Over the ground lies a mantle of white — on Pluto. Snow-capped peaks on the dwarf planet dot an otherwise ruddy terrain. But these snowy summits appear to be composed of methane, not water, researchers report online March 3.
Mountain tops in Pluto’s Cthulhu Regio, a dark landscape abutting the planet’s famous heart, reflect more light than the surrounding area. The New Horizons spacecraft, which flew past Pluto on July 14, found that the bright regions correspond to surface deposits of methane. Mission scientists speculate that perhaps methane in the atmosphere on Pluto behaves like water in the air on Earth, building up on the ground as frost at the highest (and coldest) elevations.
Two small comets — or rather two chunks of the same comet — will slip by Earth on March 21 and March 22, each on a different side of the planet. Comet 252P/LINEAR passed at a distance of about 5.2 million kilometers (13.5 times as far as the moon) around 8:14 a.m. Eastern on Monday, while comet P/2016 BA14 (PANSTARRS) will fly by at 10:30 a.m. Tuesday, coming no closer than about 3.5 million kilometers, just over nine times the distance to the moon. Neither comet poses any danger to Earth.
Comet BA14 was discovered in January. Its orbit is strikingly similar to that of fellow traveler252P, a comet first seen 16 years ago. Researchers suspect that both bodies are fragments of a larger comet that broke apart. Despite their close approach, neither comet is visible to the naked eye.
New microscopy images of the virus reveal a bumpy, golf ball‒shaped structure, similar to that of the dengue and West Nile viruses, researchers report March 31 in Science. It’s the first time scientists have gotten a good look at Zika, the infamous virus that has invaded the Americas and stoked fears that it is causing birth defects and a rare autoimmune disease (SN: 4/2/16, p. 26). Cracking Zika’s structure is like getting the blueprints of an enemy’s base: Now scientists have a better idea of where to attack. “This certainly gives us great hope that we will be able to find a vaccine or antiviral compounds,” says study coauthor Michael Rossmann of Purdue University in West Lafayette, Ind., who’s known for mapping the first structure of a common cold virus in 1985.
Researchers have been racing to solve Zika’s structure, says UCLA microbiologist Hong Zhou. “I was trying to work on the same thing myself.” But the new study’s authors beat everybody. “I was impressed they were able to do it so quickly,” Zhou says.
Rossmann and colleagues imaged a strain of Zika collected from a patient during a 2013‒2014 outbreak in French Polynesia (the strain is nearly identical to the one now spreading through Latin America).
The team used a technique called cryoelectron microscopy to create a three-dimensional picture of Zika. It’s a pretty sharp image, says study coauthor Devika Sirohi, also of Purdue. She and colleagues can clearly see the virus’ shape and can even make out sugars protruding from its surface.
These sugars, which look like little red doorknobs, hang from proteins in Zika’s shell. The knobs may help Zika attach to — and infect — human cells. The team discovered that Zika’s knobby regions look slightly different from those of related viruses. Zika’s sugar-decorated proteins “fold a little differently,” Sirohi says. And that might let Zika make different contacts with attachment sites on cells, called receptors. That could “influence what kind of cell the virus infects,” she says. These differences could explain why Zika infects cells not typically targeted by dengue or West Nile. One of the receptors targeted by Zika could be AXL, a protein crowded on the surface of neural stem cells, researchers propose March 30 in a separate study published online in Cell Stem Cell. Zika virus is thought to preferentially infect these early-development brain cells, and it could potentially use AXL as an easy entry point, study coauthor Arnold Kriegstein of the University of California, San Francisco and colleagues suggest.
Of course, exactly what role subtle structural differences play in Zika’s infection ability is “only speculation at this point,” Sirohi says. The team now plans to test how tweaking the knobby regions of the virus affects Zika’s virulence.
Some people can evade diseases even though they carry genetic mutations that cause serious problems for others.
