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My companions scanned the treetops with binoculars and a thermal-imaging monocular. I stared at the branches and leaves, pretending I knew what to look for. It was a cool June evening just before sunset on a village road on Langkawi Island, Malaysia.

“There’s one! Up there,” one of the biologists called out. I squinted at the spot, about five meters up the tree trunk, and saw only a brown knob speckled with gray. Where? Then the knob stirred. Its top edge rose and turned, and I was staring into a pair of bulging eyes set on a small head with a short snout.

My first colugo. The size of a house cat, colugos are nocturnal mammals that live in trees. Colugos are also called “flying lemurs,” which is a misnomer because they cannot fly and they are not lemurs. A colugo has a cape of skin that stretches from its neck to the tips of its four limbs and tail. That skin, furry on top, helps colugos glide far and hide well in the canopy.

“Wait … Oh, it has a baby!” called zoologist Priscillia Miard of Universiti Sains Malaysia in Penang and leader of that evening’s search. She passed me her binoculars as the team discussed the identity of this colugo.

A tiny head popped out from beneath the mother’s fur, like a child peering out from under a blanket. Baby colugos cling to their mother’s furless undersides until about age 6 months, nursing on nipples near mom’s armpits.

I had seen two colugos just 15 minutes into our search!

The mother colugo lifted her tail. “It’s pooping,” said Miard, without the slightest note of concern that we were standing right below. Miard later told me that colugo feces are like dried lentils — nothing messy.

For an animal that is the closest living relative to all primates, having branched off about 80 million years ago, colugos remain a big mystery (SN: 9/3/16, p. 17). Today, the two living species of colugos are found only in Southeast Asia, though recent studies suggest that two is an imperfect count. Miard and other scientists have begun to upend what little knowledge exists about these mammals, revealing how colugos communicate and how they glide more than the length of a football field.

Into the night

Colugos popped unexpectedly into Miard’s life three years ago. The then 28-year-old French researcher had spent five years in Borneo studying nocturnal primates, including tarsiers and slow lorises. In 2017, Miard visited Langkawi, famous for its beaches and paddy fields, where she saw colugos “everywhere” — in orchards, on golf courses, at resorts and along well-traveled village roads. Because colugos were abundant and easy to find and observe in Langkawi, Miard pivoted to study them. In August, she successfully defended her Ph.D. thesis at Universiti Sains Malaysia for her research on colugo ecology.

But as I stood by her side looking up, Miard did not mention her Ph.D. She focused on the mother colugo — now a few dried lentils lighter — which seemed ready to start her night. The colugo climbed to the far end of a branch and turned her head toward the road. Then she leaped.

The colugo spun around, stretched her legs and tail, and glided like a magic carpet across the road to another tree trunk. Then she hopped, hopped, hopped up the tree into the leaves and out of sight.

She glided to four other trees over the next 15 minutes. By then, Miard and her teammates — biologists Muhammad Fizri bin Ahmad Zubir and Célia Lacomme — had recognized the mother colugo’s fur coloration. They had been following her for some time, naming her “Batwoman” because, months ago, locals thought the researchers were looking into the trees for bats.

Streetlights and passing cars and motorcycles lit the road, but a few meters away, the trees were dark. Miard and Lacomme switched on their red-light head lamps to illuminate the treetops. Something moved on a nearby tree trunk. Another colugo! Miard pointed her camera, saw testicles and announced that the colugo was male.

Master gliders

All colugos are master gliders, considered among the best of the 60-odd species of mammals that can glide. One Sunda colugo (Galeopterus variegatus) was recorded gliding 145 meters, almost the length of three Olympic swimming pools.

That sustained glide was reported in 2011 in the Journal of Experimental Biology by Gregory Byrnes, a biologist at Siena College in Loudonville, N.Y., and colleagues. At the time, most researchers assumed gliding was an energy-efficient way for colugos to travel. Byrnes’ team tested that idea by gluing data loggers onto wild Sunda colugos in Singapore and recording almost 260 glides among four individuals.

Sunda colugos often climb before gliding. In the study, a Sunda colugo could climb a total of 320 meters and glide 1,342 meters in one night. “No one ever took into consideration that in order to glide, you’ve got to climb,” Byrnes says. His team fed colugo data into metabolic models of other tree-dwelling mammals to estimate how much energy colugos expend to both glide and climb. When climbing is included as part of gliding behavior, and in forests where treetops overlap, a colugo could save energy crawling through the canopy rather than gliding, he says.

The “big advantage” of gliding is that it saves colugos time, Byrnes says. Gliding lets an animal cross open space in a few seconds so that it can spend more time feeding or traveling even farther, he says.

Colugos pull off those long-distance glides with their gliding skin, known as a patagium. While other gliders like flying squirrels have a patagium that stretches to the hind feet, a colugo’s patagium continues all the way to the tip of the tail. A more expansive patagium gives a colugo extra “wing area,” which lifts and slows the animal, allowing a gentler descent than other gliders, Byrnes says. The extra skin also helps the animal glide far.

And there is more to the patagium than skin and fur. Byrnes and his collaborators have found that the thin patagium is rich in muscles, and some parts are stiffer than others. A colugo may be able to flex those muscles to change the shape and stiffness of its patagium and thereby adjust its aerodynamics midair. Understanding the gliding biomechanics of colugos might help in the design of robotics and wing technology, Byrnes says.

