(Phys.org)—In 1952, chemists Stanley Miller and Harold Urey conducted a famous experimental simulation of the conditions thought to prevail on early Earth in order to determine possible pathways to the creation of life. The Miller-Urey experiment used water (H2O), methane (CH4), ammonia (NH3) and hydrogen (H2) sealed inside a glass flask. They introduced water vapor from a separate flask while firing electrical sparks between electrodes to simulate lightning. The chemists maintained this reaction for a week, and then chemically halted it.