The early earth

The early earth

It is believed that the Earth was formed about 4.5 billion years ago

• Heavy bombardment by rubble ceased about 3.8 billion years ago.

• Reducing atmosphere: much free H

• also H2O, NH3, CH4

• little, if any, free O2

• with numerous H electrons, require little energy to form organic compounds with C

• Warm oceans, estimated at 49-88°C

• Lack of O2 and consequent ozone (O3) meant considerable UV energy

Chemical reactions on early earth

• UV and other energy sources would promote chemical reactions and formation of organic molecules

• Testable hypothesis: Miller-Urey experiment

• simulated early atmospheric conditions

• found amino acids, sugars, etc., building blocks of life

• won Nobel prize for work

• experiment showed prebiotic synthesis of biological molecules was possible

Issues

• Miller later conceded that the conditions in his experiments were not representative of what is currently thought to be those of early earth

• He also conceded that science has no answer for how amino acids could self-organize into replicating molecules and cells

• In the 50 years since Miller-Urey, significant issues and problems for Biogenesis have been identified. This is a weak hypothesis at this time.

Conclusion- life exist we don’t know why

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