A coastwide index of Atlantic sturgeon abundance has been rising steadily since 2013, the Atlantic States Marine Fisheries Commission found in its 2024 stock assessment update, published in August 2024.
The update extends the commission’s 2017 benchmark assessment with data from 2016 to 2022. It combines nine fishery-independent surveys into a single index of relative abundance, which the commission describes as variable from 1990 to 2022.
The composite index had a 100 per cent probability of being above its 1998 value, the year a coastwide moratorium on Atlantic sturgeon fishing took effect, and showed a statistically significant positive trend over the time series. The probability that total mortality exceeded the assessment’s threshold was less than 2 per cent.
Several states had closed their Atlantic sturgeon fisheries in the mid to late 1990s. New York imposed its own statewide moratorium in 1997.
The increase appears as a steady upward trend in the composite index. Most of the nine individual surveys showed either no trend or an increase. The commission still rates Atlantic sturgeon as depleted relative to historic levels, both coastwide and in every regional population it assessed.
That term covers more than the directed fishing that ended in 1998. The commission said the term acknowledges bycatch mortality, ship strikes and reductions in productivity from habitat loss. Bycatch in other fisheries, for which data begin in the 2000s, has generally been decreasing in recent years, the update said, except for estimates from gill nets in the federal observer programme.
Results for individual populations were more mixed. The New York Bight and Carolina indices had average probabilities of 59 per cent and 77 per cent of sitting above their reference year values. The other three populations came in below 50 per cent, with the Chesapeake Bay lowest at 27 per cent. The Gulf of Maine had a 56 per cent probability that total mortality exceeded the threshold.
The Hudson River, part of the New York Bight population, is presumed to be one of the two healthiest Atlantic sturgeon populations in the United States, alongside the Altamaha, according to the New York State Department of Environmental Conservation’s species status assessment for its 2025 State Wildlife Action Plan.
The same document reports that the department has monitored juvenile Atlantic sturgeon in the Hudson since 2004 and built a relative abundance index from fish aged about one to six years. The trends in that survey were initially positive but have declined in recent years, the assessment says.
A New York juvenile survey covering 2004 to 2022 is one of the nine indices in the commission’s coastwide composite. Genetic work on more than 500 juvenile and subadult sturgeon caught at Haverstraw Bay between 2017 and 2022 assigned the majority to the Hudson River population. The commission said this indicates the long-term survey data collected at Haverstraw Bay primarily reflects demographic trends in the Hudson River population.
Earlier estimates cited by the department put the Hudson’s spawning population at about 870 adults a year, against 343 for the Altamaha. A study published in 2020 and cited in the commission’s update used side-scan sonar and acoustic telemetry to estimate the Hudson’s 2014 spawning run at 466 fish, with a 95 per cent confidence interval of 310 to 745.
The commission said that once reported spawning intervals are taken into account, the 2014 estimate appears similar to the earlier total adult population estimate.
Atlantic sturgeon were listed under the Endangered Species Act in February 2012. The New York Bight, Chesapeake Bay, Carolina and South Atlantic populations are designated endangered. The Gulf of Maine population is designated threatened. The species was reported present in 32 US rivers, with spawning in at least 14 of them, according to figures from 1998 cited in the New York assessment.
The Hudson’s Atlantic sturgeon are distinct from the river’s shortnose sturgeon, a separate species. On 27 June 2025 the department announced a study, coauthored by the US Geological Survey, that estimated the Hudson’s shortnose population at nearly 70,000, a figure that does not describe Atlantic sturgeon numbers.
The coastwide moratorium is meant to stay in force until each spawning stock has at least 20 protected year classes, a point the New York assessment says could take 40 years.
This year’s photomicrography contest captured the wonders of the very small, from flying ink droplets to the most adorable jumping spider you've ever seen.
The movie Disclosure Day, directed by Spielberg, investigates a conspiracy about government suppression of alien evidence dating back to Roswell. This review questions current societal beliefs about extraterrestrials and Darwinian evolution. It exposes the deception, ultimately portraying alien visitation as a misunderstood age-old phenomenon rather than a new factual reality.
Where did it start? How did it grow complex? Why did it get big? Three moments in Earth’s early history when evolution suddenly, inexplicably turned up the dial.
Austin, Texas: A meteorite impact buried under the town of Ames, Oklahoma, struck about 370 million years ago, nearly 100 million years later than previously believed, University of Texas at Austin researchers have found.
