Science

these-scientists-explored-the-good-vibrations-of-the-bundengan-and-didgeridoo

These scientists explored the good vibrations of the bundengan and didgeridoo

12 days of Christmas, acoustics, bundengan, didgeridoo, Musical Instruments, Physics, Science / /

On the fifth day of Christmas —

Their relatively simple construction produces some surprisingly complicated physics.

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Indonesian performers onstage with one playing a bundengan

Enlarge / The bundengan (left) began as a combined shelter/instrument for duck hunters but it is now often played onstage.

There’s rarely time to write about every cool science-y story that comes our way. So this year, we’re once again running a special Twelve Days of Christmas series of posts, highlighting one science story that fell through the cracks in 2020, each day from December 25 through January 5. Today: the surprisingly complex physics of two simply constructed instruments: the Indonesian bundengan and the Australian Aboriginal didgeridoo (or didjeridu).

The bundengan is a rare, endangered instrument from Indonesia that can imitate the sound of metallic gongs and cow-hide drums (kendangs) in a traditional gamelan ensemble. The didgeridoo is an iconic instrument associated with Australian Aboriginal culture that produces a single, low-pitched droning note that can be continuously sustained by skilled players. Both instruments are a topic of scientific interest because their relatively simple construction produces some surprisingly complicated physics. Two recent studies into their acoustical properties were featured at an early December meeting of the Acoustical Society of America, held in Sydney, Australia, in conjunction with the Australian Acoustical Society.

The bundengan originated with Indonesian duck hunters as protection from rain and other adverse conditions while in the field, doubling as a musical instrument to pass the time. It’s a half-dome structure woven out of bamboo splits to form a lattice grid, crisscrossed at the top to form the dome. That dome is then coated with layers of bamboo sheaths held in place with sugar palm fibers. Musicians typically sit cross-legged inside the dome-shaped resonator and pluck the strings and bars to play. The strings produce metallic sounds while the plates inside generate percussive drum-like sounds.

Gea Oswah Fatah Parikesit of Universitas Gadja Mada in Indonesia has been studying the physics and acoustics of the bundengan for several years now. And yes, he can play the instrument. “I needed to learn to do the research,” he said during a conference press briefing. “It’s very difficult because you have two different blocking styles for the right and left hand sides. The right hand is for the melody, for the string, and the left is for the rhythm, to pluck the chords.”

Much of Parikesit’s prior research on the bundengan focused on the unusual metal/percussive sound of the strings, especially the critical role played by the placement of bamboo clips. He used computational simulations of the string vibrations to glean insight on how the specific gong-like sound was produced, and how those vibrations change with the addition of bamboo clips located at different sections of the string. He found that adding the clips produces two vibrations of different frequencies at different locations on the string, with the longer section having a high frequency vibration compared to the lower frequency vibration of the shorter part of the string. This is the key to making the gong-like sound.

This time around, Parikesit was intrigued by the fact many bundengan musicians have noted the instrument sounds better wet. In fact, several years ago, Parikesit attended a bundengan concert in Melbourne during the summer when it was very hot and dry—so much so that the musicians brought their own water spray bottles to ensure the instruments stayed (preferably) fully wet.

A bundengan is a portable shelter woven from bamboo, worn by Indonesian duck herders who often outfit it to double as a musical instrument.

Enlarge / A bundengan is a portable shelter woven from bamboo, worn by Indonesian duck herders who often outfit it to double as a musical instrument.

Gea Oswah Fatah Parikesit

“A key element between the dry and wet versions of the bundengan is the bamboo sheaths—the material used to layer the wall of the instrument,” Parokesit said. “When the bundengan is dry, the bamboo sheaths open and that results in looser connections between neighboring sheaths. When the bundengan is wet, the sheaths tend to form a curling shape, but because they are held by ropes, they form tight connections between the neighboring sheaths.”

The resulting tension allows the sheaths to vibrate together. That has a significant impact on the instrument’s sound, taking on a “twangier” quality when dry and a more of metallic gong sound when it is wet. Parikesit has tried making bundengans with other materials: paper, leaves, even plastics. But none of those produce the same sound quality as the bamboo sheaths. He next plans to investigate other musical instruments made from bamboo sheaths.“As an Indonesian, I have extra motivation because the bundengan is a piece of our cultural heritage,” Parikesit said. “I am trying my best to support the conservation and documentation of the bundengan and other Indonesian endangered instruments.”

Coupling with the human vocal tract

Meanwhile, John Smith of the University of New South Wales is equally intrigued by the physics and acoustics of the didgeridoo. The instrument is constructed from the trunk or large branches of the eucalyptus tree. The trick is to find a live tree with lots of termite activity, such that the trunk has been hollowed out leaving just the living sapwood shell. A suitably hollow trunk is then cut down, cleaned out, the bark removed, the ends trimmed, and the exterior shaped into a long cylinder or cone to produce the final instrument. The longer the instrument, the lower the pitch or key.

Players will vibrate their lips to play the didgeridoo in a manner similar to lip valve instruments like trumpets or trombones, except those use a small mouthpiece attached to the instrument as an interface. (Sometimes a beeswax rim is added to a didgeridoo mouthpiece end.) Players typically use circular breathing to maintain that continuous low-pitched drone for several minutes, basically inhaling through the nose and using air stored in the puffed cheeks to keep producing the sound. It’s the coupling of the instrument with the human vocal tract that makes the physics so complex, per Smith.

Smith was interested in investigating how changes in the configuration of the vocal tract produced timbral changes in the rhythmic pattern of the sounds produced. To do so, “We needed to develop a technique that could measure the acoustic properties of the player’s vocal tract while playing,” Smith said during the same press briefing. “This involved injecting a broadband signal into the corner of the player’s mouth and using a microphone to record the response.” That enabled Smith and his cohorts to record the vocal tract impedance in different configurations in the mouth.

Producing complex sounds with the didjeridu requires creating and manipulating resonances inside the vocal tract.

Enlarge / Producing complex sounds with the didjeridu requires creating and manipulating resonances inside the vocal tract.

Kate Callas

The results: “We showed that strong resonances in the vocal tract can suppress bands of frequencies in the output sound,” said Smith. “The remaining strong bands of frequencies, called formants, are noticed by our hearing because they fall in the same ranges as the formants we use in speech. It’s a bit like a sculptor removing marble, and we observe the bits that are left behind.”

Smith et al. also noted that the variations in timbre arise from the player singing while playing, or imitating animal sounds (such as the dingo or the kookaburra), which produces many new frequencies in the output sound. To measure the contact between vocal folds, they placed electrodes on either side of a player’s throat and zapped them with a small high frequency electric current. They simultaneously measured lip movement with another pair of electrics above and below the lips. Both types of vibrations affect the flow of air to produce the new frequencies.

As for what makes a desirable didgeridoo that appeals to players, acoustic measurements on a set of 38 such instruments—with the quality of each rated by seven experts in seven different subjective categories—produced a rather surprising result. One might think players would prefer instruments with very strong resonances but the opposite turned out to be true. Instruments with stronger resonances were ranked the worst, while those with weaker resonances rated more highly.  Smith, for one, thinks this makes sense. “This means that their own vocal tract resonance can dominate the timbre of the notes,” he said.

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This bird is like a GPS for honey

Behavioral science, Biology, birds, culture, honeyguide, language, Science / /

Show me the honey —

The honeyguide recognizes calls made by different human groups.

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A bird perched on a wall in front of an urban backdrop.

Enlarge / A greater honeyguide

With all the technological advances humans have made, it may seem like we’ve lost touch with nature—but not all of us have. People in some parts of Africa use a guide more effective than any GPS system when it comes to finding beeswax and honey. This is not a gizmo, but a bird.

The Greater Honeyguide (highly appropriate name), Indicator indicator (even more appropriate scientific name), knows where all the beehives are because it eats beeswax. The Hadza people of Tanzania and Yao people of Mozambique realized this long ago. Hadza and Yao honey hunters have formed a unique relationship with this bird species by making distinct calls, and the honeyguide reciprocates with its own calls, leading them to a hive.

Because the Hadza and Yao calls differ, zoologist Claire Spottiswoode of the University of Cambridge and anthropologist Brian Wood of UCLA wanted to find out if the birds respond generically to human calls, or are attuned to their local humans. They found that the birds are much more likely to respond to a local call, meaning that they have learned to recognize that call.

Come on, get that honey

To see which sound the birds were most likely to respond to, Spottiswoode and Wood played three recordings, starting with the local call. The Yao honeyguide call is what the researchers describe as “a loud trill followed by a grunt (‘brrrr-hm’) while the Hadza call is more of “a melodic whistle,” as they say in a study recently published in Science. The second recording they would play was the foreign call, which would be the Yao call in Hadza territory and vice versa.

