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#technology #engineering #freshwater #density

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Researchers from MIT and China have developed a solar desalination device that could provide a family of four with all the drinking water it needs - and it can be made from just $4 worth of materials.

Solar desalination: Water covers more than two-thirds of Earth's surface, but 97% of it is saltwater. The salt concentration in that water is far too high for our bodies to process - if you drank too much of it, you'd actually become dehydrated and die.

What we need is freshwater, meaning a salt concentration of less than 1%, and since this water isn't as abundant, humans have come up with lots of ways to remove enough salt from saltwater to make it drinkable.

"I think a real opportunity is the developing world."
Evelyn Wang

One of those is solar desalination.

While the specifics vary, the basic idea is that the sun's heat is applied to saltwater. The water evaporates, leaving behind the salt, and the water vapor is then collected and condensed, leaving you with liquid freshwater.

Getting salty: Engineers have created countless solar desalination devices, but for the devices to make a difference in the places that need them the most, they need to be not only cheap and efficient, but also durable and long-lasting.

"We see these very attractive performance numbers, but they're often limited because of longevity."
Evelyn Wang

The problem is that salt tends to build up in these devices, particularly on the wick used to pull water through the device. Those wicks are difficult to clean, and over time, the salt accumulation means they have to be replaced.

"The challenge has been the salt fouling issue, that people haven't really addressed," researcher Evelyn Wang told MIT News. "So, we see these very attractive performance numbers, but they're often limited because of longevity. Over time, things will foul."

The idea: Researchers from MIT and China's Shanghai Jiao Tong University have now created a wick-free solar desalination device that uses gravity-driven convection to move the water.

Natural convection is a type of movement that occurs when a liquid isn't one uniform density. In that situation, the less dense liquid will rise, while the denser liquid falls. (The same is true of gasses - because hot air is less dense than cold air, it rises while cold air falls.)

How it works: The new solar desalination device consists of several layers. Salt water is added to the top layer. Black paint draws the sun's heat to that layer, causing the desired creation of water vapor for collection.

Any water left behind in that layer is then extra salty and, therefore, extra dense.

The very bottom layer of the device contains more saltwater. The layers between it and the top are designed to keep heat in the top layer, while allowing the super-dense saltwater to move downward to mix with the normal density saltwater under the power of natural convection.

Looking ahead: The device worked for a week straight with no signs of salt accumulation, but we still don't know exactly how long it could operate.

But the best news is that it would cost just $4 to build a solar desalination device large enough to meet the drinking water needs of a family of four, according to the MIT team. If it does prove durable, it could be a relatively cheap way to get freshwater to people in need of it.

"I think a real opportunity is the developing world," Wang said. "I think that is where there's [the] most probable impact near-term, because of the simplicity of the design."
We'd love to hear from you! If you have a comment about this article or if you have a tip for a future Freethink story, please email us at .

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MIT's $4 desalination device creates enough drinking water for an entire family

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Researchers from MIT and China have developed a solar desalination device that could provide a family of four with all the drinking water it needs - and it can be made from just $4 worth of materials. Solar desalination : Water covers more than two-thirds of Earth's surface, but 97% of it is saltwater.

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#energy #waves #renewable #technology #earthscience #physics

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‘Wave Energy:’ This Floating Spine-Like Device Generates Sea Waves Into Electricity!

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This sea wave energy generator can produce up to 100 MW of electricity and compete with fossil fuels due to its cheap production costs.

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#extinction #conservation #diversity #biology #humanimpacts #ecology

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The dugong, a gentle marine mammal that has frequented China's southern waters for hundreds of years, has become functionally extinct in the country, a new study said on Wednesday.

Research by the Zoological Society of London (ZSL) and the Chinese Academy of Sciences said fishing, ship strikes and human-caused habitat loss have seen the number of dugongs in Chinese waters decrease rapidly from the 1970s onwards.

With no evidence of their presence in China since 2008, the research shows that "this is the first functional extinction of a large mammal in China's coastal waters," the report said.

The dugong, whose diet is highly dependent on seagrass, has been classified as a Grade 1 National Key Protected Animal since 1988 by China's State Council.

Their marine habitats have been rapidly degraded by humans and although restoration and recovery efforts are a key priority in China, "restoration takes time that dugongs may no longer have," the report said.

Found in coastal waters from East Africa to Vanuatu, and as far north as Japan, they are listed as vulnerable by the International Union for Conservation of Nature.

Some believe the dugong is the inspiration for ancient seafaring tales of mermaids and sirens.

This may be because from a distance, female dugongs sometimes look like they are nursing their young in a similar way to a woman breastfeeding her baby, leaving their heads and chests exposed out of the water, according to the South China Sea Institute of Oceanology.

Professor Samuel Turvey of ZSL's Institute of Zoology, a co-author of the study, said the likely disappearance of dugongs in China was a devastating loss.

"Their absence will not only have a knock-on effect on ecosystem function, but also serves as a wake-up call - a sobering reminder that extinctions can occur before effective conservation actions are developed."

The study was done by a team of international scientists who conducted interviews in 66 fishing communities across four Chinese provinces along the coastal region of the South China Sea.

The authors said they would welcome any evidence that dugongs might still exist in China. They recommended that the species regional status be reassessed as Critically Endangered (Possibly Extinct).

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Sea creature that inspired mermaid tales declared extinct in China

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The dugong, a gentle marine mammal that has frequented China's southern waters for hundreds of years, has become functionally extinct in the country, a new study said on Wednesday. Research by the Zoological Society of London (ZSL) and the Chinese Academy of Sciences said fishing, ship strikes and human-caused habitat loss have seen the number of dugongs in Chinese waters decrease rapidly from the 1970s onwards.

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#blackholes #gravitationalwaves #LIGO #astrophysics #cosmology

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Two black holes merged despite being born far apart in space

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A closer look at gravitational wave data reveals 10 overlooked mergers, including one between black holes that probably found each other late in life.

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#iguanas #reptiles #extinction #galapagos #conservation #environment #ecology #earthscience #biology

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subscribe to Short Wave podcast

A species of iguana that went extinct nearly 200 years ago on one of the Galápagos Islands appears to be making a comeback, with some help from a team of conservationists.

The last person to spot a Galápagos land iguana on Santiago Island in Ecuador was Charles Darwin in 1835. When an expedition team from California arrived in 1906, the iguanas were nowhere to be found.

And though this kind of iguana can still be found on the other Galápagos Islands, it's believed to have been extinct on Santiago for the past 187 years - until now.

A team of scientists and park rangers discovered new lizards of various ages while walking the island in late July, which suggests the species has been successfully reintroduced. And according to Jorge Carrión, director of conservation of the Galápagos Conservancy, the ecosystem is thriving as a result.

The evidence is in the details, he explained. Seeing lizards of different ages and coming across unmarked specimens means the iguanas are breeding in their natural environment.