That evening in Langkawi, Batwoman glided down the road, across the road and up the road. Never a sound. Once, she was gliding straight toward a tree, and just before impact, she turned, cut a sharp arc and landed on the next trunk. Wow.

High talk

When Batwoman reached her fifth tree of the night, another colugo swooped in from the dark and hopped up the trunk toward her.

Colugos were once thought to be solitary animals, Miard says. Social interactions were brief and rarely seen. But newer observations by Miard and others suggest that colugos form loose social groups of females or a mother and her offspring — even those that are weaned. Miard has seen up to six colugos in a tree. Males, though, seem to travel alone, joining groups of females only temporarily.

Miard trained her camera on the newcomer, which passed by Batwoman and continued into the canopy. Not a glance. Miard looked disappointed. “Oh no, he didn’t even say hi.”

To my ear, Batwoman hasn’t made a sound. But she may have been calling in ultrasound, inaudible to humans. Miard and colleagues discovered ultrasound calls from colugos, reporting the finding in 2019 in Bioacoustics. A microphone picked up the ultrasound signals during a bat survey, and Miard tracked the source to colugos. Many nocturnal animals, including bats, tarsiers and slow lorises, communicate in ultrasound, probably to avoid detection by predators. Colugos likely do the same. In November, Miard and colleagues will play the ultrasound calls in the field and listen for colugo responses.

It’s 8:15 p.m., dinnertime. Batwoman crawled into the thick foliage and gingerly pulled some leaves for a sniff. Miard explained that colugos eat mostly leaves. Batwoman shoved some leaves into her mouth and began to chew. Fizri and Lacomme recorded the observations on a behavior checklist on their smartphones.

“Wait, the baby is trying to eat leaves,” said Miard, looking through the binoculars. Lacomme shined her red-light head lamp at Batwoman. The baby colugo reached out from under its mother, tugged a few small leaves and tried to nibble them. Maybe the baby is learning what to eat from its mother, Miard said. It was too dim for me to tell if the baby actually ate the leaves. Lacomme’s red-light head lamp wasn’t bright enough. White light might have offered a better view.

But Miard won’t shine white light on nocturnal mammals. “When we use white light on colugos, they freeze, but not when we use red light,” she told me later. The freezing, she says, is a sign that white light disturbs the nocturnal mammals.

Miard’s concern makes sense. White light, which is commonly used in nocturnal animal studies, can quickly saturate the sensitive optic cells in nocturnal animals’ eyes and cause temporary blindness, says primatologist Amanda Melin of the University of Calgary in Canada. “These moments of blindness are likely disorienting and potentially harmful,” Melin says. “Red light is likely far less disruptive as it will be much lower intensity” than white light.

Eager pursuit

Around 9 p.m., another colugo glided in and joined Batwoman on a tree. This one seemed more interested than the last; he poked Batwoman and bit her sides. The newcomer, a male, wanted to mate, Miard said. But every time he got close, Batwoman pulled away.

Miard clutched her camera tight. Colugo romance makes prized footage. Gazing into the canopy, Miard backed away from the tree and onto the road — into the path of an oncoming car that just managed to stop before hitting her.

“F—, we are going to miss the most important part. We know they are going to make babies, but I can’t see them,” Miard said. She turned to Fizri: “Where’s the thermal camera?”

Minutes later, Miard spotted the colugos near the top of the tree. “You are really lucky,” she told me. “Many exciting things tonight.”

Batwoman continued to test the male, which I decided to name “Eager.” She glided to another tree, then another and yet another with Eager close behind. The colugos lingered on one tree. Miard sat by the road, camera in hand, eyes on Batwoman.

“Come on guys…. Please let him do it, please … Batwoman,” Miard muttered.

Our small group piqued the curiosity of locals. A couple, standing at the porch of a nearby house, watched us for about 10 minutes, then came over. “It’s a kubong,” Fizri told them, giving the local Malay name for colugo.

The couple knew the name but not the animal. They thought colugos lived only in forests. “Does it eat fruit? Is it like a bat?” they asked in hushed tones. Fizri lowered his smartphone and began to explain colugo ecology. The opportunity to talk colugo with local residents and correct misconceptions is one of the reasons Miard likes to study colugos in villages.

Colugo conservation

Perhaps because they are nocturnal and well camouflaged, colugos live hidden in plain sight. Zoologist Dzulhelmi Nasir, now with the Malaysian Palm Oil Board, has studied colugos in Borneo. Most locals have never heard of colugos, he says. People often confuse the animals with flying squirrels or a giant fruit bat called kluang in Malay.

Confusion or misconceptions about the colugos can be deadly for the animals. In parts of Malaysia, orchard and plantation owners see colugos as fruit pests and kill them, Miard told me. But colugos rarely eat fruits and flowers, according to a study published in 2006 in Biodiversity & Conservation, as well as Miard’s own unpublished research. Fortunately, here in Langkawi, there are few commercial orchards, and locals leave colugos alone.

But across Southeast Asia, colugos are losing their forest homes to agriculture and development. The region lost 293,000 square kilometers of forest from 2000 to 2014, an area about the size of Arizona, according to a 2018 report in Nature Geoscience.

On the International Union for Conservation of Nature’s Red List of Threatened Species, the Sunda colugo and the Philippine colugo (Cynocephalus volans) are categorized as “least concern” for risk of extinction. The Sunda colugo, in particular, with its wide distribution from Vietnam to Indonesia, is unlikely to be threatened.

