This is a cool video that shows the comparative sizes of different moons in our solar system compared to the Earth. One of the things that always cracks me up is when people talk about sending a mission to Titan or Europa (or any other moon) to study the possibility of life, they never consider just how big that area would be. These moons are like less than 50% the size of Earth, but there are still places on this planet that we have not explored. There are definitely places where we find life and scientists are surprised.
Obviously the hope would be that life is abundant on one of those moons, but what if it were just localized to one very small patch? It would be almost impossible to just stumble upon it. Granted, scientists would try to determine the most likely sites to search before they went, but even still, it is such a difficult prospect.
That does not mean we should not try though. It just means we need to be realistic.