Before joining the Galápagos Conservancy, Carrión worked for the Galápagos National Park Directorate, the caretakers of the islands' ecosystems and resources. The GNPD is also the authority spearheading the iguana reintroduction project, with funding and assistance coming from the Conservancy.

He said the collaborative has released more than 3,000 land iguanas on the island since January 2019.

Conservationists decided to reintroduce the land iguana after carefully considering how a return ofthe species would affect the ecosystem. These lizards are what's known as an engineering species, like the Galápagos giant tortoise, in that they play a critical role in maintaining a healthy balance in an ecosystem.

As the primary herbivores on the Galápagos Islands, the land iguanas and tortoises spread seeds across the landscape and help model the plant communities, Carrión explained. Their movement patterns also create open spaces used by other animals.

"This kind of species are critical for ecosystem in general," Carrión said. "In this case it was the justification for the reintroduction of land iguanas, to [return] the natural dynamic to Santiago Island. When engineer species are not present, many imbalances occur in the ecosystem."

What caused the iguanas' extinction?

It's believed that the Galápagos land iguanas were wiped out by invasive species, including feral pigs, cats, goats and donkeys. These unwelcomed animals were introduced to some of the islands, including Santiago, by whalers and other mariners. They wreaked havoc on the ecosystem, devouring plants other species relied on, and some even ate the iguanas.

Thatis why scientists had to rid the island of non-native animals before the iguanas could be reintroduced. This was accomplished over a nine-year period through the Galápagos Conservancy's Project Isabela, which was completed in 2006.

Carrión said he and his colleagues believe they have learned an important lesson through the reintroduction of the land iguanas: if you remove the source of the ecological disturbance (the invasive species in this case), the ecosystem can recover and return to its natural dynamic.

The Galápagos Conservancy and the National Park Directorate are also working together to reintroduce the giant tortoise on another island. The native tortoise has been extinct on Floreana Island since the 1800s, according to the Galápagos Conservancy, and reintroduction and breeding efforts began in 2017.

The ecosystems found on the Galápagos Islands are home to some of the most fascinating plants and animals in the world. The islands were made famous largely due to Darwin and his 1835 expedition, according to the Conservancy, which led to his theory of evolutionby natural selection.

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An island in the Galápagos reintroduced iguanas after nearly 200 years of extinction

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subscribe to Short Wave podcast A species of iguana that went extinct nearly 200 years ago on one of the Galápagos Islands appears to be making a comeback, with some help from a team of conservationists. The last person to spot a Galápagos land iguana on Santiago Island in Ecuador was Charles Darwin in 1835.

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#darkmatter #universe #cosmology #astrophysics #bigbang #light #cosmicbackgroundradiation

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Scientists mapped dark matter around galaxies in the early universe

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A technique used to reveal dark matter could also shed light on a disagreement about the clumpiness of matter in the cosmos.

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#beavers #dams #climatechange #ecology #watertable #earthscience #biology

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In the upper reaches of the Skykomish River in Washington state, a pioneering team of civil engineers is keeping things cool. Relocated beavers boosted water storage and lowered stream temperatures, indicating such schemes could be an effective tool to mitigate some of the effects of climate change.

In just one year after their arrival, the new recruits brought average water temperatures down by about 2 degrees Celsius and raised water tables as much as about 30 centimeters, researchers report in the July Ecosphere. While researchers have discussed beaver dams as a means to restore streams and bulk up groundwater, the effects following a large, targeted relocation had been relatively unknown ( SN: 3/26/21).

"That water storage is so critical during the drier periods, because that's what can keep the ecosystem resilient to droughts and fires," says Emily Fairfax, an ecohydrologist at California State University Channel Islands in Camarillo who was not involved with the study.

The Skykomish River flows down the west side of Washington's Cascade Mountains. Climate change is already transforming the region's hydrology: The snowpack is shrinking, and snowfall is turning to rain, which drains quickly. Waters are also warming, which is bad news for salmon populations that struggle to survive in hot water.

Beavers are known to tinker with hydrology too ( SN: 7/27/18). They build dams, ponds and wetlands, deepening streams for their burrows and lodges (complete with underwater entrances). The dams slow the water, storing it upstream for longer, and cool it as it flows through the ground underneath.

From 2014 to 2016, aquatic ecologist Benjamin Dittbrenner and colleagues relocated 69 beavers ( Castor canadensis) from lowland areas of the state to 13 upstream sites in the Skykomish River basin, some with relic beaver ponds and others untouched. As beavers are family-oriented, the team moved whole clans to increase the chances that they would stay put.

The researchers also matched singletons up with potential mates, which seemed to work well: "They were not picky at all," says Dittbrenner, of Northeastern University in Boston. Fresh logs and wood cuttings got the beavers started in their new neighborhoods.

At the five sites that saw long-term construction, beavers built 14 dams. Thanks to those dams, the volume of surface water - streams, ponds, wetlands - increased to about 20 times that of streams with no new beaver activity. Meanwhile below ground, wells at three sites showed that after dam construction the amount of groundwater grew to more than twice that was stored on the surface in ponds. Stream temperatures downstream of the dams fell by 2.3 degrees C on average, while streams not subject to the beavers' tinkering warmed by 0.8 degrees C. These changes all came within the first year after relocation.

"We're achieving restoration objectives almost instantly, which is really cool," Dittbrenner says.

Crucially, the dams lowered temperatures enough to almost completely take the streams out of the harmful range for salmon during a particularly hot summer. "These fish are also experiencing heat waves within the water system, and the beavers are protecting them from it," Fairfax says. "That to me was huge."

The study also found that small, shallow abandoned beaver ponds were actually warming streams, perhaps because the cooling system had broken down over time. Targeting these ponds as potential relocation sites could be the most effective way to bring temperatures down, the researchers say. When relocated populations establish and breed, young beavers leaving their homes could seek those abandoned spots out first, Dittbrenner says, as it uses less energy than starting from scratch. "If they find a relic pond, it's game on."

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Relocated beavers helped mitigate some effects of climate change

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In the upper reaches of the Skykomish River in Washington state, a pioneering team of civil engineers is keeping things cool. Relocated beavers boosted water storage and lowered stream temperatures, indicating such schemes could be an effective tool to mitigate some of the effects of climate change.

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#climatechange #arctic #warming #meltingglaciers #heat #earthscience

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The Arctic is warming even faster than scientists realized

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The Arctic isn’t just heating up two to three times as quickly as the rest of the planet. New analyses show that warming is almost four times as fast.

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#stars #astronomy #stellarevolution #earthscience #astrophysics

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The star Betelgeuse has always been a diva.