The study, published in July 2026 in Meteoritics & Planetary Science as an open access paper, dated zircon crystals from granite struck by the impact. Zircon is a mineral that forms small crystals and is used in uranium-lead dating.
The earlier age of 467 million years placed the impact in the Ordovician period. It was grouped with a series of North American impacts centred around 467.5 million years ago, called the Ordovician Meteor Event, according to a University of Texas press release.
The new date puts Ames in the Late Devonian, close to the Frasnian-Famennian mass extinction about 372 million years ago. The release says that event led to the extinction of a huge percentage of marine life on Earth.
Whether the impact and the extinction are connected remains an open question.
“Our results establish a new hypothesis that the Ames impact is linked to the Late Devonian mass extinction, but they do not demonstrate the causal relationship,” Elizabeth Catlos, lead author and associate professor in the Department of Earth and Planetary Sciences at UT’s Jackson School of Geosciences, said in an email.
“Establishing this connection requires additional evidence, such as finding impact-related material in Late Devonian sedimentary rocks, identifying other impact structures of this age and understanding their environmental consequences,” she said.
Catlos said she had “a high degree of confidence in the age”. It came from two independent radiometric dating approaches, laser ablation and ion-beam methods, applied to zircon grains taken directly from the impacted granite, she said.
For an impact structure, the strongest age constraint comes from dating minerals in the impacted material directly and showing that they record the impact, she said. That is what the team did.
“No matter what technique we used, it was coming back to this younger signal,” Catlos said in the university’s press release. The release says the result means Ames could not have been part of the Ordovician Meteor Event.
Doubts over the fossil date
The old date was biochronological, meaning it came from fossils. Researchers had found teeth of conodonts, eel-like creatures that lived during the Ordovician, in rock from the site. The teeth were probably already millions of years old when the asteroid struck and got jumbled in the impact, Catlos said in the release.
Catlos said in an email that she does not question the identification of the Ordovician conodonts. “The issue is whether they remain in their original stratigraphic position and can therefore reliably date the impact itself,” she said.
The conodont evidence came from a conference abstract and a PhD dissertation, Catlos said. Those sources did not go through the same formal peer review as a journal paper, but they gave the historical basis for assigning an Ordovician age to the structure.
To show the zircons recorded the impact, the team worked with NASA to image the crystals using cathodoluminescence and electron backscatter diffraction, two imaging methods. A zircon hit by an impact recrystallises in a specific way that these methods reveal, the release says.
Danny Stockli, dean of the Jackson School and a co-author, said in the release that uranium-lead dating of zircon is the most accurate way to tell when such events occurred. Microstructures in zircon can also record the shock pressures of impacts, he said.
He said he would like to see the same done for more impact sites across the continent to build a more accurate timeline of these events.
Catlos said in the release that a more accurate timeline for mass extinctions and other big moments in Earth’s history is needed to understand how the planet works. The question is whether such extinctions were driven by an extraterrestrial force or an interior one such as a series of massive volcanic eruptions, she said.
In her email, Catlos said the findings allow researchers to investigate a possible connection that had not been considered before.
The work was begun by Andrew Parisi, a Jackson School graduate student who collected the Ames rock core from the Oklahoma Geological Survey, extracted the zircons and helped date them. He graduated in 2018 and has since died, as has co-author Michael Brookfield. Sean Gulick and Mark Cloos of the Jackson School also contributed.
The Ames impact structure is a major oil and gas producer, the release says. The crater is more than eight miles wide and lies about 20 miles southwest of Enid under 9,000 feet of sediment, according to the American Oil & Gas Historical Society.
It went unrecognised until 1991, when Continental Resources found an oilfield there. Many geologists had believed impact craters were unlikely places for petroleum, the society says.
Theropods are a group of dinosaurs. Their name means “beast-footed.” The group includes many extinctspecies, such as Tyrannosaurus rex and Velociraptor. It also includes modern birds.
Theropods first emerged about 230 million years ago. Early theropod species appear to have been mostly carnivorous. Over time, however, the group evolved into a diverse range of creatures. These included herbivores and omnivores. All non-bird theropods died out with the rest of the dinosaurs about 66 million years ago.
Theropods share certain characteristics, such as two legs, three forward-facing toes and hollow bones. Light, hollow bones allowed some members of the group to evolve flight.
