Scientists are excitedly finding extrasolar planets, planets that orbit distant stars. How excited would they be to find life? The search for exterrestrial life in the universe is ongoing. It’s quieter than the search for new planets. Mainly because they haven’t found it yet. As a writer of science fiction, this topic interests me. what if we haven’t found it because we aren’t looking wide enough?
Life on earth consists of cells that contain DNA. That’s a good definition of life, right? Well, not exactly, that definition leaves out the viruses. Are viruses alive? Let’s determine that. what is life? What do we mean by the word? Wikipedia says that “Life is a characteristic distinguishing physical entities having biological processes (such as signaling and self-sustaining processes) from those that do not, either because such functions have ceased (death), or because they lack such functions and are classified as inanimate.” That’s a good definition, but again we have to define what biological processes we are talking about.
Life on earth consists of organisms consisting of at least one or two cells – that leaves out the viruses and viroids. Do you see the problem here?
Most things we classify as life on earth have some sort of blueprint – DNA or RNA and self-replicate. So now we have included viruses. We have just defined life. Or have we? DNA is a repeating series of molecules involving sugars and phosphates. Sugar is based on carbon, hydrogen, and oxygen. Phosphates consist of Phosphorus and oxygen. So life requires carbon, hydrogen, phosphorus, and oxygen – to be simplistic.
Carbon could be replaced by at least six other elements, silicon, germanium, tin, lead and something called flerovium. The same is true of phosphorus, except the elements that could replace it are nitrogen, arsenic, antimony, bismuth, and unumpentium.
That’s thirty-six combinations to think about and that’s not taking into consideration any variations for oxygen and hydrogen – although hydrogen is somewhat special and might not vary as much as the other main chemicals.
I’m being overly simplistic here as I am no chemist, but I do think that the search for life in the universe should include these considerations. For all I know it does. My point here, which has nearly gotten lost is that alien life would be alien – maybe to the point where we don’t recognize it as life. That’s what makes it hard to locate life on other planets – we only know what it is here on Earth. We could even be wrong about that as well. there could be other forms of life on this world that we simply haven’t realized is living.
So when you are thinking about the life and the universe, take a moment and think how amazing it is that life on earth evolved. Try to broaden your thoughts into the other forms it might have taken– or did take. Have fun with that.