Astronomers from antiquity through the present day have watched the red supergiant pulsing at the shoulder of the constellation Orion, and the star has continually put on a show, two new studies suggest. Betelgeuse may still be recovering from a deep dimming episode a few years ago, one team reports. And the star appears to have put on its reddish stage makeup just 2,000 years ago, before which it wore yellow, another team says.

Together, these studies could tell researchers about how stars spew their guts into space and hint at how long it will be before Betelgeuse explodes in a supernova.

"This star always fools you," says astronomer Edward Guinan of Villanova University in Pennsylvania, who has studied Betelgeuse for decades and was not involved in the new works. "You think you have it, and all of a sudden, it changes."

The "Great Dimming"

In late 2019, Betelgeuse captured astronomers' attention when it suddenly grew dark for several months - an event astronomers now call the Great Dimming. Months of subsequent observations led researchers to an explanation: The star had coughed out a big bubble of plasma. That material cooled, condensed into dust and blocked the star's face from the perspective of Earth months later ( SN: 11/29/20). The surface of the star also cooled down, contributing to the dimming ( SN: 6/16/21).

But what happened next was equally surprising, astrophysicist Andrea Dupree and colleagues report in a paper submitted August 2 to arXiv.org. The star's regular pulsating brightness, it seems, went completely out of whack.

In its non-Great Dimming life, Betelgeuse's brightness was on a quasi-periodic dimmer switch. As the star breathed in and out - ballooning out before shrinking back down - its brightness went up and down. "For 200 years, it had a nice, 400-day oscillation in brightness," says Dupree, of the Harvard & Smithsonian Center for Astrophysics in Cambridge, Mass. "But that's gone now."

That regular drumbeat has since grown erratic. Instead of a regular thrum, the oscillations are "like an unbalanced washing machine, going 'wonka wonka wonka,'" Dupree says.

The wonkiness is a sign of the star struggling to recover from the loss of material in 2019, Dupree says. She calculates that Betelgeuse ejected several times the mass of the moon from its surface, leaving a large cool spot behind. The star's surface plasma is sloshing around as it returns to equilibrium.

Lost rhythm

Betelgeuse's brightness, or stellar magnitude, used to change with a steady, 400-day rhythm (dashed line). But shortly after the Great Dimming in early 2019, the brightness changes became erratic. The different plot symbols and colors denote stellar magnitude measurements from different observatories.

Betelgeuse's brightness over time, 2019-2022

Source: A.K. Dupree et al/arXiv.org 2022

If this picture is correct, it means red supergiants like Betelgeuse can spray material into interstellar space in discrete bursts, rather than a continuous stream. That's important to know because many of the elements that make up planets and people were formed in stars undergoing what Betelgeuse is going through right now. Studying Betelgeuse's growing pains and death throes can tell us about our own origins.

But while this picture of Betelgeuse holds together, it is still speculative, Guinan cautions.

One confounding factor is a new set of observations of Betelgeuse during the four-month period when it's usually out of view. From May through August every year, Betelgeuse is too close to the sun from Earth's perspective to be seen at night. Usually that leaves a hole in the datasets of astronomers who track its periodic behavior.

But amateur observer Otmar Nickel of Mainz, Germany, developed a technique to measure Betelgeuse's brightness using multiple images taken during the day. Dupree's paper is the first to include those daytime data.

"That's cool," Guinan says. "You can follow the star all year round."

Those extra observations might reveal recurring changes that have always been there, rather than picking up on something truly new. "Those little variations you're seeing...could easily be present right before the Great Dimming," Guinan says.

Dupree's team predicts that the dust Betelgeuse lost could become visible to some telescopes on Earth in 2023. "That would be proof" that the brightness changes were due to a single outburst, Guinan says.

Seeing yellow

The Great Dimming isn't the first time humans have recorded a major change in Betelgeuse's personality. Two millennia ago, the star was a completely different color, astrophysicist Ralph Neuhäuser and colleagues report in a paper in press in Monthly Notices of the Royal Astronomical Society.

The team analyzed ancient descriptions of more than 200 stars whose colors should have been visible to the naked eye in the past few thousand years. Most stars observed over human history had the same color recorded in the past as they display today, the team found. But not Betelgeuse.

The ancient Roman astronomer Gaius Julius Hyginus, who lived from about 64 B.C. to A.D. 17, and is thought to have written the Latin work De Astronomia, described the star in the right shoulder of Orion has having a similar color to Saturn - which is yellow. Astrologer and archivist Sima Qian, working during the Chinese Han dynasty around 100 B.C., independently described the star as yellow. Observers from other ancient cultures conspicuously left Betelgeuse out of their lists of red stars.

"I thought, 'Oh, how can this be?'" says Neuhäuser, of AIU Jena in Germany. "I was not expecting such a result ... to find a star to change color in historical time."

A star's color is a sign of its evolutionary stage ( SN: 7/23/21). When stars burn through the hydrogen fuel in their cores, they puff up and expel gases into space. That expansion makes their surface temperatures drop, and they change color from blue to red in fairly short order - about 10,000 years for a giant star like Betelgeuse, which is around 14 times as massive as the sun.

Measuring a star's age isn't as easy as you'd think. Here's how scientists get their ballpark estimates.

That relatively recent color change suggests Betelgeuse has just reached the end of its hydrogen-burning life and became the red supergiant we know it as today while human observers were watching.

"It's fully consistent with astrophysical knowledge," Neuhäuser says. "It could have been expected, but no one really checked."

That result means anyone waiting for Betelgeuse to go supernova will have a very long wait. If the star just became a supergiant in the last few millennia, it has more than 1 million years to go before the boom.

Questions or comments on this article? E-mail us at feedback@sciencenews.org

Lisa Grossman is the astronomy writer. She has a degree in astronomy from Cornell University and a graduate certificate in science writing from University of California, Santa Cruz. She lives near Boston.

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Over time, Betelgeuse changed color. Now it's also lost its rhythm

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The star Betelgeuse has always been a diva. Astronomers from antiquity through the present day have watched the red supergiant pulsing at the shoulder of the constellation Orion, and the star has continually put on a show, two new studies suggest. Betelgeuse may still be recovering from a deep dimming episode a few years ago, one team reports.

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#mosquitoes #senses #scents #nervecells #biology

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Some mosquitoes have a near-foolproof thirst for human blood. Previous attempts to prevent the insects from tracking people down by blocking part of mosquitoes' ability to smell have failed. A new study hints it's because the bloodsuckers have built-in workarounds to ensure they can always smell us.

For most animals, individual nerve cells in the olfactory system can detect just one type of odor. But Aedes aegypti mosquitoes' nerve cells can each detect many smells, researchers report August 18 in Cell. That means if a cell were to lose the ability to detect one human odor, it still can pick up on other scents.

The study provides the most detailed map yet of a mosquito's sense of smell and suggests that concealing human aromas from the insects could be more complicated than researchers thought.

