In samples from the Ryugu asteroid brought to Earth. for the first time, the building blocks of RNA and even a vitamin have been found. The discovery may serve as further evidence for the hypothesis that life on Earth originated with the participation of complex molecules brought from space, according to the study. published in the journal Nature Communication.
In 2014, Japan launched the Hayabusa-2 spacecraft to the asteroid Ryugu, which arrived at the target in 2018, and in December 2020 dropped a capsule containing 5.4g of asteroid material to Earth. It was previously reported that more than ten types of amino acids were found in the delivered samples, including glycine and L-alanine, the building blocks of proteins that living organisms synthesize based on their DNA code.
Now, scientists from Hokkaido University, led by Professor Yasuhiro Oba, have announced the discovery of uracil in samples from the asteroid. It is one of the four bases that make up ribonucleic acids (RNA) – macromolecules that play an important role in gene coding, reading and regulation in living organisms. Additionally, vitamin B3 (nicotinic acid) was found in the samples, which is involved in redox reactions, lipid metabolism and enzyme formation in living cells. These molecules and other nitrogen-containing organic substances were found by modern methods of liquid chromatography and high-resolution mass spectrometry.
“Scientists have found nucleic acid bases and vitamins in some carbon-rich meteorites before, but there has always been the problem of sample contamination under terrestrial conditions,” Ohba explained. “Because Hayabusa 2 took two samples directly from asteroid Ryugu and returned them to Earth in sealed capsules, contamination is ruled out. We found uracil at low levels, in the range of 6-32 parts per billion, while vitamin B3 was higher – 49-99 parts per billion. Other biological molecules have also been discovered, including a range of amino acids, amines and carboxylic acids, which are found in proteins and metabolism respectively.
According to the scientists, these molecules show differences from similar compounds found earlier in carbonaceous meteorites. “The discovery of uracil in samples from Ryugu reinforces existing theories regarding the origin of nucleic acid bases on early Earth,” Oba said.