But that assessment might be too rosy. Those two species may actually be eight, or as many as 14, based on genetic evidence reported in 2016 in Science Advances. If so, instead of the Sunda colugo being one widely distributed species, there are several colugo species confined to smaller areas that may be more susceptible to local extinction.

Zoologists had always noted that colugos look different across Southeast Asia. By the 1950s, about 20 species and subspecies were recognized based on physical differences. But zoologists decided to simplify things and lump all subspecies into two species, says geneticist Victor Mason, an author of the 2016 report, who studied colugo phylogeny at Texas A&M University in College Station.

Mason and colleagues looked for signs of species diversity hidden in the genetic makeup of colugos, a task that required samples of colugo DNA from across Southeast Asia. The researchers turned to museum specimens in Singapore and the United States. “There’s hundreds of colugo skulls just sitting in drawers in tiny boxes collecting dust” amassed more than a century ago by European explorers, says Mason, now at the University of Bern’s Institute of Cell Biology in Switzerland.

Using DNA from the museum specimens, Mason and colleagues found up to 14 colugo groups with significant genetic differences. More work is needed to weigh these differences and review the diversity of colugo species. And more surveys of colugo populations and their whereabouts are needed, Miard says, to reliably tell if and where colugos are threatened.

The good news is that colugos appear to adapt well to forested human environments, including the villages in Langkawi. The animals feed on the leaves of five to seven different trees nightly, Dzulhelmi says based on his studies in Langkawi and Borneo. He says that if a township could plant enough trees in gardens, parks and zoos to support free-living colugos, locals could see and learn about the animals and appreciate them.

After 50 minutes of courtship, Eager the male colugo has given up. Batwoman glided back up the road — with four humans on her tail — and began feeding again. We spotted a few more colugos that night, but we stayed close to Batwoman.

Around 11 p.m., Batwoman was still plucking leaves. Suddenly, I felt the air brush my hair — a colugo glided past me to land on a tree about three meters away. I moved in for a closer look at the only colugo I spotted before my guides. But it began to rain, and we ran for shelter.

The next morning, we moved our survey to a leafy resort on the island. In two hours, we found 17 colugos, all hugging trees, motionless in the daylight. I spotted two before Miard did and tried to hide my glee. But the thrill was not mine alone. Soon after we found the 11th colugo, Miard couldn’t hold it in any longer: “I love colugos!”

In the film The Martian, astronaut Mark Watney (played by Matt Damon) survives being stranded on the Red Planet by farming potatoes in Martian dirt fertilized with feces.

Future Mars astronauts could grow crops in dirt to avoid solely relying on resupply missions, and to grow a greater amount and variety of food than with hydroponics alone (SN: 11/4/11). But new lab experiments suggest that growing food on the Red Planet will be a lot more complicated than simply planting crops with poop (SN: 9/22/15).

Researchers planted lettuce and the weed Arabidopsis thaliana in three kinds of fake Mars dirt. Two were made from materials mined in Hawaii or the Mojave Desert that look like dirt on Mars. To mimic the makeup of the Martian surface even more closely, the third was made from scratch using volcanic rock, clays, salts and other chemical ingredients that NASA’s Curiosity rover has seen on the Red Planet (SN: 1/31/19). While both lettuce and A. thaliana survived in the Marslike natural soils, neither could grow in the synthetic dirt, researchers report in the upcoming Jan. 15 Icarus.

“It’s not surprising at all that as you get [dirt] that’s more and more accurate, closer to Mars, that it gets harder and harder for plants to grow in it,” says planetary scientist Kevin Cannon of the Colorado School of Mines in Golden, Colo., who helped make the synthetic Mars dirt but wasn’t involved in the new study.

Soil on Earth is full of microbes and other organic matter that helps plants grow, but Mars dirt is basically crushed rock. The new result “tells you that if you want to grow plants on Mars using soil, you’re going to have to put in a lot of work to transform that material into something that plants can grow in,” Cannon says.

Biochemist Andrew Palmer and colleagues at the Florida Institute of Technology in Melbourne planted lettuce and A. thaliana seeds in imitation Mars dirt under controlled lighting and temperature indoors, just as astronauts would on Mars. The plants were cultivated at 22° Celsius and about 70 percent humidity.

Seeds of both species germinated and grew in dirt mined from Hawaii or the Mojave Desert, as long as the plants were fertilized with a cocktail of nitrogen, potassium, calcium and other nutrients. No seeds of either species could germinate in the synthetic dirt, so “we would grow up plants under hydroponic-like conditions, and then we would transfer them” to the artificial dirt, Palmer says. But even when given fertilizer, those seedlings died within a week of transplanting.

Palmer’s team suspected that the problem with the synthetic Mars dirt was its high pH, which was about 9.5. The two natural soils had pH levels around 7. When the researchers treated the synthetic dirt with sulfuric acid to lower the pH to 7.2, transplanted seedlings survived an extra week but ultimately died.

The team also ran up against another problem: The original synthetic dirt recipe did not include calcium perchlorate, a toxic salt that recent observations suggest make up to about 2 percent of the Martian surface. When Palmer’s team added it at concentrations similar to those seen on Mars, neither lettuce nor A. thaliana grew at all in the dirt.

