Beneath the town of Ames, Oklahoma, lies a meteor impact structure that stretches for miles underground. Layers of sediment now cover the crater, but it remains significant both scientifically and economically. The Ames impact structure is also a major producer of oil and gas.

A Crater Long Linked to an Ancient Meteor Event

For years, the Ames crater was thought to belong to a cluster of major meteor impacts across North America dating to roughly 467.5 million years ago. That period is known as the Ordovician Meteor Event.

Because so many impact structures appear to date from around the same time, some researchers have proposed that Earth may once have been surrounded by a Saturn-like ring of asteroid debris during the Middle Ordovician.

New work from UT researchers now shows that the Ames impact does not belong to that episode.

By dating zircon crystals taken from granite altered by the impact, the team determined that the meteorite struck about 370 million years ago during the Late Devonian. That makes the crater nearly 100 million years younger than previously believed.

“No matter what technique we used, it was coming back to this younger signal,” said lead author Elizabeth Catlos, associate professor at UT’s Department of Earth and Planetary Sciences.

The research was published in July in Meteoritics & Planetary Science.

Why the Earlier Date Was Misleading

Before this study, the Ames impact had only been dated using biological evidence. Researchers had found teeth from an ancient eel-like animal called a conodont preserved in the rock. Those fossils came from organisms that lived during the older Ordovician period.

But Catlos said the teeth were probably already millions of years old by the time the asteroid struck. The impact likely churned up older material and mixed the fossils into the rocks while still preserving them.

The zircon dating provides a very different timeline. It shows that the Ames crater could not have formed during the Ordovician Meteor Event.

Instead, its new age places it close to the Frasnian-Famennian mass extinction event, which occurred about 372 million years ago and wiped out a large proportion of marine life on Earth.

Tiny Zircon Crystals Preserve the Impact

Danny Stockli, dean of the Jackson School of Geosciences and a co-author of the study, said zircon U-Pb dating offers one of the most accurate ways to determine when events occurred deep in Earth’s past.

Zircon crystals can also preserve microscopic structures created by the intense pressures generated during an impact.

“These small crystals allow us to go back in time and learn about the major changes to Earth’s ancient landscapes,” Stockli said. “It would be great to do this for more of the meteor impact sites across the continent so we could get a more accurate timeline for these major events.”

To confirm that the zircons had actually been affected by the meteor strike, the team worked with NASA to image the crystals using cathodoluminescence and electron backscatter diffraction.

When zircon experiences the extreme conditions of an impact, it recrystallizes in a distinctive way. Those changes can be detected with these imaging techniques, allowing researchers to verify that the crystals recorded the collision itself.

A New Piece of a Mass Extinction Puzzle

According to Catlos, establishing more precise dates for mass extinctions and other major events is essential for understanding how Earth has changed over time.

One key question is whether extinction events were triggered primarily by forces from space, such as meteor impacts, or by processes within Earth, including episodes of massive volcanic activity.

“With this research, we’re basically taking a major pawn out of the Ordovician Meteor Event and dumping it into the Frasnian-Famennian event, and saying, ‘This is where this impact belongs,'” she said.

The project was initiated by former Jackson School of Geosciences graduate student Andrew Parisi, who graduated in 2018 and has since passed away. Parisi traveled to Oklahoma to obtain the Ames rock core from the Oklahoma Geological Survey, extracted zircon crystals from the material, and helped determine their ages.

Co-author Michael Brookfield, an affiliated researcher at the school, also passed away before the paper was published.

Research Professor Sean Gulick and Professor Emeritus Mark Cloos at the Jackson School also contributed to the research.

Two of our best ways of measuring the cosmic expansion rate, the Hubble constant, give answers that are stubbornly at odds. This presents a major problem in modern cosmology known as the Hubble tension.

However, we wondered if an idea originally proposed to solve another cosmic mystery — the origin of cosmic magnetic fields — could help us unlock the mystery of the Hubble tension.