Many extinct theropods sported feathers, scales or a mix of both. Yutyrannus huali was a dinosaur whose name means “feathered tyrant.” This species lived about 125 million years ago. It was one of the largest feathered species that ever lived. The oldest fossil of this species is about 10 meters (33 feet) long. These fossils show clear imprints of long feathers, which may have helped keep Y. huali warm.
All modern birds — from hummingbirds to emus to hawks — are theropods. Scientists learned this link between extinct dinos and modern animals thanks to theropod fossils. For instance, Archaeopteryx was a theropod that lived about 150 million years ago. Its hollow bones, clawed toes and feathers helped show how birds inherited features from their dino ancestors.
In a sentence
Famous dinosaurs such as Tyrannosaurus rex and Allosaurus were meat-eating theropods that stood on two legs.
Lead-melting temperatures on the surface of Venus should make life as we know it impossible there. But scientists have detected some curious chemicals in clouds above the planet’s surface. At those heights, temps and pressures would be similar to those on Earth.
These clouds sit 48 to 60 kilometers (30 to 37 miles) above the surface. Potential traces of oxygen, methane and phosphine gas have shown up in them. This has led some scientists to suspect the clouds might host microbes. But those single-celled life forms would have to survive harsh conditions when they occasionally sank into lower, hotter layers of the atmosphere.
In 2021, researchers at the Massachusetts Institute of Technology, in Cambridge, suggested how microbes might survive in clouds high above Venus. They would just need to tolerate briefly drying out whenever they sank into hotter cloud layers. Later, when swept back into cooler, wetter layers, the cells could revive. Noelle Bryan, Sara Seager and their colleagues proposed this idea.
NASA’s first close-up of the swirling clouds that obscure the surface of Venus. It was taken by the Mariner 10 on Feb. 5, 1974. Scientists have recently found that those clouds contain the chemical signatures of gas that might have been made by microbial life. NASA
Bryan had reasons for thinking this might be possible. Years before, she had collected microbes from Earth’s stratosphere. This hostile zone sits dozens of kilometers (miles) above our planet’s surface. The microbes she found seemed to survive extreme drying while up there — much as the Venus microbes would have to survive drying out.
For instance, some bacteria on Earth produce colorful pigments. These molecules can protect the cells from harmful ultraviolet (UV) radiation. Finding them on other worlds might point to life there. Extraterrestrial cells might use similar pigments to protect themselves from UV too.
Future telescopes looking at planets orbiting distant stars might be able to detect the colors of those pigments. This could reveal microbial life living in the clouds of faraway worlds, says Lígia Coelho. An astrobiologist, she works at Cornell University in Ithaca, N.Y.
Coelho recently analyzed pigments in Bryan’s stratospheric bacteria. The pigments absorbed or reflected specific wavelengths of light, she found. She hopes to look for similar light and color patterns in distant planets.
Lindsay Hays, a NASA program scientist, describes what researchers mean when they talk about looking for a “biosignature” of life, especially extraterrestrial life.
Scouting for tiny Martians
The recent discovery of microbes in Earth’s stratosphere is probably most relevant to imagining life on Mars. After all, cells high above Earth endure conditions similar to those on the Red Planet’s surface.
Andrew Schuerger has spent years hunting Earthly microbes that might be able to survive on Mars. He works at the University of Florida in Gainesville. He recently teamed up with Rachel Harris. She’s an astrobiologist at NASA and Harvard University in Cambridge, Mass. Last year, the duo found a microbe that seems to check many of the boxes needed to make it on Mars.
Its name is a mouthful: Methanosarcina barkeri (Meh-THAAN-oh-sar-SEE-nuh BARK-er-eye). It gets its energy by turning carbon dioxide and hydrogen into methane.
M. barkeri normally lives in sewage, landfills, rice paddies and lake bottoms. Those buried habitats would hardly mimic Mars’ thin, dry air. But unlike microbes in Earth’s stratosphere, M. barkeri can live without oxygen, which is absent on Mars. And even at low, Mars-like pressures, M. barkeri can still make methane, Schuerger and Harris have shown.
That’s big news, because Mars orbiters and rovers have detected methane gas seeping into Mars’ atmosphere.
Unfortunately, methane-making critters on Mars would likely be hard to spot. They might need to hide deep underground to survive the planet’s low atmospheric pressure.
