The evidence for the origin of life from inanimate matter was provided through an experiment, conducted in 1953, by Stanley L. Miller and Harold C. Urey. In experiment, they assembled an atmosphere containing molecules like ammonia, methane and hydrogen sulphide, but no oxygen, over water. This was similar to atmosphere that thought to exist on early earth . This was maintained at a temperature just below 100°C and sparks were passed through the mixture of gases to simulate lightning. At the end of a week, 15% of the carbon from methane was converted to simple compounds of carbon including amino acids which make up protein molecules and support the life in basic form. From this it was inferred that life arose afresh on earth.