The field of astrobiology addresses the issues of life and habitability in the universe. While there is still no conclusive evidence that points towards life outside of Earth, there is certainly evidence that suggests habitability on other planets and moons. Given that advanced life already exists on Earth though, there are important considerations (social, religious, individual) regarding the discovery, or lack of discovery, of life.
First of all, if we never discover any signs of current life, or any life for that matter (which seems increasingly unlikely as more discoveries are made), this will impart a significant impact upon human life. This would mean that we are the only living beings in the universe. Although it is quite doubtful that we would ever have the capability to confirm this, the prospect of solitude within the universe, considering its absolute vastness, would be staggering. In addition to a sense of loneliness, knowing that there are no alien brethren out there, this raises questions of purpose. If we truly are the only life in the universe, one has to ask why. Is it possible that there is some reason behind our creation, evolution, and development, that life here, on Earth, has some higher meaning than just a chain of coincidental chemical reactions. Is perhaps our meaning in existence to make it to the point in evolved thought and interpretation that we can understand why and how we came about, chemically and biologically, in our world, such as aspects of the anthropic principle might imply. Or is there some religious truth to our existence, some higher meaning to life and a higher being who oversees it. While it is also unlikely that we will ever discover a “meaning of life”, it is certain that there are many interpretations of our meaning as living beings, and while some are scientifically unlikely, none of them are necessarily wrong. This, in and of itself, gives a bright tint to our dark and lonely existence, the idea that individuals are independent in how they view our purpose on Earth and free to act upon those views however they see fit.
The other possibility is that life is plentiful in the universe, that it is a rather common occurrence, and that our existence on Earth is really nothing special. Given the sheer number of galaxies in the universe containing stars just like our sun, and likely planets just like ours, it seems increasingly doubtful that we are alone in the universe. Now, it is true that we have not found concrete evidence suggesting life that is currently in existence outside of Earth. But this is no reason not to believe that, at some point during the universe’s 4.6 billion year existence, in some corner of its hundreds of billions of galaxies, life has arisen. It seems almost foolish to think that we are truly the only life around. So, if (and I do believe when…) we discover life elsewhere in the universe, there are also some implications for humans. This possibility for life in the universe makes our existence seem far less significant. There is probably no higher meaning or purpose for human life, a potentially large blow to the religious interest on life in the universe. It implies that humans are just another creation of the right combination of planetary conditions. But this doesn’t necessarily mean that life on Earth is pointless and insignificant. While we have no idea if there may be much further evolved societies out among the stars, the things that we humans have accomplished as a race during our time on Earth, in addition to all of the living organisms on Earth, are an incredible feat and a definite “success story” for life in the universe.
So right now, we don’t really know what to think. While there is plentiful evidence suggesting potential life, or at least the necessary conditions for it, we have no definitive evidence for life outside of our home planet. Only time and continued research will tell whether we are the sole inhabitants of the universe, or just another creation of coincidence. No matter what we discover though, the societal impacts here on Earth will be felt.