Mercury has gotten some new wrinkles in its old age. The innermost planet shows signs of relatively recent tectonic activity, a new study suggests.

Tiny cliffs on the surface — just tens of meters high and a few kilometers long — resemble breaks in the planet’s crust, researchers report online September 26 in Nature Geoscience. The diminutive sizes of the cliffs, their sharp edges and lack of large overlapping craters imply that the faults are geologically young — less than 50 million years old. That’s much younger than Mercury’s larger, eroded scarps seen elsewhere, which probably arose more than 3.5 billion years ago. The small scarps indicate that the surface still fractures as Mercury cools and contracts, the researchers suggest, though other explanations are possible.
Thomas Watters, a geologist at the Smithsonian Institution in Washington, D.C., and colleagues discovered the young escarpments in images taken by NASA’s MESSENGER spacecraft, which orbited Mercury from 2011 to 2015. During the last 18 months of the mission, the spacecraft inched closer to the surface of Mercury, revealing new details such as these small scarps. The mission ended with an intentional crash landing on April 30, 2015 (SN Online: 4/30/15).

Mercury’s continued contraction isn’t surprising, says Sean Solomon, a planetary scientist at Columbia University. “It’s demanded by physics,” he says. Mercury has gradually cooled over its 4.6-billion-year history. As it cools, it shrinks. Sometimes that shrinkage cracks the surface. All of the other rocky planets shrivel over time as well, but their atmospheres have erased much of the evidence. Only on Mercury and the moon — both airless — is the history of contraction preserved because of limited erosion.

It’s not clear, though, if these new faults are related to that shrinking. “In and of themselves, they don’t tell us very much,” says Paul Byrne, a planetary geologist at North Carolina State University in Raleigh. Without an analysis of how the small, young scarps relate to the large, old scarps, he says, it’s hard to draw conclusions. The new arrivals could just as well be produced by shifting rubble or shock waves from run-ins with asteroids, and if so would not be a sign of continuing tectonic activity.

A closer inspection of Mercury will have to wait until the European spacecraft BepiColombo, scheduled to launch in 2018, arrives in late 2024. While its altitude will be similar to MESSENGER’s, BepiColombo will get a better look at Mercury’s southern hemisphere, which should allow researchers to get a more global view of how all these wrinkles in the surface tie together.

Metallic odyssey
Scientists are getting closer to turning hydrogen into a solid metal, Emily Conover reported in “Chasing a devious metal” (SN: 8/20/16, p. 18).

“If, as some scientists think, [metallic hydrogen] formed under intense pressure remains solid at room temperature, why don’t we find any on our planet?” asked Michael Brostek. “If formed in a star that subsequently explodes, wouldn’t some make its way to us like other elements we have that were formed within stars?
“We do not believe that conditions exist in stars for solid metallic hydrogen to form,” says Harvard University physicist Isaac Silvera. “The temperatures are too high.” Above a certain temperature, solid metallic hydrogen would convert to a more stable phase. If that transition temperature is low enough, it could explain why we don’t see metallic hydrogen on Earth.

The relationship between metallic hydrogen and everyday hydrogen is similar to the relationship between diamond and graphite, a more stable phase. “If diamond is heated to a few thousand degrees Kelvin, it will convert to graphite,” Silvera says. “I do not recommend experimenting with a valuable stone!”

Pass the salt
In “Quenching society’s thirst” (SN: 8/20/16, p. 22), Thomas Sumner reported on next-generation desalination technologies that use improved and energy-efficient materials. Desalination efforts could help meet the world’s growing need for freshwater.

Reader Sallie Reynolds wondered what happens to the salt left behind.
Most desalination plants end up with briny leftover water that they pump deep underground (away from sources of drinking water) or dilute into a nearby water source, such as the ocean. But some facilities extract salt crystals from the desalination leftovers using evaporation ponds. In solid form, the salt can be stored, transported or dumped at landfills. “This salt could potentially be used for industrial
purposes, such as glassmaking, tanning, metal refining and cement manufacturing,” Sumner says. “The downside of evaporation ponds is that you need a lot of available space and a relatively warm, dry climate.”

