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NASA’s Dawn spacecraft has detected organic compounds on Ceres — the first concrete proof of organics on an object in the asteroid belt between Mars and Jupiter.

This material probably originated on the dwarf planet itself, the researchers report in the Feb. 17 Science. The discovery of organic compounds adds to the growing body of evidence that Ceres may have once had a habitable environment.

“We’ve come to recognize that Ceres has a lot of characteristics that are intriguing for those looking at how life starts,” says Andy Rivkin, a planetary astronomer at the Johns Hopkins University Applied Physics Laboratory in Laurel, Md., who was not involved in the study.
The Dawn probe has previously detected salts, ammonia-rich clays and water ice on Ceres, which together indicate hydrothermal activity, says study coauthor Carol Raymond, a planetary scientist at NASA’s Jet Propulsion Laboratory in Pasadena, Calif.

For life to begin, you need elements like carbon, hydrogen, nitrogen and oxygen, as well as a source of energy. Both the hydrothermal activity and the presence of organics point toward Ceres having once had a habitable environment, Raymond says.

“If you have an abundance of those elements and you have an energy source,” she says, “then you’ve created sort of the soup from which life could have formed.” But study coauthor Lucy McFadden, a planetary scientist at NASA’s Goddard Space Flight Center in Greenbelt, Md., stresses that the team has not actually found any signs of life on Ceres.

Evidence of Ceres’ organic material comes from areas near Ernutet crater. Dawn picked up signs of a “fingerprint,” or spectra, consistent with organics. The pattern of wavelengths of light absorbed and reflected from these areas is similar to the pattern seen in hydrocarbons on Earth such as kerite and asphaltite. But without a sample from the surface, the team can’t say definitively what organic material is present or how it formed, says study coauthor Harry McSween, a geologist at the University of Tennessee.
The team suspects that the organics formed within Ceres’ interior and were brought to the surface by hydrothermal activity. An alternative idea — that a space rock that crashed into Ceres brought the material — is unlikely, the researchers say, because the concentration of organics is so high. An impact would have mixed organic compounds across the surface, diluting the concentration.

Detecting organics on Ceres also has implications for how life arose on Earth, McSween says. Some researchers think that life was jump-started by asteroids and other space rocks that delivered organic compounds to the planet. Finding such organic matter on Ceres “adds some credence to that idea,” he says.

Big data is everywhere these days and police departments are no exception. As law enforcement agencies are tasked with doing more with less, many are using predictive policing tools. These tools feed various data into algorithms to flag people likely to be involved with future crimes or to predict where crimes will occur.

In the years since Time magazine named predictive policing as one of 2011’s best 50 inventions of the year, its popularity has grown. Twenty U.S. cities, including Chicago, Atlanta, Los Angeles and Seattle are using a predictive policing system, and several more are considering it. But with the uptick in use has come a growing chorus of caution. Community activists, civil rights groups and even some skeptical police chiefs have raised concerns that predictive data approaches may unfairly target some groups of people more than others.

New research by statistician Kristian Lum provides a telling case study. Lum, who leads the policing project at the San Francisco-based Human Rights Data Analysis Group, looked at how the crime-mapping program PredPol would perform if put to use in Oakland, Calif. PredPol, which purports to “eliminate profiling concerns,” takes data on crime type, location and time and feeds it into a machine-learning algorithm. The algorithm, originally based on predicting seismic activity after an earthquake, trains itself with the police crime data and then predicts where future crimes will occur.

Lum was interested in bias in the crime data — not political or racial bias, just the ordinary statistical kind. While this bias knows no color or socioeconomic class, Lum and her HRDAG colleague William Isaac demonstrate that it can lead to policing that unfairly targets minorities and those living in poorer neighborhoods.

By applying the algorithm to 2010 data on drug crime reports for Oakland, the researchers generated a predicted rate of drug crime on a map of the city for every day of 2011. The researchers then compared the data used by the algorithm — drug use documented by the police — with a record of overall drug use, whether recorded or not. This ground-truthing came from taking public health data from the 2011 National Survey on Drug Use and Health and demographic data from the city of Oakland to derive an estimate of drug use for all city residents.
In this public health-based map, drug use is widely distributed across the city. In the predicted drug crime map, it is not. Instead, drug use deemed worthy of police attention is concentrated in neighborhoods in West Oakland and along International Boulevard, two predominately low-income and nonwhite areas.
Predictive policing approaches are often touted as eliminating concerns about police profiling. But rather than correcting bias, the predictive model exacerbated it, Lum said during a panel on data and crime at the American Association for the Advancement of Science annual meeting in Boston in February. While estimates of drug use are pretty even across race, the algorithm would direct Oakland police to locations that would target black people at roughly twice the rate of whites. A similar disparity emerges when analyzing by income group: Poorer neighborhoods get targeted.
And a troubling feedback loop emerges when police are sent to targeted locations. If police find slightly more crime in an area because that’s where they’re concentrating patrols, these crimes become part of the dataset that directs where further patrolling should occur. Bias becomes amplified, hot spots hotter.