The third recording was an unrelated human sound meant to test whether the human voice alone was enough for a honeyguide to follow. Because Hadza and Yao voices sound similar, the researchers would alternate among recordings of honey hunters speaking words such as their names.

So which sounds were the most effective cues for honeyguides to partner with humans? In Tanzania, local Hadza calls were three times more likely to initiate a partnership with a honeyguide than Yao calls or human voices. Local Yao calls were also the most successful in Mozambique, where, in comparison to Hadza calls and human voices, they were twice as likely to elicit a response that would lead to a cooperative effort to search for a beehive. Though honeyguides did sometimes respond to the other sounds, and were often willing to cooperate when hearing them, it became clear that the birds in each region had learned a local cultural tradition that had become just as much a part of their lives as those of the humans who began it.

Now you’re speaking my language

There is a reason that honey hunters in both the Hadza and Yao tribes told Wood and Spottiswoode that they have never changed their calls and will never change them. If they did, they’d be unlikely to gather nearly as much honey.

How did this interspecies communication evolve? Other African cultures besides the Hadza and Yao have their own calls to summon a honeyguide. Why do the types of calls differ? The researchers do not think these calls came about randomly.

Both the Hadza and Yao people have their own unique languages, and sounds from them may have been incorporated into their calls. But there is more to it than that. The Hadza often hunt animals when hunting for honey. Therefore, the Hadza don’t want their calls to be recognized as human, or else the prey they are after might sense a threat and flee. This may be why they use whistles to communicate with honeyguides—by sounding like birds, they can both attract the honeyguides and stalk prey without being detected.

In contrast, the Yao do not hunt mammals, relying mostly on agriculture and fishing for food. This, along with the fact that they try to avoid potentially dangerous creatures such as lions, rhinos, and elephants, and can explain why they use recognizably human vocalizations to call honeyguides. Human voices may scare these animals away, so Yao honey hunters can safely seek honey with their honeyguide partners. These findings show that cultural diversity has had a significant influence on calls to honeyguides.

While animals might not literally speak our language, the honeyguide is just one of many species that has its own way of communicating with us. They can even learn our cultural traditions.

“Cultural traditions of consistent behavior are widespread in non-human animals and could plausibly mediate other forms of interspecies cooperation,” the researchers said in the same study.

Honeyguides start guiding humans as soon as they begin to fly, and this knack, combined with learning to answer traditional calls and collaborate with honey hunters, works well for both human and bird. Maybe they are (in a way) speaking our language.

Science, 2023.  DOI: 10.1126/science.adh412

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How watching beavers from space can help drought-ridden areas bounce back

Beavers, climate change, drought, Science, syndication / /

Busy as a… —

An algorithm can spot beaver ponds from satellite imagery.

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Beaver on a dam

Enlarge / Where beavers set up home, the dams they build profoundly change the landscape.

For the first time in four centuries, it’s good to be a beaver. Long persecuted for their pelts and reviled as pests, the dam-building rodents are today hailed by scientists as ecological saviors. Their ponds and wetlands store water in the face of drought, filter out pollutants, furnish habitat for endangered species, and fight wildfires. In California, Castor canadensis is so prized that the state recently committed millions to its restoration.

While beavers’ benefits are indisputable, however, our knowledge remains riddled with gaps. We don’t know how many are out there, or which direction their populations are trending, or which watersheds most desperately need a beaver infusion. Few states have systematically surveyed them; moreover, many beaver ponds are tucked into remote streams far from human settlements, where they’re near-impossible to count. “There’s so much we don’t understand about beavers, in part because we don’t have a baseline of where they are,” says Emily Fairfax, a beaver researcher at the University of Minnesota.

But that’s starting to change. Over the past several years, a team of beaver scientists and Google engineers have been teaching an algorithm to spot the rodents’ infrastructure on satellite images. Their creation has the potential to transform our understanding of these paddle-tailed engineers—and help climate-stressed states like California aid their comeback. And while the model hasn’t yet gone public, researchers are already salivating over its potential. “All of our efforts in the state should be taking advantage of this powerful mapping tool,” says Kristen Wilson, the lead forest scientist at the conservation organization the Nature Conservancy. “It’s really exciting.”

The beaver-mapping model is the brainchild of Eddie Corwin, a former member of Google’s real-estate sustainability group. Around 2018, Corwin began to contemplate how his company might become a better steward of water, particularly the many coastal creeks that run past its Bay Area offices. In the course of his research, Corwin read Water: A Natural History, by an author aptly named Alice Outwater. One chapter dealt with beavers, whose bountiful wetlands, Outwater wrote, “can hold millions of gallons of water” and “reduce flooding and erosion downstream.” Corwin, captivated, devoured other beaver books and articles, and soon started proselytizing to his friend Dan Ackerstein, a sustainability consultant who works with Google. “We both fell in love with beavers,” Corwin says.

Corwin’s beaver obsession met a receptive corporate culture. Google’s employees are famously encouraged to devote time to passion projects, the policy that produced Gmail; Corwin decided his passion was beavers. But how best to assist the buck-toothed architects? Corwin knew that beaver infrastructure—their sinuous dams, sprawling ponds, and spidery canals—is often so epic it can be seen from space. In 2010, a Canadian researcher discovered the world’s longest beaver dam, a stick-and-mud bulwark that stretches more than a half-mile across an Alberta park, by perusing Google Earth. Corwin and Ackerstein began to wonder whether they could contribute to beaver research by training a machine-learning algorithm to automatically detect beaver dams and ponds on satellite imagery—not one by one, but thousands at a time, across the surface of an entire state.

After discussing the concept with Google’s engineers and programmers, Corwin and Ackerstein decided it was technically feasible. They reached out next to Fairfax, who’d gained renown for a landmark 2020 study showing that beaver ponds provide damp, fire-proof refuges in which other species can shelter during wildfires. In some cases, Fairfax found, beaver wetlands even stopped blazes in their tracks. The critters were such talented firefighters that she’d half-jokingly proposed that the US Forest Service change its mammal mascot—farewell, Smoky Bear, and hello, Smoky Beaver.

Fairfax was enthusiastic about the pond-mapping idea. She and her students already used Google Earth to find beaver dams to study within burned areas. But it was a laborious process, one that demanded endless hours of tracing alpine streams across screens in search of the bulbous signature of a beaver pond. An automated beaver-finding tool, she says, could “increase the number of fires I can analyze by an order of magnitude.”

With Fairfax’s blessing, Corwin, Ackerstein, and a team of programmers set about creating their model. The task, they decided, was best suited to a convolutional neural network, a type of algorithm that essentially tries to figure out whether a given chunk of geospatial data includes a particular object—whether a stretch of mountain stream contains a beaver dam, say. Fairfax and some obliging beaverologists from Utah State University submitted thousands of coordinates for confirmed dams, ponds, and canals, which the Googlers matched up with their own high-resolution images to teach the model to recognize the distinctive appearance of beaverworks. The team also fed the algorithm negative data—images of beaverless streams and wetlands—so that it would know what it wasn’t looking for. They dubbed their model the Earth Engine Automated Geospatial Elements Recognition, or EEAGER—yes, as in “eager beaver.”

Training EEAGER to pick out beaver ponds wasn’t easy. The American West was rife with human-built features that seemed practically designed to fool a beaver-seeking model. Curving roads reminded EEAGER of winding dams; the edges of man-made reservoirs registered as beaver-built ponds. Most confounding, weirdly, were neighborhood cul-de-sacs, whose asphalt circles, surrounded by gray strips of sidewalk, bore an uncanny resemblance to a beaver pond fringed by a dam. “I don’t think anybody anticipated that suburban America was full of what a computer would think were beaver dams,” Ackerstein says.

As the researchers pumped more data into EEAGER, it got better at distinguishing beaver ponds from impostors. In May 2023, the Google team, along with beaver researchers Fairfax, Joe Wheaton, and Wally Macfarlane, published a paper in the Journal of Geophysical Research Biogeosciencesdemonstrating the model’s efficacy. The group fed EEAGER more than 13,000 landscape images with beaver dams from seven western states, along with some 56,000 dam-less locations. The model categorized the landscape accurately—beaver dammed or not—98.5 percent of the time.

That statistic, granted, oversells EEAGER’s perfection. The Google team opted to make the model fairly liberal, meaning that, when it predicts whether or not a pixel of satellite imagery contains a beaver dam, it’s more likely to err on the side of spitting out a false positive. EEAGER still requires a human to check its answers, in other words—but it can dramatically expedite the work of scientists like Fairfax by pointing them to thousands of probable beaver sites.

“We’re not going to replace the expertise of biologists,” Ackerstein says. “But the model’s success is making human identification much more efficient.”

