and so far scientists believe it is around 6 miles deep.
Why is this interesting?
When I was a little girl, my grandfather had a saying when something was deemed impossible: "You can no longer do that than place a man on the moon." Well, of course in my lifetime I've not only seen us place many men on the moon, but we've also launched satellites which are still in orbit, we've launched exploratory spacecraft both manned and unmanned, and we have the International Space Station where people live for months at a time.
So as we continue our exploration of our universe and those beyond it, it stands to reason that we'll need some pit stops along the way, especially when we begin sending men and women into the farthest reaches. Those pit stops should be able to sustain life, and the most fundamental ingredient is water. Enceladus, then, is getting scientists' attention because with water comes life forms. They might be in their infancy - microbes - or they may discover something more.
The spacecraft Cassini has, to date, flown past Endeladus 19 times. Each time it has measured the force of gravity on this moon, and in its explorations it discovered water gushing out of its south pole. It has even determined that this water is salty - another ingredient for life.
The more that is discovered about our universe, the more fascinating it becomes.