“The perchlorate is a major problem” for Martian farming, says Edward Guinan, an astrobiologist at Villanova University in Pennsylvania who was not involved in the work. But calcium perchlorate may not have to be a showstopper. “There are bacteria on Earth that enjoy perchlorates as a food,” Guinan says. As the microbes eat the salt, they give off oxygen. If these bacteria were taken from Earth to Mars to munch on perchlorates in Martian dirt, Guinan imagines that the organisms could not only get rid of a toxic component of the dirt, but perhaps also help produce breathable oxygen for astronauts.

What’s more, the exact treatment required to make Martian dirt farmable may vary, depending on where astronauts make their homestead. “It probably depends where you land, what the geology and chemistry of the soil is going to be,” Guinan says.

To explore how that variety might affect future agricultural practices, geochemist Laura Fackrell of the University of Georgia in Athens and colleagues mixed up five new types of faux Mars dirt. The recipes for these fake Martian materials, also reported in the Jan. 15 Icarus, are based on observations of Mars’ surface from the Curiosity, Spirit and Opportunity rovers, as well as NASA’s Mars Global Surveyor spacecraft and Mars Reconnaissance Orbiter.

Each new artificial Mars dirt represents a mix of materials that could be found or made on the Red Planet. One is designed to represent the average composition across Mars, similar to the synthetic material created by Cannon’s team. The other four varieties have slightly different makeups, such as dirt that is particularly rich in carbonates or sulfates. This collection “expands the palette of what we have available” as test-beds for agricultural experiments, Fackrell says.

She’s now using her stock to run preliminary plant growth experiments. So far, a legume called moth bean, which has similar nutritional content to a soybean but is more drought resistant, has grown the best. “But they’re not necessarily super healthy,” Fackrell says. Future experiments could explore what nutrient cocktails help plants survive in the various fake Martian terrains. But this much is clear, Fackrell says: “It’s not quite as easy as it looks in The Martian.”

When one of Hye-Sook Park’s experiments goes well, everyone nearby knows. “We can hear Hye-Sook screaming,” she’s heard colleagues say.

It’s no surprise that she can’t contain her excitement. She’s getting a closeup look at the physics of exploding stars, or supernovas, a phenomenon so immense that its power is difficult to put into words.

Rather than studying these explosions from a distance through telescopes, Park, a physicist at Lawrence Livermore National Laboratory in California, creates something akin to these paroxysmal blasts using the world’s highest-energy lasers.

About 10 years ago, Park and colleagues embarked on a quest to understand a fascinating and poorly understood feature of supernovas: Shock waves that form in the wake of the explosions can boost particles, such as protons and electrons, to extreme energies.

“Supernova shocks are considered to be some of the most powerful particle accelerators in the universe,” says plasma physicist Frederico Fiuza of SLAC National Accelerator Laboratory in Menlo Park, Calif., one of Park’s collaborators.

Some of those particles eventually slam into Earth, after a fast-paced marathon across cosmic distances. Scientists have long puzzled over how such waves give energetic particles their massive speed boosts. Now, Park and colleagues have finally created a supernova-style shock wave in the lab and watched it send particles hurtling, revealing possible new hints about how that happens in the cosmos.

Bringing supernova physics down to Earth could help resolve other mysteries of the universe, such as the origins of cosmic magnetic fields. And there’s a more existential reason physicists are fascinated by supernovas. These blasts provide some of the basic building blocks necessary for our existence. “The iron in our blood comes from supernovae,” says plasma physicist Carolyn Kuranz of the University of Michigan in Ann Arbor, who also studies supernovas in the laboratory. “We’re literally created from stars.”

Lucky star

As a graduate student in the 1980s, Park worked on an experiment 600 meters underground in a working salt mine beneath Lake Erie in Ohio. Called IMB for Irvine-Michigan-Brookhaven, the experiment wasn’t designed to study supernovas. But the researchers had a stroke of luck. A star exploded in a satellite galaxy of the Milky Way, and IMB captured particles catapulted from that eruption. Those messengers from the cosmic explosion, lightweight subatomic particles called neutrinos, revealed a wealth of new information about supernovas.

But supernovas in our cosmic vicinity are rare. So decades later, Park isn’t waiting around for a second lucky event.

Instead, her team and others are using extremely powerful lasers to re-create the physics seen in the aftermath of supernova blasts. The lasers vaporize a small target, which can be made of various materials, such as plastic. The blow produces an explosion of fast-moving plasma, a mixture of charged particles, that mimics the behavior of plasma erupting from supernovas.

The stellar explosions are triggered when a massive star exhausts its fuel and its core collapses and rebounds. Outer layers of the star blast outward in an explosion that can unleash more energy than will be released by the sun over its entire 10-billion-year lifetime. The outflow has an unfathomable 100 quintillion yottajoules of kinetic energy (SN: 2/8/17, p. 24).

Supernovas can also occur when a dead star called a white dwarf is reignited, for example after slurping up gas from a companion star, causing a burst of nuclear reactions that spiral out of control (SN: 4/30/16, p. 20).

In both cases, things really get cooking when the explosion sends a blast of plasma careening out of the star and into its environs, the interstellar medium — essentially, another ocean of plasma particles. Over time, a turbulent, expanding structure called a supernova remnant forms, begetting a beautiful light show, tens of light-years across, that can persist in the sky for many thousands of years after the initial explosion. It’s that roiling remnant that Park and colleagues are exploring.

Studying supernova physics in the lab isn’t quite the same thing as the real deal, for obvious reasons. “We cannot really create a supernova in the laboratory, otherwise we would be all exploded,” Park says.