According to Fairfax, EEAGER’s use cases are many. The model could be used to estimate beaver numbers, monitor population trends, and calculate beaver-provided ecosystem services like water storage and fire prevention. It could help states figure out where to reintroduce beavers, where to target stream and wetland restoration, and where to create conservation areas. It could allow researchers to track beavers’ spread in the Arctic as the rodents move north with climate change; or their movements in South America, where beavers were introduced in the 1940s and have since proliferated. “We literally cannot handle all the requests we’re getting,” says Fairfax, who serves as EEAGER’s scientific adviser.

The algorithm’s most promising application might be in California. The Golden State has a tortured relationship with beavers: For decades, the state generally denied that the species was native, the byproduct of an industrial-scale fur trade that wiped beavers from the West Coast before biologists could properly survey them. Although recent historical research proved that beavers belong virtually everywhere in California, many water managers and farmers still perceive them as nuisances, and frequently have them killed for plugging up road culverts and meddling with irrigation infrastructure.

Yet those deeply entrenched attitudes are changing. After all, no state is in more dire need of beavers’ water-storage services than flammable, drought-stricken, flood-prone California. In recent years, thanks to tireless lobbying by a campaign called Bring Back the Beaver, the California Department of Fish and Wildlife has begun to overhaul its outdated beaver policies. In 2022, the state budgeted more than $1.5 million for beaver restoration, and announced it would hire five scientists to study and support the rodents. It also revised its official approach to beaver conflict to prioritize coexistence over lethal trapping. And, this fall, the wildlife department relocated a family of seven beavers onto the ancestral lands of the Mountain Maidu people—the state’s first beaver release in almost 75 years.

It’s only appropriate, then, that California is where EEAGER is going to get its first major test. The Nature Conservancy and Google plan to run the model across the state sometime in 2024, a comprehensive search for every last beaver dam and pond. That should give the state’s wildlife department a good sense of where its beavers are living, roughly how many it has, and where it could use more. The model will also provide California with solid baseline data against which it can compare future populations, to see whether its new policies are helping beavers recover. “When you have imagery that’s repeated frequently, that gives you the opportunity to understand change through time,” says the Conservancy’s Kristen Wilson.

What’s next for EEAGER after its California trial? The main thing, Ackerstein says, is to train it to identify beaverworks in new places. (Although beaver dams and ponds present as fairly similar in every state, the model also relies on context clues from the surrounding landscape, and a sagebrush plateau in Wyoming looks very different from a deciduous forest in Massachusetts.) The team also has to figure out EEAGER’s long-term fate: Will it remain a tool hosted by Google? Spin off into a stand-alone product? Become a service operated by a university or nonprofit?

“That’s the challenge for the future—how do we make this more universally accessible and usable?” Corwin says. The beaver revolution may not be televised, but it will definitely be documented by satellite.

This story originally appeared on wired.com.

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Otherworldly mini-Yellowstone found in the deep sea

Biology, Ecology, exploration, oceanography, Science / /

Follow the crabs —

We’ve known about deep ocean vents for a while, but it’s still hard to find them.

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A large collection of white crabs arrayed across rocks on the bottom of the ocean.

Enlarge / “Leading us like breadcrumbs…” A trail of squat lobsters helped researchers locate previously unknown hydrothermal vents. The hydrothermal vents create chemosynthetic ecosystems, so in areas that are mostly barren of life, the appearance of larger animals can be an indicator of vents nearby.

Spectacular scenery, from lush rainforests to towering mountain ranges, dots the surface of our planet. But some of Earth’s most iconic landmarks––ones that may harbor clues to the origin of life on Earth and possibly elsewhere––lay hidden at the bottom of the ocean. Scientists recently found one such treasure in Ecuadorian waters: a submerged mini Yellowstone called Sendero del Cangrejo.

This hazy alien realm simmers in the deep sea in an area called the Western Galápagos Spreading Center––an underwater mountain range where tectonic plates are slowly moving away from each other. Magma wells up from Earth’s mantle here to create new oceanic crust in a process that created the Galápagos Islands and smaller underwater features, like hydrothermal vents. These vents, which pump heated, mineral-rich water into the ocean in billowing plumes, may offer clues to the origin of life on Earth. Studying Earth’s hydrothermal vents could also offer a gateway to finding life, or at least its building blocks, on other worlds.

The newly discovered Sendero del Cangrejo contains a chain of hydrothermal vents that spans nearly two football fields. It hosts hot springs and geyser chimneys that support an array of creatures, from giant, spaghetti-like tube worms to alabaster Galatheid crabs.

The crabs, also known as squat lobsters, helped guide researchers to Sendero del Cangrejo. Ecuadorian observers chose the site’s name, which translates to “Trail of the Crabs,” in their honor.

“It did feel like the squat lobsters were leading us like breadcrumbs, like we were Hansel and Gretel, to the actual vent site,” said Hayley Drennon, a senior research assistant at Columbia University’s Lamont-Doherty Earth Observatory, who participated in the expedition.

The Iguanas Vent Field, where the team did some sampling.

Enlarge / The Iguanas Vent Field, where the team did some sampling.

The joint American and Ecuadorian research team set sail aboard the Schmidt Ocean Institute’s Falkor (too) research vessel in mid-August in search of new hydrothermal vents. They did some mapping and sampling on the way to their target location, about 300 miles off the west coast of the Galápagos.

The team used a ‘Tow-Yo’ technique to gather and transmit real-time data to the crew aboard the ship. “We lowered sensors attached to a long wire to the seafloor, and then towed the wire up and down like a yo-yo,” explained Roxanne Beinart, an associate professor at the University of Rhode Island and the expedition’s chief scientist. “This process allowed us to monitor changes in temperature, water clarity, and chemical composition to help pinpoint potential hydrothermal vent locations.”

When they reached a region that seemed promising, they deployed the remotely operated vehicle SuBastian for a better look. Less than 24 hours later, the team began seeing more and more Galatheid crabs, which they followed until they found the vents.

The crabs were particularly useful guides since the vent fluids there are clear, unlike “black smokers” that create easy-to-see plumes. SuBastian explored the area for about 43 hours straight in the robot’s longest dive to date.

But the true discovery process spanned decades. Researchers have known for nearly 20 years that the area was likely home to hydrothermal activity thanks to chemical signals measured in 2005. About a decade later, teams ventured out again and collected animal samples. Now, due to the Schmidt Ocean Institute’s recent expedition, scientists have the most comprehensive data set ever for this location. It includes chemical, geological, and biological data, along with the first high-temperature water samples.

“It’s not uncommon for an actual discovery like this to take decades,” said Jill McDermott, an associate professor at Lehigh University and the expedition’s co-chief scientist. “The ocean is a big place, and the locations are very remote, so it takes a lot of time and logistics to get out to them.” The team will continue their research onshore to help us understand how hydrothermal vents influence our planet.

Genesis from hell?

Sendero del Cangrejo may compare to a small-scale Yellowstone in some ways, but it’s no tourist destination. It’s pitch-black since sunlight can’t reach the deep ocean floor. The crushing weight of a mile of water presses down from overhead. And the vents are hot and toxic. Some of them clocked in at 290º C (550º F)—nearly hot enough to melt lead.

Before scientists discovered hydrothermal vents in 1977, they assumed such extreme conditions would preclude the possibility of life. Yet that trailblazing team saw multiple species thriving, including white clams that guided them to the vents the same way the Galatheid crabs led the modern researchers to Sendero del Cangrejo.

A series of seafloor photos shows the sudden appearance of live white clams that led scientists to find hydrothermal vents for the first time.

A series of seafloor photos shows the sudden appearance of live white clams that led scientists to find hydrothermal vents for the first time.

Before the 1977 find, no one knew life could survive in such a hostile place. Now, scientists know there are microbes called thermophiles that can only live in high temperatures (up to about 120º C, or 250º F).

Bacteria that surround hydrothermal vents don’t eat other organisms or create energy from sunlight like plants do. Instead, they produce energy using chemicals like methane or hydrogen sulfide that emanate from the vents. This process, called chemosynthesis, was first identified through the characterization of organisms discovered at these vents. Chemosynthetic bacteria are the backbone of hydrothermal vent ecosystems, serving as a nutrition source for higher organisms.

Some researchers suggest life on Earth may have originated near hydrothermal vents due to their unique chemical and energy-rich conditions. While the proposal remains unproven, the discovery of chemosynthesis opened our eyes to new places that could host life.

The possibility of chemosynthetic creatures diminishes the significance of so-called habitable zones around stars, which describe the orbital distances between which surface water can remain liquid on a planet or moon. The habitable zone in our own Solar System extends from about Venus’ orbit out nearly to Mars’.

NASA’s Europa Clipper mission is set to launch late next year to determine whether there are places below the surface of Jupiter’s icy moon, Europa, that could support life. It’s a lot colder out there, well beyond our Solar System’s habitable zone, but scientists think Europa is internally heated. It experiences strong tidal forces from Jupiter’s gravity, which could create hydrothermal activity on the moon’s ocean floor.