But finding that M. barkeri is active at low pressures means life might be able to survive quite close to the Red Planet’s surface, Schuerger says. A rover might only need to drill 20 centimeters (8 inches) down to reach single-celled Martians — if they exist.
NASA rovers are scouting rocks on the Martian surface. They hope to confirm potential signs that this planet once hosted life — even if that life was only one-celled microbes.
Any pockets of microbes near Mars’ surface might be quite small and short-lived, says Lynn Rothschild. She’s an astrobiologist at NASA Ames Research Center. It’s in Mountain View, Calif. She imagines microbes using Mars’ surface the way high-flying species seem to use Earth’s stratosphere. It would be a hostile place they briefly tolerate while moving from one home to another.
If she’s right, then windstorms on Mars might sweep up not only dust, but also Martian life. Microbes could be “floating around, just looking for a place to land [where] they can survive” and grow, she says. If so, then a rover might catch life the way a fence catches blowing leaves.
NASA’s Perseverance rover took a selfie on the surface of Mars. In 2024, it came to this site, nicknamed Cheyava Falls, where it detected signs of past water, organic material and more. Last year, researchers published a study suggesting that this site might once have hosted life.NASA/JPL-Caltech/MSSS
The stratosphere is both beautiful and deadly — a boundary between Earth and space, between life and death.
Hover within it, some 30 kilometers (almost 20 miles) above the ground, and you’d be nearly twice as high as any rain cloud. You would actually see the edges of Earth curve beneath you. And the sky above? It would look black — like outer space.
The air pressure here is just one percent of that at sea level. You’d never survive in such thin air. As you gasped for oxygen, this super-low pressure would cause your blood to boil inside you.
With temps as low as −60° Celsius (−76° Fahrenheit) and intense, DNA-damaging ultraviolet (UV) radiation, the conditions here would kill most life as we know it. Yet some living things persist in the stratosphere. A surprising number of one-celled microbes somehow survive its extremes.
“If you took a microbe from [Earth’s stratosphere] and you put them on the surface of Mars, they wouldn’t even know the difference.”
Brent Christner
“If you took a microbe from those altitudes and you put them on the surface of Mars, they wouldn’t even know the difference,” says Brent Christner. A microbiologist, he works at the University of Florida in Gainesville.
His team began looking for life in the atmosphere back in 2008. They were hunting for the upper limits of Earth’s habitable zone. This, they hoped, might reveal whether life could persist on the cold, near-airless, radiation-pummeled surface of Mars.
Noelle Bryan, Christner’s graduate student at the time, sent sampling balloons as high as 38 kilometers (24 miles) into the air. What she found utterly shocked her: “We did not hit an altitude where we couldn’t find something [alive].”
In 2025, Christner’s team reported something that proved even more surprising. These microbes weren’t ones we usually imagine living in extreme conditions, such as volcanic hot springs. In fact, they were some of the same microbes found living on our crops, in our gardens and even on our skin.
Normally Earth-dwellers, these microbes seem to live a secret double life — sailing around the world at up to two or three times the height of a passenger jet.
For them, Christner says, the atmosphere “is like a highway.” It allows them “to move globally in periods of weeks.” From there, they can cross oceans to find new homes.
These discoveries could reshape what we know about how pathogens spread across our planet. They also could transform where we look for life on other worlds — from Mars to exoplanets light-years away.
Hunting for microbes in the sky
There’s a long history of looking for high-flying life.
This 1935 Explorer II balloon carried two pilots into the stratosphere above South Dakota. It set a world altitude record, reaching just over 22 kilometers (14 miles).Wikimedia Commons
In 1935, the U.S. Army Air Corps launched a helium balloon over the Black Hills in South Dakota. It reached 22 kilometers (14 miles) high, a world record. Two pilots went along in a pressurized gondola. They recorded air temperatures, magnetic fields, radiation levels and more. They also dropped a sterile sampling device designed to collect airborne microbes on its way down. After falling halfway, it closed and parachuted the rest of the way to Earth.
Scientists later grew 10 types of bacteria and fungi from that sample. But this was before scientists discovered DNA. So they never learned much more than the shapes of these mystery cells, the conditions they had survived and what nutrients they needed to grow.
Nearly four decades later, Soviet scientists launched rockets with sticky microbe collectors 48 to 77 kilometers (30 to 48 miles) into the mesosphere. It’s the layer just above the stratosphere. Those collectors parachuted back with a few living cells stuck on them. These, too, grew in the lab.
