This past year, astronomers have discovered the true age of the Universe – 13.7 billion years. Over the past decade, astronomers have discovered a plethora of planets around other stars – although none of them are Earthlike. This month, NASA landed two rovers on the surface of Mars to continue exploring our nearest neighbour – looking for water.
Seems that the more we look out into space, the more we find out that the universe is a very different place than we thought.
But thinking about the possibility of water on Mars got me thinking about what are the necessary ingredients for life. I mean, could there be gold based organisms walking on a distant planet sucking down mercury shakes? Or is all life bipedal with a head, two eyes, and a mouth the way that it is depicted in Star Trek, Star Wars, and many other sci-fi movies? Does life even have to corporeal?
Well, as far as we have been able to detect, the way that chemical elements combine with each other in the far reaches of the galaxy is the same as here on earth. This is something that we know because light from distant galaxies can be used to determine the presence of simple chemical compounds in space and those same compounds can be found here on earth.
For all intents and purposes, chemistry is the same throughout all of known space.
Hence, oxygen will always combine with two and only two hydrogen
atoms to give water. Nitrogen will combine with three hydrogen to give
ammonia and carbon with four hydrogen to give methane. There aren’t any other possibilities because chemistry is universal in the truest sense of the word.
Given this as a basis, the assumption that life in the universe is similar to life as we know it on this planet is not an unrealistic proposition. On the other hand, we haven’t even come close to understanding all of the life on this planet nor its infinite capacity to adapt to harsh and forbidding environments.
What is essential for life? A mechanism for reproduction and a method for evolution and adaptation. Ideally, this is achieved through some form of encoding molecule such as DNA but any substance that can code a blue print and then be read would do. DNA is just one such molecule and probably not the molecule that life on Earth originally used.
Life also requires some source of energy. We use sunlight and this is a source of energy that makes the most sense, as light radiation permeates the universe. Life on this planet relies on sunlight to fix carbon dioxide and water into glucose. Or, at least, the higher life forms rely on this. It is possible to have anaerobic forms which utilize sulphur as an energy source or methane or … well, as long as there is an energy source, there can be life.
What else is essential? Not much. When you come right down to it, life is simply a matter of obtaining enough energy in a useable form to produce more life forms, in an endless cycle. Everything else is just there to make that task a little easier and maybe more enjoyable.
Is there or was there life on Mars? We don’t know yet. And we may not recognize it even if we do find it. But anything that is reproducing, adapting, and using energy is a likely candidate.