About 20,000 kilometers beneath the sun’s surface, magnetic fields rise no faster than about 500 kilometers per hour. That speed (roughly one-third of previous estimates) is about the same speed that gas rises and falls within the sun, implying that moving parcels of gas help steer magnetic fields toward the surface, researchers report July 13 in Science Advances.

Aaron Birch of the Max Planck Institute for Solar System Research in Göttingen, Germany, and colleagues estimated the speed by combining observations of the sun’s surface with computer simulations of how gas moves within the hot orb. By studying the sun’s inner workings, researchers hope to understand what drives sunspots and flares — the blemishes and eruptions triggered by magnetic fields punching through the surface.

Butterflies look so delicate as they flitter from flower to flower. And yet, they are capable of migrating incredibly long distances. The monarch, for example, migrates between Canada and Mexico, covering distances of up to 4,800 kilometers, riding a combination of columns of rising air, called thermals, and air currents to travel around 80 to 160 kilometers per day.

No single monarch makes this entire journey, though. The round trip is done by a succession of as many as five generations of butterflies. But now scientists have found that there’s a species of butterfly that may rival the monarch’s migratory record — the painted lady (Vanessa cardui).

Painted ladies are found throughout much of the world, except for South America and Australia. They’ve been seen as far north as Svalbard, Norway, and nearly as far south as Antarctica. The butterflies are known to migrate, particularly between Europe and Africa, but their route has been largely unknown. Scientists had tracked the butterflies to northern Africa (the region known as the Maghreb), but there have been hints that they may fly across the Sahara. Two new studies back up this claim.

Gerard Talavera and Roger Vila of Harvard University visited four sub-Saharan nations — Benin, Chad, Ethiopia and Senegal — in 2014. They found butterflies moving south through Chad. There were dense aggregations of breeding butterflies in Benin and Ethiopia. And as the dry season approached in Senegal, the pair found butterflies old and worn, as if they had just finished a long, tortuous journey. Plus, the timing of these appearances coincided with the butterflies’ fall and winter disappearance from Europe.

“Taken together, the results of our fieldwork provide evidence suggesting that most European populations may undertake long-range migratory flights to tropical Africa, thus crossing the combined hazards of the Mediterranean Sea and the completely hostile Sahara,” the pair write September 21 in the Biological Journal of the Linnean Society.

If butterflies truly are making that flight, they could be traveling more than 4,000 kilometers in a single generation — a potential record for a migratory insect, the researchers note. And while this seems nearly impossible, it may not be. A previous study found that with favorable winds, painted butterflies could travel as fast as 45 kilometers per hour. At that speed, it would take them as little as four days to make it from Central Europe to Central Africa. Since an adult painted butterfly lives for around four weeks, such a journey is feasible, Talavera and Vila argue.

But this evidence is only circumstantial; it doesn’t prove that butterflies are truly making that journey. So while Tavalera and Vila were in sub-Saharan Africa, they collected hundreds of adult painted ladies and larvae. Some of these were used in a second study, published October 4 in Biology Letters and led by Constantí Stefanescu of the Natural History Museum of Granollers in Spain. In this study, the team analyzed the isotopes of hydrogen found in the adult butterflies’ wings.
The hydrogen in the water that falls as precipitation can come in different isotopes, or forms, that vary in the number of neutrons. The ratio of these isotopes varies geographically. And the ratio present wherever the butterflies lived as larvae correlates with that later found in the adults’ wings. So researchers can tell where the adults were born.

Stefanescu and his team analyzed butterflies collected in seven European and seven African countries and developed a rough map of where the adults were moving. Those in sub-Saharan Africa had indeed started in Europe. But those in the Maghreb came from both sub-Saharan Africa and Europe.

What explains all this movement? The butterflies are following a combination of prevailing winds and favorable conditions for breeding. As rains come and go, the butterflies breed and move on. And while crossing the Sahara may seem like quite a way to go just for some rainy days and lush vegetation, painted lady butterflies are hardly the only creatures willing to go that far, Stefanescu and his colleagues note. There are plenty of other insects that make such a journey — as well as billions of birds.

Observations of the dense remnant of an exploded star have provided the first sign of a quantum effect on light passing through empty space.