Researchers found 13 of these genetic escape artists after examining DNA from nearly 600,000 people, the scientists report online April 11 in Nature Biotechnology. Learning how such people dodge genetic bullets may help move inherited-disease research from diagnosis to prevention.
Hundreds of mutations that lead to genetic diseases have been uncovered since the discovery of a disease-causing flaw in the “cystic fibrosis gene” in 1989. But, says study coauthor Stephen Friend, “finding the gene that causes the disease is not the same as finding a way to prevent the symptoms or manifestations of that disease.” Clues to preventing genetic diseases could come from studying people who should have gotten sick but didn’t, suggest Friend, of the Icahn School of Medicine at Mount Sinai in New York City, and colleagues. Finding people like that is a challenge, though, because they don’t have symptoms.
To find such people, the team assembled existing genetic data from 589,306 adults who had their DNA tested as part of 12 ongoing or past studies. The researchers then searched for mutations known to cause genetic diseases in childhood. Since study participants were adults, they should already have developed symptoms.
Initially, the researchers found more than 15,000 potential escape artists. Further analysis whittled the field to 42. Of those, medical records indicated that 14 had symptoms of their genetic disease after all. Another 15 were ruled out because a closer examination found that each person had only one copy of a mutated gene. The other copy was normal, so could compensate for the debilitated copy.
The remaining 13 people carried mutations associated with one of eight different diseases, but somehow had not developed symptoms. The study suggests that it is possible to find people who are resistant to getting genetic diseases.
But some resilient people may have been missed because the study included only a fraction of known disease-causing mutations, says Daniel MacArthur, a geneticist at Massachusetts General Hospital in Boston. More troubling is that the researchers could not confirm that resistant people were disease-free or verify that they really have mutations. That’s because consent forms signed when participants agreed to share their genetic information did not contain provisions for researchers to contact volunteers later for retesting. “Some of their resilient cases may be mirages,” MacArthur wrote in a commentary, also in Nature Biotechnology. Garry Cutting, a medical geneticist at Johns Hopkins School of Medicine, is also concerned that some of the lucky 13 may not be true escape artists. Cutting studies genes and environmental factors that determine the severity of cystic fibrosis, a disease in which thick mucus builds up in the lungs, pancreas and other organs. People develop the disease when they inherit two defective copies of the CFTR gene. More than 1,800 mutations in that gene can cause the disease if inherited in double copies or in combinations of mutations.
Of the 13 resilient people in the study, three carry dual copies of a very rare mutation in the CFTR gene, but don’t have cystic fibrosis.
Only one person in a database of 88,000 cystic fibrosis patients carries two copies of the rare mutation. So finding three people with double copies of the mutation is extraordinary, Cutting says. “It’s so exceptional that I believe it requires more extensive verification.”
He says he would be “delighted” if the people really turn out to be resistant to getting cystic fibrosis, but he’s puzzled why that mutation alone allows escape. It could be that a variant in another gene counteracts that specific mutation in the CFTR gene. Or a second mutation in the mutant CFTR gene may reverse the effect of the disease-causing one. However, it is possible that the three people avoided cystic fibrosis because they have only one copy of the mutated gene and one healthy copy that the researchers missed with the methods they used, Cutting says.
MacArthur points out another potential drawback to the study: Even if the researchers expand the study to 1 million or more people, they may not discover enough “genetic superheroes” to create a sample size large enough to detect protective genes. Such an effort may require participation from hundreds of millions of people and researchers willing to share data on a global scale.
Normal is the new strange for the world’s largest cave salamanders.
Biologists are thinking deep thoughts about why some of Europe’s olm salamanders living in darkness have (gasp!) skin coloring and eyes with lenses.
