Chemical compounds called nucleobases, the essential building blocks that make up DNA, have been detected for the first time in a lab-based simulation designed to mimic the gaseous clouds that are found lingering in the vast areas of space between stars.
The discovery brings us closer to understanding the origins of life on Earth, the researchers say.
“This result could be key to unravelling fundamental questions for humankind, such as what organic compounds existed during the formation of the Solar System and how they contributed to the birth of life on Earth,” said Dr Yasuhiro Oba of Hokkaido University’s Institute of Low Temperature Science, leader of the research team that made the discovery.
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The basic structural unit of DNA is called a nucleotide and is composed of a nucleobase, a sugar, and a phosphate. Previous studies mimicking the conditions expected in interstellar molecular clouds have detected the presence of sugar and phosphate, but never nucleobases.
To make the discovery, the team set up a simulation of an interstellar molecule cloud by pumping a gaseous mixture of water, carbon monoxide, ammonia into a vacuum chamber filled with simulation cosmic dust and cooling it to -263°C.
Next, they shone a pair of specially designed ultraviolet lamps into the chamber to kick-start chemical reactions. This led to an icy film forming on the surface of the dust.
They then warmed this substance up to room temperature analysed its chemical composition using a high-resolution mass spectrometer. In this way, They were able to identify the presence of several nucleobases including cytosine, thymine and adenine – three of the four bases that make up all DNA.
Dr Yasuhiro Oba and his team found the building blocks of life in simulated deep space conditions © Hokkaido University
They also identified several amino acids, which are the building blocks of proteins, another key element for the formation of life.
The team suspects that past experiments simulating interstellar molecular cloud environments would in fact also have produced nucleobases, but that the analytical tools available at the time were not sensitive enough to detect them in complex mixtures.
“Our findings suggest that the processes we reproduced could lead to the formation of the molecular precursors of life,” said Oba. “The results could improve our understanding of the early stages of chemical evolution in space.”