A cosmic dust grain is covered in ice, and on this ice, like in a tiny kitchen, molecules are cooked. One of them is methanol, an alcohol that serves as a building block for more complex compounds in space. Previously, it was thought that methanol only forms when hydrogen atoms stick one by one to a carbon monoxide molecule. But there is another pathway: methane meets a hydroxyl (a fragment of water) and swaps parts with it.

In the new experiment, ice was held at temperatures from 10 to 60 kelvins — colder than on Pluto. Methane gas was let onto the ice and illuminated with ultraviolet light to produce hydroxyls from water. The instrument caught cesium ions and, by their motion, determined which molecules appeared on the surface. It turned out that methanol appears even at 10 kelvins, even though at such cold temperatures molecules barely move.

The secret lies in the heat from the first reaction. When methane gives a hydrogen atom to a hydroxyl, a bit of energy is released, and the methane fragment, the CH3 group, briefly heats up. That is enough for it to crawl over to another hydroxyl and combine with it. So in two steps, methanol is produced.

This pathway explains why methanol is found even in the coldest clouds, where hydrogen cannot stick to the ice. This means organics in space may arise earlier and more simply than we thought. Same kitchen on a dust grain, but the fire here is the heat of a chemical reaction.