The small exoplanets of our Sun’s second-nearest neighbor, Barnard’s Star, are inhospitable wastelands, British astronomers say.

Located six light-years from Earth, Barnard’s Star is separated from our closest neighbor, Alpha Centauri, by about 66° in our sky. Now, University of Cambridge researchers have revealed their findings on this exosolar system in a recent paper published in the Monthly Notices of the Royal Astronomical Society.

After careful analysis, the astronomers announced that the exoplanets are unlike any in our solar system, presenting a brutal and barren environment.

Barnard’s Star Exoplanets

Scientists only discovered these four small planets orbiting Barnard’s Star in 2025. Unlike anything in our solar system, these orbital bodies fit into a size range larger than Mars, but smaller than Earth or Venus.

Like a peeled onion, these smaller planets are rich in a mineral only found deep below the Earth’s surface. Chemical analysis revealed large amounts of the mineral periclase on the surface of these planets, something typically only found hundreds of kilometers deep on our planet.

“Barnard’s Star has an enormous amount of the element magnesium compared to other stars, so its planets are likely to be rich in magnesium too,” said lead author Xander Byrne from Cambridge’s Institute of Astronomy. “On Earth, that magnesium goes into making minerals called olivines, which are really important for storing water within the planet.”

A Lack of Water and Atmosphere

Unfortunately for those looking for extraterrestrial life, magnesium serves a different purpose on these exoplanets. Instead of water-storing olivine, it produces the abundant periclase, which is a poor store of water.

Even worse, these inhospitable exoplanets likely no longer have an atmosphere. According to the University of Cambridge team, these ten-billion-year-old planets probably only managed to hold an atmosphere for two billion years at most.

“These planets were always going to be hostile, because they’re really close to their star,” said Byrne. “Even the outermost planet orbits ten times closer than Mercury orbits the Sun. When you’re that close to your star, and have such little gravity, your atmosphere just gets blown off.”

In addition to the lack of atmosphere, the planets’ proximity to Barnard’s Star leaves them tidally locked, like our Moon, with one side always facing toward the star.

Exoplanet Stability

However, there is one positive element to these small planets. Typically, such close-orbiting systems are highly unstable, with the planets shooting out from the system, falling into their host star, or catastrophically colliding. Yet in this case, the system is as ordered as a piece of music. 

The three inner planets of the exosolar system have years in a 9:12:16 ratio, producing two of what is known as a “perfect fourth” in music. This musical harmony is known as an orbital resonance, with the same type of effect stabilizing Jupiter’s moons in their orbits around that planet. 

While our ability to view Barnard’s Star from Earth may be limited, the European Space Agency’s upcoming Plato mission may allow astronomers to discover ever smaller worlds orbiting in the nearby exosolar system.

“Larger planets are much easier to detect than small ones, so we know about very few sub-Earth planets like the ones in this system,” said Byrne. “But the sensitivity of these new missions will help to reduce this bias, allowing us to discover more and more planets that are small and rocky, like Earth.”

The true significance of the research may lie in the value of a null result. While these planets are bleakly hostile to life, observing this exosolar system’s composition can aid future astronomers in narrowing down the search for extraterrestrial life.

The paper, “The Barnard’s Star Planetary System: Stability, Composition, and Evolution of Four Sub-Earth Exoplanets,” appeared in Monthly Notices of the Royal Astronomical Society on June 24, 2026.

Ryan Whalen covers science and technology for The Debrief. He holds an MA in History and a Master of Library and Information Science with a certificate in Data Science. He can be contacted at ryan@thedebrief.org, and follow him on Twitter @mdntwvlf.

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A rocky planet orbiting in the habitable zone of a sun-like star may look like a perfect place for life to thrive — but not if it's too small to hold onto its atmosphere.

So, we may wonder: How much smaller Earth could be and still have its delightfully breathable atmosphere? How small could an exoplanet be to sustain life as we know it?

With these questions in mind, University of California Riverside planetary scientist Michelle Hill and her colleagues recently simulated what happens to the atmospheres of different sizes of rocky worlds. The worlds tested were similar to Earth and orbited in the habitable zones around sun-like stars. It turns out for a world to maintain an atmosphere long enough for life to gain a foothold (a few billion years at minimum), it needs to be at least as big as Mars.

Narrowing down the search for life

The habitable zone — the area around a star where temperatures are right for liquid water to exist on a planet's surface — is prime real estate in the hunt for alien life. It's also a tough neighborhood for exoplanet atmospheres, because the closer a planet is to a star, the more ways in which radiation and stellar wind will try to strip away an atmosphere.

This is why Hill and her colleagues recently simulated how long it would take rocky, Earth-like planets of various sizes, in the habitable zone of a star like our sun, to lose their atmospheres. In other words, how much smaller could Earth, or a similar planet, be and still keep an atmosphere?