Most salamanders, of course, have skin pigments and grow adult eyes like other vertebrates. But after eons of cave life, olms (Proteus anguinus) have become mostly pinkish-white beasts, about 30 centimeters head to tail, that spend long lifetimes (maybe 70 years) slinking in cold, subterranean water. Living at 11 to 12° Celsius, olms don’t mature sexually until about age 11 for males and 14 for females. Even then, they never really grow up, staying in water like giant larvae and keeping such youthful features as neck fluff gills into old age. “They look a little creepy, especially if you look at the skull,” says Stanley Sessions of Hartwick College in Oneonta, N.Y. Their blunt heads have no real upper jaw, and their adult eyes start to form but then regress to nubbins buried under skin. These salamanders live frugally. They can go more than a year without eating. (Lilijana Bizjak Mali of the University of Ljubljana in Slovenia says a lab-dwelling olm survived even after more than 10 years without food.) Females take six-to-12-year breaks between laying eggs, which “develop extraordinarily slowly,” Sessions says. Recently laid olm eggs in Slovenia’s Postojna Cave took about seven weeks to start forming a nervous system; a common spotted salamander takes about one.
Among extreme cave-lifers, the oddballs are the more normal-looking salamanders (for now, called subspecies parkelj), with dark skin and better-developed eyes. For decades, biologists treated these curios as remnants of the most ancient olms that haven’t shed all their daylight ways. But rather than putting the dark salamanders at the base of the genealogical tree of olms, a genetic analysis places them higher among more recent, pale lineages.
“This forces you to consider that the black one probably evolved from white ancestors by reversing cave adaptations,” Sessions says. In evolution, “weirder things have happened.”
Three Earth-sized planets orbiting a star practically next-door might be a good place to hunt for alien life — or at least check out some worlds that are different from anything in our solar system.
The planets orbit a dim, cool star just 39 light-years away in the constellation Aquarius. Each is outside or possibly on the edge of the star’s habitable zone — where average temperatures are just right for liquid water. But there could be niche locales on these worlds where alien life might thrive, Michaël Gillon, an astrophysicist at University of Liège in Belgium, and colleagues report online May 2 in Nature. A year on the two inner planets lasts just a couple of days. Data on the third world are sparse; it could take anywhere between 4.5 and 72.8 days to trek around its sun. The star, designated 2MASS J23062928−0502285, is roughly the size of Jupiter — about one-tenth as wide as our sun — and about 3,200 degrees Celsius cooler than the sun. Such runts make up about 15 percent of the stars in the galaxy, though astronomers had not found planets around one before. All three planets were discovered as periodic dips in starlight in late 2015 using TRAPPIST, a telescope at La Silla Observatory in Chile.
If anything does crawl or grow on these worlds, it bathes in mostly infrared light. The innermost planets receive several times as much energy from their star as Earth does from our sun, which technically puts them outside the star’s habitable zone (SN: 4/30/16, p. 36). But the planets are huddled up so close to the star that gravity might keep them from spinning, creating a temperate zone along the line where day turns to night, the researchers suggest.
Faint red stars such as this one are the best place to look for warm rocky planets, says Nicolas Cowan, an astronomer at McGill University in Montreal. Planets, even small ones, are easier to see around these dim bulbs rather than sunlike stars. NASA’s planet-hunting Kepler space telescope has already shown that planets exist around similar stars, but those are too far away to investigate further. “This [study] finds a nearby example,” says Cowan.
Being nearby is important for studying the atmospheres of such worlds, or learning whether they have atmospheres at all. They may not. Red dwarf stars take a long time to form; planets arise while their sun is still a puffy, temperamental ball of contracting gas. “That might bake off all the water and the atmosphere,” Cowan says. Astronomers won’t know, though, until they point some big telescopes toward these worlds.
The Hubble Space Telescope might be able to get a crude look. But NASA’s James Webb Space Telescope, scheduled to launch in 2018, could gaze at these planets and measure how much starlight is being absorbed by molecules in their atmospheres. If there is an atmosphere, James Webb could look for such gases as oxygen and methane (SN: 4/30/16, p. 32). On Earth, at least, those gases are produced by plants and microbes.