Light from the stellar remnant, a neutron star located about 400 light-years away, is polarized, meaning that its electromagnetic waves are oriented preferentially in a particular direction like light that reflects off the surface of water (SN: 7/8/06, p. 24). That polarization is evidence of “vacuum birefringence,” a quantum effect first predicted 80 years ago caused by light interacting with the vacuum of space in a strong magnetic field. Scientists report the result in a paper to be published in the Feb. 11, 2017 issue of Monthly Notices of the Royal Astronomical Society.
“It’s the most natural explanation,” says astrophysicist Jeremy Heyl of the University of British Columbia in Vancouver, who was not involved with the new result. But he cautions, other sources of polarization could mimic the effect, and additional observations are necessary.

According to quantum electrodynamics, the theory describing how light interacts with charged particles such as electrons, empty space isn’t really empty. It is filled with a roiling soup of ethereal particles, constantly blipping into and out of existence (SN: 11/26/16, p. 28). As light passes through the void, its wiggling electromagnetic waves interact with those particles. Under strong magnetic fields, light waves that wiggle along the direction of the magnetic field will travel slightly slower than light oscillating perpendicular to the direction of the magnetic field, which rotates the overall polarization of light coming from the star.

A similar effect commonly occurs in a more familiar situation, in what are known as birefringent materials. The liquid crystals in computer monitors similarly rotate the polarization of light. Horizontally polarized light, for example, is sent to each pixel, but a filter lets only vertically polarized light escape. To switch on a pixel, the liquid crystals twist the light waves 90 degrees so the waves will pass through.

But evidence for the quantum version of the effect was not easy to come by. Observing it requires a magnetic field stronger than those that can be produced in the laboratory, says astrophysicist Roberto Mignani of the National Institute for Astrophysics in Milan, coauthor of the new study. The magnetic field around the neutron star that Mignani and colleagues studied is about 10 trillion times the strength of Earth’s. But the star is incredibly faint, making measurements of its polarization difficult. “A neutron star of this kind is about as bright as a candle halfway between the Earth and the moon,” Mignani says.

Using the Very Large Telescope in Chile, the scientists found that visible light from the neutron star was about 16 percent polarized, a result consistent with scientists’ theories of vacuum birefringence. But, says Heyl, the polarization could also occur as a result of an unexpectedly large amount of plasma surrounding the star.
For airtight evidence of the effect, scientists could study X-rays from neutron stars, where the polarization effect should be even stronger. Although no telescope currently exists that can make such measurements, there are several proposed X-ray satellites that may soon be able to clinch the case for vacuum birefringence.

Scientists might want to keep their fingers crossed. If future measurements overturned the evidence for vacuum birefringence, the effect’s absence would be difficult to reconcile with the theory of quantum electrodynamics, Heyl says. “It’s essentially one of the basic predictions of the theory, so to fix it you’d really have to rip the theory all the way back down to the foundations and rebuild it.”

How well, not how much, people sleep may affect Alzheimer’s disease risk.

Healthy adults built up Alzheimer’s-associated proteins in their cerebral spinal fluid when prevented from getting slow-wave sleep, the deepest stage of sleep, researchers report July 10 in Brain. Just one night of deep-sleep disruption was enough to increase the amount of amyloid-beta, a protein that clumps into brain cell‒killing plaques in people with Alzheimer’s. People in the study who slept poorly for a week also had more of a protein called tau in their spinal fluid than they did when well rested. Tau snarls itself into tangles inside brain cells of people with the disease.
These findings support a growing body of evidence that lack of Zs is linked to Alzheimer’s and other neurodegenerative diseases. Specifically, “this suggests that there’s something special about deep, slow-wave sleep,” says Kristine Yaffe, a neurologist and psychiatrist at the University of California, San Francisco who was not involved in the study.

