On the molecular level, the chances of life originating at deep sea thermal vents is not likely. It is known that organic molecules are unstable at high temperatures, and are destroyed as quickly as they are produced. It has been estimated that life could not have arisen in the ocean unless the temperature was less than 25oC, or 77oF.
Duke Chem dept
chem.duke.edu
Supporters of this theory claim that the organic molecules at the thermal vents are not formed in 300oC temperatures, but rather in a gradient formed between the hydrothermal vent water, and the extremely cold water, 4oC (39.2oF), which surrounds the vent at the bottom of the ocean.
The temperatures at this gradient would be suitable for organic chemistry to occur. Debates still remain, however, as to the gradient's effectiveness in producing organic compounds.
Frozen Ocean
Three billion years ago, the Sun which lights our solar system was thirty percent less luminous than it is today. Mant people believe that if the Earth's atmosphere was the same then as it is today, the oceans would be frozen. But recently, Jeffrey Bada of the Scripps Institution of Oceanography has proposed that the oceans would not completely freeze. Instead, he calculates that only the top 300 meters of the ocean would freeze over.
You might think that icy cold water trapped under hundreds of meters of ice would not be beneficial to life beginning, but in fact it is advantageous in many aspects. One advantage is that the layer of ice would provide a protective shield by preventing ultra-violet light, which enters the earth's atmosphere and destroys organic compounds, from reaching the developing molecules.
Another advantage is that it would provide safety from the devestating effects of impact frustration. ( Definition Box -Impact frustration is a theory which says that life may potentially have arisen many times, but was wiped out due to severe bolide impacts) The water beneath the ice would be cold, allowing for organic molecules to survive over much longer periods of time. These organic molecules could have been provided by the hydrothermal vents still prevalent on the ocean floor today. With a sufficient supply of organic molecules safe from ultra-violet radiation and bolide impact frustration, many believe that this was the environment allowing life to get a foothold on a hostile earth. meme
With a barrier between the atmosphere and the ocean, the debate concerning the composition of the atmosphere becomes much less significant. All of the components needed for organic syntheses such as the Strecker synthesis would be provided and kept stable, while the bottom of the ocean would provide a place for organics to gather and react. Following this reasoning, the atmospheric composition may only be important after life came out of the water, when life had already begun.
EZ, Peazy... |
