Prebiotic Complex Organic Molecules in Space

Abstract

As of 2017, about 200 complex organic molecules have been detected in interstellar molecular clouds. It was 1969 when the first organic molecule in space, H₂CO, was discovered. Since then many organic molecules were discovered by using the NRAO 11 m (upgraded later to 12 m), Nobeyama 45 m, IRAM 30 m, and other highly sensitive radio telescopes as a result of close collaboration between radio astronomers and microwave spectroscopists. It is noteworthy that many well-known organic molecules such as CH₃OH, C₂H₅OH, (CH₃)₂O, and CH₃NH₂ were detected in the 1970s. It is thought that organic molecules are formed on surfaces of cold dust particles in a molecular cloud and then are evaporated by the UV photons emitted from a star inside the molecular cloud.

Organic molecules are known to exist in star-forming regions and in protoplanetary disks where planets are formed. Therefore it was a natural consequence that astronomers considered a relationship between organic molecules in space and the origin of life. Several astronomers challenged to detect glycine and other prebiotic molecules without success. ALMA is expected to detect such important materials to further examine the “exogenous delivery” hypothesis of organic molecules.

In this chapter I summarize the history of the searches for complex organic molecules in space together with difficulties in observing very weak signals from larger molecular species.