Are we alone? In order to answer that, we have to look at what makes life..life.
The question of extraterrestrial life, or the possibility thereof, has been a constant source of fascination for scientists and the general public for thousands of years. There are those who spend their entire lives trying to prove that there are others like us, that we are indeed not alone. Why are so many intrigued by the mystery of whether or not there is life on other worlds? It is hard to explain the thrill of how it feels to think there might be someone out there, wondering if they are alone out there too. Nevertheless, the question remains.Are we alone? Is it possible that there are other forms of life in the vast reaches of space? Perhaps it could be sentient life or “merely” bacteria; just knowing that this is not the only life-abundant planet would be reassuring to some, terrifying to others.
So, what would it take for there to be extra-terrestrial life out there, similar to ours? Life on Earth (or “Terra” as it’s more formally known) is categorized as a carbon-based planet. Part of the life-giving process on this planet requires carbon, whether in the atmosphere or in our bodies. This is but one factor of what is necessary to have a planet where the process of development of life can occur. Since Earth is the only planet with sentient and non-sentient life that we know of, it is vital to understand what qualifications there are on this planet that makes it “life-giving.” Aside from carbon, there are other criteria that have been established that we can use when studying potential places in our quest for extra-terrestrial life.
One of these is oxygen. Water molecules can only be split apart by using ultraviolet light from the sun. The only way this process can occur is through photosynthesis, which is a process only a life-giving atmosphere can make happen.
Another criterion is chlorophyll. Life, as we know it, requires chlorophyll in order to aid the formation and sustenance of life.
A third requisite would appear to be the presence of methane in the atmosphere. Observations have shown that there is always a small presence of methane in the atmosphere, which is unusual because of the process of oxidation. When methane oxidizes, it forms water and carbon, so there shouldn’t be any remaining methane in the atmosphere. The fact that even a trace amount exists shows that the methane supply is continuously being replenished.
Finally, the presence of radio waves not normally present in the atmosphere is a requisite for establishing the presence of life. Unusual and varying frequencies of radio waves suggest technology, which is a by-product of civilization. Of course, this criterion would be useful in establishing a presence of highly sentient life.
One of the more simple approaches to determining whether or not the possibility of extra-terrestrial life exists is to look for the water. As most people are aware, Mars has a significant water source contained in the ice caps at the poles. In addition, Europa (a moon of Jupiter) has been the source of quite a bit of scrutiny in the last decade. It has been determined that because of the magnetic fields and gravity of Jupiter, there is water in a permanently liquid state under the surface of the moon. This is particularly exciting because that would be a similar scenario to our own oceans…and we know our oceans contain life!
Europa and Mars are but two examples of where at least one or two criteria for life are met. It is also clear that various ingredients for extra-terrestrial life are scattered around the galaxy. As the Terran solar system is but one of millions of solar systems in the universe, it is getting increasingly more difficult to believe that we are indeed entirely alone. Do we know for certain there is life on other planets, comets or asteroids? No, at least, not yet.
What we do know is that the ability for extra-terrestrial life to exist is not out of the realm of possibility. Will there be others like us? Perhaps. However, as no two planets form in exactly the same way with the same exact conditions, it is indeed difficult to tell just what kind of “not alone” we could be. The possibilities are endless.