People with Alzheimer’s are notoriously poor sleepers, but scientists aren’t sure if that is a cause or a consequence of the disease. Evidence from recent animal and human studies suggests the problem goes both ways, Yaffe says. Lack of sleep may make people more prone to brain disorders. And once a person has the disease, disruptions in the brain may make it hard to sleep. Still, it wasn’t clear why not getting enough shut-eye promotes Alzheimer’s disease.
Researchers led by neurologist David Holtzman of Washington University School of Medicine in St. Louis speculated that lower levels of brain cell activity during deep sleep would produce less A-beta, tau and other proteins than other stages of sleep or wakefulness. Holtzman, Washington University sleep medicine physician Yo-El Ju and colleagues recruited 17 volunteers, all healthy adults between ages 35 and 65, who had no sleep disorders. “These are good sleepers,” Ju says.
Volunteers wore activity monitors to track their sleep at home and visited the sleep lab at least twice. On one visit, the volunteers slept normally while wearing headphones. On the other visit, researchers played beeps through headphones whenever the volunteers were about to go into deep sleep. The sounds usually didn’t wake the people up but kept them from getting any slow-wave sleep. Volunteers slept just as much on the night when deep sleep was disrupted as they did on the night when no sound was played through the headphones.
Spinal taps showed that the more deep sleep people missed out on, the higher their levels of A-beta in the morning. Tau levels didn’t budge because of just one night of slow-wave sleep disruption, but people whose activity monitors indicated they had slept poorly the week before the test also had higher levels of that protein.

“This study in humans is really an elegant experimental demonstration” that bolsters Holtzman’s hypothesis that lack of rest for brain cells could be detrimental, says Adam Spira, a psychologist at Johns Hopkins Bloomberg School of Public Health. Without proper deep sleep, brain cells continue to churn out, producing more A-beta and tau than a well-rested brain.

Some research has suggested that toxic proteins get flushed out of the brain during sleep (SN: 11/16/13, p. 7). Messing with slow-wave sleep doesn’t seem to interfere with this wash cycle, Ju says. Levels of other proteins made by nerve cells didn’t vary with the lack of deep sleep, she says.

The tempo of a male elephant seal’s call broadcasts his identity to rival males, a new study finds.

Every male elephant seal has a distinct vocalization that sounds something like a sputtering lawnmower — pulses of sound in a pattern and at a pace that stays the same over time.

At a California state park where elephant seals breed each year, researchers played different variations of an alpha male’s threat call to subordinate males who knew him. The seals weren’t as responsive when the tempo of that call was modified substantially, suggesting they didn’t recognize it as a threat. Modifying the call’s timbre — the acoustic quality of the sound — had the same effect, researchers report August 7 in Current Biology. Unlike dolphins and songbirds, elephant seals don’t seem to vary pitch to communicate.
Those vocal name tags serve a purpose. During breeding season, male elephant seals spend three months on land without food or water, competing with rivals for social status and mating rights. Fights between two blubbery car-sized animals can be brutal.

“We’ve seen males lose their noses,” says Caroline Casey, a biologist at the University of California, Santa Cruz. For lower-ranking males, identifying an alpha male by his call and then backing off might prevent a beach brawl.

Cube-shaped ice is rare, at least at the microscopic level of the ice crystal. Now researchers have coaxed typically hexagonal 3-D ice crystals to form the most cubic ice ever created in the lab.

Cubed ice crystals — which may exist naturally in cold, high-altitude clouds — could help improve scientists’ understanding of clouds and how they interact with Earth’s atmosphere and sunlight, two interactions that influence climate.

Engineer Barbara Wyslouzil of Ohio State University and colleagues made the cubed ice by shooting nitrogen and water vapor through nozzles at supersonic speeds. The gas mixture expanded and cooled, and then the vapor formed nanodroplets. Quickly cooling the droplets further kept them liquid at normally freezing temperatures. Then, at around –48° Celsius, the droplets froze in about one millionth of a second.

The low-temperature quick freeze allowed the cubic ice to form, the team reports in the July 20 Journal of Physical Chemistry Letters. The crystals weren’t perfect cubes but were about 80 percent cubic. That’s better than previous studies, which made ice that was 73 percent cubic.

Neandertals took stick-to-itiveness to a new level. Using just scraps of wood and hot embers, our evolutionary cousins figured out how to make tar, a revolutionary adhesive that they used to make formidable spears, chopping tools and other implements by attaching sharp-edged stones to handles, a new study suggests.