Several other moons in our Solar System also host subsurface oceans and experience the same tidal heating that could potentially create habitable conditions. By exploring Earth’s hydrothermal vents, scientists could learn more about what to look for in similar environments elsewhere in our Solar System.

“The Ocean’s Multivitamin”

While hydrothermal vents are relatively new to science, they’re certainly not new to our planet. “Vents have been active since Earth’s oceans first formed,” McDermott said. “They’ve been present in our oceans for as long as we’ve had them, so about 3 billion years.”

During that time, they’ve likely transformed our planet’s chemistry and geology by cycling chemicals and minerals from Earth’s crust throughout the ocean.

“All living things on Earth need minerals and elements that they get from the crust,” said Peter Girguis, a professor at Harvard University, who participated in the expedition. “It’s no exaggeration to say that all life on earth is inextricably tied to the rocks upon which we live and the geological processes occurring deep inside the planet…it’s like the ocean’s multivitamin.”

But the full extent of the impact hydrothermal vents have on the planet remains unknown. In the nearly 50 years since hydrothermal vents were first discovered, scientists have uncovered hundreds more spread around the globe. Yet no one knows how many remain unidentified; there are likely thousands more vents hidden in the deep. Detailed studies, like those the expedition scientists are continuing onshore, could help us understand how hydrothermal activity influences the ocean.

ROV SuBastian takes water and chemical samples from a black smoker hydrothermal vent in the Iguanas Vent Field, Galapagos Islands.

Enlarge / ROV SuBastian takes water and chemical samples from a black smoker hydrothermal vent in the Iguanas Vent Field, Galapagos Islands.

The team’s immediate observations offer a good starting point for their continued scientific sleuthing.

“I actually expected to find denser animal populations in some places,” Beinart said.

McDermott thinks that could be linked to the composition of the vent fluids. “Several of the vents were clear—not very particle-rich,” she said. “They’re probably lower in minerals, but we’re not sure why.” Now, the team will measure different metal levels in water samples from the vent fluids to figure out why they’re low in minerals and whether that has influenced the animals the vents host.

Researchers are learning more about hydrothermal vents every day, but many mysteries remain, such as the eventual influence ocean acidification could have on vents. As they seek answers, they’re sure to find more questions and open up new avenues of scientific exploration.

Ashley writes about space as a contractor for NASA’s Goddard Space Flight Center by day and freelances as an environmental writer. She holds a master’s degree in space studies from the University of North Dakota and is finishing a master’s in science writing through The Johns Hopkins University. She writes most of her articles with one of her toddlers on her lap.

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saving-the-african-penguin-from-climate-change-and-overfishing

Saving the African penguin from climate change and overfishing

climate change, Penguins, Science, South Africa, syndication / /
penguins

Enlarge / African penguins on a beach near Simon’s Town in South Africa.

CAPE TOWN, South Africa—A weathered, green building stands at the edge of the cozy suburban Table View neighborhood in Cape Town, just a few blocks down from a Burger King and a community library. Upon stepping inside, visitors’ feet squelch on a mat submerged in antibacterial liquid—one of the first signs this isn’t just another shop on the street.

A few steps further down the main hallway, a cacophony of discordant brays and honks fill the air. A couple more strides reveal the source of these guttarall calls: African penguins.

Welcome to the nonprofit Southern African Foundation for the Conservation Of Coastal Birds’ hatchery and nursery, where hundreds of these birds are hand-reared after being injured or abandoned in the wild.

While this conservation center is a flourishing refuge for African penguins, the species as a whole is in dire straits. Over the past century, African penguin populations have plummeted, dropping from around one million breeding pairs in the early 1900s to less than 10,000 in 2023 as environmental conditions have worsened due to increased fishing pressure and climate change, which have both decreased fish populations on which penguins rely.

The climate crisis has also fueled more frequent and severe weather events in South Africa such as floods and heat waves, resulting in an increased number of penguin parents abandoning their eggs to seek refuge.

The staff at the Foundation is working to hand-rear penguins with the goal to release most of them back into one of the threatened Cape colonies they came from. But some of these penguins are destined for a different destination: a rocky outcropping along the Eastern Cape of South Africa within the De Hoop Nature Reserve.

There, scientists and conservationists are working to establish a new penguin colony, which they hope will become a stronghold for the entire African penguin species.

The ecological trap

It’s difficult to pin a single threat to the demise of African penguins; oil spills, avian flu and extreme weather events have wreaked havoc on colonies across South Africa. These chronic issues combine with freak incidents: In 2021, a swarm of bees killed more than 60 African penguins on the popular Boulders Beach in Cape Town and, a year later, two huskies killed 19 penguins in the same area.

However, scientists say that one of the main causes of the seabirds’ decline is the intense fishing pressure on sardines and anchovies, the penguin’s main diet.

Fighting unemployment, low-income people fish around coastal beaches to support themselves, said Shanet Rutgers, an animal health technician at the Two Oceans Aquarium in South Africa, and there is a large commercial industry for purse-seine fishing, in which a wall of netting is cast around a school of fish.

“When they pull out too much fish in the ocean, they leave the colonies with almost little to nothing to feed on,” she said.

Saving the African penguin from climate change and overfishing Read More »

a-forensic-artist-has-given-a-500-year-old-inca-“ice-maiden”-a-face

A forensic artist has given a 500-year-old Inca “ice maiden” a face

12 days of Christmas, forensic anthropology, forensic archaeology, forensic reconstruction, inca, Science / /

On the fourth day of Christmas —

Dubbed “Juanita,” the young woman was likely killed during a sacrificial ritual.

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The final approximation of the Incan girl wearing clothing that's similar to what she wore when she died.

Enlarge / The final approximation of the Incan girl dubbed “Juanita” wearing clothing similar to what she was wearing when she died.

Dagmara Socha

There’s rarely time to write about every cool science-y story that comes our way. So this year, we’re once again running a special Twelve Days of Christmas series of posts, highlighting one science story that fell through the cracks in 2023, each day from December 25 through January 5. Today: Swedish forensic artist Oscar Nilsson combined CT scans of frozen mummified remains with skull measurements and DNA analysis to reconstruct the face of a 500-year-old Inca girl.

In 1995, archaeologists discovered the frozen, mummified remains of a young Inca girl high in the mountains of Peru, thought to have died as part of a sacrificial ritual known as Capacocha (or Ohapaq hucha). In late October, we learned how she most likely looked in life, thanks to a detailed reconstruction by Swedish forensic article Oscar Nilsson. A plaster bust of the reconstruction was unveiled at a ceremony at the Andean Sanctuaries Museum of the Catholic University of Santa Maria in Arequipa, Peru, where the girl’s remains (now called Juanita) have been on near-continuous display since her discovery.

“I thought I’d never know what her face looked like when she was alive,” archaeologist Johan Reinhardt told the BBC. Reinhardt had found the remains with Peruvian mountaineer Miguel Zárate at an altitude of 21,000 feet (6,400 meters) during an expedition to Ampato, one of the highest volcanos in the Andes. “Now 28 years later, this has become a reality thanks to Oscar Nilsson’s reconstruction.”

According to Reinhardt, Spanish chroniclers made reference to the Inca practice of making offerings to the gods: not just statues, fine textiles, and ceramics, but also occasionally human sacrifices at ceremonial shrines (huacas) built high on mountain summits. It’s thought that human sacrifices of young girls and boys were a means of appeasing the Inca gods (Apus) during periods of irregular weather patterns, particularly drought. Drought was common in the wake of a volcanic eruption.

During those periods, the ground on summits would unfreeze sufficiently for the Incas to build their sites and bury their offerings. The altitude is one reason why various Inca mummified remains have been found in remarkable states of preservation.

Earlier discoveries included the remains of an Inca boy found by looters in the 1950s, as well as the frozen body of a young man in 1964 and that of  a young boy in 1985. Then Reinhardt and Zárate made their Ampato ascent in September 1995. They were stunned to spot a mummy bundle on the ice just below the summit and realized they were looking at the frozen face of a young girl. The body was surrounded by offerings for the Inca gods, including llama bones, small carved figurines, and bits of pottery. Juanita was wrapped in a colorful burial tapestry and wearing a feathered cap and alpaca shawl, all almost perfectly preserved. Reinhardt and Zárate subsequently found two more ice mummies (a young boy and girl) the following month, and yet another female mummy in December 1997.

Reconstructing the face of the Incan

Enlarge / Reconstructing the face of the Incan “ice maiden” took nearly 400 hours.

Oscar Nilsson

It was a bit of a struggle to get Juanita’s body down from the summit because it was so heavy, the result of its flesh being so thoroughly frozen. That’s also what makes it such an exciting archaeological find. The remains of meal of vegetables were in her well-reserved stomach, although DNA analysis from her hair showed that she also ate a fair amount of animal protein. That, and the high quality of her garments, suggested she came from a noble family, possibly from the city of Cusco.

