We do not yet know exactly how the first life on earth came to be. According to one version, the “building blocks” needed for life here came from space; New research on several carbon-rich meteorites adds weight to this view.
Using a new method of extremely sensitive analysis of these meteorites, a team of researchers at the University of Hokkaido in Japan has identified organic compounds that form the backbone of nucleic acid molecules that are known to all forms of life in general – DNA and RNA.
Researchers have studied three carbon-rich meteorites: the Murcison meteorite that crashed in Australia in 1969; Murray Meteorite, which crashed in Kentucky in 1950, and Lake Tagishi Meteorite, which crashed in 2000 in the Canadian province of British Columbia.
Although these meteorites fell on our planet in the fairly recent past, they are indeed the oldest cosmic rocks, presumably formed in the early stages of the solar system.
Carbon-rich meteorites are a treasure trove of organic compounds. When it comes to the emergence of DNA and RNA molecules on Earth, of particular interest are compounds called nitrogenous bases – fragments that combine to form a long chain of genetic information.
There are two main classes of nitrogenous bases: pyramids and purines. Thanks to the incredible sensitivity of the analysis method, the authors of the new study found several pyramids in meteorite samples that could not be detected until now.
“In both samples taken from the Murcison meteorite, we observed a wide variety of pyramidal nitrogen bases and their structural isomers, most of which have not been observed in meteorites before,” the study authors wrote in the publication.
Experiments simulating the content of cosmic materials indicate the presence of different nitrogenous bases in space, which researchers say means that organic compounds of this class must be universally present in the extraterrestrial environment, both in the solar system and beyond.
Why are these compounds so important? DNA and RNA helices have a structural “backbone” consisting of a sugar-phosphate chain. Nitrogen stems themselves attach to these sugars; In DNA, they pair in a specific way to form a spiral staircase.
Purine and pyramidine Nitrogenous bases in DNA are always linked to each other because of their structure and the types of hydrogen bonds they can produce. This means that the proportion of purine and pyramidine nitrogenous bases in the DNA molecule is always constant.
These nitrogenous bases must have been formed by photochemical reactions in many different bodies in space, even before the formation of the solar system.
The authors of the study suggest that about 4 – 3.8 billion years ago, during the late, heavy bombardment of early Earth, a wide variety of these building blocks must have hit our planet through meteorite strikes.
“Consequently, the influx of such organic matter is thought to have played an important role in the evolution of the Earth’s primordial stage,” the researchers wrote.
We will get more information on this issue in the coming years as samples from the asteroids Benu and Ryugu offer a new opportunity to study extraterrestrial materials.
The study of contaminated specimens will give scientists more convincing conclusions as to whether these molecules hit here through meteorites. What else do we have left, let’s wait.
The study was published in Nature Communications.
Prepared according to ScienceAlert.