Researchers have discovered a roughly 9 million year old tooth belonging to a large, water-loving relative of modern day capybaras in the Atacama Desert of northern Chile. The fossilized molar adds to previous evidence suggesting that it's unlikely the Atacama, one of the driest places on Earth, was continuously dry for the last 40 million years.

The Atacama Desert, possibly the oldest desert on Earth, takes up the northern third of Chile. It's bounded by the Chilean Coast Range to the west, which blocks rain from the Pacific Ocean, and the enormous Andes to the east, which obstruct rain from the Atlantic Ocean. The driest part of the desert's hyperarid region gets less than 0.08 inches (2 mm) of rainfall a month.

Recent research estimates the Atacama's hyperarid core started forming between 47.8 million and 33.9 million years ago, in the Mid- to Late-Eocene, 20 million years before the Andes formed. It suggests the mountain ranges weren't the cause for the desert's aridification, and may have only intensified it.

Capybaras (Hydrochoerus hydrochaeris) ‪—‬ the world's largest rodent ‪—‬ exclusively live close to stable freshwater sources and feed on plants that also require water to grow, so the discovery of an extinct capybara relative (Hydrochoerus Cardiatherium) tooth in the Atacama Desert is very strange.

"Finding a capybara tooth in a marine deposit in what today is one of the driest regions on Earth is just freakish," Priscilla Martinez, a geoscientist at the University of Arizona and co-author of a new paper describing the discovery, said in a statement.

Capybaras are native to South America, although today, they are not found in Chile, where the tooth was unearthed, according to the International Union for Conservation of Nature (IUCN).

The tooth isn't the only clue that the Atacama was a wetter place in the late Miocene. Researchers found it in a layer holding the remains of a shallow marine environment that existed between 7 million and 10 million years ago, according to the statement. And they've also found microscopic pieces of plants, known as phytoliths, revealing that palm trees, grasses, gingers and other flowering plants grew there in what may have been a subtropical forest.

These findings and others are part of a growing body of evidence that the Atacama Desert was once wet enough for crocodiles and freshwater fish to thrive and palms to grow. The new study, published Sept. 5 in the journal Scientific Reports, shows that capybara relatives lived there as well during the late Miocene, which, because they are semiaquatic animals, is further evidence to support the hypothesis of a sporadically moist Atacama.

The researchers aren't sure how exactly capybaras moved into the Atacama Desert. Although there were capybaras in South America at the time, the Andes created an 18,000-foot-high (5,500 meters) barrier between their current habitats and the site where the tooth was found. The researchers theorized that, instead of traversing the mountains, the ancient capybaras migrated along the western coast of South America, following wetlands, rivers and other water sources.

According to Samantha Hopkins, an Earth sciences professor at the University of Oregon who was not involved in the study, it's unlikely the tooth found its way to the site without capybaras living there.

"If you wanted to find a way that this capybara could be here while the Atacama was still as dry as it is today, you'd have a hard row to hoe," she told Live Science in an email, because the size of the tooth makes it hard to transport it long distances. The desert wind couldn't have blown it such a long way, and while large carcasses can float down waterways for miles, "if you're going to invoke a large enough waterway to do this, you've demonstrated that the Atacama wasn't as dry as it is today anyway."

'> 'Freakish' discovery of 9 million-year-old capybara tooth supports idea that Atacama wasn't always a desert

The event, named FRB 20240304B, is known as a fast radio burst (FRB). Astronomers have detected thousands of FRBs before this. But because these events last only milliseconds, they are extremely difficult to study and their origin stories remain unclear.

In this case, however, astronomers managed to use a radio telescope array and the James Webb Space Telescope (JWST) to chart the event, with JWST narrowing down the precise host galaxy that FRB 20240304B came from. The study, published Thursday (Oct. 8) in the journal Science , sheds more light on a time when the universe was only about 3 billion years old, showing that FRBs arose early in our cosmos' history. The detection more than doubles the previous distance record for FRBs.

The JWST played an instrumental role in the discovery, study co-author Themiya Nanayakkara, a senior lecturer at the Sydney Institute for Astronomy, told Live Science in an email. The email was written in collaboration with study first author Manisha Caleb, a senior lecturer in astrophysics at the same university.

For example, JWST's observations showed that the host galaxy was smaller than expected, was "metal-poor" (had few elements besides hydrogen and helium), and was forming a lot of stars. These characteristics could offer new clues about the environments in which FRBs arise, giving more information about the mysterious events. Researchers suggest that this FRB may have been linked to a magnetar, a highly magnetic star core left after a supernova.

Zooming in with the James Webb telescope

The ancient FRB was initially detected with MeerKAT, an array of 64 radio telescopes in South Africa. Nanayakkara said MeerKAT revealed "both the detection of the fast radio burst and, importantly, a very precise position on the sky."