Repellents that block mosquitoes from detecting human-associated scents could be especially tricky to make. "Maybe instead of trying to mask them from finding us, it would be better to find odorants that mosquitoes don't like to smell," says Anandasankar Ray, a neuroscientist at the University of California, Riverside who was not involved in the work. Such repellents may confuse or irritate the bloodsuckers and send them flying away ( SN: 9/21/11; SN: 3/4/21).

Effective repellents are a key tool to prevent mosquitoes from transmitting disease-causing viruses such as dengue and Zika ( SN: 7/11/22). "Mosquitoes are responsible for more human deaths than any other creature," says Olivia Goldman, a neurobiologist at Rockefeller University in New York City. "The better we understand them, the better that we can have these interventions."

Mosquitoes that feed on people home in on a variety of cues when hunting, including body heat and body odor. The insects smell using their antennae and small appendages close to the mouth. Using three types of sensors in olfactory nerve cells, they can detect chemicals such as carbon dioxide from exhaled breath or components of body odor ( SN: 7/16/15).

In previous work, researchers thought that blocking some sensors might hide human scents from mosquitoes by disrupting the smell messages sent to the brain ( SN: 12/5/13). But even those sensor-deprived mosquitoes can still smell and bite people, says neurobiologist Margo Herre also of Rockefeller University.

So Goldman, Herre and colleagues added fluorescent labels to A. aegypti nerve cells, or neurons, to learn new details about how the mosquito brain deciphers human odors. Surprisingly, rather than finding the typical single type of sensor per nerve cell, the team found that individual mosquito neurons appear more like sensory hubs.

Genetic analyses confirmed that some of the olfactory nerve cells had more than one type of sensor. Some cells produced electrical signals in response to several mosquito-attracting chemicals found in humans such as octenol and triethyl amine - a sign the neurons could detect more than one type of odor molecule. A separate study published in April in eLife found similar results in fruit flies, which suggests such a system may be common among insects.

It's unclear why having redundant ways of detecting people's odors might be useful to mosquitoes. "Different people can smell very different from one another," says study coauthor Meg Younger, a neurobiologist at Boston University. "Maybe this is a setup to find a human regardless of what variety of human body odor that human is emitting."

Questions or comments on this article? E-mail us at feedback@sciencenews.org

Erin I. Garcia de Jesus is a staff writer at Science News. She holds a Ph.D. in microbiology from the University of Washington and a master's in science communication from the University of California, Santa Cruz.

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Why mosquitoes are especially good at smelling you

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Some mosquitoes have a near-foolproof thirst for human blood. Previous attempts to prevent the insects from tracking people down by blocking part of mosquitoes' ability to smell have failed. A new study hints it's because the bloodsuckers have built-in workarounds to ensure they can always smell us.

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#spiders #technology #bioengineering #biology #ethicsinscience

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Scientists have literally reanimated dead spiders to do their bidding.

In a new field dubbed "necrobotics," researchers converted the corpses of wolf spiders into grippers that can manipulate objects. All the team had to do was stab a syringe into a dead spider's back and superglue it in place. Pushing fluid in and out of the cadaver made its legs clench open and shut, the researchers report July 25 in Advanced Science.

The idea was born from a simple question, explains Faye Yap, a mechanical engineer at Rice University in Houston. Why do spiders curl up when they die?

The answer: Spiders are hydraulic machines ( SN: 4/25/22). They control how much their legs extend by forcing blood into them. A dead spider no longer has that blood pressure, so its legs curl up.

"We were just thinking that was so cool," Yap says. "We wanted to leverage it."

Her team first tried putting dead wolf spiders in a double boiler, hoping that the wet heat would make the spiders expand and push their legs outward. That didn't work. But when the researchers injected fluid straight into a spider corpse, they found that they could control its grip well enough to pull wires from a circuit board and pick up other dead spiders. Only after hundreds of uses did the necrobots start to become dehydrated and show signs of wear.

T.F. Yap and coauthors

In the future, the researchers will coat spiders with a sealant to hold off that decline. But the next big step is to control the spiders' legs individually, Yap says, and in the process, figure out more about how spiders work. Then her team could translate their understanding into better designs for other robots.

"That would be very, very interesting," says Rashid Bashir, a bioengineer at the University of Illinois Urbana-Champaign who wasn't involved in the new study. A spider corpse itself would probably have problems as a robot, he says, because it won't perform consistently like "hard robots" and its body will break down over time. But spiders can definitely offer lessons to engineers ( SN: 4/2/19). "There's a lot to be learned from biology and nature," Bashir says.

Despite the whole reanimating dead spiders thing, Yap is no mad scientist. She wonders whether it's okay to play Frankenstein, even with spiders. "No one really talks about the ethics" when it comes to this sort of research, she says.

Scientists need to figure out the morality of this sort of bioengineering before they get too good at it, Bashir agrees. The question is, he says, "how far do you go?"

Questions or comments on this article? E-mail us at feedback@sciencenews.org

Asa Stahl is the 2022 AAAS Mass Media fellow with Science News. He is a 5th year Astrophysics Ph.D. student at Rice University, where his research focuses on detecting and characterizing young stars and planets.

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Scientists turned dead spiders into robots

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In a new field dubbed “necrobotics,” researchers used a syringe and some superglue to control the dead bodies of wolf spiders.

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#batteries #mining #naturalresources #energy #earthscience #physics

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Lithium is an essential component of most rechargeable batteries, powering everything from iPhones to Teslas. However, increased lithium mining due to rising demand will deplete known land-based supplies by 2080.

A team of scientists at King Abdullah University of Science and Technology, in Saudi Arabia, says they already have a solution in the works: before land-based lithium runs out, shift lithium mining to the ocean. The team claims they've created an affordable method for extracting lithium from the seawater, potentially unlocking a practically infinite supply of lithium.

The challenge: Land-based lithium mining is incredibly damaging to the environment, and it wastes huge amounts of water - up to 500,000 gallons of water per ton of lithium extracted.

Seawater contains 5,000 times the amount of lithium found on land, but only in very low concentrations, which has made previous attempts to extract lithium from the ocean ineffective.

What they did: The team, led by Zhiping Lai, took a unique approach to lithium mining, explained in a paper in the journal Energy & Environmental Science. They created an electrochemical cell, containing a ceramic membrane made from lithium lanthanum titanium oxide (LLTO). It sounds like a mouthful, but you can think of it as a simple mesh that filters out lithium.

The cell's crystal structure has tiny pores. As a result, lithium ions can travel through gaps in the membrane, while bigger metal ions are blocked.

Inside the cell are three chambers. First, the seawater flows into a central feed chamber, where the positive and negative ions are separated. Then, positive ions move through the LLTO membrane into a side chamber, while negative ions exit into a separate third chamberThen, the lithium-concentrated water is fed through the system again.

With each processing cycle, the lithium concentration gets higher and higher, the team explained in a statement.

