We are all dust of stars – but how this star dust came to life on Earth is a mystery. The complexity of a single one of your cells, where small proteins walk with a load on your back and enzymes pass through your DNA to read the instructions, is enormous and unknown.
But scientists have a theory about how it all started, and it starts with the cousin of DNA, RNA. These filamentous molecules are made up of compounds called nucleotides and are responsible for transmitting genetic messages and building proteins. Their single-stranded structure, unlike dual strands of DNA, makes them less stable and easier to assemble, potentially easy enough to emerge from the mixture of molecules that extend to the surface of the Earth about 3.8 billion years ago.
Now, scientists have found more ingredients for this stew in a gaseous cloud toward the center of our galaxy, providing more clues as to what kind of molecules might have been to form the first life on Earth.
What’s new – In the new study, researchers scoured a cloud of gas more than 27,000 light-years away to find compounds called nitriles. These molecules have complex chemistry and are involved in the reactions that create the building blocks of RNA. They are also more than likely the base of your healthcare provider’s gloves and other PPE.
Ribonucleid acid, or RNA, is a versatile strand made up of molecules called nucleotides. We could not live without these complex compounds, which build proteins from our genetic models. CHRISTOPH BURGSTEDT / SCIENCE PHOTO LIBRARY / Science Photo Library / Getty Images
The researchers first identified six nitriles in a region of one of the largest molecular clouds in the center of our Milky Way galaxy, with the sticky name G + 0.693-0.027. These nitriles play a role in the formation of life-critical molecules, or biomolecules, such as nucleotides (the basis of genetic material), lipids (fats), and amino acids (the building block of proteins).
“We certainly need nitriles for the formation of biomolecules on primitive Earth, so the fact that nitriles are in outer space shows how distributed are the foundations of life in the universe,” says Thomas Carell . Carell is a professor of organic chemistry at Ludwig Maximilian University in Munich. Carell did not participate in the recent study.
The results were published Friday, July 8 a Frontiers in astronomy and space sciences.
How they did it – Nitriles are a diverse group of molecules, but they all contain a carbon atom attached to a nitrogen atom. This is one of the most common links in the chemistry of life, but is less common in gaseous clouds around the center of the Milky Way.
The 30 m IRAM telescope looks at the sky from the Sierra Nevada mountain range in southern Spain. Rob Millenaar / Moment Open / Getty Images
The researchers spent hundreds of hours collecting data from the G + 0.693 cloud using two radio telescopes in Spain, the 40-meter Yebes and 30-meter IRAM telescopes. They used a method called molecular spectroscopy to identify signatures of specific molecules in the cloud.
When light passes through or around an object or material in space, the composition of that object changes the qualities of light. These features can be used to decipher the composition of the material. Each molecule has a distinctive pattern almost like a fingerprint, which radio telescopes can detect when adjusted to the correct frequency range.
The signals that nitriles emit are very weak compared to other molecules in the cloud, such as carbon monoxide and ammonia, says Victor Rivilla, one of the co-authors of the study. Technological innovation has recently made it possible to detect these distant molecules, he says.
“If we want to detect them, we need very sensitive and deep observations,” Rivilla says. He is an astronomer at the Center for Astrobiology of the Higher Council for Scientific Research.
Rivilla and his team discovered four nitriles (cyanic acid, cyanoalene, propargyl cyanide, and cyanopropy) with a high degree of certainty that they were in the cloud, and they also identified two (cyanoformaldehyde and glycolonitrile) on a temporary basis. .
Why does it matter – This is not the first time astrophysicists have found nitriles in this particular cloud. But each new discovery expands what we know is possible. These molecular clouds are an “impressive chemical reactor,” says Grégoire Danger, who specializes in prebiotic chemistry at the University of Aix-Marseille in France and did not participate in the new study.
What’s inside? Sarote Impheng / EyeEm / EyeEm / Getty Images
“This work is a new example of the molecular diversity that is generated in this environment,” he says.
Drawing the molecular diversity of the primordial space cloud helps us understand the ingredients that may have entered the “primordial soup” from which life arose on Earth, and potentially elsewhere in the galaxy.
Here is the timeline:
- About 4.5 billion years ago, the planet Earth was formed, probably from the debris left after the sun rose.
- About 3.9 billion years ago, the Earth was hit by asteroids, some of which may have carried molecules such as nitriles that could help form the first blocks of life.
- About 100 million years later, the first life forms on our planet began to emerge.
There are millions of years of blank dots in this timeline. The journey from the molecular cloud to the nascent asteroid would probably significantly alter any molecule, so we cannot point out nitriles in space and assume that they would have reached Earth in this way, Danger points out.
What follows – To fill the gaps in our home history, scientists will continue to look for space for other molecules that could have been precursors to life.
“There are still key molecules that are missing that are hard to spot,” Rivilla says.
He and his team plan to expand their interstellar search for other basic ingredients that would have been needed for RNA to form and eventually evolve into the first living cells.
“It simply came to our notice then studying the chemical content of other molecular clouds at the center of our galaxy, and also of other regions where stars and planets are forming, ”he says.
Each new discovery will help us understand how the limited chemistry available on Earth could have created complexity around and within us.
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