The Miller-Urey Experiment: Simulating Early Earth
- Miller and Urey proposed that Earth’s early atmosphere was reducing, containing gases such as methane (CH₄), ammonia (NH₃), hydrogen (H₂), and water vapor (H₂O).
- They reasoned that these gases could react to form organic compounds when energy was supplied.
Definition
Abiogenesis
The origin of life from non-living matter, such as simple organic compounds.
Experimental Setup
- The experiment used a closed system of two connected flasks to simulate early Earth conditions.
- Steps:
- Evaporation: Water was boiled to create water vapor (simulating the ocean).
- Gas Mixture: The vapor mixed with methane, ammonia, and hydrogen (simulating the atmosphere).
- Energy Source: Electrical sparks represented lightning, providing energy for reactions.
- Condensation: A condenser cooled the vapor, recycling liquid water back into the flask.
- Key Process to Remember:
- The system continuously cycled water and gases, mimicking Earth’s natural evaporation–condensation–lightning cycle.
- This constant recycling allowed ongoing chemical reactions, gradually producing more complex organic molecules over time.
Results
- After several days, the solution turned reddish-brown and chemical analysis revealed over 20 amino acids and other simple organic molecules.
- This demonstrated that organic compounds could form spontaneously under simulated early Earth conditions.
Significance
- The experiment showed that:
- Complex organic molecules (like amino acids) can form from simple inorganic gases.
- Abiogenesis is chemically plausible, life’s building blocks could arise naturally.