The final touch was a slight adjustment to the solutions' pH, ensuring the final lithium solution barely had any traces of other metals. This made sure the final product was pure enough to fulfill the specifications of battery makers, reports Mining Dot Com.

Is it economical? The system can't replace lithium mining yet. The process has only seen early tests and has to prove it can scale, but the team says it could eventually become cost-effective.

They conducted an economic study and concluded that if power costs $65 per MWh (close to the average for businesses in Saudi Arabia), the process would only require $5 of electricity to extract 1 kilogram of lithium from saltwater.

The process may not be ready for prime time yet, but if the price of lithium spikes, expect battery makers to look to the sea.
We'd love to hear from you! If you have a comment about this article or if you have a tip for a future Freethink story, please email us at [email protected] .

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Lithium mining just became a water sport

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Lithium is an essential component of most rechargeable batteries, powering everything from iPhones to Teslas. However, increased lithium mining due to rising demand will deplete known land-based supplies by 2080. A team of scientists at King Abdullah University of Science and Technology, in Saudi Arabia, says they already have a solution in the works: before land-based lithium runs out, shift lithium mining to the ocean.

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#multiplesclerosis #medicine #biology #immunesystem #immunedisorder

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As Tanina Agosto went through her normal morning routine in July 2007, she realized something was wrong. The 29-year-old couldn't control her left side, even her face. "Literally the top of my head to the bottom of my foot on the left side of my body could not feel anything."

The next day, Agosto spoke with a doctor at the New York City hospital where she works as a medical secretary. He told her that she probably had a pinched nerve and to see a chiropractor.

But chiropractic care didn't help. Months later, Agosto needed a cane to get around, and moving her left leg and arm required lots of concentration. She couldn't work. Numbness and tingling made cooking and cleaning difficult. It felt a bit like looping a rubber band tightly around a finger until it loses sensation, Agosto says. Once the rubber band comes off, the finger tingles for a bit. But for her, the tingling wouldn't stop.

Finally, she recalls, one chiropractor told her, "I'm not too big of a person to say there's something very wrong with you, and I don't know what it is. You need to see a neurologist." In November 2008, tests confirmed that Agosto had multiple sclerosis. Her immune system was attacking her brain and spinal cord.

Agosto knew nothing about MS except that a friend of her mother's had it. "At the time, I was like, there's no way I've got this old lady's condition," she says. "To be hit with that and know that there's no cure - that was just devastating."

Why people develop the autoimmune disorder has been a long-standing question. Studies have pointed to certain gene variations and environmental factors. For decades, a common virus called Epstein-Barr virus has also been high on the list of culprits.

Now recent studies paint a clearer picture that Epstein-Barr virus instigates MS when the central nervous system gets caught in the cross hairs of an immune response to the virus's attack. This recognition opens new options for treatment, or even vaccines. Perhaps therapies that target Epstein-Barr itself - or remove the cells in the body where the virus camps out - could jettison the virus before damage is done.

ADRIAN AGOSTO

Vaccines might one day "make multiple sclerosis become a historical disease like polio," says Lawrence Steinman, a neurologist at Stanford University. "The trials will be arduous," Steinman says. Still, "I think we might be able to put MS in the rearview mirror."

For now, there's a lot to learn, including how exactly the virus triggers MS, says Francesca Aloisi, a neuroscientist at the Italian National Institute of Health in Rome.

For many people with MS, even with current therapies, the disease can progress. Right now, Agosto's symptoms are largely under control. Thanks to physical therapy, an anti-inflammatory diet and medication, she has about 90 percent function on the left side of her body. "Things like long-distance running are out of the question," she says. Carrying grocery bags with her left arm is a challenge.

Studying the virus's role in MS "will be an amazing game changer," says Agosto, who is a patient advocate with the National Multiple Sclerosis Society's New York City chapter. If Epstein-Barr virus is driving her disease, she wants to know: "How do we get this virus out of the driver's seat?"

A familiar virus

Multiple sclerosis is an uncommon disease, affecting nearly 3 million people globally. Yet Epstein-Barr virus is almost everywhere.

The virus, discovered in 1964, infects an estimated 90 percent of people around the world. People infected as young children might have a mild cold or show no symptoms. Teenagers or young adults may experience a bout of debilitating fatigue called infectious mononucleosis, or mono, that can last weeks or months.

These symptoms eventually fade. But Epstein-Barr infections hang on. The virus belongs to the herpesvirus family - a group known for instigating lifelong infections. The herpesviruses behind cold sores, genital herpes and chicken pox also stick around for life, usually staying quiet for long stretches. For example, varicella-zoster virus, which causes chicken pox, goes latent inside nerve cells but can resurface to cause the painful disease shingles ( SN: 3/2/19, p. 22).

In the body, Epstein-Barr virus slips into the epithelial cells that line the surface of the throat, allowing the virus to spread to other people via saliva - hence mono's nickname, "the kissing disease." The virus also infects a type of immune cell called B cells, where it enters viral hibernation.

Epstein-Barr virus can cause problems long after the initial infection. People who had mono are more likely to develop cancers such as Hodgkin's lymphoma than people who didn't. And they are more likely to be diagnosed with MS. A teenage case of mono doesn't mean long-term problems are inevitable. But avoiding mono-related fatigue doesn't guarantee an escape from risk either. Agosto, for instance, doesn't recall ever having mono.

Lifelong infection

Epstein-Barr virus infects the throat's epithelial cells and the immune system's B cells. Inside B cells, the virus can hibernate for long stretches of time - sometimes reemerging and doing new damage.

Establishing the link

In March 2000, epidemiologist Alberto Ascherio of the Harvard T.H. Chan School of Public Health published research exploring the link between Epstein-Barr virus and MS. With colleague Mette Munch of the University of Aarhus in Denmark, Ascherio analyzed data from eight studies suggesting that MS patients are more likely to have had an Epstein-Barr infection than those without MS. Studies over the next 20 years continued to hint that the virus plays a role, but "the problem is to go from a suggestion or suspicion to proof," says Ascherio. Getting that proof is difficult, because nearly everyone has been infected with Epstein-Barr virus, or EBV, yet very few have MS.

"If it's true that EBV causes MS, then you would expect to find that those individuals who are not infected with EBV, they will not get MS," Ascherio says. "It's very simple." He and colleagues needed to follow a large group of young adults who had never been infected.

The researchers found such a group in the U.S. military. Through the Department of Defense Serum Repository, the team had access to repeated blood samples from more than 10 million individuals, taken when active-duty members were screened for diseases such as HIV at the start of their service and then every two years. Using blood samples taken between 1993 and 2013, Ascherio and colleagues could identify people who had never been infected with Epstein-Barr virus, track new infections and learn when people who developed MS started showing symptoms.

