Astrochemistry of Complex Organic Molecules

The study of complex organic molecules in space explores the synthesis, distribution, and evolution of carbon‐bearing species beyond Earth. These molecules, ranging from simple nitriles and alcohols to nucleobases and polycyclic aromatic hydrocarbons, are found in diverse environments including cold molecular clouds, hot cores, protoplanetary disks and small bodies such as comets and asteroids. Formation pathways involve both gas‐phase reactions and surface processes on icy dust grains, where radicals migrate and combine during warming phases. Observational advances in laboratory spectroscopy, radio and millimetre‐wave astronomy, and in situ sample return missions have revealed a growing inventory of species relevant to prebiotic chemistry. The astrochemical networks that model this chemistry are constantly refined by experimental and theoretical rate data, while space missions provide direct samples that ground‐truth remote observations. Understanding this inventory informs theories of the origin of life and the delivery of organic matter to planetary surfaces.

Research from Nature Portfolio

Analyses of pristine material returned from a near‐Earth carbonaceous asteroid have revealed the extraterrestrial occurrence of uracil, a key RNA nucleobase, alongside nicotinic acid derivatives and nitrogen heterocycles. Variations in the abundance of uracil across different sample fragments point to alteration by ultraviolet photons and cosmic rays prior to delivery. This discovery demonstrates that nucleobases formed in small Solar System bodies are widespread and could have been delivered to the early Earth, reinforcing the role of asteroidal bodies as reservoirs of prebiotic molecules.

Astrochemistry of Complex Organic Molecules publication trend

The graph below shows the total number of articles in astrochemistry of complex organic molecules across all publications each year (not limited to Nature Index journals).

Technical terms

iCOMs (Interstellar Complex Organic Molecules): Molecules of multiple carbon‐containing atoms detected in space, often linked to prebiotic processes.

Nucleobase: Aromatic heterocyclic compound forming the informational units of nucleic acids.

Hot molecular core: Compact, warm, dense region around a nascent star rich in complex organic species.

Gas‐grain chemistry: Reactions occurring in the gas phase and on the surfaces of dust grains, enabling formation of complex molecules.

Polycyclic aromatic hydrocarbon (PAH): Organic molecule composed of fused aromatic rings found throughout interstellar and circumstellar media.

References

1. Uracil in the carbonaceous asteroid (162173) Ryugu. Nature Communications (2023).
2. Re-exploring Molecular Complexity with ALMA (ReMoCA): interstellar detection of urea. Astronomy & Astrophysics (2019).
3. Discovery of Interstellar 2-Cyanoindene (2-C9H7CN) in GOTHAM Observations of TMC-1. The Astrophysical Journal Letters (2022).
4. The Genealogical Tree of Ethanol: Gas-phase Formation of Glycolaldehyde, Acetic Acid, and Formic Acid. The Astrophysical Journal (2018).