Whether or not life has found a home on these worlds, all offer a peek at unfamiliar environments. The two planets closest to the star, for example, are bombarded with more energy than Venus, notes Lisa Kaltenegger, an astronomer at Cornell University. “How would Venus evolve if you heat it up even more?” she asks. “We don’t have such planets in our own solar system, so it is really interesting to find out what such planets can be like.”
New sperm-catching beads could someday help prevent pregnancy — or enable it.
Researchers created microscopic polymer beads that mimic unfertilized eggs and trap passing sperm. The beads are coated in the sperm-binding section of a protein called ZP2. In mammals, ZP2 is found in membranes around unfertilized eggs; sperm must bind to the protein before entering the egg.
The beads could be used as short-term contraceptives, Jurrien Dean of the National Institutes of Health in Bethesda, Md., and colleagues report in the April 27 Science Translational Medicine. In the laboratory, human sperm attached to the beads within five minutes. The researchers then mixed 100,000 human sperm with 1.5 million beads and 28 mouse eggs containing human ZP2 proteins. After 16 hours, only one sperm reached an egg. In another experiment, beads coated with mouse ZP2 delayed pregnancy when injected into the uteruses of mating female mice. Bead-free mice took just over 28 days, on average, to conceive and give birth; bead-treated mice didn’t have babies for nearly 73 days on average. The beads didn’t appear to cause swelling or damage, and treated mice were able to give birth again within five months.
The beads could also help combat infertility. In an egg-penetration test, researchers gently detached bead-captured sperm and pitted those sperm against a control batch of sperm that had not been exposed to the beads. More than half of eggs (mouse eggs with human ZP2) exposed to the bead-selected sperm ended up with three or more sperm attached to them; none of the eggs exposed to the control group snagged three or more sperm. In fact, the control group failed to penetrate 38 out of 50 eggs. So the beads could someday be used to select healthy sperm for assisted reproduction, the researchers say.
But it’s not clear if the ability to bind to ZP2 necessarily indicates a healthy sperm, says Andrew La Barbera, chief scientific officer of the American Society for Reproductive Medicine in Birmingham, Ala. “Sperm selection is a very complex undertaking because of the fact that sperm are very complex,” he says. “We don’t know what makes a good sperm.”
Contraception might be a more reasonable future use for the beads, although allowing fertilization of one in 28 eggs is underwhelming, La Barbera says. Birth control should be closer to 99.9 percent effective. “It only takes one sperm to fertilize an egg,” he says. Still, the beads’ performance at blocking pregnancy in mice seems promising, La Barbera says. Future experiments would need to determine if the beads are safe and effective in women, and how many beads are needed to prevent conception.
Dean notes that the study is a proof of principle. Many unknowns must be evaluated before using the beads for birth control, including the side effects of long-term use, he says. “Although promising, we are a long way from translating these basic laboratory observations into useful clinical applications that provide people with better reproductive choices.”
During the rainy season in the Orinoco Llanos of Columbia and Venezuela, an odd landscape feature appears in places: mounds of grassy plants, as big as five meters across and two meters tall, surrounded by water. Traversing this landscape, called surales, requires either hopping from mound to mound or trudging through the boggy bits in between.
Locals and scientists have generally agreed that some kind of earthworm creates the mounds, but what species and how it does so has been a mystery. Now Anne Zangerlé of the Braunschweig University of Technology in Germany and colleagues report that they’ve found the culprit — giant Andiorrhinus earthworms, which can grow to a meter in length as juveniles. And the mounds themselves, the team reports May 11 in PLOS ONE, are actually made mostly of earthworm poop.
Zangerlé and her colleagues used Google Earth images to locate surales landscapes, finding that they come in the shape of both mounds and labyrinths. Leaving the complex labyrinths for a future study, the team studied the mounds and the lands on which they were found in both the rainy and dry seasons. They characterized the soil and the plants and worms living in and on the mounds. And then they pieced all of that information together to come up with a scenario that they think explains the construction of the mounds. Andiorrhinus earthworms deposit feces, or casts, in towers that give the worms access to the air so they can breathe. The worms then return to the tower, depositing more and more material, building the tower into a mound. These young mounds, the researchers found, are dominated by Andiorrhinus earthworms. But over time, as the mounds get even bigger, other worm species begin to make their home there, as well as plants and, eventually, if the mounds get big enough, trees.