Over that 20-year span, 801 people whose blood was tested were diagnosed with MS. Thirty-five of those people had no signs of Epstein-Barr virus infection in their first blood sample. But all but one became infected before their MS diagnosis. People infected with the virus were 32 times as likely to develop MS as uninfected people. What's more, the researchers found that blood concentrations of a nervous system protein that is a signal of nerve damage rose after Epstein-Barr virus infection, before an MS diagnosis. The results prompted Ascherio and his team to make a bold claim in Science in January: "These findings cannot be explained by any known risk factor for MS and suggest EBV as the leading cause of MS."

It is still possible that infection with Epstein-Barr virus is a time stamp for something else, perhaps not yet identified, that's also relevant for MS, says Mark Allegretta, vice president of research at the National Multiple Sclerosis Society. "The way we talk about it now is that it's very strong evidence that it's necessary for development of MS, but it's insufficient on its own."

Ascherio isn't deterred. "After 20 years of talking about EBV and MS, it's quite exciting that we've finally nailed it down," he says. "There was a lot of skepticism until now and that is fading away."

32

times

Increased chance of developing MS if infected with Epstein-Barr virus, in one study

A skeptic convinced

The fact that Epstein-Barr virus is implicated in so many diseases had many researchers skeptical of its link to MS, says Tobias Lanz, a neurologist at Stanford University. "It's involved in tumors, it's involved in MS, it's involved in lupus, it's in chronic fatigue syndrome. Somehow, people link it to everything and that makes us reasonably suspicious."

Lanz's mentor, Stanford rheumatologist William Robinson, was one of those skeptics. Once Lanz, Robinson and their colleagues found hints of how Epstein-Barr virus could spark nerve damage, however, Robinson became a believer.

The team discovered that immune proteins called antibodies from some MS patients attach to a key Epstein-Barr virus protein, as well as to a protein from the central nervous system. This finding, described in the March 10 Nature, suggests that as the immune system learns how to recognize the virus, it may also learn to attack nerve cells.

The viral protein, called EBNA1, helps Epstein-Barr virus persist in the body for life, hidden away inside B cells. Its molecular twin in the central nervous system, a portion of a protein called GlialCAM, is so similar that antibodies for the virus recognize and bind tightly to it too, the team found in lab experiments.

"That really changed everything," Robinson says, calling it "an in-your-face result that you can't dismiss as not being real." In addition to adding to the evidence that Epstein-Barr virus causes MS, the finding also provides a hint of a possible mechanism: GlialCAM is found in glial cells, which support nerve cells and form the insulating layer myelin that helps nerve cells send signals ( SN: 8/22/15, p. 18). Myelin is the very thing that is destroyed in MS.

About a quarter of patients in the study had antibodies that recognize both EBNA1 and GlialCAM. The similarities between the two proteins, called molecular mimicry, means that EBNA1 may not be a good viral protein to include in vaccines to curb diseases related to Epstein-Barr virus, says Steinman, the Stanford neurologist, who was also involved with the research. If the virus indeed sparks an autoimmune reaction, vaccines that target this viral protein or other mimics could harm myelin and spur MS.

Molecular mimic

As the body mounts an attack against Epstein-Barr virus, the immune system may learn to turn against nerve cells too. Some researchers hypothesize that virus-attacking antibodies might also attack nerve-protecting myelin and drive MS.

Viral damage

Several studies support the idea that molecular mimicry causes MS damag e. But other hypotheses are on the table.

Those B cells, for instance, where Epstein-Barr viruses hide out, produce antibodies. One possibility is that B cells infected with Epstein-Barr virus transform in ways that encourage the immune system to attack the body's own tissues.

Aloisi, the neuroscientist in Rome, backs a different hypothesis: Perhaps the immune system's attack on the virus itself is behind the damage.

"The biology of the virus is so similar to the biology of the disease," Aloisi says. For some people, MS can go through phases of silence where the disease is stable, no better, no worse. The disease then reactivates, producing new brain lesions and worsening symptoms. Epstein-Barr virus can similarly come out of latency, perhaps causing a surge of problems before returning to hibernation inside host cells.

In 2007, Aloisi and colleagues discovered unexpected clusters of B cells within the membranes that cover and protect the brain. In all but one of 22 patients studied, some of those B cells were infected with Epstein-Barr virus.

The finding "was like a bomb in the field," Aloisi says, "because nobody ever thought about this possibility." Other researchers initially failed to replicate the results. But "little by little other work came out [in support]," she says. "It's difficult to find these [clusters of B cells] in the brain because people with MS don't have large, inflamed brains. It's small spots here and there."

It's possible that the central nervous system becomes a stronghold for the virus, Aloisi says. Immune cells called T cells, which can either coordinate an attack or kill infected cells, rush in. Some virus-infected B cells die, but the immune system can't eliminate the virus. Myelin gets caught in the cross fire. "This creates a situation that is extremely detrimental to the tissue," she says.

Treatment tactics

Regardless of whether Epstein-Barr virus drives MS symptoms directly or causes the body's immune response to go haywire, the big question is what to do about it.

One obvious path is to develop MS drugs that go after the virus, Aloisi says. Some drugs that block hepatitis B virus and HIV have shown potential against Epstein-Barr virus in lab-grown cells, says Ascherio, the Harvard epidemiologist. But those results are very preliminary.

Another option is to go after the infected cells. A few MS therapies may do that already. The existing MS therapy natalizumab already prevents B and T cells from crossing into the central nervous system. Fingolimod may do that as well. Another drug called ocrelizumab, approved for patients with MS in 2017, is an antibody that attaches to a protein on B cells and triggers cell death. The drug helps patients, like Agosto, who have relapsing-remitting MS, but it's less effective for people with a progressive form of the disease, who have fewer treatment options ( SN: 12/9/17, p. 20).

Researchers thought the drug dampened faulty immune responses by depleting B cells, Lanz says. "But it could also well be that we're hitting those particular pathogenic B cells that are infected with Epstein-Barr virus. So the B cell depletion might actually be an anti-EBV drug and nobody appreciated that."

Aloisi agrees. "Now we need something that targets the EBV-infected cells, not all of the B cells," she says. Indiscriminately killing B cells puts patients at risk for other infections. One way to get around that could come in the form of T cell therapies that go after only infected cells. Such therapies are already in clinical trials in MS patients.

Some researchers suspect that antiviral treatments would probably make the most sense when used early on, before the immune system eats away at the myelin around the nerve cells. Once the virus has kick-started an immune response to attack the nervous system, "the train may already be out of the station," says neuroimmunologist Emily Harrington of Ohio State University's Wexner Medical Center in Columbus.

A vaccine

Even better than stopping the infection once it starts would be to build defenses before the virus invades, or to stop it from reawakening. Enter vaccines.

