Important precursors for life on Earth abound in the interstellar molecular clouds and can reach Earth through comets and meteors.
Nitriles, a class of living molecules with a group of cyano (a carbon atom bound to a triple bond that is not filled with a nitrogen atom), are generally toxic. Ironically, however, they also form the primary precursor to life-sustaining cells on Earth, such as ribonucleotides, composed of nucleobases or ‘letters’ A, U, C, and G, bound by a group of ribose and phosphate, which combine to form RNA. . Now, a team of scientists from Spain, Japan, Chile, Italy, and the United States is showing that a wide range of nitriles occurs in the starry heavens within the molecular cloud G + 0.693-0.027, located near the center of the Milky Way, Galaxy.
“Here we show that the chemical reaction that occurs in the galaxy is capable of producing many nitriles, which can precede the major molecular markers of ‘RNA World’,” says Drs. Víctor M. Rivilla, a researcher at the Astrobiology Institute of the Spanish National Research Council (CSIC) and the National Institute of Aerospace Technology (INTA) in Madrid, Spain, and the first author of a new study.
Possible world for ‘RNA only.’
In this context, life on Earth was initially based solely on RNA, and protein and DNA enzymes emerged later. RNA can perform both functions: stimulating reactions as enzymes and storing and copying DNA-like information. According to RNA World theory, nitriles and other life-forms have not originated on Earth itself: they may also have originated in space and ‘climbed’ on the small Earth within comets and meteorites during the ‘Later Difficulty. The time of the bombing was between 4.1 and 3.8 billion years ago. In support, nitriles and other molecules precede nucleotides, lipids, and amino acids within meteors and comets.
Where did these molecules come from? Prime candidates are molecular clouds, dense and cold regions of the interstellar medium, and are suitable for forming complex molecules. For example, the molecular cloud G + 0.693-0.027 has a temperature of about 100 K, is about three light-years wide, and is a thousand times heavier than our Sun. Although scientists suspect it may evolve into an astronomical observatory in the future, there is no evidence that the stars are currently building within G + 0.693-0.027.
“The chemical composition of G + 0.693-0.027 is similar to that of other galaxies in our galaxy, as well as those of the solar system such as comets. This means that its research can provide us with valuable insights into the chemical elements found in the nebula that make up our planetary system,” explains Rivilla.