BBC: Water in liquid form is thought to be a necessity for life on Earth.
Naturally, some say that life may flourish under other conditions, and perhaps even in the absence of water.
While that may be true, take a look around - life seems to do quite well here on Earth and we've yet to find it elsewhere in our Solar System.
Based on this, let's look at the classical definition for the habitable zone as the region around a star, such as our own Sun, where the temperature of any orbiting planet...