The answer turns out to be that an atmosphere-sustaining planet needs to be about 80% as wide as Earth, but could technically be as small as 60%. This offers astrobiologists a clue about which planets to focus on in the search for habitable worlds and signs of alien life.

"The plethora of exoplanets creates an interesting challenge in the search for potentially habitable planets," wrote Hill and her colleagues. "Of the many targets in the habitable zones of their star, which are the best candidates for follow-up observations with the aim of detecting biosignatures?" In other words, astrobiologists now have almost too many planets to choose from and not enough telescope time to search them all. So, it's time to narrow the search.

One way to do that is to figure out which planets are most likely to be habitable — and for life as we know it, that habitability means having an atmosphere.

Modeling atmospheres — and volcanoes

Hill and her colleagues' "Smaller Than Earth Habitability Model" simulates the fate of atmospheres around digital versions of Earth. Some of the simulated worlds are exactly like ours but smaller, with the same chemical makeup and the same proportions of core, mantle and crust. Others have slightly different amounts of carbon, larger or smaller cores, or different starting temperatures. The model traces what happens to these worlds over a few billion years, based on two things: how quickly stellar wind and radiation strip away gas from the planet's atmosphere and how quickly volcanoes pump out gas (mostly carbon dioxide) to replace it.

The model is how the team realized a scaled-down version of Earth needs to be at least 80% as wide as true Earth (0.8 Earth radii) to maintain an atmosphere in the long run. Smaller planets tend to lose gas faster than volcanic eruptions can replace it.

That's because smaller planets have less gravity and weaker magnetic fields with which to hold onto their thin envelopes of gas. They also don't usually release enough gas from within to make up for the loss. Their mantles — the churning layer of magma beneath the crust — tend to release less volcanic gas over time, and their upper layers cool and harden much faster. The latter process cuts off volcanic eruptions much earlier in a planet's lifespan.

Smaller planets clinging onto atmospheres

By changing some of Earth's parameters, the team managed to get planets as small as 0.6 Earth radii to maintain a stable atmosphere. Carbon was the key: planets with more carbon in their mantles tend to release more carbon dioxide gas in eruptions, and that turns out to be the biggest factor (other than size) in whether a planet keeps its atmosphere.

"Carbon dioxide is a heavy molecule," Hill and her colleagues wrote, "which can make it a difficult molecule to lose. We focus on a pure carbon dioxide atmosphere as a best-case scenario for atmospheric retention." Of course, that's only a best-case scenario for some relatively simple forms of life, so your astrobiological mileage may vary.

It took tons more carbon than Earth contains to make a significant difference to the fate of a planet's atmosphere — but because it's theoretically possible for a planet to form with that much carbon in its makeup, that's useful knowledge. Planets with relatively smaller cores, and therefore relatively thicker mantles, also had better luck on the atmospheric retention front. Starting with a larger supply of radioactive elements, which decay and release heat into the surrounding rock, helped keep the mantle molten and the volcanic gases churning skyward.

Starting with a cooler mantle also helps — which sounds surprising. You'd think a hotter mantle would be more likely to spew volcanic gases into the atmosphere. Yet, a cooler mantle takes longer to start erupting in earnest, which means the planet gets to hold onto its reservoir of gases until its star is older and more settled.

Newborn stars are prone to violent bursts of radiation and plasma, which would sweep away the volcanic gas as fast as it erupted. With a cooler mantle and later eruptions, the planet gets to keep more of the erupted gas.

A second chance for airless worlds

There's still hope of life for smaller worlds.

Even planets that lose their initial atmospheres entirely — instead of gradually replacing them with things like carbon dioxide and methane — might have a second chance to build a new atmosphere.

Hill and her colleagues suggest that one way for a planet to regain its lost atmosphere could be comet and asteroid impacts, which might deliver volatile elements like hydrogen, oxygen and carbon. These elements can combine to form all sorts of atmospheric gases.

Such impacts could be especially helpful if they happen later in the star system's life, like after the star is past its youthful phase of intense flares.

"While smaller planets face greater challenges in retaining atmospheres, our model suggests that they can develop atmospheres under the right conditions," wrote Hill and her colleagues, so, "even those that initially lose their atmospheres should not be immediately discounted as potentially habitable worlds."

What's next?

Future simulations using the Smaller Than Earth Habitability Model could study worlds around smaller, cooler stars called red dwarfs — stars like TRAPPIST-1, which is home to at least seven rocky planets, with three of them in the habitable zone. These stars make up about 75% of the stars in our galaxy, and their relatively dim light makes it easier for telescopes like the James Webb Space Telescope (JWST) to capture images of starlight filtering through the atmospheres of planets that pass between Earth and their host stars.