In lieu of self-annihilation, Park and others focus on versions of supernovas that are scaled down, both in size and in time. And rather than reproducing the entirety of a supernova all at once, physicists try in each experiment to isolate interesting components of the physics taking place. Out of the immense complexity of a supernova, “we are studying just a tiny bit of that, really,” Park says.

For explosions in space, scientists are at the mercy of nature. But in the laboratory, “you can change parameters and see how shocks react,” says astrophysicist Anatoly Spitkovsky of Princeton University, who collaborates with Park.

The laboratory explosions happen in an instant and are tiny, just centimeters across. For example, in Kuranz’s experiments, the equivalent of 15 minutes in the life of a real supernova can take just 10 billionths of a second. And a section of a stellar explosion larger than the diameter of Earth can be shrunk down to 100 micrometers. “The processes that occur in both of those are very similar,” Kuranz says. “It blows my mind.”

Laser focus

To replicate the physics of a supernova, laboratory explosions must create an extreme environment. For that, you need a really big laser, which can be found in only a few places in the world, such as NIF, the National Ignition Facility at Lawrence Livermore, and the OMEGA Laser Facility at the University of Rochester in New York.

At both places, one laser is split into many beams. The biggest laser in the world, at NIF, has 192 beams. Each of those beams is amplified to increase its energy exponentially. Then, some or all of those beams are trained on a small, carefully designed target. NIF’s laser can deliver more than 500 trillion watts of power for a brief instant, momentarily outstripping the total power usage in the United States by a factor of a thousand.

A single experiment at NIF or OMEGA, called a shot, is one blast from the laser. And each shot is a big production. Opportunities to use such advanced facilities are scarce, and researchers want to have all the details ironed out to be confident the experiment will be a success.

When a shot is about to happen, there’s a space-launch vibe. Operators monitor the facility from a control room filled with screens. When the time of the laser blast nears, a voice begins counting down: “Ten, nine, eight …”

“When they count down for your shot, your heart is pounding,” says plasma physicist Jena Meinecke of the University of Oxford, who has worked on experiments at NIF and other laser facilities.

At the moment of the shot, “you kind of want the Earth to shake,” Kuranz says. But instead, you might just hear a snap — the sound of the discharge from capacitors that store up huge amounts of energy for each shot.

Then comes a mad dash to review the results and determine if the experiment has been successful. “It’s a lot of adrenaline,” Kuranz says.

Lasers aren’t the only way to investigate supernova physics in the lab. Some researchers use intense bursts of electricity, called pulsed power. Others use small amounts of explosives to set off blasts. The various techniques can be used to understand different stages in supernovas’ lives.

A real shocker

Park brims with cosmic levels of enthusiasm, ready to erupt in response to a new nugget of data or a new success in her experiments. Re-creating some of the physics of a supernova in the lab really is as remarkable as it sounds, she says. “Other­wise I wouldn’t be working on it.” Along with Spitkovsky and Fiuza, Park is among more than a dozen scientists involved in the Astrophysical Collisionless Shock Experiments with Lasers collaboration, or ACSEL, the quest Park embarked upon a decade ago. Their focus is shock waves.

The result of a violent input of energy, shock waves are marked by an abrupt increase in temperature, density and pressure. On Earth, shock waves cause the sonic boom of a supersonic jet, the clap of thunder in a storm and the damaging pressure wave that can shatter windows in the aftermath of a massive explosion. These shock waves form as air molecules slam into each other, piling up molecules into a high-density, high-pressure and high-temperature wave.

In cosmic environments, shock waves occur not in air, but in plasma, a mixture of protons, electrons and ions, electrically charged atoms. There, particles may be diffuse enough that they don’t directly collide as they do in air. In such a plasma, the pileup of particles happens indirectly, the result of electromagnetic forces pushing and pulling the particles. “If a particle changes trajectory, it’s because it feels a magnetic field or an electric field,” says Gianluca Gregori, a physicist at the University of Oxford who is part of ACSEL.

But exactly how those fields form and grow, and how such a shock wave results, has been hard to decipher. Researchers have no way to see the process in real supernovas; the details are too small to observe with telescopes.

These shock waves, which are known as collisionless shock waves, fascinate physicists. “Particles in these shocks can reach amazing energies,” Spitkovsky says. In supernova remnants, particles can gain up to 1,000 trillion electron volts, vastly outstripping the several trillion electron volts reached in the biggest human-made particle accelerator, the Large Hadron Collider near Geneva. But how particles might surf supernova shock waves to attain their astounding energies has remained mysterious.

Magnetic field origins

To understand how supernova shock waves boost particles, you have to understand how shock waves form in supernova remnants. To get there, you have to understand how strong magnetic fields arise. Without them, the shock wave can’t form.

Electric and magnetic fields are closely intertwined. When electrically charged particles move, they form tiny electric currents, which generate small magnetic fields. And magnetic fields themselves send charged particles corkscrewing, curving their trajectories. Moving magnetic fields also create electric fields.

The result is a complex feedback process of jostling particles and fields, eventually producing a shock wave. “This is why it’s so fascinating. It’s a self-modulating, self-controlling, self-reproducing structure,” Spitkovsky says. “It’s like it’s almost alive.”

All this complexity can develop only after a magnetic field forms. But the haphazard motions of individual particles generate only small, transient magnetic fields. To create a significant field, some process within a supernova remnant must reinforce and amplify the magnetic fields. A theoretical process called the Weibel instability, first thought up in 1959, has long been expected to do just that.