Sun spotting
The sun’s magnetic field rises to the surface no faster than about 500 kilometers per hour — the same speed that gas rises and falls within the sun. Moving gas may help guide the field, Christopher Crockett reported in “Gas steers sun’s magnetic fields” (SN: 8/20/16, p. 5).

Mary Jane Knox wondered whether planets, moons and other celestial bodies in the solar system might contribute to the formation of sunspots and other solar activity: “Could they be reflecting the sun’s rays back on it causing hot spots which might allow the eruption of the magnetic fields?”

Planets don’t have anything to do with dark spots on our sun, Crockett says. Sunspots, which are cooler than the surrounding gas, are caused by strong magnetic fields that prevent hot gas from bubbling up to the surface. “Planets were once considered culprits,” he notes. In 1972, aerospace engineer Karl Wood calculated that periodic planetary alignments seemed to correspond to upticks in sunspot activity. But later work showed no link.

For other stars, planets may play a role in boosting solar activity. Some stars host planets roughly the size of Jupiter on very tight orbits. Magnetic fields from a few of these worlds appear to trigger hot spots on their parent stars.

Correction
“Quenching society’s thirst” (SN: 8/20/16, p. 22) states that a floating desalination farm would cover three-tenths of a square kilometer of ocean. In fact, each floating farm would stretch 300 meters long by 100 meters wide, covering only three-hundredths of a square kilo­meter of ocean. This area could provide about a square kilometer’s worth of stacked cultivable surfaces, depending on the crop.

Scientists may soon find out how tiny neutrinos really are. On October 14, scientists switched on the Karlsruhe Tritium Neutrino experiment, or KATRIN, located at the Karlsruhe Institute of Technology in Germany, which aims to measure the mass of the petite particles for the first time.

KATRIN will study neutrinos, which are less than a millionth the mass of an electron, by sifting through the aftermath of radioactive decays of tritium, an isotope of hydrogen with two neutrons. Tritium decays into helium-3, emitting a neutrino and an electron in the process. Because neutrinos are hard to detect, scientists measure the energy of the electrons emitted and use that information to deduce the neutrino mass.

KATRIN has begun taking test data, but the experiment is not yet filled with the radioactive tritium gas necessary to collect data for analysis. “This was a big milestone because it means that all the other systems are up and ready to go, and we’re taking data,” says KATRIN member Joseph Formaggio of MIT. Official data taking should begin in 2017.

Maps have long been used to show the animal kingdom’s range, regional mix, populations at risk and more. Now a new set of maps reveals the global distribution of genetic diversity.

“Without genetic diversity, species can’t evolve into new species,” says Andreia Miraldo, a population geneticist at the Natural History Museum of Denmark in Copenhagen. “It also plays a fundamental role in allowing species populations to adapt to changes in their environment.”
Miraldo and her colleagues gathered geographical coordinates for more than 92,000 records of mitochondrial DNA from 4,675 species of land mammals and amphibians. The researchers compared changes in cytochrome b, a gene often used to measure genetic diversity within a species, and then mapped the average genetic diversity for all species within roughly 150,000 square-kilometer areas.
For both mammals and amphibians, the tropical Andes and the Amazon have high genetic diversity, shown in dark blue. The same is true for mammal species in subtropical regions of South Africa and amphibian species in eastern North America, Miraldo and colleagues report in the Sept. 30 Science.
Areas affected by people, such as cities and croplands, show lower genetic diversity. The maps are a snapshot and so can’t quantify humans’ impact on this key marker, Miraldo notes. But she hopes the work provides a baseline to monitor how human activity and changes in climate affect the distribution of genetic diversity around the globe.

Tweaking activity of one protein may help protect against 10 autoimmune diseases, a new study suggests. The protein, tyrosine kinase 2 or TYK2, helps regulate how strongly the immune system responds to threats.

