Astronomers have made the first interstellar detection of fully deuterated methanol around a young protostar, offering a new window into how planets get their chemistry.

The molecule, CD3OD, was spotted around IRAS 4A2, a protostar in the Perseus cloud about 1,000 light-years away. It was found by the ALMA telescope as part of the COMPASS programme.

Seven papers published on October 7 detail the findings. Researchers including Belloche and Jes Jorgensen say the deuteration levels act as a fossil record of the cold conditions where the molecule formed.

Methanol is a key building block. It forms on icy dust grains and later seeds the chemistry that can produce more complex organic molecules.

Finding its fully deuterated form tells scientists about temperatures and timescales in the planet-forming disc, conditions that prevailed before planets existed.

The results add to a growing picture of young star systems as chemical factories, already stocked with the ingredients of future worlds.