How life begins remains an unresolved question. can be a major component RNA, a molecular cousin of DNA It is found in every form of life on Earth, and now scientists say they have shown how it may have formed on our planet eons ago. But not everyone is convinced, and RNA is likely just one of many molecules that could give rise to life on different worlds.
in a paper published in today Proceedings of the National Academy of Sciences, USAAstronomer Yuta Hirakawa and colleagues describe how conditions on Earth might have been suitable for the emergence of life about 4.3 billion years ago. In his experiment, he showed that, after a large impact on Earth, RNA and subsequently life could have formed.
“The steps the team has taken suggest that RNA is an intrinsic result of planets everywhere,” says Steven Benner of the Foundation for Applied Molecular Evolution (FFAME) in Florida, a co-author of the paper. And he, in turn, “would mean that there is life everywhere.” Unlike proteins, which carry out most of the chemistry in modern cells, and DNA, which stores genetic information, RNA can do a little of both – one reason it has long been considered a promising candidate for the first molecule of life.
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Led by Hirakawa, the research team prepared test tubes containing aqueous mixtures similar to materials known to be common on early Earth, then heated them and allowed them to dry. The mixture contained a chemical soup of minerals containing ribose sugar, nucleobases, a reactive source of phosphorus, and a compound called borate.
Hirakawa says that the process of heating and drying would have been “ubiquitous on the early Earth”. “So this reaction must have happened.” The result of the experiment was the creation of RNA-like molecules that, with minimal chemical reactions, could become RNA. The team says this shows RNA can be made Naturally near the dawn of our planet.
Lee Cronin, an expert in prebiotic chemistry at the University of Glasgow, who was not involved in the paper, says he is unsure about its findings because human input was required to obtain and mix the various components. “The fact that they reverse engineered the synthesis of RNA under the right conditions says nothing,” he says. “The justification of plausibility is false.”
One of the key findings in the paper is that the compound borate does not prevent the formation of life’s precursor materials, as previously thought, but actually aids the production of RNA. “Borate is very important for stabilizing sugars, which are unstable molecules,” says Hirakawa, while also noting that borate reactions can create ribose phosphate and dehydrated phosphate, two key molecules for the subsequent synthesis of RNA. “The biggest discovery of my research is that borate facilitates these reactions.”
Researchers have also discovered borate on marsBenner says, raising the possibility that life could have arisen independently on the Red Planet. “Earth’s early atmosphere was no different from the present-day atmosphere of Mars,” he says.
That said, the research team’s hypothesis still requires some heavy-handed outside influence. That is, a large object hitting Earth would be the most obvious way to deliver the RNA precursors. They estimate that something about the size of Vesta, an asteroid located in the asteroid belt, should suffice. This impactor would have been different and much smaller than the Mars-sized object that is believed to have collided with Earth to form the Moon. The known physics of planet formation strongly suggests that the medium-sized impacts proposed in the new study were relatively common in Earth’s early ages.
This means, Benner says, that it’s likely that impact events may have occurred on other rocky planets that could have created similar conditions. “The argument is this: The history of influence is universal,” he says. “As a planet is accumulating a small part of its orbit around a star, it’s going to clear its field,” obtain RNA precursors and possibly cook the RNA. And if that scenario is true, he says, “it means life is everywhere, including almost certainly rocky planets among the billions of other stars like the Sun (in the Milky Way).”
The team says the most notable input from the alleged large impact may have been the molecules needed to convert ribose, a sugar, into ribose phosphate.
A recent analysis of samples of asteroid Bennu, taken by NASA’s OSIRIS-REx spacecraft in 2020 and returned to Earth in 2023, also Presence of ribose detected On that asteroid. Yoshihiro Furukawa of Tohoku University, who led the discovery of ribose and was also a co-author of the new paper, says the discovery shows that ribose was present on early Earth, as Bennu is indicative of the same type of primitive material that may have initially formed our planet. “So meteorites like Bennu should have provided the building blocks of life on prebiotic Earth,” he says.
However, Cronin says that Benner and the new study still rely on human input to produce the RNA, even though it appears to have been the result of a natural process. And even with all the right materials, the chances of actually producing RNA without human input are very slim, he says, similar to pulling a royal flush in a poker game. Cronin concluded, “The mathematical probability of finding RNA anywhere else in the universe is basically zero.”
Instead, he says, many other molecules besides RNA may be components of life on other worlds. “RNA is a super boring molecule,” he says. “There’s nothing special about it, and there are plenty of alternatives that can do the trick.”
However, borate’s role in this process is “extremely interesting,” says Cronin. The researchers’ “work on borate is tremendous,” he says. “It shows how many strange things molecules can do that we didn’t think about.”
