While detailed images of distant galaxies taken by the James Webb Space Telescope show us more of the vast universe, scientists still aren’t divided on how life arose here on Earth. One hypothesis is that meteorites brought amino acids, the building blocks of life, to our planet. Now researchers have published in the journal ACS Center ScienceHe experimentally demonstrated that amino acids may have formed in these early meteorites as a result of reactions induced by gamma rays produced within space rocks.

Ever since the Earth was just formed, a sterile planet, meteors have been blasting through the atmosphere towards its surface at high velocities. If primitive space debris included carbonaceous chondrites, a class of meteorites whose members contain significant amounts of water and small molecules such as amino acids, then it may have contributed to the evolution of life on Earth. However, it is difficult to determine the source of amino acids in meteorites.

In previous laboratory experiments, Yoko Kebukawa and colleagues showed that reactions between simple molecules such as ammonia and formaldehyde can synthesize amino acids and other macromolecules, but require liquid water and heat. Radioactive elements such as aluminum-26 (²⁶Known to exist in early carbonaceous chondrites, Al) emit gamma rays, a high-energy form of radiation, when they decay. This process can provide the heat needed to form biomolecules. Therefore, Kebukawa and the new team wanted to test whether radiation contributed to amino acid formation in early meteorites.

The researchers dissolved formaldehyde and ammonia in water, sealed the solution in glass tubes, and then irradiated the tubes with high-energy gamma rays produced by the decay of cobalt-60. They found that the production of α-amino acids such as alanine, glycine, α-aminobutyric acid and glutamic acid and β-amino acids such as β-alanine and β-aminoisobutyric acid increased in irradiated solutions because of an increase in the overall gamma radiation dose.

Based on these results and the expected dose of gamma radiation from decay²⁶Researchers estimate that it will take 1,000 to 100,000 years for Al in meteorites to produce the same amount of alanine and β-alanine found in the Murchison meteorite that crashed in Australia in 1969. The researchers say the study provides evidence that reactions catalyzed by gamma rays can produce amino acids that may have contributed to life on Earth.