A new protocol for conducting Miller-Urey Experiments is comprised of a modern and simplified approach to the method used by Dr. Stanley Miller and Dr. Harold Urey in 1953. Their research evaluated the possibility of organic compounds important for the origin of life to have been formed abiologically on early Earth. 

Miller-Urey experiments study the abiotic synthesis of organic compounds by creating an environment similar to that of the early earth. An electric discharge is applied to a mixture of gases representing the early earth's atmosphere and lightening. This is done in the presence of a liquid water reservoir, representing the early oceans, as well as with an apparatus simulating evaporation and precipitation.

Miller introduced 200 ml of water, 100 mmHg of H2, 200 mmHg of CH4, and 200 mmHg of NH3 into the apparatus, then subjected this mixture, under reflux, to an electric discharge for a week, while the water was simultaneously heated. The new update provides the reader/viewer with a general experimental protocol that can be used to conduct a Miller-Urey type spark discharge experiment, using a simplified 3 L reaction flask. Since the experiment involves exposing inflammable gases to a high voltage electric discharge, it is worth highlighting important steps that reduce the risk of explosion. The general procedures described in this work can be extrapolated to design and conduct a wide variety of electric discharge experiments simulating primitive planetary environments.

After a week of sparking in a Miller-Urey experiment, the contents within the reactant flask become visibly transformed. Miller-Urey's groundbreaking work is considered to be the first deliberate, efficient synthesis of biomolecules under simulated primitive Earth conditions. Credit: JoVE—The Journal of Visualized Experiments

"The results of this study showed that amino acids, the building blocks of life, could be formed under primitive Earth conditions," said Eric Parker of  the Georgia Institute of Technology
about the original Miller-Urey Experiments. "Miller was hesitant to encourage people to repeat the experiment due to the risk of inducing an explosion. Often times, after reading a methods description it may not be fully clear how a certain research task was carried out. Therefore, this article was written to inform interested researchers how to conduct the experiment safely, in part, by giving precise instructions on evacuating [ignitable gases like oxygen, methane and hydrogen from] the reaction apparatus before initiating the spark." 

Despite these dangers, Parker said, there remains much interest among scientists to recreate the Miller-Urey experiment and to perform variations of it for testing new research ideas.  The updated method is published in
JoVE, the Journal of Visualized Experiments and they are preparing to publish a second article comparing their novel spark-discharge experimental results to original samples from the 1958 Miller-Urey cyanamide spark-discharge study that followed the landmark paper. 

In the meantime, Parker and his colleagues hope that their JoVE video (subscription required) will encourage more research with Miller-Urey type experiments. Such efforts could help answer key questions in the origin of life field, such as which prebiotic conditions may have facilitated the synthesis of specific organic compounds believed to be important for life, Parker said.

Parker, E. T., Cleaves, J. H., Burton, A. S., Glavin, D. P., Dworkin, J. P., Zhou, M., et al. Conducting Miller-Urey Experiments. J. Vis. Exp. (83), e51039, doi:10.3791/51039 (2014).