A team of researchers say they have found building blocks of RNA in a molecular cloud near the center of the Milky Way. The discovery has implications for theories about how life began on Earth – and possibly elsewhere.
The molecular cloud is named G+0.693-0.027. The team of astrophysicists, astrobiologists and chemists conducted a study of the cloud using two telescopes in Spain to uncover details of its chemistry.
Ribonucleic acid (RNA) is a molecule found in all living cells that behaves similarly to DNA, despite being single-stranded. There are evidence that RNA might have preceded DNA, based on laboratory observations of ribosomes, which are made of RNA.
Whether or not the ancient RNA was able to revive life is another matter. EThe recent team discovered several organic molecules in the cloud that are part of a group called nitriles, which may have played an important role in the generation of RNA in the early universe; the team’s results were published today in Frontiers in Astronomy and Space Sciences.
“Here we show that the chemistry taking place in the interstellar medium is capable of efficiently forming several nitriles, which are key molecular precursors to the ‘RNA World’ scenario,” said Víctor Rivilla, an astrobiologist at the National Institute of Technology aerospace of Madrid, in a Borders Release.
The RNA World Hypothesis posits that RNA with genetic and metabolic activity was fundamental in the origins of life. A some studies in the 1990s showed that RNA could have jump-started life as we know it, because it could do genetic work like DNA but could catalyze reactions like proteins. There is also problems with theorybut it is still interesting to consider.
“There are still missing key molecules that are difficult to detect,” said Izaskun Jiménez-Serra, an astrophysicist also at the National Institute of Aerospace Technology, in the same statement. “For example, we know that the origin of life on Earth probably also required other molecules such as lipids, responsible for the formation of the first cells. Therefore, we should also focus on understanding how lipids might be formed from simpler precursors available in the interstellar medium.
The earliest evidence of life on Earth comes in the form of 3.5 billion-year-old stromatolites, sedimentary concretions generated by ancient bacteria as they grew. If there is fossilized life on Mars, the best guess is that it is probably looks something like this.
But before stromatolites, something was needed to seed life after the Earth was formed. One theory is that all of the ingredients necessary for life arrived on Earth around 4 billion years ago (give or take many hundreds of millions of years), in a period called the Late Heavy Bombardment.
During the bombardment, the Earth and Moon were struck by asteroids and comets, evidence of which is now embedded in the planet’s crust (and the Moon’s surface). It is possible that nitriles like those found by the recent team have arrived on some of these ancient asteroids, just like liquid water is proposed to have arrived on our planet.
Nitriles have also been found in various protostars, meteorites and even in the atmosphere of Titan, Saturn’s Largest Moon. It’s a reminder that we’ve been in a great, stirring cosmic soup for billions of years – the ingredients are floating everywhere.
“The chemical content of G+ 0.693-0.027 is similar to other star-forming regions in our galaxy, as well as solar system objects like comets,” Rivilla said. “This means that his study can give us important information about the chemical ingredients that were available in the nebula and that gave rise to our planetary system.”
Rome wasn’t built in a day, and neither was life on Earth. However, life emerged, however, it took things like RNA to get started. The origin of this RNA remains a mystery, but the fact that its building blocks are found even near the center of the Milky Way indicates that organic molecules are diffused throughout our galaxy. Whether that means life is too…well, scientists will just have to keep looking.
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