Back in 2010, Japan’s space agency JAXA completed one of the biggest milestones in the history of space exploration: It collected samples from an asteroid and brought them back to Earth. A decade later, the agency’s Hayabusa2 mission did the same thing with another asteroid called Ryugu—with a vastly more ambitious goal of bringing back an even bigger cache of extraterrestrial rock samples. For the past few years, scientists on Earth have been uncovering the chemical secrets embedded within these samples and whether there’s anything we can glean about the origins of the solar system and its planets. As it turns out, we’ve learned that Ryugu is home to a very special compound that’s a building block of genetic information itself.
On Tuesday, Japanese scientists revealed they discovered within the Ryugu samples the presence of uracil, a component that’s critical to the makeup of RNA. They also discovered nicotinic acid, better known as Vitamin B3 or niacin, which is important for allowing organisms to run metabolic functions.
Both materials have been previously discovered in carbon-rich meteorites that have impacted Earth. But, “this is the first time they have been detected in any returned samples from space,” Yasuhiro Oba from Hokkaido University, who led the new study, told The Daily Beast in an email. “Based on this finding, we can say uracil is indeed present in space.” The findings were reported in Nature Communications.
The new discovery arrives at a time when scientists are trying to piece together a better understanding of how the building blocks to life first originated on Earth. One of the most popular theories among researchers these days is that during the formation of Earth, asteroids were responsible for bringing in water, organic molecules, nucleic acids, and other compounds that form the constituents of proteins and genes and cells.
The problem? These theories have been based on the study of meteorite samples already on Earth. There’s always been a chance that they’ve been contaminated by terrestrial factors.
But missions like Hayabusa2 enable us to study pristine samples, delivered to us in sealed capsules, that haven’t been messed up by earthly treasures.
“It’s really encouraging that these compounds are so present in space.”
— Tanja Bosak, MIT
Tanja Bosak, a geologist at MIT who was not involved with the study, told The Daily Beast that the new findings are “not so shocking” given previous research. But, she said, “it’s a really nice confirmation of these materials and these compounds being widespread.” It adds fuel to the notion that carbon-rich asteroids are likely a major mechanism for delivering pre-biological chemical compounds to other worlds, as probably was the case for Earth.
“It’s really encouraging that these compounds are so present in space,” she said.
Oba acknowledged that he and his colleagues still cannot conclude how the uracil and niacin were formed and found their way onto Ryugu. But they think a possible formation mechanism has to do with photochemical reactions of interstellar ices that contain simple compounds like water, methanol, and ammonia. These reactions would have taken place long before the solar system first came together.
"Our research shows that nature could have selected for building blocks with useful properties before Darwinian evolution."
By simulating early Earth conditions in the lab, researchers have found that without specific amino acids, ancient proteins would not have known how to evolve into everything alive on the planet today—including plants, animals, and humans.
The findings, which detail how amino acids shaped the genetic code of ancient microorganisms, shed light on the mystery of how life began on Earth.
"You see the same amino acids in every organism, from humans to bacteria to archaea, and that's because all things on Earth are connected through this tree of life that has an origin, an organism that was the ancestor to all living things," said Stephen Fried, a Johns Hopkins chemist who co-led the research with scientists at Charles University in the Czech Republic. "We're describing the events that shaped why that ancestor got the amino acids that it did."
The findings are newly published in the Journal of the American Chemical Society.
In the lab, the researchers mimicked primordial protein synthesis of 4 billion years ago by using an alternative set of amino acids that were highly abundant before life arose on Earth.
They found ancient organic compounds integrated the amino acids best suited for protein folding into their biochemistry. In other words, life thrived on Earth not just because some amino acids were available and easy to make in ancient habitats but because some of them were especially good at helping proteins adopt specific shapes to perform crucial functions.
"Protein folding was basically allowing us to do evolution before there was even life on our planet," Fried said. "You could have evolution before you had biology, you could have natural selection for the chemicals that are useful for life even before there was DNA."