In a supernova, the plasma streaming outward in the explosion meets the plasma of the interstellar medium. According to the theory behind the Weibel instability, the two sets of plasma break into filaments as they stream by one another, like two hands with fingers interlaced. Those filaments act like current-­carrying wires. And where there’s current, there’s a magnetic field. The filaments’ magnetic fields strengthen the currents, further enhancing the magnetic fields. Scientists suspected that the electromagnetic fields could then become strong enough to reroute and slow down particles, causing them to pile up into a shock wave.

In 2015 in Nature Physics, the ACSEL team reported a glimpse of the Weibel instability in an experiment at OMEGA. The researchers spotted magnetic fields, but didn’t directly detect the filaments of current. Finally, this year, in the May 29 Physical Review Letters, the team reported that a new experiment had produced the first direct measurements of the currents that form as a result of the Weibel instability, confirming scientists’ ideas about how strong magnetic fields could form in supernova remnants.

For that new experiment, also at OMEGA, ACSEL researchers blasted seven lasers each at two targets facing each other. That resulted in two streams of plasma flowing toward each other at up to 1,500 kilometers per second — a speed fast enough to circle the Earth twice in less than a minute. When the two streams met, they separated into filaments of current, just as expected, producing magnetic fields of 30 tesla, about 20 times the strength of the magnetic fields in many MRI machines.

“What we found was basically this textbook picture that has been out there for 60 years, and now we finally were able to see it experimentally,” Fiuza says.

Surfing a shock wave

Once the researchers had seen magnetic fields, the next step was to create a shock wave and to observe it accelerating particles. But, Park says, “no matter how much we tried on OMEGA, we couldn’t create the shock.”

They needed the National Ignition Facility and its bigger laser.

There, the researchers hit two disk-shaped targets with 84 laser beams each, or nearly half a million joules of energy, about the same as the kinetic energy of a car careening down a highway at 60 miles per hour.

Two streams of plasma surged toward each other. The density and temperature of the plasma rose where the two collided, the researchers reported in the September Nature Physics. “No doubt about it,” Park says. The group had seen a shock wave, specifically the collisionless type found in supernovas. In fact there were two shock waves, each moving away from the other.

Learning the results sparked a moment of joyous celebration, Park says: high fives to everyone.

“This is some of the first experimental evidence of the formation of these collisionless shocks,” says plasma physicist Francisco Suzuki-Vidal of Imperial College London, who was not involved in the study. “This is something that has been really hard to reproduce in the laboratory.”

The team also discovered that electrons had been accelerated by the shock waves, reaching energies more than 100 times as high as those of particles in the ambient plasma. For the first time, scientists had watched particles surfing shock waves like the ones found in supernova remnants.

But the group still didn’t understand how that was happening.

In a supernova remnant and in the experiment, a small number of particles are accelerated when they cross over the shock wave, going back and forth repeatedly to build up energy. But to cross the shock wave, the electrons need some energy to start with. It’s like a big-wave surfer attempting to catch a massive swell, Fiuza says. There’s no way to catch such a big wave by simply paddling. But with the energy provided by a Jet Ski towing surfers into place, they can take advantage of the wave’s energy and ride the swell.

“What we are trying to understand is: What is our Jet Ski? What happens in this environment that allows these tiny electrons to become energetic enough that they can then ride this wave and be accelerated in the process?” Fiuza says.

The researchers performed computer simulations that suggested the shock wave has a transition region in which magnetic fields become turbulent and messy. That hints that the turbulent field is the Jet Ski: Some of the particles scatter in it, giving them enough energy to cross the shock wave.

Wake-up call

Enormous laser facilities such as NIF and OMEGA are typically built to study nuclear fusion — the same source of energy that powers the sun. Using lasers to compress and heat a target can cause nuclei to fuse with one another, releasing energy in the process. The hope is that such research could lead to fusion power plants, which could provide energy without emitting greenhouse gases or dangerous nuclear waste (SN: 4/20/13, p. 26). But so far, scientists have yet to get more energy out of the fusion than they put in — a necessity for practical power generation.

So these laser facilities dedicate many of their experiments to chasing fusion power. But sometimes, researchers like Park get the chance to study questions based not on solving the world’s energy crisis, but on curiosity — wondering what happens when a star explodes, for example. Still, in a roundabout way, understanding supernovas could help make fusion power a reality as well, as that celestial plasma exhibits some of the same behaviors as the plasma in fusion reactors.

At NIF, Park has also worked on fusion experiments. She has studied a wide variety of topics since her grad school days, from working on the U.S. “Star Wars” missile defense program, to designing a camera for a satellite sent to the moon, to looking for the sources of high-energy cosmic light flares called gamma-ray bursts. Although she is passionate about each topic, “out of all those projects,” she says, “this particular collisionless shock project happens to be my love.”

Early in her career, back on that experiment in the salt mine, Park got a first taste of the thrill of discovery. Even before IMB captured neutrinos from a supernova, a different unexpected neutrino popped up in the detector. The particle had passed through the entire Earth to reach the experiment from the bottom. Park found the neutrino while analyzing data at 4 a.m., and woke up all her collaborators to tell them about it. It was the first time anyone working on the experiment had seen a particle coming up from below. “I still clearly remember the time when I was seeing something nobody’s seen,” Park recalls.

Now, she says, she still gets the same feeling. Screams of joy erupt when she sees something new that describes the physics of unimaginably vast explosions.