There’s nothing wrong with PredPol’s algorithm, Lum notes. Machine learning algorithms learn patterns and structure in data. “The algorithm did exactly what we asked; it learned patterns in the data,” she says. The danger is in thinking that predictive policing will tell you about patterns in the occurrence of crime. It’s really telling you about patterns in police records.

Police aren’t tasked with collecting random samples, nor should they be, says Lum. And that’s all the more reason why departments should be transparent and vigilant about how they use their data. In some ways, PredPol-guided policing isn’t so different from old-fashioned pins on a map.

For her part, Lum would prefer that police stick to these timeworn approaches. With pins on a map, the what, why and where of the data are very clear. The black box of an algorithm, on the other hand, lends undue legitimacy to the police targeting certain locations while simultaneously removing accountability. “There’s a move toward thinking machine learning is our savior,” says Lum. “You hear people say, “A computer can’t be racist.’”

The use of predictive policing may be costly, both literally and figuratively. The software programs can run from $20,000 to up to $100,000 per year for larger cities. It’s harder to put numbers on the human cost of over-policing, but the toll is real. Increased police scrutiny can lead to poor mental health outcomes for residents and undermine relationships between police and the communities they serve. Big data doesn’t help when it’s bad data.

It’s not the size of a snake’s muscles that matter, but how it uses them. King snakes can defeat larger snakes in a wrestling match to the death because of how they coil around their prey, researchers report March 15 in the Journal of Experimental Biology.

King snakes wrap around their food and squeeze with about twice as much pressure as rat snakes do, says David Penning, a functional morphologist at Missouri Southern State University in Joplin. Penning, along with colleague Brad Moon at the University of Louisiana at Lafayette, measured the constriction capabilities of almost 200 snakes. “King snakes are just little brutes,” Penning says.
King snakes, which are common in North American forests and grasslands, are constrictor snakes that “wrestle for a living,” Penning says. They mainly eat rodents, birds and eggs, squeezing so hard, they can stop their prey’s heart (SN: 8/22/15, p. 4). In addition, about a quarter of the king snake diet is other snakes. King snakes can easily attack and eat vipers because they’re immune to the venom, but when they take on larger constrictors, such as rat snakes, it has been unclear what gives them the edge. “That’s not how nature goes,” Penning says, because predators are usually larger than their prey.

King snakes, though, can eat snakes up to 35 percent larger than themselves. One of the largest king snake conquests on record, from 1893, is of a 5-foot-3-inch rat snake, about 17 percent larger than the 4-foot-6-inch king snake that consumed it, Penning says.
“David Penning is really one of the first researchers that has been looking at the anatomy, physiology and function of these snakes” to understand how king snakes are superior to rat snakes, says Anthony Herrel, a functional morphologist and evolutionary biologist at the French National Museum of Natural History in Paris.
To determine what makes these snakes kings, Penning and Moon compared their muscle size, ability to escape attack and the strength of their squeeze to that of rat snakes. In one test, the researchers shook dead rodents enticingly in front of the snakes to goad them into striking and squeezing. Sensors on the rodents recorded the pressure of the squeeze.

The king snakes constricted with an average pressure of about 20 kilopascals, stronger than the pumping pressure of a human heart. Rat snakes in the same tests applied only about 10 kilopascals of pressure.

But the king snakes weren’t bigger body builders. Controlling for body size, the two kinds of snakes “had the exact same quantity of muscle,” Penning says.

The snakes’ more powerful constriction is probably due to how they use their muscles, not how much muscle they have, the researchers conclude. They observed that the majority of king snakes in the study wrapped around their food like a spring in what Penning calls the “curly fry pattern.” Rat snakes didn’t always coil in the same way and often ended up looking like a “weird pile of spaghetti,” he says.

Penning plans to study how other factors influence constriction as well, such as how long the king snakes can squeeze, how hungry they are and the temperature of their environment.

I’ve been to the playground enough times to know a juicy parenting controversy when I see (or overhear) one. Bed-sharing, breastfeeding and screen time are always hot-button issues. But I’m not talking about any of those. No, I’m talking about actual juice.

Some parents see juice as a delicious way to get vitamins into little kids. Others see juice as a gateway drug to a sugar-crusted, sedentary lifestyle, wrapped up in a kid-friendly box. No matter where you fall on the juice spectrum, you can be sure there are parents to either side of you. (Disclosure: My kids don’t drink much juice, simply because the people who buy their groceries aren’t all that into it. And juice is heavy.)