Our recently published research explores whether extremely weak magnetic fields left over from the earliest moments after the Big Bang might help us unpack the Hubble tension, while offering a glimpse into physics at energies far beyond anything achievable on Earth.

The Hubble constant and tension

Astronomers use the Hubble constant as a measure of how fast the universe is expanding. It is named after the American astronomer Edwin Hubble who first discovered that the universe is expanding.

There are two conceptually different approaches to measuring the Hubble constant. One is indirect, based on predictions of our cosmological model tuned to match the patterns in the cosmic microwave background, the faint afterglow of the Big Bang.

Telescopes such as the Planck Space Telescope have measured tiny fluctuations in this ancient light, predicting a Hubble constant of about 67 kilometers per second per megaparsec (km/s/Mpc). A parsec is a unit of distance used in astronomy equal to about 3.26 light years, or 30.9 trillion kilometers. A megaparsec is one million parsecs.

The second method is more direct, similar to the one used by Hubble in the 1920s when he first demonstrated that the universe is expanding.

It measures how fast distant galaxies are moving away from our home galaxy, the Milky Way, by observing the brightness of supernovae explosions in these far away galaxies.

Type Ia supernovae are known to be “standard candles” because we know that their luminosity is the same wherever they are. That means we can judge the distance to them from how dim they appear to us.

To determine their intrinsic brightness, astronomers use other standard candles, such as Cepheid stars, in the galaxies nearby. These observations, which use the Hubble and James Webb space telescopes, give a higher value of around 73 km/s/Mpc.

This difference between the two measurements is called the Hubble tension. The difference between 67 and 73 may seem small, but it is statistically highly significant. If both methods are correct, then our standard model of cosmology must be missing something important.

Where did cosmic magnetic fields come from?

Magnetic fields are everywhere in the universe. Planets and stars generate their own fields, but gaps in our understanding emerge when we attempt to explain the much larger scale magnetic fields threading galaxies and clusters, and possibly even cosmic voids.

One long-studied possibility is that magnetism first arose in the very early universe, long before the first stars or galaxies formed. These so-called primordial magnetic fields have been studied for decades, and searching for their imprints in the cosmic microwave background and other data offers a way to probe the early universe and the extreme energies that would have generated these fields.

In 2011, two of us (Karsten and Tom) pointed out that primordial magnetic fields would influence recombination — when electrons and protons first combined to form neutral hydrogen — and the universe turned from opaque to transparent. The first light able to travel freely from that moment on is what we now observe as the cosmic microwave background.

If present, primordial magnetic fields would speed up recombination by pushing and pulling on charged particles, making matter slightly clumpy. Where particles are more crowded, they are more likely to meet and form hydrogen.

Shifting the moment when the universe becomes transparent changes the size of the observed patterns in the cosmic microwave background. This effectively alters the cosmic ruler used to measure distances and, in turn, the value of the Hubble constant inferred from the model, helping to ease the Hubble tension. Two of us (Karsten and Levon) demonstrated this effect in 2020 using a simplified model of recombination.

A breakthrough: What we found

In our new paper, we used the first full three-dimensional simulations of the primordial plasma with magnetic fields embedded in it, tracking how hydrogen forms.

We used the hydrogen formation history found through these simulations to compute predictions for how cosmic microwave background should appear if there were primordial magnetic fields, and tested these predictions against observations of the background.

The cosmic microwave background is extraordinarily sensitive to changes in recombination. If primordial magnetic fields altered it in a way that disagreed with observations, the idea could be ruled out. Instead, the data showed that our proposal remains viable.

Across multiple combinations of datasets, we find a consistent, mild preference for primordial magnetic fields, ranging from about 1.5 to three standard deviations. This is not yet a discovery, but a meaningful hint that they exist.

Equally important, the field strengths favored by the data, about five to 10 pico-Gauss today, are close to what would be needed for galaxy and cluster magnetic fields to originate from primordial seeds alone. A pico-Gauss is a unit used to measure the strength of magnetic fields.

