Peter may have already mentioned something like this, but anyway, the odds of life existing independently on other planets (I say independently, because, since the discovery of tardigrades, which can survive in space, the theory that life can be transmitted on asteroids has gained more support) is extremely slim. I don't know if you've heard of the Anthropic Principle, but basically, it says that because the odds for life existing are so astronomical (I don't remember the number, but it might have been over a billion to one), the Universe is fine-tuned for life to develop somewhere, perhaps to observe the Universe, since quantum dynamics states that particles behave differently when observed. And if we were the first life forms, then that fine-tuning might no longer apply (there's obviously really not a lot of scientific evidence for the Anthropic Principle so it's hard to say how it works if it turns out to be an actual function of the Universe), and the fact that the odds of life developing are so slim, it's not inconceivable that life on Earth is the only life in the Universe.

However, extraterrestrial life, even if it developed from the same kind of microscopic organisms as life did on Earth, would be vastly different from life on Earth. The development of brains capable of invention and scientific curiosity would be statistically impossible, and even if organisms did develop brains, they would not design space ships with lights and other features similar to those that we equip Earth vehicles with. On a completely different planet with completely different organisms, natural selection would take organisms down a very different path.