Many Precursors For RNA Have Been Detected In Our Galactic Center

The heart of the Milky Way appears to be a hotspot for molecules that combine to form RNA.

A new survey of the thick molecular cloud that shrouds the galactic center has revealed the presence of various nitriles – organic molecules that are often toxic in isolation, but are also molecular building blocks essential for life.

The increase in prebiotic molecules (molecules involved in the emergence of life) identified at the center of galaxies, particularly those associated with RNA, has implications for our understanding of how life emerged in the Universe – and how it happened on Earth.

“Here we show that the chemistry occurring in the interstellar medium is able to efficiently form some of the nitriles, which are key molecular precursors of the ‘RNA World’ scenario,” explains astrobiologist Víctor Rivilla of the Spanish National Research Council and National Institutes. Aerospace Technology in Spain.

Exactly how life arose on Earth is a mystery that basic scientists are eager to achieve. The information will yield important clues for finding exoplanets that might host living organisms.

One version is that RNA first emerged from the metaphorical stream, self-replicating and diversifying all by itself; this is called the RNA World Hypothesis.

We’re unlikely to get any direct evidence from Earth, but we can gather more clues to find out how plausible and likely this scenario is. One of the questions raised by this hypothesis is about the source of prebiotic RNA molecules such as nitriles. Were they on Earth from the start, or could they be brought from space by meteorites and asteroids?

We know the inner Solar System, including Earth, experienced a period of intense asteroid bombardment early in its history. We’ve also found prebiotic molecules in meteors, comets, and asteroids roaming the Solar System today. And where do meteors, comets and asteroids get them from?

Well, maybe the clouds they’re born into: cold molecular clouds that give birth to stars. Once a star has finished forming from part of the cloud, the remnants of the cloud will continue to form everything else in the planetary system – planets, comets, asteroids, dwarf planets, and anything else that might be lurking.

The birth clouds of the Solar System are long gone, but the galactic center is thick with molecular clouds. It’s called the Central Molecular Zone, and scientists have found a bunch of prebiotic molecules hanging around there.

One particular cloud, named G+0.693-0.027, is particularly interesting. There is no evidence of star formation there yet, but scientists believe that a star or stars will form there in the future.

“The chemical composition of G+0.693-0.027 is similar to that of other star-forming regions in our galaxy, and also to Solar System objects such as comets,” Rivilla said.

“This means his research could provide us with important insights into the chemicals available in the nebula that gave rise to our planetary system.”

The researchers used two telescopes to study the spectrum of light coming from the clouds. When certain elements or molecules absorb and re-emit light, this can be seen on the spectrum as darker or lighter lines. Interpreting these absorption and emission lines can be tricky, but it can also be used to identify which molecules are present: each has its own spectral signature.

By carefully studying and analyzing the emission features of G+0.693-0.027, Rivilla and his colleagues identified a variety of nitriles, including cyanic acid, cyanoallen, propargyl cyanide, and cyanopropine. They also made tentative detections of cyanoformaldehyde, and glycolonitrile.

Previous observations of G+0.693-0.027 revealed the presence of cyanoformaldehyde, and glycolonitrile. This suggests that nitriles are one of the most abundant chemical families in the Milky Way, and that the most basic building blocks for RNA can be found in the clouds that give birth to stars and planets.

But there is – of course, as always – more work to be done.

“We have detected so far several simple precursors of ribonucleotides, the building blocks of RNA,” explains astrobiologist Izaskun Jiménez-Serra, also of the Spanish National Research Council and the National Institute of Aerospace Technology.

“But there are still key missing molecules that are difficult to detect. For example, we know that the origin of life on Earth may also have required other molecules such as lipids, which were responsible for the formation of the first cells. Therefore, we should also focus on understanding how lipids can be formed from simple precursors available in the interstellar medium.”

This research has been published in Frontiers in Astronomy and Space Science.

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