Hill and her colleagues also hope to explore what happens to atmospheres around tidally-locked planets, or planets where tidal forces keep the interior hot and seismically active, similar to Jupiter's moon Io.

The researchers published their work in June in The Planetary Science Journal.

A scientifically accurate depiction of Pompeii is shocking. Interview with Kevin Wright, executive producer.

© National Geographic & Disney

A team of scientists exploring a possible deep-sea coral reef off the coast of Benin that 1960s researchers had deemed likely dead found a living, thriving reef supporting a complex underwater ecosystem, including several coral and fish species.

Led by scientists from the Institut de Recherches Halieutiques et Océanologiques du Bénin, the discovery is the first known mesophotic coral reef in the region and offers scientists a tantalizing target for future deep-sea marine-life expeditions.

Deep-Sea Coral Reef Spotted in the 1960s was Considered Dead

According to a statement announcing the unexpected discovery, previous historical surveys of the area had indicated a possible reef more than 50 meters below the water’s surface. When a 1960s survey detected the unusual feature, they suspected it was a coral reef that was likely dead.

When team leader Gérard Zinzindohoué and colleagues studied the features, they suspected that the team from the 60s may have provided them with a golden scientific opportunity. Although the feature’s depth ruled out a typical shallow-water coral reef, the researchers note that it could be an entirely different kind of reef structure, known as a mesophotic coral ecosystem, that can inhabit such depths.

“A mesophotic coral ecosystem lives deeper than the usual shallow coral reefs, in zones where light is much more limited,” Zinzindohoué explained. “Unlike typical shallow reefs, it does not always form a single continuous reef structure. Instead, it can appear as patchy or scattered coral communities spread across the seafloor.”

Instead of using mid-twentieth-century technology to settle the debate, the team turned to the National Geographic Exploration Technology Lab, which provided access to its Deep-Sea Camera System.

“We Could Actually See the Sea Floor”

Following the path set out by the 1960s survey, the team used the underwater camera to map the seafloor with sonar. After several passes, the team covered a total of 11.5 kilometers. Zinzindohoué highlighted the difficulty of the effort, noting that it was “not an easy field campaign.”

“It was a mix of long days at sea, technical problems, and a lot of uncertainty,” the researcher explained. “But then we saw structures on the sonar that looked like they could be reef signatures, which gave us hope that we were close.”

The closer the team drove the Deep-Sea Explorer’s cameras, the more the shockingly unexpected scene began to unfold.

“That was a big moment for us, because suddenly we could actually see the seafloor,” Zinzindohoué said.

Instead of the dark, lifeless structure anticipated by the original survey team, the new team found a healthy reef containing eight distinct types of coral. The system was also actively supporting eight fish species, with the camera capturing them feeding and sheltering among the corals. The species identified by the team include golden African snappers, blackbar soldierfish, Guinean angelfish, West African goatfish, the Monrovia doctorfish, three-banded butterflyfish, and two distinct species of damselfish.

“I still remember seeing those first images,” Zinzindohoué recalled of the vibrant ecosystem lying directly in front of the cameras. “It was a mix of excitement and disbelief, because after all this time thinking about this reef, suddenly there was something real in front of us.”

More Research Needed to Determine if the Coral Reef Was Ever Dead

When discussing the discovery’s significance, Zinzindohoué said that to the team’s knowledge, “this is the first confirmed record of a living mesophotic coral ecosystem on the Gulf of Guinea continental shelf.”

Although the cameras captured a complex ecosystem, the researchers said that the reef does not appear to be a continuous barrier. Instead, the deep-sea environment consists of several patches of coral that occupy rocky seabed areas most suitable for their survival. Still, they add that further surveys may identify more reefs in the same area.

“I think what we found is probably not an exception,” Zinzindohoué said. “It is more likely a reflection of how little we still know about coastal regions in West Africa and elsewhere. If we were able to find this reef again after 60 years, how many others are still undocumented or simply forgotten?”

Since the team was unable to sample the corals directly, they were unable to confirm the species identification with genetic analysis. The team was also hesitant to condemn the original 1960s survey, noting that it is impossible to tell, without more data, whether the corals were dead at the time and have since rebounded.

“This is still an initial exploration,” Zinzindohoué said. “The historical reports suggested that this could be a continuous coral reef barrier extending roughly 40 kilometers parallel to the coast. We only surveyed a small section of this area, and we had a limited number of visual transects.”

Although there are no immediate plans for a return expedition, the research leader said the only thing holding them back from learning more about these ecosystems, which are “still poorly known in this part of the world,” is adequate financial support.

“If I had all the grant money in the world, the first thing I would do is return to the site with a proper scientific diving and sampling program,” he said, before adding that “every additional piece of information matters.”