There were also traces of coca and alcohol, likely administered before Juanita’s death—a common Inca practice when sacrificing children. A CT scan of her skull revealed that Juanita had died from a a sharp blow to the head, similar to the type of injury made by a baseball bat, causing a massive hemorrhage. This, too, was a common Inca sacrificial custom.

Nilsson was able to draw upon those earlier analyses for his reconstruction, since he needed to know things like her age, gender, weight, and ethnicity. He started with the CT scan of Juanita’s skull and used the data to 3D print a plastic replica of her head. He used wooden pegs on the bust to mark out the various measurements and added clay to mold the defining details of her face, drawing on clues from her nose, eye sockets, and teeth. The DNA indicated the likely color of her skin. “In Juanita’s case, I wanted her to look both scared and proud, and with a high sense of presence at the same time,” Nilsson told Live Science. “I then cast the face in silicone [using] real human hair [that I] inserted hair by hair.”

A forensic artist has given a 500-year-old Inca “ice maiden” a face Read More »

40%-of-us-electricity-is-now-emissions-free

40% of US electricity is now emissions-free

coal, Energy, hydroelectric, natural gas, nuclear power, renewable energy, Science, solar, Sustainability, Wind / /

Decarbonizing, but slowly —

Good news as natural gas, coal, and solar see the biggest changes.

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Image of electric power lines with a power plant cooling tower in the background.

Just before the holiday break, the US Energy Information Agency released data on the country’s electrical generation. Because of delays in reporting, the monthly data runs through October, so it doesn’t provide a complete picture of the changes we’ve seen in 2023. But some of the trends now seem locked in for the year: wind and solar are likely to be in a dead heat with coal, and all carbon-emissions-free sources combined will account for roughly 40 percent of US electricity production.

Tracking trends

Having data through October necessarily provides an incomplete picture of 2023. There are several factors that can cause the later months of the year to differ from the earlier ones. Some forms of generation are seasonal—notably solar, which has its highest production over the summer months. Weather can also play a role, as unusually high demand for heating in the winter months could potentially require that older fossil fuel plants be brought online. It also influences production from hydroelectric plants, creating lots of year-to-year variation.

Finally, everything’s taking place against a backdrop of booming construction of solar and natural gas. So, it’s entirely possible that we will have built enough new solar over the course of the year to offset the seasonal decline at the end of the year.

Let’s look at the year-to-date data to get a sense of the trends and where things stand. We’ll then check the monthly data for October to see if any of those trends show indications of reversing.

The most important takeaway is that energy use is largely flat. Overall electricity production year-to-date is down by just over one percent from 2022, though demand was higher this October compared to last year. This is in keeping with a general trend of flat-to-declining electricity use as greater efficiency is offsetting factors like population growth and expanding electrification.

That’s important because it means that any newly added capacity will displace the use of existing facilities. And, at the moment, that displacement is happening to coal.

Can’t hide the decline

At this point last year, coal had produced nearly 20 percent of the electricity in the US. This year, it’s down to 16.2 percent, and only accounts for 15.5 percent of October’s production. Wind and solar combined are presently at 16 percent of year-to-date production, meaning they’re likely to be in a dead heat with coal this year and easily surpass it next year.

Year-to-date, wind is largely unchanged since 2022, accounting for about 10 percent of total generation, and it’s up to over 11 percent in the October data, so that’s unlikely to change much by the end of the year. Solar has seen a significant change, going from five to six percent of the total electricity production (this figure includes both utility-scale generation and the EIA’s estimate of residential production). And it’s largely unchanged in October alone, suggesting that new construction is offsetting some of the seasonal decline.

Coal is being squeezed out by natural gas, with an assist from renewables.

Enlarge / Coal is being squeezed out by natural gas, with an assist from renewables.

Eric Bangeman/Ars Technica

Hydroelectric production has dropped by about six percent since last year, causing it to slip from 6.1 percent to 5.8 percent of the total production. Depending on the next couple of months, that may allow solar to pass hydro on the list of renewables.

Combined, the three major renewables account for about 22 percent of year-to-date electricity generation, up about 0.5 percent since last year. They’re up by even more in the October data, placing them well ahead of both nuclear and coal.

Nuclear itself is largely unchanged, allowing it to pass coal thanks to the latter’s decline. Its output has been boosted by a new, 1.1 Gigawatt reactor that come online this year (a second at the same site, Vogtle in Georgia, is set to start commercial production at any moment). But that’s likely to be the end of new nuclear capacity for this decade; the challenge will be keeping existing plants open despite their age and high costs.

If we combine nuclear and renewables under the umbrella of carbon-free generation, then that’s up by nearly 1 percent since 2022 and is likely to surpass 40 percent for the first time.

The only thing that’s keeping carbon-free power from growing faster is natural gas, which is the fastest-growing source of generation at the moment, going from 40 percent of the year-to-date total in 2022 to 43.3 percent this year. (It’s actually slightly below that level in the October data.) The explosive growth of natural gas in the US has been a big environmental win, since it creates the least particulate pollution of all the fossil fuels, as well as the lowest carbon emissions per unit of electricity. But its use is going to need to start dropping soon if the US is to meet its climate goals, so it will be critical to see whether its growth flat lines over the next few years.

Outside of natural gas, however, all the trends in US generation are good, especially considering that the rise of renewable production would have seemed like an impossibility a decade ago. Unfortunately, the pace is currently too slow for the US to have a net-zero electric grid by the end of the decade.

40% of US electricity is now emissions-free Read More »

injection-of-“smart-insulin”-regulates-blood-glucose-levels-for-one-week

Injection of “smart insulin” regulates blood glucose levels for one week

biochemistry, diabetes, glucose, health, insulin, Science / /

Sugary treat treatment —

Tests in animals show the material works like the body’s own system.

–

Image of a syringe above three drug vials

Enlarge / Smart insulin has the potential to make injections far less frequent.

People with type I diabetes have to inject themselves multiple times a day with manufactured insulin to maintain healthy levels of the hormone, as their bodies do not naturally produce enough. The injections also have to be timed in response to eating and exercise, as any consumption or use of glucose has to be managed.

Research into glucose-responsive insulin, or “smart” insulin, hopes to improve the quality of life for people with type I diabetes by developing a form of insulin that needs to be injected less frequently, while providing control of blood-glucose levels over a longer period of time.

A team at Zhejiang University, China, has recently released a study documenting an improved smart insulin system in animal models—the current work doesn’t involve any human testing. Their insulin was able to regulate blood-glucose levels for a week in diabetic mice and minipigs after a single subcutaneous injection.

“Theoretically, [smart insulin is] incredibly important going forward,” said Steve Bain, clinical director of the Diabetes Research Unit in Swansea University, who was not involved in the study. “It would be a game changer.”

Polymer cage

The new smart insulin is based on a form of insulin modified with gluconic acid, which forms a complex with a polymer through chemical bonds and strong electrostatic attraction. When insulin is trapped in the polymer, its signaling function is blocked, allowing a week’s worth of insulin to be given via a single injection without a risk of overdose.

Crucial to the “glucose responsive” nature of this system is the fact that the chemical structures of glucose and gluconic acid are extremely similar, meaning the two molecules bind in very similar ways. When glucose meets the insulin-polymer complex, it can displace some of the bound insulin and form its own chemical bonds to the polymer. Glucose binding also disrupts the electrostatic attraction and further promotes insulin release.

By preferentially binding to the polymer, the glucose is able to trigger the release of insulin. And the extent of this insulin release depends on how much glucose is present: between meals, when the blood-glucose level is fairly low, only a small amount of insulin is released. This is known as basal insulin and is needed for baseline regulation of blood sugar.

But after a meal, when blood-glucose spikes, much more insulin is released. The body can now regulate the extra sugar properly, preventing abnormally high levels of glucose—known as hyperglycemia. Long-term effects of hyperglycemia in humans include nerve damage to the hands and feet and permanent damage to eyesight.

This system mimics the body’s natural process, in which insulin is also released in response to glucose.

Better regulation than standard insulin

The new smart insulin was tested in five mice and three minipigs—minipigs are often used as an animal model that’s more physiologically similar to humans. One of the three minipigs received a slightly lower dose of smart insulin, and the other two received a higher dose. The lower-dose pig showed the best response: its blood-glucose levels were tightly controlled and returned to a healthy value after meals.

During treatment, the other two pigs had glucose levels that were still above the range seen in healthy animals, although they were greatly reduced compared to pre-injection levels. The regulation of blood-glucose was also tighter compared to daily insulin injections.

It should be noted, though, that the minipig with the best response also had the lowest blood-glucose levels before treatment, which may explain why it seemed to work so well in this animal.