Just how hot is your chili pepper? A new chili-shaped device could quickly signal whether adding the pepper to a meal might set your mouth ablaze.

Called the Chilica-pod, the device detects capsaicin, a chemical compound that helps give peppers their sometimes painful kick. In general, the more capsaicin a pepper has, the hotter it tastes. The Chilica-pod is sensitive, capable of detecting extremely low levels of the fiery molecule, researchers report in the Oct. 23 ACS Applied Nano Materials.

The device could someday be used to test cooked meals or fresh peppers, says analytical chemist Warakorn Limbut of Prince of Songkla University in Hat Yai, Thailand. People with a capsaicin allergy could use the gadget to avoid the compound, or farmers could test harvested peppers to better indicate their spiciness, he says.      

A pepper’s relative spiciness typically is conveyed in Scoville heat units — an imperfect measurement determined by a panel of human taste testers. Other more precise methods for determining spiciness are time-intensive and involve expensive equipment, making the methods unsuitable for a quick answer.

Enter the portable, smartphone-compatible Chilica-pod. Built by Limbut and colleagues, the instrument’s sensor is composed of stacks of graphene sheets. When a drop of a chili pepper and ethanol solution is added to the sensor, the capsaicin from the pepper triggers the movement of electrons among the graphene atoms. The more capsaicin the solution has, the stronger the electrical current through the sheets.

The Chilica-pod registers that electrical activity and, once its “stem” is plugged into a smartphone, sends the information to an app for analysis. The device can detect capsaicin levels as low as 0.37 micromoles per liter of solution, equivalent to the amount in a pepper with no heat, one test showed.

Limbut’s team used the Chilica-pod to individually measure six dried chili peppers from a local market. The peppers’ capsaicin concentrations ranged from 7.5 to 90 micromoles per liter of solution, the team found. When translated to Scoville heat units, that range corresponds to the spice of peppers like serrano or cayenne — mild varieties compared to the blazing hot Carolina reaper, one of the world’s hottest peppers (SN: 4/9/18).   

Paul Bosland, a plant geneticist and chili breeder at New Mexico State University in Las Cruces who wasn’t involved in the study, notes that capsaicin is just one of at least 24 related compounds that give peppers heat. “I would hope that [the device] could read them all,” he says.

To err is human, which is really not a very good excuse.

And to err as a scientist is worse, of course, because depending on science is supposed to be the best way for people to make sure they’re right. But since scientists are human (most of them, anyway), even science is never free from error. In fact, mistakes are fairly common in science, and most scientists tell you they wouldn’t have it any other way. That’s because making mistakes is often the best path to progress. An erroneous experiment may inspire further experiments that not only correct the original error, but also identify new previously unsuspected truths.

Still, sometimes science’s errors can be rather embarrassing. Recently much hype accompanied a scientific report about the possibility of life on Venus. But instant replay review has now raised some serious concerns about that report’s conclusion. Evidence for the gas phosphine, a chemical that supposedly could be created only by life (either microbes or well-trained human chemists), has started to look a little shaky. (See the story by well-trained Science News reporter Lisa Grossman.)

While the final verdict on phosphine remains to be rendered, it’s a good time to recall some of science’s other famous errors. We’re not talking about fraud here, or just bad ideas that were worth floating but flopped instead, or initial false positives due to statistical randomness. Rather, let’s just list the Top 10 erroneous scientific conclusions that got a lot of attention before ultimately getting refuted. (With one exception, there will be no names, for the purpose here is not to shame.)

10.  A weird form of life

A report in 2010 claimed that a weird form of life incorporates arsenic in place of phosphorus in biological molecules. This one sounded rather suspicious, but the evidence, at first glance, looked pretty good. Not so good at second glance, though. And arsenic-based life never made it into the textbooks.

9. A weird form of water

In the 1960s, Soviet scientists contended that they had produced a new form of water. Ordinary water flushed through narrow tubes became denser and thicker, boiled at higher than normal temperatures and froze at much lower temperatures than usual. It seemed that the water molecules must have been coagulating in some way to produce “polywater.” By the end of the 1960s chemists around the world had begun vigorously pursuing polywater experiments. Soon those experiments showed that polywater’s properties came about from the presence of impurities in ordinary water.

8. Neutrinos, faster than light

Neutrinos are weird little flyweight subatomic particles that zip through space faster than Usain Bolt on PEDs. But not as fast as scientists claimed in 2011, when they timed how long it took neutrinos to fly from the CERN atom smasher near Geneva to a detector in Italy. Initial reports found that the neutrinos arrived 60 nanoseconds sooner than a beam of light would. Faster-than-light neutrinos grabbed some headlines, evoked disbelief from most physicists and induced Einstein to turn over in his grave. But sanity was restored in 2012, when the research team realized that a loose electrical cable knocked the experiment’s clocks out of sync, explaining the error.

7. Gravitational waves from the early universe

All space is pervaded by microwave radiation, the leftover glow from the Big Bang that kicked the universe into action 13.8 billion years ago. A popular theory explaining details of the early universe —  called inflation — predicts the presence of blips in the microwave radiation caused by primordial gravitational waves from the earliest epochs of the universe.

In 2014, scientists reported finding precisely the signal expected, simultaneously verifying the existence of gravitational waves predicted by Einstein’s general theory of relativity and providing strong evidence favoring inflation. Suspiciously, though, the reported signal was much stronger than expected for most versions of inflation theory. Sure enough, the team’s analysis had not properly accounted for dust in space that skewed the data. Primordial gravitational waves remain undiscovered, though their more recent cousins, produced in cataclysmic events like black hole collisions, have been repeatedly detected in recent years.