Using genetic data from more than 36,000 people with a variety of auto­immune diseases, researchers found that one genetic variant in the gene that codes for the TYK2 protein protects against a wide range of diseases that cause the immune system to attack the body. The variant changes one amino acid in the protein. As a result, the protein’s activity is greatly reduced, but not completely eliminated, researchers report November 2 in Science Translational Medicine.

The researchers say the variant strikes just the right balance between incapacitating the immune system and protecting against overreactions that lead to multiple sclerosis, Crohn’s disease and other autoimmune disorders. New drugs that reduce TYK2’s activity would need similar Goldilocks-like precision. But if such a drug could be developed, it could prove useful against a broad range of diseases.

Plastic smells like supper for some seabirds. When the ubiquitous material ends up in the ocean, it gives off a chemical that petrels, prions and shearwaters often use to locate food, researchers report November 9 in Science Advances. That might lead the birds to ingest harmful junk instead of a real meal.

Researchers at the University of California, Davis let small beads of three common plastics linger off the coast of California. After a few weeks, the once-clean plastic accumulated grit, grime and bacteria that gave off an odiferous gas called dimethyl sulfide (SN: 2/20/16, p. 20). Phytoplankton give off the same gas, and certain seabirds use the odor as a cue that dinner is nearby. Birds that rely more heavily on dimethyl sulfide as a beacon for a nearby meal are more likely to ingest plastic than birds that don’t, the team found. Other marine animals that use the cue could also be fooled.

NEW ORLEANS — Chronic sleep problems are associated with atrial fibrillation — a temporary but dangerous disruption of heart rhythm — even among people who don’t suffer from sleep apnea. An analysis of almost 14 million patient records has found that people suffering from insomnia, frequent waking and other sleep issues are more likely than sound sleepers to experience a condition in which the upper chambers of the heart quiver instead of rhythmically beating, allowing blood to briefly stagnate.

“Even if you don’t have sleep apnea, is there something about sleep disruption that puts you at a higher risk of fibrillation,” said Gregory Marcus, a cardiologist at the University of California, San Francisco. “We should put a higher priority on studying sleep itself.” Marcus and Matthew Christensen, from the University of Michigan, presented their results November 14 at the annual meeting of the American Heart Association.
People with atrial fibrillation have double the risk of having a heart attack, and up to five times the risk of stroke. Although the heart condition can be a consequence of aging, its prevalence is rising at about 4 percent per year for reasons that aren’t totally explained. In the United States, about 5 million people currently have the condition, and that number is expected to rise to 12 million by 2030.

A large body of studies has found that sleep apnea, which occurs when a person stops breathing during the night, can lead to atrial fibrillation and a host of other health concerns. Identifying a risk of atrial fibrillation among people with no sleep apnea is unexpected, says Richard Becker, director of the University of Cincinnati Heart, Lung & Vascular Institute, who was not part of the study.

Marcus, Christensen and colleagues analyzed data from three different sources, including the California Healthcare Cost and Utilization Project, a database of almost 14 million patients. They also drew on records from more than 4,600 participants of Health eHeart Study who had filled out a sleep survey, and from the Cardiovascular Health Study, which has tracked more than 5,700 people for more than a decade. Those data allowed the researchers to follow patients over time, tracking which came first — the fibrillation or the sleep issues. The researchers included a variety of sleep disorders, such as insomnia, nighttime waking and shortened periods of rapid eye movement, or REM, sleep.

Among the results: People who frequently woke had a 33 percent greater chance of developing atrial fibrillation in one analysis, and a 47 percent higher chance in another. For the eHeart group, insomnia increased the odds by 17 percent. And among more than 14 million California records studied, insomnia increased the odds of future atrial fibrillation by 36 percent. Analysis of a subgroup undergoing sleep studies showed that less REM sleep also was associated with a higher probability of developing atrial fibrillation.

The study can’t explain why a lack of sleep even with normal breathing might hurt the heart, but the authors hypothesize that the mechanism could be tied to the body’s stress response.