Crucially, these effects were all long lasting—better regulation could be seen a week after treatment. And injecting the animals with the smart insulin didn’t result in a significant immune response, which can be a common pitfall when introducing biomaterials to animals or humans.

Don’t sugarcoat it

The study is not without its limitations. Although long-term glucose regulation was seen in the mice and minipigs examined, only a few animals were involved in the study—five mice and three minipigs. And of course, there’s always the risk that the results of animal studies don’t completely track over to clinical trials in humans. “We have to accept that these are animal studies, and so going across to humans is always a bit of an issue,” said Bain.

Although more research is required before this smart insulin system can be tested in humans, this work is a promising step forward in the field.

Nature Biomedical Engineering, 2023. DOI: 10.1038/s41551-023-01138-7

Ivan Paul is a freelance writer based in the UK, finishing his PhD in cancer research. He is on X @ivan_paul_.

Injection of “smart insulin” regulates blood glucose levels for one week Read More »

getting-to-the-bottom-of-how-red-flour-beetles-absorb-water-through-their-butts

Getting to the bottom of how red flour beetles absorb water through their butts

12 days of Christmas, agricultural sciences, animals, beetles, Biology, Biomechanics, genomes, Genomics, red flour beetle, Science / /

On the third day of Christmas —

A unique group of cells pumps water into the kidneys to help harvest moisture from the air.

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Who <em>doesn’t</em> thrill to the sight of a microscopic cross-section of a beetle’s rectum? You’re welcome.” src=”https://cdn.arstechnica.net/wp-content/uploads/2023/03/beetle-butt-TOP-800×536.jpg”></img><figcaption> <p><a data-height=Enlarge / Who doesn’t thrill to the sight of a microscopic cross-section of a beetle’s rectum? You’re welcome.

Kenneth Veland Halberg

There’s rarely time to write about every cool science-y story that comes our way. So this year, we’re once again running a special Twelve Days of Christmas series of posts, highlighting one science story that fell through the cracks in 2023, each day from December 25 through January 5. Today: red flour beetles can use their butts to suck water from the air, helping them survive in extremely dry environments. Scientists are honing in on the molecular mechanisms behind this unique ability.

The humble red flour beetle (Tribolium castaneum) is a common pantry pest feeding on stored grains, flour, cereals, pasta, biscuits, beans, and nuts. It’s a remarkably hardy creature, capable of surviving in harsh arid environments due to its unique ability to extract fluid not just from grains and other food sources, but also from the air. It does this by opening its rectum when the humidity of the atmosphere is relatively high, absorbing moisture through that opening and converting it into fluid that is then used to hydrate the rest of the body.

Scientists have known about this ability for more than a century, but biologists are finally starting to get to the bottom (ahem) of the underlying molecular mechanisms, according to a March paper published in the Proceedings of the National Academies of Science. This will inform future research on how to interrupt this hydration process to better keep red flour beetle populations in check, since they are highly resistant to pesticides. They can also withstand even higher levels of radiation than the cockroach.

There are about 400,000 known species of beetle roaming the planet although scientists believe there could be well over a million. Each year, as much as 20 percent of the world’s grain stores are contaminated by red flour beetles, grain weevils, Colorado potato beetles, and confused flour beetles, particularly in developing countries. Red flour beetles in particular are a popular model organism for scientific research on development and functional genomics. The entire genome was sequenced in 2008, and the beetle shares between 10,000 and 15,000 genes with the fruit fly (Drosophila), another workhorse of genetics research. But the beetle’s development cycle more closely resembles that of other insects by comparison.

Food security in developing nations is particularly affected by animal species like the red flour beetle which has specialized in surviving in extremely dry environments, granaries included, for thousands of years.

Enlarge / Food security in developing nations is particularly affected by animal species like the red flour beetle which has specialized in surviving in extremely dry environments, granaries included, for thousands of years.

Kenneth Halberg

The rectums of most mammals and insects absorb any remaining nutrients and water from the body’s waste products prior to defecation. But the red flour beetle’s rectum is a model of ultra-efficiency in that regard. The beetle can generate extremely high salt concentrations in its kidneys, enabling it to extract all the water from its own feces and recycle that moisture back into its body.

“A beetle can go through an entire life cycle without drinking liquid water,” said co-author Kenneth Veland Halberg, a biologist at the University of Copenhagen. “This is because of their modified rectum and closely applied kidneys, which together make a multi-organ system that is highly specialized in extracting water from the food that they eat and from the air around them. In fact, it happens so effectively that the stool samples we have examined were completely dry and without any trace of water.” The entire rectal structure is encased in a perinephric membrane.

Halberg et al. took took scanning electron microscopy images of the beetle’s rectal structure. They also took tissue samples and extracted RNA from lab-grown red flour beetles, then used a new resource called BeetleAtlas for their gene expression analysis, hunting for any relevant genes.

One particular gene was expressed sixty times more in the rectum than any other. Halberg and his team eventually honed in a group of secondary cells between the beetle’s kidneys and circulatory system called leptophragmata. This finding supports prior studies that suggested these cells might be relevant since they are the only cells that interrupt the perinephric membrane, thereby enabling critical transport of potassium chloride. Translation: the cells pump salts into the kidneys to better harvest moisture from its feces or from the air.

Model of the beetle's inside and how it extracts water from the air.

Enlarge / Model of the beetle’s inside and how it extracts water from the air.

Kenneth Halberg

The next step is to build on these new insights to figure out how to interrupt the beetle’s unique hydration process at the molecular level, perhaps by designing molecules that can do so. Those molecules could then be incorporated into more eco-friendly pesticides that target the red flour beetle and similar pests while not harming more beneficial insects like bees.

“Now we understand exactly which genes, cells and molecules are at play in the beetle when it absorbs water in its rectum. This means that we suddenly have a grip on how to disrupt these very efficient processes by, for example, developing insecticides that target this function and in doing so, kill the beetle,” said Halberg. “There is twenty times as much insect biomass on Earth than that of humans. They play key roles in most food webs and have a huge impact on virtually all ecosystems and on human health. So, we need to understand them better.”

DOI: PNAS, 2023. 10.1073/pnas.2217084120  (About DOIs).

Getting to the bottom of how red flour beetles absorb water through their butts Read More »

researchers-argue-back-and-forth-about-whether-we’ve-spotted-an-exomoon

Researchers argue back and forth about whether we’ve spotted an exomoon

astronomy, exomoons, exoplanets, kepler, Kepler telescope, Science / /

That’s no moon! —

Years after Kepler shut down, people are arguing over whether it spotted exomoons.

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Image of two planets orbiting together around a distant star.

In 2017, the astronomy world was abuzz at the announcement that exoplanet Kepler-1625b potentially had its own moon—an exomoon. This was the first hint anyone had seen of an exomoon, and was followed five years later by another candidate around the planet Kepler-1708b.

There are over five thousand exoplanets discovered so far, and we don’t know for certain whether any have moons orbiting, which is what made these announcements so exciting. Exomoons provide more potentially habitable areas in which we can search for extraterrestrial life, and the study of moons can be a valuable window into the formation of the host planet.

But there has been much debate about these exomoon candidates, with multiple groups combing through the data obtained from the Kepler and Hubble space telescopes.

The most recent paper on the topic, published by astronomers in Germany, has come to the conclusion that the exomoon candidates around Kepler-1625b and Kepler-1708b are unlikely. Previous work has also cast doubt on the exomoon candidate around Kepler-1625b.

This is not a clear cut case, though. David Kipping, the leader of the group that made both original discoveries, and assistant professor of astronomy at Columbia University, disagrees with the new analysis. He and his group are in the process of preparing a manuscript that responds to the latest publication.

A needle in a haystack

The most common method of detecting exoplanets is the transit method. This technique measures the brightness of a star, and looks for a small dip in brightness that corresponds to a planet transiting in front of the star.

Stellar photometry can be extended to look for exomoons, an approach pioneered by Kipping. As well as the main dip caused by the planet, if a moon is orbiting the planet you should be able to see an additional, smaller dip   caused by the moon also shielding some of the star’s light.

An example of what a transit detection of an exomoon might look like.

As moons are smaller they generate a smaller signal, making them more challenging to spot. But what makes this particular case even more challenging is that the host stars Kepler-1625 and Kepler-1708 aren’t that bright. This makes the light dip even fainter—in fact these systems   have to have large moons to be within the threshold of what the Kepler space telescope can detect.

Models, models, models

Until scientists get more data from James Webb, or future missions such as ESA’s PLATO launch, it’s all down to what they can do with the existing numbers.

“The aspects here that are relevant are how the data itself is processed, what physics you put in when you’re modelling that data, and then what possible false positive signals might be out there that could reproduce the sort of signal that you’re looking for,” Eamonn Kerins, senior lecturer in astronomy at the University of Manchester who was not involved with the study, told Ars. “I think this whole debate centers around those questions essentially,” he added.

