There are some interesting theories that speculate where and a bit of how life might have begun.
What is DNA? DNA is a self-replicating material present in all living organisms as the main constituent of chromosomes.
According to the fossil record life on Earth began somewhere around 3.5 billion years ago. But how did that life come to be? According to scientists as the Earth cooled down, simple organisms came into existence, slowly forming into complex compounds. There is evidence that suggests these first cells replicated not DNA but RNA and then evolution shifted to DNA, a much harder to replicate but more stable substance.
Professor Brenner at the Westheimer Institute for Science and Technology has suggested a different theory which understands the difficulty involved in the change from RNA to DNA and considers outside influence. Influence from Mars.
Apparently back when life began, our planet was still submerged in water and very low in dioxygen. Benner doesn’t believe that under those conditions life could not have begun – without some help that is.
While Earth was lacking several things, such as borate or molybdate : borate helps organic molecules to form the carbohydrate rings and molybdate then rearranges the rings to form ribose, a building block of RNA. Since the minerals were scarce here on Earth but existed on Mars, well, you fill it in. Evidence? We have 120 Martian Meteorites and some contain the evidence we require. They certainly show that boron was on Mars and quite obviously, came here to Earth. Add in the oxidized form of molybdenum and now you got yourself some life.
BUT THEN THERE IS ANOTHER CONSIDERATION. This theory is not offered by some famous scientist, but it is brought up by me. The facts that lead me to consider this, are as follows. I give you the red rain of Kerala, India. Dr. Godfrey Louis had some samples from the red rain that occurred there in 2001. What did he find? Microbes from outer space. Red-tinted cells that replicated with ease and in extreme conditions. The biggest discovery? These items replicated without having DNA.
So, what is my theory? First of all this isn’t the only case of no DNA, but it is in recent history with lab tools that can be trusted. Given that fact, I suggest that maybe DNA isn’t the ONLY building block to life. That ET doesn’t necessarily look humanoid and that water isn’t required. Although given the frequency with which we are finding Deuterium, perhaps it is or was more plentiful than we think.
NOW think about having water, the temperature can go from boiling point to freezing point. And in the case of heavy water (Deuterium not simple H) What does that mean to our search for intelligent life? We need to put away any pre-conceived notions that life will take a form similar to ours. These “humanoid” inhabitants of the alien planets is an idea that has been helped along through years of Sci Fi books, movies, and television shows.
That does not mean that all the creatures differ from us, after-all evolution decided that we arrive at our current status, but in a Methane world or lava planet, or some other extreme, we may be surprised at not only the way life manifests itself but also that the alien may not utilize DNA in choosing its big orange eyes.
Perhaps the best tool that we have is our imagination. Through that we can take what is possible and go to its extremes. That being said, imagine if you will.