Even though the primordial Earth had hundreds of amino acids, all living things use the same 20 of these compounds. Fried calls those compounds "canonical." But science has struggled to pinpoint what's so special—if anything—about those 20 amino acids.
In its first billion years, Earth's atmosphere consisted of an assortment of gases like ammonia and carbon dioxide that reacted with high levels of ultraviolet radiation to concoct some of the simpler canonical amino acids. Others arrived via special delivery by meteorites, which introduced a mixed bag of ingredients that helped life on Earth complete a set of 10 "early" amino acids.
How the rest came to be is an open question that Fried's team is trying to answer with the new research, especially because those space rocks brought much more than the "modern" amino acids.
"We're trying to find out what was so special about our canonical amino acids," Fried said. "Were they selected for any particular reason?"
Scientists estimate Earth is 4.6 billion years old, and that DNA, proteins, and other molecules didn't begin to form simple organisms until 3.8 billion years ago. The new research offers new clues into the mystery of what happened during the time in between.
"To have evolution in the Darwinian sense, you need to have this whole sophisticated way of turning genetic molecules like DNA and RNA into proteins. But replicating DNA also requires proteins, so we have a chicken-and-egg problem," Fried said. "Our research shows that nature could have selected for building blocks with useful properties before Darwinian evolution."
Scientists have spotted amino acids in asteroids far from Earth, suggesting those compounds are ubiquitous in other corners of the universe. That's why Fried thinks the new research could also have implications for the possibility of finding life beyond Earth.
"The universe seems to love amino acids," Fried said. "Maybe if we found life on a different planet, it wouldn't be that different."
This research is supported by the Human Frontier Science Program grant HFSP-RGY0074/2019 and the NIH Director's New Innovator Award (DP2-GM140926).
The study's authors include Anneliese M. Faustino, of Johns Hopkins; Mikhail Makarov, Alma C. Sanchez Rocha, Ivan Cherepashuk, Robin Krystufek, and Klara Hlouchova, of Charles University; Volha Dzmitruk, Tatsiana Charnavets, and Michal Lebl, of the Czech Academy of Sciences; and Kosuke Fujishima, of Tokyo Institute of Technology.
"It would take billions of years to create a structure of this size."
The discovery of giant superclusters of galaxies are challenging our very understanding of the Universe.
In 2021, British PhD student Alexia Lopez was analysing the light coming from distant quasars when she made a startling discovery.
She detected a giant, almost symmetrical arc of galaxies 9.3 billion light years away in the constellation of Boötes the Herdsman. Spanning a massive 3.3 billion light years across, the structure is a whopping 1/15th the radius of the observable Universe. If we could see it from Earth, it would be the size of 35 full moons displayed across the sky.
Known as the Giant Arc, the structure throws into question some of the basic assumptions about the Universe. According to the standard model of cosmology – the theory on which our understanding of the Universe is based – matter should be more-or-less evenly distributed across space. When scientists view the Universe on very large scales there should be no noticeable irregularities; everything should look the same in every direction.
Yet the Giant Arc isn't the only example of its kind. These gargantuan structures are now forcing scientists to reassess their theory of how the Universe evolved.
What Lopez' "happy accident" uncovered was astonishing. When looking towards the constellation Boötes, a cluster of between 45 to 50 gas clouds, each associated with at least one galaxy, seemed to arrange themselves in an arc 3.3 billion light years across. That is a considerable size given the observable Universe is 94 billion light years wide.
According to Lopez's article, it is extremely unlikely (a probability of just 0.0003 per cent) that such a large structure could have arisen by chance. It suggests that it may have formed due to something in the natural physics of the Universe that we currently don't account for. Her findings directly challenge a central facet of the standard cosmological model – the best explanation we have for how the Universe started and evolved.