One key phenomenon that needs accurate modelling is known as the stellar limb darkening effect. Stars, including our Sun, appear dimmer at their edge than at the centre due to effects of the stellar atmosphere. As this affects the apparent brightness of the star, it’s clearly important to understand in the context of searching for exomoons by measuring a star’s brightness.

“We have models for this, but we don’t really know exactly how a specific star behaves in terms of this stellar limb darkening effect,” said René Heller, lead author of the study and astrophysicist at the Max Planck Institute for Solar System Research, in an interview for Ars. How specific stars behave can be deduced, but this isn’t always trivial. By including improved models for stellar limb darkening, the authors found that they can explain signals previously attributed to an exomoon.

Data processing is also paramount, especially a type of processing known as detrending. This takes into account long-term variability in the brightness data that is caused by random stellar variation and instrument variability, among other things. The new research shows that the statistical outcome, moon or no moon, is extremely dependent on how you carry out this detrending.

What’s more, the authors say that the data obtained from the Hubble telescope, which is primarily where the claim for the moon around Kepler-1625b comes from, can’t be properly detrended and thus shouldn’t be relied on for exomoon searches.

Two sides

Until more data is obtained, this is likely to remain an ongoing scientific discussion with no definitive conclusion.

Kerins points out that Kipping and his team have been very measured in their announcements. “They’re very, very careful to not claim it as a cast-iron detection. They’ve done comprehensive testing of the data they’ve been given, and really I think the difference here is all about what physics you put in, how you process the data, and ultimately the fact that the Kepler data set is really on the edge of finding exomoons.”

Heller, though, remains unconvinced. “My impression is that in the Kepler data, we and also other teams have done what’s currently possible and there’s no compelling object that really sticks out.”

Moons far outnumber planets in our own Solar System—two hundred and ninety to eight to date—so it’s reasonable to assume that we will come across exomoons as we continue exploring the skies. “It would be quite extraordinary, I think, if we continue to go over the next few years and not find an exomoon,” said Kerins. “I think it can only be a matter of time.”

Nature Astronomy, 2023.  DOI: 10.1038/s41550-023-02148-w

Ivan Paul is a freelance writer based in the UK, finishing his PhD in cancer research. He is on Twitter @ivan_paul_.

Researchers argue back and forth about whether we’ve spotted an exomoon Read More »

watch-sand-defy-gravity-and-flow-uphill-thanks-to-“negative-friction”

Watch sand defy gravity and flow uphill thanks to “negative friction”

12 days of Christmas, collective motion, engineering, fluid dynamics, granular flow, granular materials, Physics, Science / /

On the second day of Christmas —

Applying magnetic forces to single iron oxide-coated particles spurs strange collective motion.

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There’s rarely time to write about every cool science-y story that comes our way. So this year, we’re once again running a special Twelve Days of Christmas series of posts, highlighting one science story that fell through the cracks in 2023, each day from December 25 through January 5. Today: how applying magnetic forces to individual “micro-roller” particles spurs collective motion, producing some pretty counter-intuitive results.

Engineering researchers at Lehigh University have discovered that sometimes sand can actually flow uphill.

Enlarge / Engineering researchers at Lehigh University have discovered that sometimes sand can actually flow uphill.

Lehigh University

We intuitively understand that the sand pouring through an hourglass, for example, forms a neat roughly pyramid-shaped pile at the bottom, in which the grains near the surface flow over an underlying base of stationary particles. Avalanches and sand dunes exhibit similar dynamics. But scientists at Lehigh University in Pennsylvania have discovered that applying a magnetic torque can actually cause sand-like particles to collectively flow uphill in seeming defiance of gravity, according to a September paper published in the journal Nature Communications.

Sand is pretty fascinating stuff from a physics standpoint. It’s an example of a granular material, since it acts both like a liquid and a solid. Dry sand collected in a bucket pours like a fluid, yet it can support the weight of a rock placed on top of it, like a solid, even though the rock is technically denser than the sand. So sand defies all those tidy equations describing various phases of matter, and the transition from flowing “liquid” to a rigid “solid” happens quite rapidly. It’s as if the grains act as individuals in the fluid form, but are capable of suddenly banding together when solidarity is needed, achieving a weird kind of “strength in numbers” effect.

Nor can physicists precisely predict an avalanche. That’s partly because of the sheer number of grains of sand in even a small pile, each of which will interact with several of its immediate neighboring grains simultaneously—and those neighbors shift from one moment to the next. Not even a supercomputer can track the movements of individual grains over time, so the physics of flow in granular media remains a vital area of research.

But grains of sand that collectively flow uphill? That is simply bizarre behavior. Lehigh University engineer James Gilchrist manages the Laboratory for Particle Mixing and Self-Organization and stumbled upon this odd phenomenon while experimenting with “micro-rollers”: polymer particles coated in iron oxide (a process called micro-encapsulation). He was rotating a magnet under a vial of micro-rollers one day and noticed they started to pile uphill. Naturally he and his colleagues had to investigate further.

For their experiments, Gilchrist et al. attached neodymium magnets to a motorized wheel at 90-degree intervals, alternating the outward facing poles. The apparatus also included a sample holder and a USB microscope in a fixed position. The micro-rollers were prepared by suspending them in a glass vial containing ethanol and using a magnet to separate them from dust or any uncoated particles. Once the micro-rollers were clean, they were dried, suspended in fresh ethanol, and loaded onto the sample holder. A vibrating motor agitated the samples to produce flattened granular beds, and the motorized wheel was set in motion to apply magnetic torque. A gaussmeter measured the magnetic field strength relative to orientation.

Uphill granular flow of microrobotic microrollers. Credit: Lehigh University.

The results: each micro-roller began to rotate in response to the magnetic torque, creating pairs that briefly formed and then split, and increasing the magnetic force increased the particle cohesion. This in turn gave the micro-rollers more traction and enabled them to move more quickly, working in concert to counterintuitively flow uphill. In the absence of that magnetic torque, the miro-rollers flowed downhill normally. The torque-induced action was so unexpected that the researchers coined a new term to describe it: a “negative angle of repose” caused by a negative coefficient of friction.

“Up until now, no one would have used these terms,” said Gilchrist. “They didn’t exist. But to understand how these grains are flowing uphill, we calculated what the stresses are that cause them to move in that direction. If you have a negative angle of repose, then you must have cohesion to give a negative coefficient of friction. These granular flow equations were never derived to consider these things, but after calculating it, what came out is an apparent coefficient of friction that is negative.”

It’s an intriguing proof of principle that could one day lead to new ways to control how substances mix or separate, as well as potential swarming microrobotics applications. The scientists have already started building tiny staircases with laser cutters and videotaping the micro-rollers climbing up and down the other. One micro-roller can’t overcome the height of each step, but many working collectively can do so, per Gilchrist.

DOI: Nature Communications, 2023. 10.1038/s41467-023-41327-1  (About DOIs).

Listing image by Lehigh University

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science-lives-here:-take-a-virtual-tour-of-the-royal-institution-in-london

Science lives here: take a virtual tour of the Royal Institution in London

chemistry, Humphrey Davy, Michael Faraday, Physics, Royal Institution, Science, Science communication, science museums, science outreach / /

a special kind of place —

No less than 14 Nobel laureates have conducted ground-breaking research at the Institution.

–

The exterior of the Royal Institution

Enlarge / The Royal Institution was founded in 1799 and is still located in the same historic building at 21 Albermarle Street in London.

If you’re a fan of science, and especially science history, no trip to London is complete without visiting the Royal Institution, browsing the extensive collection of artifacts housed in the Faraday Museum and perhaps taking in an evening lecture by one of the many esteemed scientists routinely featured—including the hugely popular annual Christmas lectures. (The lecture theater may have been overhauled to meet the needs of the 21st century but walking inside still feels a bit like stepping back through time.) So what better time than the Christmas season to offer a virtual tour of some of the highlights contained within the historic walls of 21 Albemarle Street?

The Royal Institution was founded in 1799 by a group of leading British scientists. This is where Thomas Young explored the wave theory of light (at a time when the question of whether light was a particle or wave was hotly debated); John Tyndall conducted experiments in radiant heat; Lord Rayleigh discovered argon; James Dewar liquified hydrogen and invented the forerunner of the thermos; and father-and-son duo William Henry and William Lawrence Bragg invented x-ray crystallography.

No less than 14 Nobel laureates have conducted ground-breaking research at the Institution over the ensuing centuries, but the 19th century physicist Michael Faraday is a major focus. In fact, there is a full-sized replica of Faraday’s magnetic laboratory—where he made so many of his seminal discoveries—in the original basement room where he worked, complete with an old dumbwaiter from when the room was used as a servant’s hall. Its arrangement is based on an 1850s painting by one of Faraday’s friends and the room is filled with objects used by Faraday over the course of his scientific career.

