Alcohol Formation in Cold, Deep Space Explained by 'Quantum Tunneling'

The harsh environment of deep space doesn't seem like it would be conducive to chemical reactions. The impossibly cold temperatures should technically put a stop to any reactions. Yet alcohols are both formed and destroyed in space; now, scientists have discovered that a quantum mechanical phenomenon known as "quantum tunneling" may be to blame.

Deep space has temperatures that can plummet below minus 210 degrees Celsius. At these temperatures, chemical reactions should, theoretically, halt. There's simply not enough energy to rearrange chemical bonds. Yet this new theory may explain why these reactions still occur in space.

There have been theories as to how these reactions occur before, though. The general idea is that dust grains, found in interstellar clouds, act as a staging post for the reactions to occur. Yet when a highly reactive molecule called the "methoxy radical" was discovered last year, its formation couldn't be explained by space dust alone.

In order to get a better look at these reactions, researchers conducted laboratory experiments. They found that when an icy mixture containing methanol was blasted with radiation--like what would occur in space--methoxy radicals weren't released in the emitted gases. This suggested that methanol gas was involved in the production of the methoxy radicals found in space, rather than any process on the surface of dust grains. Yet this brought the scientists back to the issue of how gases can react in these extremely cold temperatures.

The answer apparently lies in quantum mechanics. "Chemical reactions get slower as temperatures decrease, as there is less energy to get over the 'reaction barrier,'" said Dwayne Heard, the lead researcher, in a news release. "But quantum mechanics tells us that it is possible to cheat and dig through this barrier instead of going over it. This is called 'quantum tunneling.'"

Essentially, incredibly cold temperatures are needed to actually dig through the reaction barrier. There's an intermediary product that forms in the first stage of the reaction, which can only survive long enough for quantum tunneling to occur at cold temperatures. In an experiment, the scientists recreated the cold environment of space and watched a reaction of alcohol methanol and the hydroxyl radical. They found that not only do these gases react to create methoxy radicals, but that the rate of the reaction is 50 times faster than at room temperature.

Currently, the researchers are investigating the reactions of other alcohols at cold temperatures. This could help them better understand the rates of formation and destruction of complex molecules in space.

The findings are published in the journal Nature Chemistry.