Asteroid Dragon Palace sample

The lack of pyrimidine diversity in meteorites remains a mystery. Scientists from Japan believe that the samples collected by the Japan Aerospace Exploration Agency (JAXA) from the “Dragon Palace” asteroid and the samples collected by the National Aeronautics and Space Administration (NASA) from “Benu” 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 online a study jointly completed by Hokkaido University, Japan Marine Science and Technology Center (JAMSTEC) and other teams. They pointed out that the pyrimidine bases essential to the composition of DNA and RNA may have been brought to earth by carbon rich meteorites.

Base, as one of the structural components of nucleic acid, has previously been detected in carbonaceous chondrite. There are two types of bases in DNA and RNA, namely pyrimidine and purine. Among them, pyrimidine includes cytosine, uracil and thymine, and purine includes guanine and adenine.

The research team said that a series of exogenous meteorite organics, including bases, may have been transported to the early Earth during the later heavy bombing period (also known as the “lunar disaster”, about 4-3.8 billion years ago). The influx of these organics is considered to have played an important role in the chemical evolution of the primitive stage of the earth.

However, so far, only purine bases have been found in meteorites. Yasuhiro oba of Hokkaido University and his colleagues used the advanced analysis technology of small-scale quantification specially optimized for bases to optimize the small-scale quantification range of bases. They analyzed three carbon rich meteorites: Murchison meteorite, Murray meteorite and tajish Lake meteorite.

The paper shows that in addition to the purine bases previously found in meteorites, such as guanine and adenine, the research team also detected various pyrimidine bases, such as cytosine, uracil and thymine, as well as their isomers for the first time. The concentrations of these compounds are similar to those predicted by experiments simulating the pre formation conditions of the solar system.

The team believes that these results suggest that such compounds may be produced by photochemical reactions in the interstellar medium, and then incorporated into asteroids during the formation of the solar system. These compounds eventually reached the earth through meteorites, and the diversity of meteorite bases can be used as modules to build the DNA and RNA of the early Earth.

Paper link: https://www.nature.com com/articles/s41467-022-29612-x