The son of an English blacksmith, Faraday was apprenticed to a bookbinder at 14, a choice of profession that enabled him to read voraciously, particularly about the natural sciences. In 1813, a friend gave Faraday a ticket to hear the eminent scientist Humphry Davy lecture on electrochemistry at the Royal Institution. He was so taken by the presentation that he asked Davy to hire him. Davy initially declined, but shortly afterwards sacked his assistant for brawling, and hired Faraday to replace him. Faraday helped discover two new compounds of chlorine and carbon in those early days, learned how to make his own glass, and also invented an early version of the Bunsen burner, among other accomplishments.

  • Painting of the Royal Institution circa 1838, by Thomas Hosmer Shepherd.

    Public domain

  • Michael Faraday giving one of his famous Christmas lectures.

    Royal Institution

  • A Friday Evening Discourse at the Royal Institution; Sir James Dewar on Liquid Hydrogen, by Henry Jamyn Brooks, 1904

    Public domain

  • The Lecture Theatre as it looks today

  • Faraday’s magnetic laboratory in the basement of the Royal Institution

    Royal Institution

  • A page from one of Faraday’s notebooks

    Royal Institution

Faraday was particularly interested in the new science of electromagnetism, first discovered in 1820 by Hans Christian Ørsted. In 1821, Faraday discovered electromagnetic rotation—which converts electricity into mechanical motion via a magnet—and used that underlying principle to build the first electric motor. The Royal Institution’s collection includes the only surviving electric motor that Faraday built: a wire hanging down into a glass vessel with a bar magnet at the bottom. Faraday would fill the glass with mercury (an excellent conductor), then connect his apparatus to a battery, which sent electricity through the wire in turn. This created a magnetic field around the wire, and that field’s interaction with the magnet at the bottom of the glass vessel would cause the wire to rotate in a clockwise direction.

Ten years later, Faraday succeeded in showing that a jiggling magnet could induce an electrical current in a wire. Known as the principle of the dynamo, or electromagnetic induction, it became the basis of electric generators, which convert the energy of a changing magnetic field into an electrical current. One of Faraday’s induction rings is on display, comprised of coils of wire wound on opposites sides of the ring, insulated with cotton. Passing electricity through one would briefly induce a current in the other. Also on display is one of Faraday’s generators: a bar magnet and a simple cotton-insulated tube wound with a coil of wire.

In yet another experiment, Faraday placed a piece of heavy leaded glass on a magnet’s poles to see how light would be affected by a magnet. He passed light through the glass and when he turned on the electromagnet, he found that the polarization of the light had rotated slightly. This is called the magneto-optical effect (or Faraday effect), demonstrating that magnetism is related not just to electricity, but also to light. The Royal Institution has a Faraday magneto-optical apparatus with which he “at last succeeded in… magnetizing a ray of light.” In 1845, Faraday discovered diamagnetism, a property of certain materials that give them a weak repulsion from a magnetic field.

  • Equipment used by Faraday to make glass

  • Drawing of Faraday’s electromagnetic rotation experiment.

    Public domain

  • Faraday motor (electric magnetic rotation apparatus), 1822

    Royal Institution

  • Faraday’s dynamo (generator), October 1831

    Royal Institution

  • Faraday’s induction ring

    Royal Institution

  • Faraday’s magneto-optical apparatus

    Royal Institution

  • One of Faraday’s iron filings (1851) showing magnetic lines of force

    Royal Institution

  • Faraday’s original gold colloids are still active well over a century later

  • Shining a laser light through a gold colloid mixture produces the Faraday-Tyndall Effect.

    Royal Institution

Faraday concluded from all those experiments that magnetism was the center of an elaborate system of invisible curved tentacles (electric lines of force) that spread throughout space like the roots of trees branching through the earth. He was able to demonstrate these lines of force by coating sheets of paper with wax and placing them on top of bar magnets. When he sprinkled powdery iron filings on the surface, those iron filings were attracted to the magnets, revealing the lines of force. And by gently heating the waxed paper, he found that the iron filings would set on the page, preserving them.

In the 1850s, Faraday’s interests turned to the properties of light and matter. He made his own gold slides and shone light through them to observe the interactions. But commercial gold leaf, typically made by hammering the metal into thin sheets, was still much too thick for his purposes. So Faraday had to make his own via chemical means, which involved washing gold films. The resulting faint red fluid intrigued Faraday and he kept samples in bottles, shining light though the fluids and noting an intriguing “cone effect” (now known as the Faraday-Tyndall Effect)—the result of particles of gold suspended in the fluid that were much too small to see.

One might consider Faraday an early nanoscientist, since these are now known as metallic nanoparticles. The Institution’s current state-of-the-art nanotechnology lab is appropriately located right across from Faraday’s laboratory in the basement. And even though Faraday’s gold colloids are well over a century old, they remain optically active. There’s no way to figure out why this might be the case without opening the bottles but the bottles are too valuable as artifacts to justify doing that.

Plenty of other scientific luminaries have their work commemorated in the Royal Institution’s collection, including that of Faraday’s mentor, Humphry Davy, who discovered the chemical elements barium, strontium, sodium, potassium, calcium and magnesium. Early in the 19th century, there were several explosions in northern England’s coal mines caused by the lamps used by the miners accidentally igniting pockets of flammable gas. Davy was asked to come up with a safer lighting alternative.

  • Schematic for the Davy lamp

    Public domain

  • Humphry Davy’s miner’s lamp (left) displayed alongside his rival George Stephenson’s lamps

    Royal Institution

  • Schematic for John Tyndall’s radiant heat apparatus

    Royal Institution

  • Tyndall’s radiant heat tube

    Royal Institution

  • Tyndall’s blue sky tube, 1869

    Royal Institution

  • Title page of Tyndall’s Heat: A Mode of Motion

    Paul Wilkinson/Royal Institution

After experimenting with several prototypes, Davy finally settled on a simple design in 1815 consisting of a “chimney” made of wire gauze to enclose the flame. The gauze absorbed heat to prevent igniting flammable gas but still let through sufficient light. The invention significantly reduced fatalities among coal miners. Davy had a rival, however in a mining engineer named George Stephenson who independently developed his own design that was remarkably similar to Davy’s. Samples of both are displayed in the Institution’s lower ground floor “Light Corridor.” Davy’s lamp would ultimately triumph, while Stephenson later invented the first steam-powered railroad locomotive.

Atmospheric physicist John Tyndall was a good friend of Faraday and shared the latter’s gift for public lecture demonstrations. His experiments on radiation and the heat-absorptive power of gases were undertaken with an eye toward developing a better understanding of the physics of molecules.  Among the Tyndall artifacts housed in the Royal Institution is his radiant heat tube, part of an elaborate experimental apparatus he used to measure the extent to which infrared radiation was absorbed and emitted by various gases filling its central tube. By this means he concluded that water vapor absorbs more radiant heat than atmospheric gases, and hence that vapor is crucial for moderating Earth’s climate via a natural “greenhouse effect.”

The collection also includes Tyndall’s “blue sky apparatus,” which the scientist used to explain why the sky is blue during the day and takes on red hues at sunset—namely, particles in the Earth’s atmosphere scatter sunlight and blue light is scattered more strongly than red light. (It’s the same Faraday-Tyndall effect observed when shining light through Faraday’s gold colloids.)

  • James Dewar in the Royal Institution, circa 1900

    Public domain

  • A Dewar flask

    Royal Institution

  • The x-ray spectrometer developed by William Henry Bragg.

    Royal Institution

  • Bragg’s rock salt model

On Christmas Day, 1892, James Dewar exhibited his newly invented Dewar flask at the Royal Institution for the first time, which he used for his cryogenic experiments on liquefying gases. Back in 1872, Dewar and Peter Tait had built a vacuum-insulated vessel to keep things warm, and Dewar adapted that design for his flask, designed to keep things cold—specifically cold enough to maintain the extremely low temperatures at which gases transitioned into liquid form. Dewar failed to patent his invention, however; the patent eventually went to the Thermos company in 1904, which rebranded the product to keep liquids hot as well as cold.

As for William Henry Bragg, he studied alpha, beta, and gamma rays early in his career and hypothesized that both gamma rays and x-rays had particle-like properties. This was bolstered by Max Von Laue‘s Nobel Prize-winning discovery that crystals could diffract x-rays. Bragg and his son, William Lawrence—then a student at Trinity College Cambridge—began conducting their own experiments. Bragg pere invented a special “ionization spectrometer,” in which a crystal could be rotated to precise angles so that the different scattering patterns of x-rays could be measured. The pair used the instrument to determine the structure of crystals and molecules, winning the 1915 Nobel Prize in Physics for their efforts. That spectrometer, the prototype of today’s x-ray diffractometers, is still housed in the Royal Institution, as well as their model of the atomic structure of rock salt.

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