“I do believe there are more coral systems out there that we have not yet documented,” he said. “But we should not assume they are everywhere. Each discovery needs to be confirmed. Without going back into the field, we are really just guessing.”

On a personal note, the team leader said the most exciting part is understanding the reef’s history and the lessons that can be gleaned from this underexplored region.

“It feels like we have only just started to read an archive that has been there for a very long time.”

The study “First evidence of live mesophotic coral reefs on the Benin continental shelf” was published in Frontiers in Marine Science.

Christopher Plain is a Science Fiction and Fantasy novelist and has spent the last six years as Associate News Editor and Head Science Writer at The Debrief. Follow and connect with him on X, learn about his books at plainfiction.com, or email him at christopher@thedebrief.org

The mass extinction event known as the Great Dying, which occurred 252 million years ago, resulted in the loss of 96% of marine species, and for many years, scientists could not fully explain why certain animals disappeared while others survived.

That longstanding mystery may be closer to a resolution, thanks to a recent study in the Proceedings of the National Academy of Sciences, which suggests that differences in physiology, metabolism, and oxygen use helped determine which marine animals survived the catastrophe.

Stanford University researchers found that physiological differences largely determined which marine animals survived the end-Permian mass extinction after warming oceans lost much of their oxygen. Animals whose bodies could not meet rising oxygen demands, including brachiopods and crinoids that had long ruled the seafloor, had a hard time surviving as ocean temperatures rose and oxygen in the water dropped.

By contrast, mollusks and fish possessed body plans better suited to supplying oxygen as temperatures climbed, allowing them to survive in greater numbers.

“With this study, we essentially wanted to solve the mystery of why, when you go to the beach, you collect the shells of clams and snails rather than those of brachiopods,” said lead author Jose Andres Marquez, a former PhD student in the lab of Stanford’s Erik Anders Sperling.

Marquez and his team developed a model based on species’ metabolic oxygen balance and tested it using direct measurements of oxygen use in living relatives of both ancient groups. This included brachiopods collected from the San Juan Islands in Washington. Their results revealed that the risk of extinction closely aligned with how much oxygen a species required and how effectively it could transport oxygen within its body.

A Body Built for Survival

Modern sea animals, such as bivalves, gastropods, and fish, have become more active and muscular over time. Their hunting habits demand more oxygen, even under normal conditions. Although this could seem like a disadvantage during harsh times, it actually worked in their favor. When ocean temperatures rose and oxygen levels dropped during the Permian-Triassic period, these animals already relied on features such as gills, strong blood flow, and larger muscles to get more oxygen when needed.

On the other hand, Paleozoic animals like brachiopods and crinoids were slow-moving filter feeders that thrived in low-oxygen environments when things were stable. However, as temperatures rose, they required more oxygen, and their bodies could not keep up with the demand in the now-oxygen-poor waters.

“Our findings show that, across different organism groups, extinctions happened at much higher rates for those more vulnerable to increases in water temperature and decreases in oxygen availability,” Marquez said.

The findings support decades of evidence from the fossil record. Brachiopods, which once accounted for thousands of species, now number about 400. In contrast, bivalves have diversified and now account for between 10,000 and 15,000 species.

Settling the Debate

Sperling previously co-authored a 2018 study that identified oxygen loss and warming as the main causes of the Great Dying. However, that earlier research used only physiological data from modern species, so the results were influenced by data from commercially important fish and crustaceans rather than from the ancient groups that have largely disappeared. The new study addresses this limitation by directly measuring the physiology of living representatives of ancient animal groups, including brachiopods.

“This study is really the final nail in the coffin for what caused the Permian-Triassic mass extinction,” Sperling said.

A Familiar Climate

The environmental changes that led to the Great Dying began in oceans that were relatively cool and well-oxygenated, similar to present-day conditions. A massive release of volcanic carbon dioxide altered the atmosphere, driving global temperatures up by 8 to 12 degrees Celsius over several thousand years. By comparison, current climate projections estimate a rise of 1.5 to 4 degrees Celsius above preindustrial levels by 2100, but over a much shorter timescale. “The bad news is, we are on track for Permian-Triassic levels of warming in worst-case scenario projections,” Sperling said.

By comparing more groups of marine animals, the researchers hope to determine whether the physiological patterns that shaped Earth’s greatest mass extinction could help predict which species are most vulnerable as today’s oceans continue to warm. “We’re still at the point where we can change things and do something about it,” Sperling emphasized.

Austin Burgess is a writer and researcher with a background in sales, marketing, and data analytics. He holds an MBA, a Bachelor of Science in Business Administration, and a data analytics certification. His work focuses on breaking scientific developments, with an emphasis on emerging biology, cognitive neuroscience, and archaeological discoveries.