Aside from helping ease the Hubble tension, if primordial magnetic fields are confirmed, they would open a new window into how the universe was when it was only split seconds old, perhaps offering a glimpse into important events such as the Big Bang itself.

Our results show that the proposal survives the most detailed test available today and provides clear targets for future observations. Over the next several years, we will learn whether tiny magnetic fields from the dawn of time helped shape the universe we see today and whether they hold the key to resolving the Hubble tension.

Non-nutritive sweeteners are low-calorie or calorie-free sugar substitutes commonly used in foods and beverages. The 104-week study found that NNS beverages, including diet soft drinks, performed similarly to water when it came to long-term weight management.

Professor Jo Harrold, Dean of Psychology at the University of Liverpool, led the peer-reviewed research with Professor Jason Halford, Professor, Biological Psychology & Health Behaviours at the University of Leeds (formerly of the University of Liverpool). The study was funded by the American Beverage Association. According to the researchers, the study team operated independently from the funder and retained full control over the analysis and reporting of the results.

Diet Drinks Compared With Water Over Two Years

The findings, published in the British Journal of Nutrition, provide long-term clinical evidence on beverages containing aspartame, acesulfame potassium (acesulfame-K), and sucralose. Researchers found that these drinks were comparable to water in supporting both weight loss and long-term weight maintenance.

The SWITCH trial included 493 adults with overweight or obesity who took part in a structured behavioral weight management program. Participants were randomly assigned to drink either water or commercially available diet beverages each day. The amounts of sweeteners consumed remained well within established European Food Safety Authority (EFSA) safety thresholds.

Overall, the results did not support concerns that NNS beverages interfere with appetite regulation or cause long-term metabolic harm.

Weight Loss and Metabolic Health

Key findings included:

• Weight loss was similar between the NNS beverage and water groups after 104 weeks (−4.8 kg vs −3.7 kg; nonsignificant difference).
• Both groups maintained weight reductions across the full two-year study, including during the final year when participants no longer received assistance.
• Participants in both groups had reductions in waist and hip circumference, along with improvements in body composition and several metabolic biomarkers.
• Researchers found no clinically meaningful differences in measures such as blood pressure and cholesterol linked to long-term consumption of either aspartame, acesulfame-K, or sucralose compared with water.
• Sugar intake fell in both groups, with a slightly larger reduction among participants drinking NNS beverages.

Findings Add to the Sweetener Debate

The results are relevant to recent World Health Organization (WHO) guidance advising against the use of non-sugar sweeteners for weight control because of uncertainty in observational research. The SWITCH trial adds long-term randomized controlled evidence that may help inform future global recommendations.

Professor Joanne Harrold, said: “The University of Liverpool is one of the UK’s leading research-intensive higher education institutions, with a key focus on public health. These latest findings show that concerns about sweeteners disrupting appetite or causing weight gain are not supported when tested in a rigorous, long-term randomized trial. We hope this evidence informs future WHO guidance and public health policy.

The effectS of non-nutritive sWeetened beverages on appetITe during aCtive weigHt loss (SWITCH) trial was developed to address two related questions: how reducing dietary sugar might affect weight management, and whether replacing sugar with non-nutritive sweeteners changes appetite regulation. The newly published results build on earlier findings reported in the International Journal of Obesity in 2023.

Professor Jason Halford, University of Leeds and University of Liverpool, concluded: “This study provides the long-term clinical evidence that has been missing from international discussions. For people trying to manage their weight, non-nutritive sweetened beverages offer an effective alternative to sugar-sweetened drinks — and perform equivalently to water over two years.”

The paper, ‘Effect of non-nutritive sweetened beverages versus water on body weight: long-term results of a randomised controlled trial’, was published in British Journal of Nutrition.

