¶ … Origin of Life
There are currently many different competing theories on how life originated on this planet. One of these theories involves the early state of the atmosphere. According to this theory, the first step in the origins of life was the spontaneous formation of carbon compounds in Earth's then carbon-rich atmosphere. There is substantial evidence that these compounds could have formed -- they are a common occurrence throughout space, and experiments have shown that even amino acids, the building blocks of proteins, can be formed under conditions similar to those that existed at a certain point in the Earth's past. The theory goes that after these amino acids and other organic compounds formed, they eventually came together to form more complex systems, at some point coalescing into unicellular organisms. There is no way to prove, however, that this is actually what happened, and as yet no mechanism described for how the various simple organic compounds could have organized themselves into more complex cells that exhibited signs of life. The process would have taken millennia at the least, and time is one of the few things that cannot be replicated in a lab.
A more controversial theory regarding the origins of life is that it began deep under the ocean near thermal vents. These vents, first discovered in 1979, release extremely hot gases from below the Earth's crust into water that is near freezing (Duke). The mixture of the gas and the temperatures creates a gradient around the vents that is ideal for the formation of organic molecules. There is a flourishing ecosystem around these vents, which is the evidence that first led scientists to postulate that these vents were the sites of the origin of life, but others contend that the extreme temperature of the gas released by the vents would destroy any organic molecules created long before they had time to organize into more complex, let alone living, compounds (Duke). There are many other theories in addition to these two, and though some might be disproved, it is unlikely that we will ever be able to claim with any certainty how life first came to Earth.
Works Cited
Duke University Chemistry Website. "Possible Sites for the Origin of Life." Accessed 4 December 2008. http://www.chem.duke.edu/~jds/cruise_chem/Exobiology/sites.html