The widespread impact of mono and Epstein-Barr virus's links to cancer and autoimmune disease had already spurred vaccine research, so a few potential shots are already in the pipeline. But Epstein-Barr virus has a complex way of invading the body, says vaccinologist Javier Gordon Ogembo of City of Hope, a cancer care center in Duarte, Calif. The virus uses at least five viral proteins to invade both epithelial cells and B cells. A vaccine would need to drive an immune response that blocks the virus's entry into both cell types to prevent infection. "This is the reason, I think, why there has not been a vaccine so far," Ogembo says.

Vaccine options

Recent studies suggest that vaccines being developed to prevent diseases related to Epstein-Barr virus, or EBV, such as mononucleosis or cancer, might also work for multiple sclerosis.

Moderna mRNA vaccine:

Uses mRNA to teach the body to recognize four viral proteins that help EBV enter epithelial and B cells.
Developed for: Mononucleosis
Stage of development: Phase I clinical trial

NIH nanoparticles vaccine:

Teaches the body to attack a protein called gp350, which EBV uses to infect B cells
Developed for: Mono and cancer
Stage of development: Phase I clinical trial

City of Hope modified virus vaccine:

Delivers DNA to cells so the cells can make and teach the immune system to recognize five viral proteins that help EBV enter epithelial and B cells
Developed for: Mono and cancer
Stage of development: Animal studies

BioNTech mRNA vaccine:

Blocks myelin attack
Developed for: MS
Stage of development: Animal studies

Pharmaceutical company GlaxoSmithKline took one vaccine candidate to clinical trials in the early 2000s. It seemed to stop people from developing mono, but it didn't meet the original goal of preventing infection overall. So the company abandoned the vaccine.

Moderna, the biotechnology company made famous for its effective COVID-19 vaccine, recently launched a clinical trial of an mRNA vaccine for Epstein-Barr virus. The shot teaches the body to recognize four of the five viral proteins that help the virus invade both cell types, says viral immunologist Katherine Luzuriaga of the University of Massachusetts Chan Medical School in Worcester, who is involved in the trial. For now, the team is testing whether the vaccine sparks a strong immune response and getting a sense for whether it might curb cases of mono.

In March, the U.S National Institutes of Health launched a clinical trial to test a vaccine that uses nanoparticles to teach the body to recognize the virus and get rid of it. Ogembo and colleagues at City of Hope are developing another vaccine that uses a modified virus as the immune system's instructor.

Although clinical trials could reveal within the next few years whether the vaccines can control mono, it will be decades before researchers learn anything about the potential impact on cancer or MS, Luzuriaga and Ogembo say. The hope is to see an outcome like the vaccines for human papillomaviruses, Luzuriaga says, which reduce the number of HPV infections and led to a dramatic reduction in cervical cancers.

Developing therapeutic vaccines for people who already have MS may also be possible, Ascherio says. The aim would be to stop the virus from emerging from its slumber inside B cells. It would be akin to the shingles vaccine, which prevents the painful reactivation of varicella-zoster virus in nerve cells.

That is Steinman's aim as well, but he envisions a shot that would put a check on the undesirable immune response. Steinman and colleagues have tested such a vaccine to try and teach MS patients' immune systems to ignore and not harm a protein called myelin basic protein, which helps add myelin to nerves. There were hints the vaccine might have been effective, but the team ultimately stopped the project.

"If it weren't for other very powerful therapies becoming approved in that same time frame, we may have continued," Steinman says. Now, he wants to make a vaccine that helps MS patients tolerate, rather than attack, the central nervous system protein GlialCAM.

Researchers at BioNTech, also famous for developing a COVID-19 vaccine, are working on something similar. In mice with a disease close to MS, the company showed that an mRNA vaccine could keep the immune system from attacking myelin proteins, the team reported in January 2021 in Science.

Time will tell how effective any of these shots might be. But with studies providing more and more evidence that Epstein-Barr virus is linked to many diseases, Ogembo says, "it's time to make a vaccine and get rid of it."

Questions or comments on this article? E-mail us at feedback@sciencenews.org

A version of this article appears in the August 13, 2022 issue of Science News.

Citations

G. M. Escalante et al. Four decades of prophylactic EBV vaccine research: A systemic review and historical perspective. Frontiers in Immunology. April 14, 2022. doi.org/10.3389/fimmu.2022.86.

K. Bjornevik et al. Longitudinal analysis reveals high prevalence of Epstein-Barr virus associated with multiple sclerosis. Science. Vol. 375, January 13, 2022, p. 296. doi: 10.1126/science.abj8222.

T. V. Lanz et al. Clonally expanded B cells in multiple sclerosis bind EBV EBNA1 and GlialCAM. Nature. Vol. 603, January 24, 2022, p. 321. doi: 10.1038/s41586-022-04432-7.

C. Krienke et al. A noninflammatory mRNA vaccine for treatment of experimental autoimmune encephalomyelitis. Science. Vol. 371, January 8, 2021, p. 145. doi: 10.1126/science.aay3638.

J. E. Libbey, L. L. McCoy and R. S. Fujinami. Molecular mimicry in multiple sclerosis. Int. Rev. Neurobiol. Vol. 79, May 25, 2007, p. 127. doi: 10.1016/S0074-7742(07)79006-2.

B. Serafini et al. Dysregulated Epstein-Barr virus infection in the multiple sclerosis brain. Journal of Experimental Medicine. Vol. 204, November 5, 2007, p. 2899. doi: 10.1084/jem.20071030.

A. Ascherio and M. Munch. Epstein-Barr virus and Multiple Sclerosis. Epidemiology. Vol. 11, March 2000, p. 220.

Erin I. Garcia de Jesus is a staff writer at Science News. She holds a Ph.D. in microbiology from the University of Washington and a master's in science communication from the University of California, Santa Cruz.

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Multiple sclerosis has a common viral culprit, opening doors to new approaches

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As Tanina Agosto went through her normal morning routine in July 2007, she realized something was wrong. The 29-year-old couldn't control her left side, even her face. "Literally the top of my head to the bottom of my foot on the left side of my body could not feel anything."

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#evolution #climate #earthhistory #earthscience #biology

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There's nothing like a big mass extinction to open up ecological niches and clear out the competition, accelerating evolution for some lucky survivors. Or is there? A new study suggests that the rate of climate change may play just as large a role in speeding up evolution.

The study focuses on reptile evolution across 57 million years - before, during and after the mass extinction at the end of the Permian Period ( SN: 12/6/18). That extinction event, triggered by carbon dioxide pumped into the atmosphere and oceans through increased volcanic activity about 252 million years ago, knocked out a whopping 86 percent of Earth's species. Yet reptiles recovered from the chaos relatively well. Their exploding diversity of species around that time has been widely regarded as a result of their slithering into newly available niches.