“But there’s just no way to know what [the Soviets had] sampled,” Christner says. The microbes could have been contamination from the ground. He doesn’t believe that the scientists actually found something alive at that altitude.
More recent U.S. studies started in the early 2000s.
NASA was flying a plane 20 kilometers (12 miles) up to collect cosmic dust. Its goal was to study the history of our solar system. Microbiologist Dale Griffin then worked for the U.S. Geological Survey in St. Petersburg, Fla. He arranged for sticky microbe-catchers to fly on several missions between 2003 and 2008.
NASA uses the ER-2 research aircraft (bottom right) to conduct experiments at altitudes up to 21 kilometers, such as this flight above California (top). Pilots must wear pressure suits (bottom left) because a loss of cabin pressure could cause them to lose consciousness within seconds and quickly die. From top, clockwise: Stu Broce/NASA; Carla Thomas/NASA; NASA
Griffin grew several types of bacteria from those samples. He also performed a simple test on them, called genetic barcoding. It looks at a short part of a single gene. From this, biologists can get a general idea of a life form’s family or genus. And these microbes, he realized, were related to several known from remote islands and volcanic soils.
Perhaps, Griffin thought, eruptions lofted them high into the air.
The Russian and NASA findings were based on what they learned from growing sampled microbes in the lab. Yet scientists can’t grow 99 percent of the microbes that exist most places. They just can’t recreate the environments these cells need to grow.
As such, those early tests couldn’t measure how many living cells were in the stratosphere. They usually couldn’t identify the species. The scientists didn’t even test whether these microbes could survive stratosphere-like temps, dryness or UV radiation.
And they never learned the lifestyles of these microbes on Earth’s surface — whether they lived on plants, slurped raw sewage or grew in the armpits of NFL linebackers.
At last: Tallying living space microbes
Christner was at Louisiana State University in Baton Rouge (LSU) when he and Bryan began their search for life in the stratosphere. They planned to start low and sample higher and higher. They would try to grow the cells they collected, as others had. But they would also do something new: count the total number of living cells at these altitudes.
They expected that at some height, the number of living cells would drop to zero. This would mark the outer limit of life on Earth.
Bryan built her first collectors from Styrofoam and balsa wood, purchased at hobby and hardware stores. She dangled these homemade gizmos from helium balloons launched in Texas and Louisiana. Each collector had a control chamber that didn’t open during the flight. This helped her estimate how much her samples were contaminated with ground-level germs. Eventually, she got that contamination down to almost zero.
Launch and landing
Noelle Bryan (left) preparing to launch one of her early germ catchers on a balloon over Louisiana on October 30, 2011. She built this early device mostly with foam and balsa wood (middle), making it light enough that even small balloons could lift it as high as 24 kilometers (15 miles). The model boat was added for good luck (in case her package landed in a lake, as sometimes happened.) On this day, it landed in a tree (right), with its sample safe inside.
D. Fox
In 2013, Bryan started using a more advanced system. It was developed by LSU engineer T. Gregory Guzik. Its sturdy circuits allowed it to reach even greater heights. (In the mid-stratosphere, electricity can arc from one wire to another, damaging circuits.)
Bryan and Guzik used this system in a key series of balloon launches over Fort Sumner. This little town crouches amid a dry plain of grass and yucca in eastern New Mexico. The 19th-century gunslinger Billy the Kid is buried in a cemetery at one end of town.
The samples that Bryan collected here would be the final ones for her PhD research. They would also reveal some major surprises.
On the morning of August 21, 2013, Bryan, Guzik and several others wore hard hats as they emerged from a hangar at the local airport. They grasped the tether of a round, white helium balloon the size of a small elephant. It bobbed and tugged impatiently as they walked into an open field.
Noelle Bryan and her teammates launched a microbe collector up to 29 kilometers (18 miles) on this balloon (left). A much larger balloon (right) allowed her to sample airborne microbes up to 38 kilometers (24 miles). That larger NASA balloon carried her microbe catcher along with experiments from several other researchers (center).From left: LSU, NASA; N. Bryan; N. Bryan, Arizona State Univ., NASA
Then, they let it go.
A downward-pointing camera captured video as it surged upward.
At one point, a large jet streaked by far below, tiny and silent.
