‘Microlightning’ May Have Sparked Life on Earth, New Research Suggests

While the origin of life on Earth is still up for debate, the Miller-Urey hypothesis suggests that a strike of lightning into ocean water mixed with inorganic gases may have triggered the formation of the first organic molecules. Critics of this hypothesis argue that the oceans were—and still are—too vast, and lightning too infrequent, for this explanation to be plausible. New research, however, suggests a solution to these discrepancies: microlightning.

Researchers at Stanford University have demonstrated that the electrical charge generated by spraying or splashing water can trigger chemical reactions with inorganic gases that create organic molecules. A study published on March 12 in Science Advances offers a new perspective on the Miller-Urey hypothesis, proposing that, instead of a large lightning strike, life may have originated from numerous tiny “microlightnings” between water droplets.

In the first couple billion years of Earth’s existence, scientists believe our planet lacked organic molecules containing carbon-nitrogen bonds—such as uracil (a component of DNA and RNA) and glycine (an amino acid)—which are crucial to life’s essential components, including enzymes, proteins, and nucleic acids.

The Miller-Urey hypothesis is based on a famous 1952 experiment in which researchers successfully formed these organic molecules by applying an electrical current to a mixture of water and Earth’s early inorganic gases, including methane, ammonia, and hydrogen.

In the new study, the researchers noted that, when the impact of a wave or waterfall separates water into drops, the droplets develop charges based on their size. Namely, small drops tend to carry a negative charge, while large drops usually gain a positive charge. When two differently charged water droplets come into proximity, they exchange little sparks of energy: what senior author Richard Zare dubbed “microlightning.” The team photographed the microlightning with high-speed cameras.

“We usually think of water as so benign, but when it’s divided in the form of little droplets, water is highly reactive,” Zare said in a Stanford statement. Zare and his colleagues then replicated a different version of Miller-Urey experiment—instead of applying electricity to a gas and water blend, they sprayed room temperature water into a mixture of early Earth gases.

Through this process, the team demonstrated that “microelectric discharges between oppositely charged water microdroplets make all the organic molecules observed previously in the Miller-Urey experiment, and we propose that this is a new mechanism for the prebiotic synthesis of molecules that constitute the building blocks of life,” Zare explained.

“On early Earth, there were water sprays all over the place—into crevices or against rocks, and they can accumulate and create this chemical reaction,” he concluded. “I think this overcomes many of the problems people have with the Miller-Urey hypothesis.”

Perhaps the spiritual leader Emmet Fox might have been right when he said that “a small spark can start a great fire.”