Scientific studies on the effects of juice have been somewhat sparse, allowing deeply held juice opinions to run free. One of the chief charges against juice is that it’s packed with sugar. An 8-ounce serving of grape juice, even with no sugar added, weighs in at 36 grams. That tops Coca-Cola, which delivers 26 grams of sugar in 8 ounces. And all of those extra sweet calories can lead to extra weight.

A recent review of eight studies on juice and children’s body weight, published online March 23 in Pediatrics, takes a look at this weight concern. It attempts to clarify whether kids who drink 100 percent fruit juice every day are at greater risk of gaining weight. After sifting through the studies’ data, researchers arrived at an answer that will please pro-juicers: Not really.

“Our study did not find evidence that consuming one serving per day of 100 percent fruit juice influenced BMI to a clinically important degree,” says study coauthor Brandon Auerbach of the University of Washington in Seattle.

The analysis found that for children ages 1 to 6, one daily serving of juice (6 to 8 ounces) was associated with a sliver of an increase in body mass index, or BMI. Consider a 5-year-old girl who started out right on the 50th percentile for weight and BMI. After a year of daily juice, this girl’s BMI may have moved from the 50th to the 52nd or 54th percentile, corresponding to a weight increase of 0.18 to 0.33 pounds over the year. That amount “isn’t trivial, but it’s not enough on its own to lead to poor health,” Auerbach says.

The results, of course, aren’t the final word. The analysis was reviewing data from other studies, and those studies came with their own limitations. For one thing, the studies didn’t assign children to receive or not receive juice. Instead, researchers measured the children’s juice-drinking behavior that was already under way and tried to relate that to their weight. That approach means that it’s possible that differences other than juice consumption could influence the results.
It’s important to note the distinction here between the 100 percent fruit juice in the studies and fruit cocktails, which are fruit-flavored drinks that often come with lots of added sugar. The data on those drinks is more damning in terms of weight gain and the risk of cavities, Auerbach says.

Also worth noting: The American Academy of Pediatrics recommends that kids between ages 1 and 6 get only 4 to 6 ounces of juice a day. That’s a smaller amount than many of the kids in the studies received. And the AAP recommends babies younger than 6 months get no juice at all.

In general, whole fruits, such as apples and oranges, are better than juice because they provide fiber and other nutrients absent from juice. (Bonus for toddlers: Oranges are fun to peel. Bummer for parents: Doing so makes a sticky mess.)

Still, the new analysis may ease some guilt around letting the juice flow. And it can enable parents to save their worries for more harmful things, of which there are plenty.

A 36-million-year-old fossil skeleton is revealing a critical moment in the history of baleen whales: what happened when the ancestors of these modern-day filter feeders first began to distinguish themselves from their toothy, predatory predecessors. The fossil is the oldest known mysticete, a group that includes baleen whales, such as humpbacks, researchers report in the May 22 Current Biology.

Scientists have made predictions about what the first mysticetes might have looked like, but until now, haven’t had much fossil evidence to back up those ideas, says Nicholas Pyenson, a paleobiologist at the Smithsonian National Museum of Natural History in Washington, D.C. “Here, we have something we’ve been waiting for: a really old baleen whale ancestor.”
The earliest whales were predators with sharp teeth — a legacy carried on by today’s orcas, dolphins and other toothed whales. But at some point during whale history, the ancestors of modern mysticetes replaced teeth with baleen, fibrous plates that filter out small bits of food from seawater like a giant sieve. Such a huge lifestyle change didn’t happen overnight, though. And the new find, dubbed Mystacodon selenensis, shows the start of that transition, its discoverers say.

Mystacodon largely fits in well with what scientists have predicted from analyzing other whales, says Mark Uhen, a paleobiologist at George Mason University in Fairfax, Va. “It fleshes out this transition, rather than being something wacky and crazy we never thought of.”

Mystacodon was unearthed in a Peruvian desert by a team of European and Peruvian scientists. Like other early mysticetes, this one still had teeth — its name means “toothed mysticete.” The creature was probably close to 4 meters long, estimates study coauthor Olivier Lambert, a paleontologist at the Royal Belgian Institute of Natural Sciences in Brussels. That’s about the size of a pilot whale, and far smaller than today’s leviathan humpbacks.
The whale holds onto some features of primitive whales, Lambert says. For instance, it still had a bit of a protruding hip bone, suggesting the presence of tiny hind legs left over from when whales’ ancestors were four-legged, terrestrial creatures. “At this transition, scientists thought that this hind limb would be more or less gone,” Lambert says. But the new find suggests that completely losing those limbs took a little longer than previously believed. And the process probably happened independently in toothed whales, instead of one time in the common ancestor of baleen and toothed whales.
But Mystacodon also shows some more modern features. Its snout was flattened, just like in modern mysticetes. In the earliest whales, the joints in the front flippers — essentially elbows — could still be flexed, a relic of when those flippers were legs. Modern whales can’t move those joints, and neither could Mystacodon.
“This is the first indication of a locked elbow — the final step of the transition of the forelimbs into flippers,” Lambert says.