The Andiorrhinus earthworms tend to stay around the same mound because, as they build, they excavate soil from the region around the mound. That moat gets deeper and deeper until it becomes a barrier to the giant earthworm that created it.
The researchers don’t quite understand everything that is happening in the system. For example, there could be an as-yet-unknown end stage to mound development, or some kind of equilibrium state for the landscape. But they note that “these ecosystems are under threat from industrial agriculture, and are being leveled to make way for highly intensified commercial production of rice.” Because of that, they say, there is a risk that these wonderfully complex and mysterious systems could disappear before anyone fully understands what made them in the first place.
Earth’s plate tectonics could be a passing phase. After simulating rock and heat flow throughout a planet’s lifetime, researchers have proposed that plate tectonics is just one stage of a planet’s life cycle.
In the simulation, the Earth’s interior was too hot and runny at first to push around the giant chunks of crust, researchers report in the June Physics of the Earth and Planetary Interiors. After the interior cooled for around 400 million years, tectonic plates began shifting and sinking, though the process was stop-and-go for about 2 billion years. The simulation suggests that Earth now is nearly halfway through its tectonic life cycle, says study coauthor Craig O’Neill, a planetary scientist at Macquarie University in Sydney. In around 5 billion years, plate tectonics will grind to a halt as the planet chills.
The long delay before full-blown plate tectonics hints that the process could one day begin on currently stagnant planets, says Julian Lowman, a geodynamicist at the University of Toronto who was not involved in the research. “There is a possibility that plate tectonics could start up on Venus if conditions were right,” he says. Plate tectonics regulates a planet’s climate by adding and removing carbon dioxide from the atmosphere. This climate control helps maintain Earth’s habitability. Plate movement is driven by heat flow through the planet’s interior. Simulating that heat flow requires complex calculations. Previous simulations were simplified and typically considered only snapshots of Earth’s history and missed how plate tectonics evolves over time.
O’Neill and colleagues simulated Earth’s full tectonic life span, starting with the planet’s formation around 4.5 billion years ago and looking ahead to around 10 billion years in the future. Even using a supercomputer and simulating only a two-dimensional cross section of the planet, the calculations took weeks.
The new timeline suggests that Earth’s plate tectonics is just a midpoint in the planet’s evolution between two stagnant states. Planets with different starting temperatures than Earth’s follow different trajectories, the team found. Colder planets may exhibit plate tectonics throughout their history while hotter planets could go for billions of years without plate tectonics.
Just because a planet currently lacks plate tectonics doesn’t make it uninhabitable, O’Neill says. Life potentially appeared on Earth as early as around 4.1 billion years ago (SN Online: 10/19/2015), a time when the new simulation suggests that Earth lacked full-blown plate tectonics. “Stagnant planets, depending on when they are in their history, can be equally likely of supporting habitable conditions” as planets with plate tectonics, O’Neill says.
Childhood fears are common, normal — Some behavior, such as nail biting, bed-wetting and fearfulness, may actually represent a temporary phase in normal development…. A most important finding [in a recent study] was that the fearful or anxious children, defined … as those with seven or more worries, did not seem to be in any particular psychological trouble.…Anxieties may be part of normal child development. — Science News, June 25, 1966
UPDATE Actually, there is reason to worry about anxious children. Kids with anxiety disorders, depression or behavioral problems are especially likely to develop a range of difficulties as young adults, say researchers who conducted a long-term study published in 2015. The same goes for kids whose anxiety, mood or behavior issues cause daily problems but don’t qualify as psychiatric ailments. Problems that later dogged the study’s troubled youngsters, who grew up in rural North Carolina, included drug addiction, teenage parenthood, dropping out of high school and criminal arrests.