But rapid climate fluctuations were already taking place much earlier in the Permian, and so were surges of reptile diversification, researchers say. Analyzing fossils from 125 reptile species shows that bursts of evolutionary diversity in reptiles were tightly correlated with relatively rapid fluctuations in climate throughout the Permian and millions of years into the next geologic period, the Triassic, researchers report August 19 in Science Advances.

Scientists' understanding of evolution is expanding as they become more tuned into the connection between it and environmental change, says Jessica Whiteside, a geologist at the University of Southampton in England who works on mass extinctions but was not involved in the new work. "This study is bound to become an important part of that conversation."

To investigate reptile evolution, evolutionary paleobiologist Tiago Simões of Harvard University and colleagues precisely measured and scanned reptile fossils ranging from 294 million to 237 million years old. In all, the researchers examined 1,000 specimens at 50 research institutions in 20 countries. For climate data, the team used an existing large database of sea surface temperatures based on oxygen isotope data, extending back 450 million years, published in 2021.

By closely tracking changes in body and head size and shape in so many species, paired with that climate data, the researchers found that the faster the rate of climate change, the faster reptiles evolved. The fastest rate of reptile diversification did not occur at the end-Permian extinction, the team found, but several million years later in the Triassic, when climate change was at its most rapid and global temperatures witheringly hot. Ocean surface temperatures during this time soared to 40° Celsius, or 104⁰ Fahrenheit - about the temperature of a hot tub, says Simões.

A few species did evolve less rapidly than their kin, Simões says. The difference? Size. For instance, reptiles with smaller body sizes are already preadapted to live in rapidly warming climates, he says. Due to their greater surface area to body ratio, "small-bodied reptiles can better exchange heat with their surrounding environment," so stay relatively cooler than larger animals.

"The smaller reptiles were basically being forced by natural selection to stay the same, while during that same period of time, the large reptiles were being told by natural selection 'You need to change right away or you're going to go extinct,'" Simões says.

This phenomenon, called the Lilliput effect, is not a new proposal, Simões says, adding that it's been well established in marine organisms. "But it's the first time it's been quantified in limbed vertebrates across this critical period in Earth's history."

Simões and colleagues' detailed work has refined the complex evolutionary tree for reptiles and their ancestors. But, for now, it's unclear which played a bigger role in reptile evolution long ago - all those open ecological niches after the end-Permian mass extinction, or the dramatic climate fluctuations outside of the extinction event.

"We cannot say which one was more important," Simões says. "Without either one, the course of evolution in the Triassic and the rise of reptiles to global dominance in terrestrial ecosystems would have been quite different."

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Extreme climate shifts long ago may have helped drive reptile evolution

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There's nothing like a big mass extinction to open up ecological niches and clear out the competition, accelerating evolution for some lucky survivors. Or is there? A new study suggests that the rate of climate change may play just as large a role in speeding up evolution.

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#dinosaurs #asteroid #extinction #seafloor #earthhistory #seismic #earthscience

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Chicxulub, the asteroid that wiped out most dinosaurs, might have had a little sibling.

Off the coast of West Africa, hundreds of meters beneath the seafloor, scientists have identified what appears to be the remains of an 8.5-kilometer-wide impact crater, which they've named Nadir. The team estimates that the crater formed roughly around the same time that another asteroid - Chicxulub, the dinosaur killer - slammed into modern day Mexico ( SN: 1/25/17). If confirmed, it could mean that nonbird dinosaurs met their demise by a one-two punch of asteroids, researchers report in the Aug. 17 Science Advances.

"The idea that [Chicxulub] had help - for want of a better phrase - would have really added insult to serious injury," says study coauthor Veronica Bray, a planetary scientist at the University of Arizona in Tucson.

Nearly 200 impact craters have been discovered on Earth ( SN: 12/18/18), the vast majority of which are on land. That's because impact craters at sea gradually become buried under sediment, Bray says, which makes the Nadir structure a valuable scientific find, regardless of its birthdate.

Geologist Uisdean Nicholson of Heriot-Watt University in Edinburgh happened upon the structure while analyzing data collected by seismic waves transmitted underground to detect physical structures offshore of Guinea. Lurking beneath the seafloor - and under nearly 1 kilometer of water - he discerned a bowl-shaped structure with a broken-up, terraced floor and a pronounced central peak - features expected of a large impact.

Based on the structure's dimensions, Bray, Nicholson and their colleagues calculate that, if an asteroid was responsible for the terrain, it would probably have been over 400 meters wide. What's more, the researchers estimate that the impact would have rocked the ground like a magnitude 7 earthquake and stirred tsunamis hundreds of meters high.

Despite that fallout, the Nadir impact would have been far less devastating than the one from the roughly 10-kilometer-wide Chicxulub asteroid, says Michael Rampino, a geologist from New York University who was not involved in the study. "It certainly wouldn't have had global effects," he says.

Using geologic layers adjacent to Nadir, some with ages obtained by past studies, the team estimated the structure to have formed around the end of the Cretaceous period - 66 million years ago. The Nadir asteroid may even have formed a pair with the Chicxulub asteroid, the two having been ripped apart by gravitational forces during a previous Earth flyby, the researchers speculate.

But the study's conclusions have some experts wary. "It looks like an impact crater, but it could also be something else," says geologist Philippe Claeys of Vrije Universiteit Brussel in Belgium, who was not involved in the research. Confirming that the structure is an impact crater will require drilling for solid evidence, such as shocked quartz, he says. Alternative explanations for the structure's identity include a collapsed volcanic caldera or a squeezed body of salt called a salt diapir.

The Nadir structure's age is another uncertainty. The seismic data shows it appears to have formed sometime near the end the Cretaceous period or maybe a little later, Claeys says. "But that's around the best they can say." Drilling in the crater for minerals that contain radioactive elements could provide a more precise date of formation, Rampino says.

It's not the first time that scientists have investigated whether Chicxulub had an accomplice. Some studies have suggested that the Boltysh crater in Ukraine may have formed at the same time as Chicxulub, though researchers have since determined that Boltysh formed 650,000 years later.

Bray and her colleagues are currently negotiating for funding to collect samples from the crater, with aspirations to drill in 2024. That will hopefully settle some of the debate surrounding Nadir's origins, Bray says, though new questions will probably arise too. "If we do prove that this is the sister of the dinosaur killer, then how many other siblings are there?"

Questions or comments on this article? E-mail us at feedback@sciencenews.org

Nikk Ogasa is a staff writer who focuses on the physical sciences for Science News. He has a master's degree in geology from McGill University, and a master's degree in science communication from the University of California, Santa Cruz.

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Not one, but two asteroids might have slain the dinosaurs

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Chicxulub, the asteroid that wiped out most dinosaurs, might have had a little sibling. Off the coast of West Africa, hundreds of meters beneath the seafloor, scientists have identified what appears to be the remains of an 8.5-kilometer-wide impact crater, which they've named Nadir.