Later, the balloon was tossed by violent winds as it entered the stratosphere. At 18 kilometers (11 miles), an electric motor opened one of two collectors. It exposed a sticky surface to the air.
Catch!
Left: A germ catcher Bryan used in 2013 (captured here by a downward-pointing camera during a flight over Fort Sumner, N.M.). The device has two identical sealed boxes, one on each side. One opens and closes at preset altitudes to collect microbes. The other doesn’t open. That way, scientists could later see if their boxes had any contamination before launch.
N. Bryan/LSU
Right: A view inside one of Bryan’s germ collectors shows two rows of small plastic rods coated in oil. That oil captures airborne cells that bump into it on its way down through the atmosphere.
Minutes later, as the balloon ascended past 23 kilometers (14 miles), the collector closed. An electric heating coil severed the tether. This sent the balloon’s payload parachuting back to Earth. Using a GPS tracker, Bryan drove to where the collector had landed between a yucca and a prickly pear cactus.
In all, the team launched six balloons over three weeks. Some reached as high as 29 kilometers (18 miles). A seventh launch, on a larger NASA balloon, reached 38 kilometers (24 miles).
Microbes in living color
Bryan spent months growing her samples. The one from August 21 spawned a glistening orange colony of bacteria. She named it L6-1.
Samples from other launches grew into yellow, pink and black colonies. The colors likely came from protective pigments that shield the microbes against harmful UV light.
Bryan assumed that these still-unidentified cells would turn out to be tough cookies. For example, some bacteria can form dry spores that survive boiling. But as she isolated and barcoded the cells’ DNA, a very different picture emerged.
These cells “should have been nothing but spore-formers,” Bryan says. They “should have been nothing but extremophiles.” But only one out of a dozen or so bacteria were.
L6-1 and several others belonged to a genus often found on plants: Curtobacterium. Others belonged to groups that live in soil. The fact that these critters came from such everyday places posed a mystery that Bryan desperately wanted to solve.
Stratosphere samples
Petri dishes of bacteria that Bryan initially isolated from altitudes of 18 to 24 kilometers (11 to 15 miles). These colonies are often either brightly colored or dark colored. Their hues reveal pigments that the cells use to avoid harm from intense ultraviolet radiation, which is plentiful in Earth’s stratosphere.
D. FOX
Radiation? No biggie
Bryan spent most of 2014 and 2015 running lab experiments. From these, she estimated that at 24 kilometers (15 miles) up, each cubic meter (m3) of air held about 100,000 living cells. At 36 kilometers (22 miles), the air still held nearly 8,000 cells/m3.
In 2016, Bryan exposed her stratospheric cells to UV-C radiation to see how tough they were. These wavelengths of ultraviolet light kill cells better than the UV-A and UV-B types that cause sunburns. UV-C is absent at Earth’s surface, because the ozone layer blocks it. But this radiation is plentiful in the mid-stratosphere.
In these experiments, Bryan compared her stratospheric germs to a bacterium called Deinococcus radiodurans (Dye-noh-KOK-us Ray-dee-oh-DUR-uns). It is said to be the toughest organism on Earth. It can survive roughly 1,000 times the gamma radiation needed to kill a human. It’s also uniquely resistant to UV-C radiation.
Tough stuff
Some microbes found living in the stratosphere proved about as resistant to ultraviolet radiation as the hardy bacterium Deinococcus radiodurans (left).
Michael Daly/USU/Scientific Reports 2025
None of the germs isolated from Earth’s stratosphere would likely survive on Mars. They need oxygen, which Mars’ atmosphere lacks. But Methanosarcina barkeri (right) might make it on the Red Planet. It thrives without oxygen in sewage and landfills. In the lab, it can tolerate extremely low-pressure and oxygen-free conditions, like those on Mars.
Surprisingly, her L6-1 cells tolerated UV-C just as well as D. radiodurans did. Some of her other plant and soil bacteria from the stratosphere weren’t far behind. Bryan was shocked to see this. “I [fudged] up,” she remembers thinking.
Bryan repeated the experiments over many months, looking for mistakes she might have made. But her results never changed.
As the team realized the results were actually correct, it “all sort of came together,” Christner recalls. These plant-dwelling bacteria had a secret talent: They could survive, at least briefly, on the edge of space.
Were these cells infectious?
Bryan got her PhD in 2017. (She now works at Mass General Brigham in Boston, Mass.) Around that same time, Christner moved to the University of Florida. There, he began looking into a strange question.