6. A one-galaxy universe

In the early 20th century, astronomers vigorously disagreed on the distance from Earth of fuzzy cloudlike blobs shaped something like whirlpools (called spiral nebulae). Most astronomers believed the spiral nebulae resided within the Milky Way galaxy, at the time believed to comprise the entire universe. But a few experts insisted that the spirals were much more distant, themselves entire galaxies like the Milky Way, or “island universes.” Supposed evidence against the island universe idea came from measurements of internal motion in the spirals. It would be impossible to detect such motion if the spirals were actually way far away. But by 1924, Edwin Hubble established with certainty that at least sone of the spiral nebulae were in fact island universes, at vast distances from the Milky Way. Those measurements of internal motion were difficult to make — and they just turned out to be wrong.

5. A supernova’s superfast pulsar

Astronomers rejoiced in 1987 when a supernova appeared in the Large Magellanic Cloud, the closest such stellar explosion to Earth in centuries. Subsequent observations sought a signal from a pulsar, a spinning neutron star that should reside in the middle of the debris from some types of supernova explosions. But the possible pulsar remained hidden until January 1989, when a rapidly repeating radio signal indicated the presence of a superspinner left over from the supernova. It emitted radio beeps nearly 2,000 times a second — much faster than anybody expected (or could explain). But after one night of steady pulsing, the pulsar disappeared. Theorists raced to devise clever theories to explain the bizarre pulsar and what happened to it. Then in early 1990, telescope operators rotated a TV camera (used for guiding the telescope) back into service, and the signal showed up again — around a different supernova remnant. So the supposed signal was actually a quirk in the guide camera’s electronics — not a message from space.

4. A planet orbiting a pulsar

In 1991, astronomers reported the best case yet for the existence of a planet around a star other than the sun. In this case, the “star” was a pulsar, a spinning neutron star about 10,000 light-years from Earth. Variations in the timing of the pulsar’s radio pulses suggested the presence of a companion planet, orbiting its parent pulsar every six months. Soon, though, the astronomers realized that they had used an imprecise value for the pulsar’s position in the sky in such a way that the signal anomaly resulted not from a planet, but from the Earth’s motion around the sun.

3. Age of Earth

In the 1700s, French naturalist Georges-Louis Leclerc, Comte de Buffonestimated an Earth age of about 75,000 years, while acknowledging it might be much older. And geologists of the 19th century believe it to be older still — hundreds of millions of years or more — in order to account for the observation of layer after layer of Earth’s buried history. After 1860, Charles Darwin’s new theory of evolution also implied a very old Earth, to provide time for the diversity of species to evolve. But a supposedly definite ruling against such an old Earth came from a physicist who calculated how long it would take an originally molten planet to cool. He applied an age limit of about 100 million years, and later suggested that the actual age might even be much less than that. His calculations were in error, however — not because he was bad at math, but because he didn’t know about radioactivity.

Radioactive decay of elements in the Earth added a lot of heat into the mix, prolonging the cooling time. Eventually estimates of the Earth’s age based on rates of radioactive decay (especially in meteorites that formed around the same time as the Earth) provided the correct current age estimate of 4.5 billion years or so.

2. Age of the universe

When astronomers first discovered that the universe was expanding, at the end of the 1920s, it was natural to ask how long it had been expanding. By measuring the current expansion rate and extrapolating backward, they found that the universe must be less than 2 billion years old. Yet radioactivity measurements had already established the Earth to be much older, and it was very doubtful (as in impossibly ridiculous) that the universe could be younger than the Earth. Those early calculations of the universe’s expansion, however, had been based on distance measurements relying on Cepheid variable stars.

Astronomers calculated the Cepheids’ distances based on how rapidly their brightness fluctuated, which in turn depended on their intrinsic brightness. Comparing intrinsic brightness to apparent brightness provided a Cepheid’s distance, just as you can gauge the distance of a lightbulb if you know its wattage (oh yes, and what kind of lightbulb it is). It turned out, though, that just like lightbulbs, there is more than one kind of Cepheid variable, contaminating the expansion rate calculations. Nowadays converging methods give an age of the universe of 13.8 billion years, making the Earth a relative newcomer to the cosmos.

1. Earth in the middle

OK, we’re going to name and blame Aristotle for this one. He wasn’t the first to say that the Earth occupies the center of the universe, but he was the most dogmatic about it, and believed he had established it to be incontrovertibly true — by using logic. He insisted that the Earth must be in the middle because earth (the element) always sought to move toward its “natural place,” the center of the cosmos. Even though Aristotle invented formal logic, he apparently did not notice a certain amount of circularity in his argument. It took a while, but in 1543 Copernicus made a strong case for Aristotle being mistaken. And then in 1610 Galileo’s observation that Venus went through a full set of phases sealed the case for a sun-centered solar system.

Now, it would be nice if there were a lesson in this list of errors that might help scientists do better in the future. But the whole history of science shows that such errors are actually unavoidable. There is a lesson, though, based on what the mistakes on this list have in common: They’re all on a list of errors now known to be errors. Science, unlike certain political philosophies and personality cults, corrects its mistakes. That’s the lesson, and that’s why respecting science is so important to avoiding errors in other realms of life.