The lack of pyrimidine diversity in meteorites remains a mystery. Scientists from Japan believe that samples taken by the Japan Aerospace Exploration Agency (JAXA) from the Asteroid Ryugu and nasa from Bennu provide important insights for scientists to understand the evolution of extraterrestrial organic molecules.
On the evening of April 26, the international academic journal Nature Communication published a study jointly completed online by a team of Hokkaido University and the Japan Marine Science and Technology Center (JAMSTEC). They note that the pyrimidine bases, which are essential for the composition of DNA and RNA, may have been brought to Earth by carbon-rich meteorites.
Bases, as one of the structural components of nucleic acids, have previously been detected in carbonaceous chondrites. There are two types of bases in DNA and RNA, namely pyrimidine and purine. Among them, pyrimidine includes cytosine, uracil, thymine, purine includes guanine, adenine.
A range of exogenous meteorite organics, including bases, could have been transported to early Earth during the late heavy bombardment period (aka the "lunar catastrophe," about 4 billion to 3.8 billion years ago), the research team said. The influx of these organic matter is thought to have played an important role in the chemical evolution of the Earth's primordial stages.
However, as of now, only purine bases have been found in meteorites. Yasuhiro Oba of Hokkaido University and his colleagues optimized the small-scale quantification range of bases using advanced analytical techniques that are optimized specifically for small-scale quantification of bases. They analyzed three carbon-rich meteorites: the Murchison meteorite, the Murray meteorite, and the Lake Tagish meteorite.
Detection of purine bases.
The paper shows that in addition to the purine bases previously found in meteorites, such as guanine and adenine, the research team also detected for the first time various pyrimidine bases, such as cytosine, uracil and thymine, as well as their isomers. The concentrations present in these compounds are similar to those predicted by experiments simulating the conditions before the formation of the solar system.
Detection of pyrimidine bases.
The team believes that these results suggest that such compounds may have been produced by photochemical reactions in the interstellar medium and subsequently incorporated into asteroids during the formation of the solar system. These compounds eventually reach Earth through meteorites, and the diversity of meteorite bases could serve as modules for building DNA and RNA from early Earth.
Thesis link: https://www.nature.com/articles/s41467-022-29612-x