Bryan’s DNA barcoding had showed that L6-1 and several of the other stratospheric bacteria were closely related to a germ that sickens crops. It’s called Curtobacteriumflaccumfaciens. From the 1920s to the 1970s, it had browned and wilted Midwestern bean fields. After disappearing for a while, C.flaccumfaciens reemerged around 2003.
Christner and Bryan wondered: Did L6-1 also cause disease?
“Plant pathogens in the stratosphere — that was the furthest thing that we expected to run into.”
Brent Christner
To find out, Christner teamed up with two plant pathologists. Brian Kvitko works at the University of Georgia in Athens. Robert Harveson is at the University of Nebraska in Scottsbluff. Last year, they reported that L6-1 really does cause bean plants to yellow and wilt. So do two other Curtobacterium microbes that Bryan collected from as high as 29 kilometers (18 miles).
Adam Ellington was a graduate student in Christner’s lab in Florida. In 2020, he sequenced the full genome of L6-1. This showed it to be a new species. It also was a genetic match for an unidentified germ that Harveson had isolated from diseased millet years earlier.
Christner’s group described it in Microbiology Spectrum in 2025. They named it C.aetherium.
“Plant pathogens in the stratosphere — that was the furthest thing that we expected to run into,” Christner says.
Harveson, a Curtobacterium expert, had long thought this germ spread through infected seeds. Learning that at least some members of its genus could survive high in the atmosphere stunned him. This discovery, he says, could “change our thought processes about movement of diseases.”
By flying through the atmosphere, a microbe could cross oceans and drop into new ecosystems. A pathogen like C. aetherium could escape regions where plants had become resistant to it and land on new hosts.
Leaf-dwelling bacteria are known to experience frequent drying. This can damage their DNA in a manner similar to radiation. So some of these microbes have evolved ways to repair their DNA fairly well. Such tricks might help them survive other harsh conditions, too.
Leaf bacteria can also enter the air with surprising ease.
Once microbes are aloft, big thunderstorms, dust storms, hurricanes and volcanic eruptions can lift them into the upper atmosphere. Smoke plumes from large wildfires can also ferry billions of live cells into the air.
Ellington’s work suggested that C. aetherium could have started as one of these leaf-squatters. Over time, as it got lofted higher, it could have evolved new traits to survive extreme altitudes.
He learned this by studying a Curtobacterium species that has never been found in the atmosphere. When exposed to UV-C, it quickly adapted. This indicates that some plant-dwelling bacteria already have a flair for evolving strong radiation resistance.
Ellington also found that UV-C radiation turns on several DNA-repair enzymes in C. aetherium. One of them repaired an unusual type of UV damage. This type occurs only when a cell is so dehydrated that its DNA folds into a somewhat different structure. Cells drifting in the stratosphere are very dried out. So their DNA might actually fold this way, Ellington notes. Having this enzyme might allow them to repair a type of DNA damage that often happens up there.
Still, many mysteries remain.
Bryan was able to grow only 12 or so species of bacteria from the stratosphere. For every type that did grow in the lab, 100 to 1,000 others might have also been present and alive. They might not have grown for Bryan simply because she didn’t provide them with the right conditions.
Burak Erkorkmaz wonders about these other microbes.
“The next question would be to understand the whole community” up there, he says. He’s a microbiologist at the University of Gothenburg in Sweden. He’d like to take those thousands of live cells per cubic meter of stratospheric air and sequence all of their genomes. It would provide a fuller picture of the diversity of species there. It also could hint at whether they, too, carry genes for surviving high altitudes.
Erkorkmaz and other scientists have already started doing this with airborne cells caught a few meters above the ground.
Most aerial microbes likely never reach the stratosphere. They probably travel at lower altitudes, where conditions are milder. But finding even a few microbes alive in the stratosphere has huge implications. It might hint at whether microbes can survive in other worlds (see sidebar).
Many years may pass before these lessons from Earth’s stratosphere are applied to the search for extraterrestrial life. But for Bryan, the excitement of it began years ago when she made her first shopping trips to buy materials for her germ catchers.
“It was space exploration,” she says. “It was uncharted territory.”
The iPhone 18 Pro Max has a battery capacity over 20 watt-hours, which means there are additional shipping requirements. If an iPhone 18 Pro Max needs to be shipped somewhere, its maximum battery capacity has to be limited through firmware.