An estimated 100 million people in the U.S. have metabolic dysfunction-associated steatotic liver disease (MASLD), formerly called nonalcoholic fatty liver disease, according to the American Liver Foundation. Roughly 20% to 25% of those affected go on to develop metabolic dysfunction-associated steatohepatitis (MASH), a more serious form of the condition in which excess liver fat is accompanied by inflammation, cell injury and scarring.

Why MASH Is Difficult to Treat

Current care mainly centers on lifestyle changes and efforts to limit additional liver damage. Although medications are available, treatment options are still limited, and there is currently no cure for MASH.

Earlier research has suggested that damaged mitochondria, the structures that produce energy for cells, may contribute to the development and progression of MASH. In the new multicenter study, Cedars-Sinai researchers found that levels of an enzyme called UBE2N decline in liver cells as the disease becomes more advanced.

“The UBE2N enzyme appears to protect the liver from the inflammation and damage associated with MASH by helping remove damaged mitochondria and supporting the breakdown of fat,” said Ekihiro Seki, MD, PhD, professor of Medicine and Biomedical Sciences at Cedars-Sinai and co-corresponding author of the study. “When levels of the enzyme fell, we saw more damaged cells and injury to the liver.”

Restoring UBE2N Reduced Liver Damage in Mice

The researchers then restored UBE2N to normal levels in the livers of laboratory mice. After doing so, they observed reductions in fat accumulation, inflammation and scarring.

Those results suggest that UBE2N could become a potential treatment target for preventing MASLD from advancing to MASH.

“The identification of this enzyme’s role in regulating mitochondria in the liver is an important advance in understanding steatotic liver disease,” said Shelly Lu, MD, the Women’s Guild Chair in Gastroenterology and director of the Karsh Division of Gastroenterology and Hepatology at Cedars-Sinai. “Future studies can test whether enhancing this protective pathway can complement existing treatments, identify patients most likely to benefit and lead to new therapeutic approaches for preventing advanced disease.”

Additional Cedars-Sinai authors include Michitaka Matsuda, So Yeon Kim, Takashi Tsuchiya and Yoon Seok Roh.

Additional authors include: Feng Wang, Jin Lee, Jeong-Su Park, Meizhou Huang, Hwan Ma, Guoyan Sui, Zixiong Zhou, Xufeng Wu, Haram Lee, Soohwan Oh, Hanseul Park, Key-Hwan Lim, Chun-Woong Park, Sang-Bae Han, Jin Tae Hong and Michael Karin.

Funding: This work was supported by the National Research Foundation of Korea (grant nos. RS-2025-02273102 and RS-2025-02603096), Regional Innovation System & Education (RISE) programme of Chungbuk (grant no. 2025-RISE-11-014-03), the Pinnacle Research Award of American Association for the Study of Liver Diseases (AASLD, to J.L.), the San Diego Digestive Diseases Research Center (SDDRC) Pilot/Feasibility Grant (NIDDK P30 DK120515, to J.L.), the National Institutes of Health (grant nos. R01DK085252, R01DK138591 and R01CA301632) and the National Natural Science Foundation of China (grant no. 82404726).

The carefully planned gravity assist changed Juice’s direction by 20° relative to its previous trajectory and increased its speed by 3.5 km/s. During the four weeks leading up to the encounter, mission controllers needed to make only one small course correction (out of six opportunities set aside) to place the spacecraft on the precise approach needed to take full advantage of Earth’s gravity.

Controllers began monitoring Juice particularly closely on August 17 and will continue that intensive tracking through October 10.

Juice Makes a Close Pass Over Earth

Juice reached its closest point to Earth at 13:45 CEST (11:45 UTC) on September 28. At that moment, the spacecraft passed just 8640 km above the Indian Ocean while taking a sequence of images with its onboard monitoring cameras.

“The flyby required ultra-precise navigation in real time. Thanks to our very careful planning, we used only a small amount of the propellant reserved for this flyby,” says Angela Dietz, Juice’s Spacecraft Operations Manager. “This gives us more to use at Jupiter to carry out observations of the planet’s icy moons.”