Becker believes that cardiologists should emphasize sleep just as they do diet and exercise for lifestyle management. To workaholic, screen-fixated Americans, “this study sends a powerful message about wellness as a continuum throughout the day and night,” he says. “It offers clinicians and the public a 360-degree view of what is important for good health.”

Bedbugs give me nightmares. Really. I have dreamt of them crawling up my legs while I lie in bed. These are common bedbugs, Cimex lectularius, and after largely disappearing from our beds in the 1950s, they have reemerged in the last few decades to cause havoc in our homes, offices, hotels and even public transportation.

Now there’s a new nightmare. Or rather, another old one. It’s the tropical bedbug, C. hemipterus. Its presence has been confirmed in Florida, and the critters could spread to other southern states, says Brittany Campbell, a graduate student at the University of Florida in Gainesville, who led a new study that tracked down the pests.

Tropical bedbugs can be found in a geographic band of land running between 30° N latitude and 30° S. In the last 20 years or so, they’ve been collected from Tanzania, Sri Lanka, Malaysia, Australia, Rwanda and more. Back in 1938, some were collected in Florida. There were more reports of the species in the following years, but none since the 1940s.

Then, in 2015, researchers at the Insect Identification Laboratory at the University of Florida identified bedbugs sent to the lab from a home in Brevard County, Florida, as tropical bedbugs. To confirm the analysis, researchers went to the home and collected more samples. They were indeed tropical bedbugs, the team reports in the September Florida Entomologist.

The family thought that the bedbugs must have been transported unknowingly into the house by one of the people who lived there. But no one living in the home had traveled outside the state recently, let alone outside the country. This suggests that tropical bedbugs can be found elsewhere in Florida, the team concludes.

Additional evidence comes from the Florida State Collection of Arthropods, which holds two female tropical bedbugs that, according to their label, were collected in Orange County, Florida, on June 11, 1989, from bedding. “Whether this species has been present in Florida and never disappeared, or has been reintroduced and remains in small populations, is not currently known,” the researchers write.

Why hasn’t anyone noticed? Well, people don’t usually send bedbugs to entomologists when they have an infestation, and your average victim isn’t going to notice the difference between the two species. “Both species are very similar,” Campbell says. Not only do they look alike, but they also both “feed on blood, hide in cracks and crevices and have similar lifestyles.” Plus, there’s been little research directly comparing the two species, she notes, so scientists don’t know how infestations might differ.

Just to give us all a few more nightmares, Campbell points out something else: While there’s probably no reason to worry that the creepy critters will spread as climate change warms the globe, she says that there is a potential for the species to move north “because humans provide nice conditions for bedbugs to develop.”

When I first found out my daughter existed, she was about half the size of a mini chocolate chip.

I was six weeks pregnant; she was four weeks into development. (The pregnancy timer officially begins two weeks before conception.) Already, the structures that would become her eyes had formed rudimentary orbs and the four tiny chambers of her heart were taking shape. At this stage of development, the embryo’s heart is huge, like a dumpling squeezed inside the torso.

You can see this early human heart and what happens before and after it develops with a new tool, the 3-D Atlas of Human Embryology, published November 25 in Science. The atlas chronicles the very first stages of human development — when growth is literally exponential and an embryo is building bodily systems that will be in place for a lifetime.

Embryologist Bernadette de Bakker and colleagues at the Academic Medical Center in Amsterdam created the atlas to help students, doctors and researchers better understand what goes on in those earliest weeks.

“We might know more about the moon than about our own development,” de Bakker says. Even today, human embryology textbooks often rely on pictures of chick or mouse embryos to describe how humans grow. Any human embryonic data used “is often based on just one or two specimens,” she says.
And that’s a problem because, as de Bakker has discovered, not all human embryos are the same.
Her team photographed nearly 15,000 cross sections of human embryos from the Carnegie Collection, a famous set of historical specimens collected from hysterectomies and abnormal pregnancies or miscarriages. De Bakker and colleagues uploaded the photos into a computer program, and then, using digital pencils and drawing pads, traced and labeled every organ and structure in every photo. It took some 75 people roughly 45,000 hours to complete.
What they (and we) have gained is a remarkable look at humans’ first metaphorical steps — the steady developmental march that, eventually, takes an embryo from a bundle of cells to babyhood.

