Early Earth and Origins of Organic Molecules

THE EXPERIMENT - Urey and Miller

Urey and Millers' experiment simulated hypothetical conditions thought at the time to be present on the early Earth, and tested for the occurrence of chemical origins of life. The experiment used water (H2O), methane (CH4), ammonia (NH3), and hydrogen (H2). The chemicals were all sealed inside a sterile array of glass tubes and flasks connected in a loop, with one flask half-full of liquid water and another flask containing a pair of electrodes. The liquid water was heated to induce evaporation, sparks were fired between the electrodes to simulate lightning through the atmosphere and water vapor, and then the atmosphere was cooled again so that the water could condense and trickle back into the first flask in a continuous cycle.

WHY?

To examine what kind of environment would be needed to allow life to begin.

THE GASES

The gases they used were methane (CH4), ammonia (NH3), hydrogen (H2), and water (H2O).

How did they simulate lightning?

Sparks were fired between the electrodes to simulate lightning through the atmosphere and water vapor.

RESULTS

10-15% of the carbon was now in the form of organic compounds. Two percent of the carbon had formed some of the amino acids which are used to make proteins.

IMPORTANCE AND INFLUENCE TO THE HYPOTHESES

Miller's experiment showed that organic compounds such as amino acids, which are essential to cellular life, could be made easily under the conditions that scientists believed to be present on the early earth.

WHY HIS THEORY WAS WRONG

In Miller's UV experiments, he used a select wavelength to produce amino acids and screened out other wavelengths because they destroy amino acids. Yet both chemical-building and chemical-destroying light exists in sunlight. Amino acids are actually very delicate and readily break down under natural sunlight.

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