Researchers already knew that tar-coated stones date to at least 200,000 years ago at Neandertal sites in Europe, well before the earliest known evidence of tar production by Homo sapiens, around 70,000 years ago in Africa. Now, archaeologist Paul Kozowyk of Leiden University in the Netherlands and colleagues have re-created the methods that these extinct members of the human genus could have used to produce tar.
Three straightforward techniques could have yielded enough adhesive for Neandertals’ purposes, Kozowyk’s team reports August 31 in Scientific Reports. Previous studies have found that tar lumps found at Neandertal sites derive from birch bark. Neandertal tar makers didn’t need ceramic containers such as kilns and didn’t have to heat the bark to precise temperatures, the scientists conclude.
These findings fuel another burning question about Neandertals: whether they had mastered the art of building and controlling a fire. Some researchers suspect that Neandertals had specialized knowledge of fire control and used it to make adhesives; others contend that Neandertals only exploited the remnants of wildfires. The new study suggests they could have invented low-tech ways to make tar with fires, but it’s not clear whether those fires were intentionally lit.

“This new paper demystifies the prehistoric development of birch-bark tar production, showing that it was not predicated on advanced cognitive or technical skills but on knowledge of familiar, readily available materials,” says archaeologist Daniel Adler of the University of Connecticut in Storrs, who did not participate in the study.
Kozowyk’s group tested each of three tar-making techniques between five and 11 times. The lowest-tech approach consisted of rolling up a piece of birch bark, tying it with wood fiber and covering it in a mound of ashes and embers from a wood fire. Tar formed between bark layers and was scraped off the unrolled surface. The experimenters collected up to about one gram of tar this way.

A second strategy involved igniting a roll of birch bark at one end and placing it in a small pit. In some cases, embers were placed on top of the bark. The researchers either scraped tar off bark layers or collected it as it dripped onto a rock, strip of bark or a piece of bark folded into a cup. The most tar gathered with this method, about 1.8 grams, was in a trial using a birch-bark cup placed beneath a bark roll with its lit side up and covered in embers.

Repeating either the ash-mound or pit-roll techniques once or twice would yield the relatively small quantity of tar found at one Neandertal site in Europe, the researchers say. Between six and 11 repetitions would produce a tar haul equal to that previously unearthed at another European site.

In a third technique, the scientists placed a birch-bark vessel for collecting tar into a small pit. They placed a layer of twigs across the top of the pit and placed pebbles on top, then added a large, loose bark roll covered in a dome-shaped coat of wet soil. A fire was then lit on the earthen structure. This method often failed to produce anything. But after some practice with the technique, one trial resulted in 15.7 grams of tar — enough to make a lump comparable in size to the largest chunks found at Neandertal sites.

An important key to making tar was reaching the right heat level. Temperatures inside bark rolls, vessels, fires and embers varied greatly, but at some point each procedure heated bark rolls to between around 200˚ and 400˚ Celsius, Kozowyk says. In that relatively broad temperature range, tar can be produced from birch bark, he contends.

If they exploited naturally occurring fires, Neandertal tar makers had limited time and probably relied on a simple technique such as ash mounds, Kozowyk proposes. If Neandertals knew how to start and maintain fires, they could have pursued more complex approaches.

Some researchers say that excavations point to sporadic use of fire by Neandertals, probably during warm, humid months when lightning strikes ignited wildfires. But other investigators contend that extinct Homo species, including Neandertals, built campfires (SN: 5/5/12, p. 18).

Whatever the case, Kozowyk says, “Neandertals could have invented tar with only basic knowledge of fire and birch bark.”

Planetary scientists now know how thick the Martian crust is, thanks to the strongest Marsquake ever observed.

On average, the crust is between 42 and 56 kilometers thick, researchers report in a paper to appear in Geophysical Research Letters. That’s roughly 70 percent thicker than the average continental crust on Earth.

The measurement was based on data from NASA’s InSight lander, a stationary seismometer that recorded waves rippling through Mars’ interior for four Earth years. Last May, the entire planet shook with a magnitude 4.7 quake that lasted more than six hours (SN: 5/13/22). “We were really fortunate that we got this quake,” says seismologist Doyeon Kim of ETH Zurich.
InSight recorded seismic waves from the quake that circled Mars up to three times. That let Kim and colleagues infer the crust thickness over the whole planet.