The researchers knew the FRB was far away because of the large dispersion of the radio signal, but initial searches with powerful ground-based telescopes, "saw essentially nothing; it looked like empty sky," the researchers told Live Science. "The most likely explanation was that the galaxy was simply too faint to be detected in those observations. That is where JWST became transformative."

The science team successfully got time on JWST with a program called Director’s Discretionary Time, which is aimed at time-sensitive observations. The researchers started by using JWST's Near Infrared Camera to trace the radio signal and take a very deep image of the target region.

"Suddenly, there it was: a very faint galaxy almost exactly where we expected the host of the FRB to be," Nanayakkara said. The researchers then used JWST's Near Infrared Spectrograph to obtain a spectrum (wavelengths of light broken into different chemical signatures), which showed hydrogen and oxygen.

"These spectral features act like fingerprints: because we know the wavelengths at which they are produced in the laboratory, we can measure how much they have been shifted by the expansion of the universe," Nanayakkara explained. "That gave us a very precise redshift of about 2.15. We are therefore seeing this galaxy as it was when the universe was only around three billion years old, so roughly one-fifth of its current age."

Because the host galaxy is fairly young, it supports the idea that at least some FRBs are generated by magnetars, which are more likely to appear in spry galaxies where intense star formation is occurring, the team said.

The team plans to continue hunting for FRBs with JWST.

"We do not know what the sources will be yet," Nanayakkara said, as that depends on what pops up in the sky and is spotted by ground-based radio telescopes. "Once our radio telescopes find and localize a suitable new source, we can trigger the JWST observations. So it is quite exciting, because we really have no idea what we will find when we combine the power of these two types of telescopes."

'> James Webb telescope pinpoints the most distant 'fast radio burst' ever seen Harley Katz, an assistant professor of astronomy and astrophysics at the University of Chicago, said in a statement.

To understand more about the early universe, astronomers build sophisticated computer models that encode the laws of nature to see how the cosmos may have evolved. The new work, which is the result of three years of supercomputer simulations, is the most detailed tracing yet of how a galaxy like ours came to be. It also arrives just as astronomers need a stronger yardstick for what they're seeing in the early universe.

Megatron, the cosmic transformer

The James Webb Space Telescope (JWST) can peer farther into the early universe than any previous telescope, and its discoveries have often defied computer models. For instance, JWST found surprisingly bright early galaxies and a mysterious new class of compact galaxies dubbed "Little Red Dots." These anomalies demonstrate that current computer models need an update to handle the complex physics of the early universe, the researchers said.

To bridge that gap, the scientists built a new suite of supercomputer simulations they call Megatron. By tracing ancient gas, starlight and chemistry from 180 million years to 2 billion years after the Big Bang, Megatron predicts the distinct light signatures of its virtual galaxies, according to the statement. Because JWST collects the same type of spectral data across a similar span of cosmic time, scientists can directly cross-reference the simulation against real observations to pinpoint what the old models are missing, the team said.

The simulation also tracks how the universe's first stars formed, died and forged the essential elements that make life as we know it possible. By comparing the simulation with JWST observations of early galaxies and with the chemical traces left in ancient stars, scientists can better understand how those first stars enriched their surroundings, the researchers said.

"Together, these complementary observations allow us to test competing models of the first stars in ways that weren't previously possible," study co-author Martin Rey, a theoretical astrophysicist at the University of Bath in the U.K., said in a separate statement.

The scientists detailed their findings in one of the six papers the Megatron collaboration published Sept. 30 in The Open Journal of Astrophysics.

Assembling the Milky Way

The team's simulation begins 180 million years after the Big Bang, when the universe is devoid of stars and galaxies and holds only pristine gas. As the next 2 billion years pass,, the model captures how the very first stars light up the dark universe and kick off "cosmic dawn," eventually culminating in those stars' violent deaths. As they die, the stars spread newly forged heavy elements such as carbon, oxygen and iron into the surrounding gas, laying the building blocks for future stars and planets.

The simulation ends 2 billion years after the Big Bang, but the Milky Way's mergers continued long after this point, and scientists are still discovering traces of the small galaxies that have joined it. The most recent massive merger, with the Sagittarius dwarf galaxy, began more than 6 billion years ago and is still unfolding.

The simulation results help scientists understand how certain physics parameters impact the early universe, and better match up JWST's observations with computer models. But it also highlights areas that need further study.

"But there are also things we're not getting right, which is interesting too — what are the parts we're still missing?" Katz said in the statement. "That can lead you into new directions and new questions."

Megatron team members in the U.K. are now developing the next generation of simulations, backed by dedicated time on the country's supercomputers. Those simulations will include more complex physics, such as active black holes, which JWST has revealed to be surprisingly common in the early universe, the researchers said.

How well do you know our home galaxy? Find out with our Milky Way quiz!

'> The Milky Way is one galaxy — but it used to be thousands, new simulations reveal