7. Close To Home
Of course, it's perfectly possible, and probably more likely, that if we find alien life, it's not going to be at the "radio signal" stage. So, let's dial it back a bit for the moment and imagine that we discover extraterrestrial life a little closer to home (don't worry, we'll get to the "alien overlords" bit). If it turns out that life is actually a pretty common occurrence in the universe, then there are a couple of places we might find it in our own solar system. Whilst it's unlikely that there's a hyper-advanced race living it up on Mars (unless they've got some crazy cool holographic cloaking systems or something), there might yet be microbial life present. Not exactly exciting if you've grown up on a diet of Doctor Who, but it would still essentially double the figure for "known habitable planets". There are even some who think that Venus might be hiding something beneath its thick blanket of clouds. Further afield, there could be yet more exciting things. Jupiter's moons Europa, Callisto and Ganymede appear to have a subterranean ocean each. Whilst it would be darker and colder than we can possibly imagine down there, there's still a chance that life might develop. It might not be in the "beaming out radio signals" game, but it might be more complex than microbial sludge. Moving away from planets and moons altogether, there's also a distinct possibility that something might be knocking around in the asteroid belt. The idea that the building blocks for life were delivered to Earth via asteroid impact would fit with this. As exciting as it would be to find a bunch of microbes partying it up throughout the solar system, it's probably not what most people have in mind when they think of E.T., so let's dive deeper into the hypothetical world of "contact".