Not only is the crust thicker than that of the Earth and the moon, but it’s also inconsistent across the Red Planet, the team found. And that might explain a known north-south elevation difference on Mars.

Topological and gravity data from Mars orbiters have shown that the planet’s northern hemisphere is substantially lower than the southern one. Researchers had suspected that density might play a part: Perhaps the rocks that make up northern Mars have a different density than those of southern Mars.

But the crust is thinner in the northern hemisphere, Kim and colleagues found, so the rocks in both hemispheres probably have the same average densities. That finding helps scientists narrow down the explanations for why the difference exists in the first place.

Knowing the crust’s depth, the team also calculated that much of Mars’ internal heat probably originates in the crust. Most of this heat comes from radioactive elements such as potassium, uranium and thorium. An estimated 50 to 70 percent of those elements are probably in the crust rather than the underlying mantle, computer simulations suggest. That supports the idea that parts of Mars still have volcanic activity, contrary to a long-held belief that the Red Planet is dead (SN: 11/3/22).

An ancient vegetarian dinosaur from the French countryside has given paleontologists something to sink their teeth into.

The most striking feature of a new species of rhabdodontid that lived from 84 million to 72 million years ago is its oversized, scissorslike teeth, paleontologist Pascal Godefroit, of the Royal Belgian Institute of Natural Sciences in Brussels, and his colleagues report October 26 in Scientific Reports. Compared with other dinos of its kind, Matheronodon provincialis’ teeth were at least twice as large but fewer in number. Some teeth reached up to 6 centimeters long, while others grew up to 5 centimeters wide. They looked like a caricature of normal rhabdodontid teeth, Godefroit says.
Of hundreds of fossils unearthed over the last two decades at a site called Velaux-La Bastide Neuve in the French countryside, a handful of jaw bones and teeth now have been linked to this new species, Matheronodon provincialis. The toothy dino belongs to a group of herbivorous, bipedal dinosaurs common in the Cretaceous Period. Rhabdodontids sported bladelike teeth, and likely noshed on the tough woody tissue parts of plants. Palm trees, common in Europe at the time, might have been on the menu.

Rhabdodontid teeth have ridges covered by a thick layer of enamel on one side and little to no ridges or enamel on the other. Teeth in the upper jaw have more ridges and enamel on the outer edge, while the reverse is true for bottom teeth. A closer look at the microstructure of M. provincialis’ teeth revealed an exaggerated version of this — many more ridges and lopsided enamel coating. Enamel typically protects from wear and tear, so chewing would have sharpened the dino’s teeth. “They operated like self-sharpening serrated scissors,” Godefroit says.

Regenerating body parts is never easy. For instance, some lizards can grow back their tails, but these new appendages are pale imitations of the original. Now, genetically modified stem cells are helping geckos grow back better tails.

Tweaking and implanting embryonic stem cells on the tail stumps of mourning geckos (Lepidodactylus lugubris) allowed the reptiles to grow tails that are more like the original than ever before, researchers report October 14 in Nature Communications. These findings are a stepping-stone to developing regenerative therapies in humans that may one day treat hard-to-heal wounds.

A gecko’s tail is an extension of its spine — with the vertebrae to prove it. Regenerated tails, however, are simpler affairs. “It’s just a bunch of concentric tubes of fat, muscle and skin,” says Thomas Lozito, a biologist at the University of Southern California in Los Angeles.

That’s because stem cells in adult geckos produce a molecular signal that encourages the formation of cartilage in new tails, but not bone or nervous tissues (SN: 8/17/18). Lozito and his colleagues used embryonic stem cells, which can develop into a wider range of tissues than adult stem cells, modified them to ignore this signal and then implanted them on the tail stumps of geckos that had their tails surgically removed. The tails that grew from these modified stem cells had bonelike grooves in the cartilage and generated new neural tissue at the top of the tail.

These modified tails still lack a spinal cord, making them a far cry from the original. “We fixed one problem, but there are still many imperfections,” Lozito says. “We’re still on the hunt for the perfect tail.”