When it comes to the search for extra-terrestrial life, scientists have a tendency to be a bit geocentric – i.e. they look for planets that resemble our own. This is understandable, seeing as how Earth is the only planet that we know of that supports life. As result, those searching for extra-terrestrial life have been looking for planets that are terrestrial (rocky) in nature, orbit within their stars habitable zones, and have enough water on their surfaces.