[…]
Customers who need to ship the iPhone 18 Pro Max for repair, trade-in, or other purposes have to use a new Prepare to Ship feature. Prepare to Ship discharges the battery to below 20Wh and sets a charge limit so the iPhone stays below the threshold during the shipping process.
Laptops, of course, have larger batteries, but they aren’t affected because each cell is below the limit.
When a new disease emerges, things can get a little weird. We start to clean groceries with antibacterial wipes, the sound of a sneeze can trigger our fight-or-flight response, and we generally become more cautious. Humans may not be the only primate species that change their behavior in the face of disease.
According to a study published today in the journal Royal Society Open Science, Japanese macaques (Macaca fuscata) that lived through a deadly outbreak in 2020 became noticeably more cautious about food that appeared contaminated, even though this disease was not spread by food or feces. This indicates that purposefully shifting behavior to avoid a pathogen can be shaped by our appearance and that disgust may have deep evolutionary roots. It also sheds light on the behavioral immune system—a collection of behaviors that help animals avoid an infection before the biological immune systems respond.
“We can show now, in non-human primates, that this is the same for them,” Federico Rossano, a study co-author and cognitive psychologist at the University of California San Diego, said in a statement. “Even with no knowledge of how disease is transmitted, being exposed to others getting sick and dying changes the likelihood of engaging in behaviors that potentially could lead to some form of sickness.”
2020 was a big year for outbreaks
In 2020, the staff at a primate sanctuary in southern Texas confirmed the presence of simian retrovirus Type II. This disease can cause AIDS-like immunodeficiency and is primarily transmitted through bites and scratches. It caused severe illness and death in some of the monkeys. The sanctuary staff separated the groups and implemented testing and quarantine measures in response to the outbreak. Since the groups live in separate enclosures, scientists then had the chance to compare animals with similar backgrounds that had experienced very different social and disease environments.
In total, three groups of monkeys experienced the outbreak while one had not. The team tested
55 macaques to see how they responded to a choice between food that was put on a clean wooden surface and food placed on a surface covered with real macaque feces. The food with the feces was sealed under a layer of clear epoxy, so that the monkeys could see the food and poop without risking infection.
In the group that had been exposed to the outbreak, some of the individuals had been infected while others had lived alongside sick monkeys without getting sick. This allowed the researchers to question if experiencing an outbreak without getting infected could change the macaque’s behavior. To test that further, the clean surface was replaced with a brightly colored kitchen sponge in some of the scenarios to see if the animals were just avoiding unfamiliar objects.
Previous studies found that macaques aren’t necessarily deterred by contamination—as long as the payoff is tempting. When presented with a favorite treat (such as a peanut) wild Japanese macaques would still eat food from a surface covered in feces, but will avoid it for food like grains of wheat.
Continued caution
The team found that macaques from groups that went through the outbreak were far less likely to eat the food from the contaminated surface. They ate from the fake contaminated surface in only 47 percent of trials. The monkeys that did not experience the outbreak ate from the potentially contaminated surface in 79 percent of trials.
The monkeys from outbreak-exposed groups also behaved similarly whether or not they themselves had been infected. According to the team, this suggests the behavioral change was associated with their experiencing living through the outbreak, instead of actually getting sick
“Groups have histories, and those histories show up in behavior,” added study co-author and UC San Diego cognitive psychologist Stephan Kaufhold. “Living through the disease outbreak appears to have made those monkey groups more cautious around food that looks contaminated.”
The virus was spread through blood or saliva from bites and scratches, and not through contaminated food. Interestingly, the macaques who saw their fellow primates get sick, were more reluctant to eat food placed on a surface that visually suggested contamination in some of the tests.
Disgust’s evolution
In addition to shedding light on how illness affects primate behavior, it also offers insight into the evolution of disgust. The team did not measure disgust directly, but found that monkey’s avoidance of potential sources of infection can change with their experience, similar to what humans do.
Human disgust is believed to play an important role in protecting us from pathogens. We recoil from the smell and sight of poop, spoiled food, and other potential sources of infection. Our sensitivity to those cues can also change depending on context.
Since primates are capable of social learning, the team believes that heightened pathogen avoidance could be learned from other members in the group and persist over time. Future studies could see if newly introduced animals adopt the behavior of a group that has already experienced an outbreak.
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