This facet, known as the cosmological principle, states that on a large scale, the Universe should look roughly the same everywhere, no matter your position or the direction in which you are looking. There should be no giant structures, rather space should be smooth and uniform. This is convenient, as it lets researchers draw conclusions about the whole Universe based only on what we see from our corner of it. However it also makes sense, as following the Big Bang the Universe expanded outwards, flinging matter in every direction simultaneously.
There is another problem. According to the standard model, structures like the Giant Arc simply wouldn't have had time to form.
It would take billions of years to create a structure of this size – Subir Sarkar
"The current idea for how structures formed in the Universe is through a process known as gravitational instability," says Subir Sarkar, a professor of theoretical physics at the University of Oxford.
About a million years after the Big Bang, when the Universe was expanding, tiny fluctuations in density led to bits of matter clumping together. Over billions of years, the pull of gravity eventually led these clumps to form stars and galaxies. However, there is a size limit to this process. Anything larger than about 1.2 billion light-years across simply wouldn't have had sufficient time to form.
"To form structures you need particles to congregate close to each other so gravitational collapse can occur," says Sarkar. "Those particles would have to move in from outside the structure to get there. So, if your structure is 500 million light years across, light would take 500 million years to move from one end to the other. However, the particles we are talking about are moving much more slowly than light, so it would take billions of years to create a structure of this size, and the universe has only been around for about 14 billion years."
The Giant Arc discovered by Lopez isn't the only large-scale structure discovered by astronomers.
There's the "Great Wall" (also called the CfA2 Great Wall) of galaxies discovered in 1989 by Margaret Geller and John Huchra. The wall is approximately 500 million light-years long, 300 million light years wide, and 15 million light years thick.
Even bigger is the Sloan Great Wall – a cosmic structure formed by a giant wall of galaxies, discovered in 2003 by J Richard Gott III and Mario Juric and their colleagues at Princeton University. That wall is nearly 1.5 billion light years in length.
In the last decade the discovery of these behemoths has accelerated even further. In 2014, scientists discovered the Laniakea supercluster, a collection of galaxies in which our own Milky Way resides. Lanaikea is 520 million light years across and contains roughly the mass of 100 million billion suns. Then in 2016 the BOSS Great Wall – a complex of galaxies over one billion light years across – was uncovered. BOSS is made up of 830 separate galaxies that gravity has pulled into four superclusters. The galaxies are connected by long filaments of hot gas. In 2020 the South Pole Wall, which stretches 1.4 billion light-years across was also added to the list.
However, the current record holder for the biggest of these structures is the Hercules-Corona Borealis Great Wall. Discovered in 2013, it spans 10 billion light years – more than one-10th the size of the visible Universe.
"We calculated it and then realised, 'Uh oh, this is the biggest thing in the Universe'," says Jon Hakkila, professor of physics and astronomy at the University of Alabama in Huntsville.
Their concern was justified. Both Hakkila and Lopez performed a range of statistical tests to try to prove that the results couldn't be down to chance. For the Giant Arc, the results have a confidence level of 99.9997%. In scientific research, the gold standard for statistical significance is known as 5- sigma, which equates to a probability of about 1 in 3.5 million that the results are down to chance. The Giant Arc reached a significance of 4.5 sigma, so there's still the possibility that the structure is a chance arrangement of stars.
"Our eyes are very good at seeing patterns. You might see initials in the clouds, but that's not a real structure, your mind is imposing a structure on what is actually random," explains Sarkar. "However, I don't think that is the case in this situation, I think it is a genuine physical chain of superclusters."
It isn't the first time that the model will have had to have been adapted.
If more structures like the Giant Arc and Hercules-Corona Borealis Great Wall are proven to exist, astronomers will be forced to rewrite – or at least revise – the standard model of cosmology.
"It takes a lot to make a paradigm shift, especially when people have their lives and careers invested in it, but ultimately with science we have to see who is right," says Sarkar.
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