Here are some landmarks in the first 60 days of development (links are to PDFs; save and open in Adobe Reader X or higher for interactive features):

Days 15-17: The embryo and all the membranes that surround it are no bigger than a speck of dust. The embryo itself is a speck within the speck, and consists of just three layers of cells. From these layers, all organs and body structures will form.

Days 19-21: What a difference a few days make. The embryo is now about the size of a pinhead and has laid the early groundwork for the heart, gut, skin, muscles, skeleton and brain.

Days 21-23: A furrow of tissue that gives rise to the brain and spinal cord has now begun to fold together, forming the neural tube. If the furrow doesn’t close properly, the spinal cord could protrude from the backbone, a birth defect called spina bifida.

Days 28-32: The embryo, now at the half mini-chocolate-chip size, starts to take on a textbook look, fledgling head and lower body curled toward each other — a rough draft of the classic fetal position.

Days 35-38: Short paddlelike arms and the first nubs of legs have emerged. The embryo is now almost the size of a ladybug.

Days 44-48: It’s now a slightly bigger ladybug, and leg bones and hand and finger bones have formed. The liver, suddenly, has ballooned in size, filling much of the lower half of the body cavity.

Days 51-53: Chubby fingers have sprouted from once clublike hands. Toes are not visible yet, but toe bones are in place. The embryo is roughly marble-sized.

Days 56-60: The embryonic brain is a giant bulbous globe now, more than a third of the entire body — which is about the size of a cherry tomato. Skinny arms and legs fold close, and a plate of skull has started to stretch across the back of the head.

Give it another 30 weeks or so and that tiny embryo will grow to the size of a bowling ball. Comparatively, a little chocolate chip doesn’t seem like much. But development-wise, it goes through something pretty huge.

Fewer teenagers in the United States used drugs in 2016 than in previous decades. The positive news comes from an annual survey of almost 45,500 U.S. students in grades eight, 10 and 12.

“There’s a lot of good news here,” says pediatrician Sharon Levy of Boston Children’s Hospital. Public health messages from pediatricians, educators and others seem to be sinking in, she says. “I think that’s fabulous. Substance use is one of the most important — yet modifiable — behavioral health issues of adolescents.”
Adolescents’ use of many of the substances, including alcohol and cigarettes, hit an all-time low since the survey, known as the Monitoring the Future study, began collecting data 42 years ago. Heroin, methamphetamines, inhalants and stimulants also hit lows this year.

E-cigarettes have been particularly concerning as more adolescents gave the new devices a try, reaching a high in 2015 (SN: 5/28/16, p. 4). For the first time, the number of students who vape is declining, the survey found. In 2015, 16.3 percent of 12th-graders reported vaping in the last 30 days. In 2016, that fell to 12.5. Similar declines were evident among eighth- and 10th-graders.
In a happy surprise, misuse of prescription opioid use decreased in the last five years among 12th–graders. The drop was “a big surprise,” particularly against a backdrop of a much wider opioid epidemic in the general population (SN: 9/3/16, p. 14), Nora Volkow, the director of the National Institute on Drug Abuse in Bethesda, Md., said December 13 at a news briefing.
The news isn’t all good, though. Marijuana bucked the declining trends, at least for 12th-graders. In 2016, about 6 percent of 12th-graders said they use marijuana daily — a number that hasn’t changed much in the last five years.

Researchers don’t yet know why the rates for many drugs are down, but one idea is that the drop in illegal drugs may stem in part from reductions in alcohol and tobacco use. “There is a connection there,” Lloyd Johnston, a social psychologist at the University of Michigan in Ann Arbor who led the survey, said in the news briefing.

The survey and the information it produces is “extremely important,” Levy says, “but it’s not everything.” Other measures of kids’ drug use, such as rates of substance use disorders, will offer a fuller view of how adolescents interact with drugs, she says.