Building blocks for life discovered near the center of the Milky Way

A wide range of nitriles occurs in interstellar space.

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A team of researchers from Spain, Japan, Chile, Italy, and the US recently discovered a wide range of nitriles occurs in interstellar space within the molecular cloud G+0.693-0.027, near the center of the Milky Way. They have shown that the chemistry that takes place in the interstellar medium can efficiently form multiple nitriles, which are critical molecular precursors of the ‘RNA World’ scenario.

One of the most supported hypotheses for the origin of life is known as the RNA world, in which RNA could have performed both metabolic and genetic roles. This theory has suggested that nitriles and other building blocks for life needn’t necessarily all have arisen on Earth itself: They might also have originated in space and “hitchhiked” to the young Earth inside meteorites and comets during the “Late Heavy Bombardment” period, between 4.1 and 3.8 billion years ago. Nitriles and other precursor molecules for nucleotides, lipids, and amino acids have been discovered within modern comets and meteors, which lends this claim.

Where in space would these molecules have come from, though? 

Molecular clouds are the prime suspect. These clouds are cold and dense areas of the interstellar medium. For instance, the molecular cloud G+0.693-0.027, about three light-years across and has a mass around a thousand times that of our sun, has a temperature of about 100 K. Although there is no proof that stars are developing inside G+0.693-0.027 right now, astronomers believe it may eventually change into a stellar nursery.

Dr. Víctor M. Rivilla, a researcher at the Center for Astrobiology of the Spanish National Research Council (CSIC), said, “The chemical content of G+0.693-0.027 is similar to those of other star-forming regions in our galaxy, and also to that of solar system objects like comets. This means that its study can give us important insights about the chemical ingredients available in the nebula that give rise to our planetary system.”

Using two telescopes in Spain, scientists studied electromagnetic spectra emitted by G+0.693-0.027. They detected the nitriles cyanoallene (CH2CCHCN), propargyl cyanide (HCCCH2CN), and cyanopropyne, which hadn’t yet been found in G+0.693-0.027. However, they were reported in 2019 in the TMC-1 dark cloud in Taurus and Auriga’s constellations, a molecular cloud with very different conditions than G+0.693-0.027.

Additionally, researchers discovered potential proof that glycolonitrile (HOCH2CN) and cyanoformaldehyde (HCOCN) were present in the sample G+0.693-0027. In the molecular clouds TMC-1 and Sgr B2 in the constellation of Sagittarius, cyanoformaldehyde was discovered for the first time, and glycolonitrile was found in the Sun-like protostar IRAS16293-2422 B in the constellation of Ophiuchus.

Other recent studies have also reported other RNA precursors inside G+0.693-0.027 such as glycolaldehyde (HCOCH2OH), urea (NH2CONH2), hydroxylamine (NH2OH), and 1,2-ethanediol (C2H4O2), confirming that the interstellar chemistry can provide the most basic ingredients for the “RNA World.

The final author Dr. Miguel A Requena-Torres, a lecturer at Towson University in Maryland, U.S., said, “Thanks to our observations over the past few years, including the present results, we now know that nitriles are among the most abundant chemical families in the universe. We have found them in molecular clouds in the center of our galaxy, protostars of different masses, meteorites, and comets, and also in the atmosphere of Titan, Saturn’s largest moon.”

The second author Dr. Izaskun Jiménez-Serra, likewise a researcher at CSIC and INTA, looked ahead: “We have detected several simple precursors of ribonucleotides, the building blocks of RNA. But there are still key missing molecules that are hard to detect. For example, we know that the origin of life on Earth probably also required other molecules, such as lipids, responsible for forming the first cells. Therefore, we should also focus on understanding how lipids could be formed from simpler precursors available in the interstellar medium.”

Journal Reference:

  1. Molecular precursors of the RNA-world in space: new nitriles in the G+0.693-0.027 molecular cloud, Frontiers in Astronomy and Space Sciences (2022). DOI: 10.3389/fspas.2022.876870