Preserving that fuel is especially valuable because Juice will eventually need it while carrying out its ambitious scientific campaign around Jupiter and its moons.

Earth Becomes a Test Site for Juice

Changing the spacecraft’s trajectory was the primary purpose of the flyby, but the encounter also gave the mission team a valuable chance to test Juice’s science instruments using a real planetary target.

This was the third such opportunity during the mission. The first came during Juice’s 2024 lunar-Earth gravity assist, followed by the spacecraft’s 2025 observations of Comet 3I/ATLAS.

Teams from ESA’s spacecraft operations, science operations and technical centers spent months coordinating with the outside groups responsible for Juice’s 10 scientific instruments. Their goal was to carefully schedule when each instrument could operate and extract as much science and calibration time as possible from the spacecraft’s limited resources.

“Juice’s journey to Jupiter provides only a few opportunities to calibrate and validate the instruments under well-understood environmental conditions,” explains Juice project scientist Claire Vallat, who led the effort.

“Given the limited time available and operational constraints, instrument activities sometimes have to be prioritized, for example when Juice was in Earth’s shadow this morning, and relying on battery power alone. During this flyby, calibration activities were prioritized based on their relevance to preparing the instruments for their work at Jupiter, while also considering whether an opportunity is unique or can be scheduled later in the journey.”

Preparing for Jupiter’s Icy Moons

Although the Earth encounter required extensive preparation, it is relatively simple compared with what awaits Juice at Jupiter. The spacecraft is scheduled to carry out 35 flybys of the giant planet’s large moons Ganymede, Callisto and Europa.

Planning for those encounters began years in advance. For the Europa flybys, discussions about how the instruments will operate began about 10 years ago and will continue until Juice finally passes the moon in the early 2030s.

Earth therefore serves as an important rehearsal. Scientists can use the flyby to calibrate the instruments, learn how they behave once they are operating in space (where they always work a little differently to on Earth!), and refine the tools that will later be used to analyze the data.

The encounters with Jupiter’s icy moons will be much more scientifically demanding. By then, Juice will need to be ready to capture as much high-quality information as possible during each precious flyby.

Juice Explores Earth’s Magnetic Tail

The spacecraft also spent several days traveling through Earth’s magnetotail, the long extension of Earth’s magnetic field that stretches away from the Sun.

That gave Juice an opportunity to measure magnetic fields and electrically charged particles far from Earth. At the same time, the European-Chinese Smile mission has been observing the northern lights while measuring magnetic fields and particles much closer to the planet.

Combining measurements from Juice and Smile could give scientists a rare way to link activity deep in Earth’s magnetotail with events occurring around the planet’s polar regions.

Scientists expect to release images and spectra from some of Juice’s instruments in the coming weeks, once the data have reached Earth and instrument teams have had time to evaluate them. Among the anticipated results are high-resolution images of Earth and the Moon taken by JANUS, Juice’s scientific camera.

Juice Will Return to Earth One More Time

Juice is not finished with Earth yet.

In January 2029, the spacecraft will return for a third and final flyby of our planet. That encounter will place Juice on the final trajectory needed to reach Jupiter in 2031.

About Juice

ESA’s Jupiter Icy Moons Explorer, ‘Juice’, is humankind’s next bold mission to the outer Solar System. It will make detailed observations of gas giant Jupiter and its three large ocean-bearing moons – Ganymede, Callisto and Europa. This ambitious mission will characterise these moons with a powerful suite of remote sensing, geophysical and in situ instruments to discover more about these compelling destinations as potential habitats for past or present life.

Juice will monitor Jupiter’s complex magnetic, radiation and plasma environment in depth and its interplay with the moons, studying the Jupiter system as an archetype for gas giant systems across the Universe.

Juice launched on an Ariane 5 from Europe’s Spaceport in Kourou in April 2023. It has an eight-year cruise with flybys of Earth and Venus to slingshot it to Jupiter. It will make 35 flybys of the three large moons while orbiting Jupiter, before changing orbits to Ganymede.