Early molecules would have been destroyed by UV light (Talk.Origins)
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Since the early atmosphere had no ozone layer, ultraviolet (UV) light would have irradiated organic molecules that formed in the atmosphere, destroying complex molecules.
- Watchtower Bible and Tract Society. 1985. Life--How Did It Get Here? Brooklyn, NY, p. 41.
(Talk.Origins quotes in blue)
1. When simple organic molecules are held together in a fairly concentrated area, such as stuck to a dust or ice grain, the UV light actually enhances the formation of more complex molecules by breaking some bonds and allowing the molecules to recombine (Bernstein et al. 1999; Cooper et al. 2001).
What Talk Origins left out is that no amino acids were produced. What were produced were aromatic alcohols, ketones, ethers, and aromatic hydrocarbons. There are plenty of molecules between the products and RNA and DNA that would still be destroyed by UV.
It also needs to be noted that this only works at just a few degrees above absolute zero. While this is fine for deep space, UV will become a problem as near to a star as the Earth is to the sun.
DNA and RNA are relatively resistant to UV light, because some parts of the molecules shelter others and damage to the bases can provide the materials to repair the backbone.
This works fine for DNA and RNA but not their constituent molecules.
UV light gives nucleic acids a selective advantage and may in fact have been an essential ingredient for abiogenesis (Mulkidjanian et al. 2003; Mullen 2003).
It needs to be noted that this is an as yet untested theory. Even if it pans out it would only render this claim out of date. There would still be the chasm between raw RNA / DNA and a living cell, with all its cellular machinery and stored information.
2. The molecules need not all have stayed exposed to UV for long. Some would have dissolved in oceans and lakes. In one proposed scenario, the complex organic molecules form in the deep ocean around geothermal vents, well away from ultraviolet light.
First of all these geothermal vents are known to be as hot as 380 degrees Celsius. However, even if amino acids and nucleotides formed at such high temperature they would not last long. While life does exist near these vents, their organic compounds are maintained by the internal machinery of living cells. However, raw amino acids and nucleotides would not stand a chance. Furthermore, the hot water near the vents tends to rise to the surface, just as hot air rises. So any surviving amino acids and nucleotides would get pushed to surface by heat driven water currents, where they would be zapped by UV.
- Reference: Exploring the deep ocean floor: Hot springs and strange creatures
- Reference: Why abiogenesis is impossible