Wear patterns on Mystacodon’s teeth suggest that the whale was a suction feeder — vacuuming up its prey instead of chomping it. That could have been a step toward the filter-feeding strategies used by today’s baleen whales, Lambert suggests. (Other early mysticetes show similar wear, also suggesting suction-feeding tendencies.)

But the connection between suction feeding and filter feeding isn’t well-established, Pyenson says. Mysticetes didn’t become true filter feeders until millions of years later, he says. And scientists still don’t know what series of changes in the ocean environment and in mysticetes’ bodies led to the transformation. “I don’t think suction feeding alone is the primary step.”

Lambert and his colleagues will be looking for more ancient whales to further flesh out the story of early mysticetes. The region where the skeleton was found — the Pisco Basin on the southern coast of Peru — is a hot spot for evidence of ancient whales and dolphins that was overlooked for many years, Lambert says. “There is huge potential for the area where we excavated.”

Like 1980s hair bands, male cockatoos woo females with flamboyant tresses and killer drum solos.

Male palm cockatoos (Probosciger aterrimus) in northern Australia refashion sticks and seedpods into tools that the animals use to bang against trees as part of an elaborate visual and auditory display designed to seduce females. These beats aren’t random, but truly rhythmic, researchers report online June 28 in Science Advances. Aside from humans, the birds are the only known animals to craft drumsticks and rock out.
“Palm cockatoos seem to have their own internalized notion of a regular beat, and that has become an important part of the display from males to females,” says Robert Heinsohn, an evolutionary biologist at the Australian National University in Canberra. In addition to drumming, mating displays entail fluffed up head crests, blushing red cheek feathers and vocalizations. A female mates only every two years, so the male engages in such grand gestures to convince her to put her eggs in his hollow tree nest.

Heinsohn and colleagues recorded more than 131 tree-tapping performances from 18 male palm cockatoos in rainforests on the Cape York Peninsula in northern Australia. Each had his own drumming signature. Some tapped faster or slower and added their own flourishes. But the beats were evenly spaced — meaning they constituted a rhythm rather than random noise.

From bonobos to sea lions, other species have shown a propensity for learning and recognizing beats. And chimps drum with their hands and feet, sometimes incorporating trees and stones, but they lack a regular beat.

The closest analogs to cockatoo drummers are human ones, Heinsohn says, though humans typically generate beats as part of a group rather than as soloists. Still, the similarity hints at the universal appeal of a solid beat that may underlie music’s origins.

Quantum particles can burrow through barriers that should be impenetrable — but they don’t do it instantaneously, a new experiment suggests.

The process, known as quantum tunneling, takes place extremely quickly, making it difficult to confirm whether it takes any time at all. Now, in a study of electrons escaping from their atoms, scientists have pinpointed how long the particles take to tunnel out: around 100 attoseconds, or 100 billionths of a billionth of a second, researchers report July 14 in Physical Review Letters.
In quantum tunneling, a particle passes through a barrier despite not having enough energy to cross it. It’s as if someone rolled a ball up a hill but didn’t give it a hard enough push to reach the top, and yet somehow the ball tunneled through to the other side.

Although scientists knew that particles could tunnel, until now, “it was not really clear how that happens, or what, precisely, the particle does,” says physicist Christoph Keitel of the Max Planck Institute for Nuclear Physics in Heidelberg, Germany. Theoretical physicists have long debated between two possible options. In one model, the particle appears immediately on the other side of the barrier, with no initial momentum. In the other, the particle takes time to pass through, and it exits the tunnel with some momentum already built up.

Keitel and colleagues tested quantum tunneling by blasting argon and krypton gas with laser pulses. Normally, the pull of an atom’s positively charged nucleus keeps electrons tightly bound, creating an electromagnetic barrier to their escape. But, given a jolt from a laser, electrons can break free. That jolt weakens the electromagnetic barrier just enough that electrons can leave, but only by tunneling.

Although the scientists weren’t able to measure the tunneling time directly, they set up their experiment so that the angle at which the electrons flew away from the atom would reveal which of the two theories was correct. The laser’s light was circularly polarized — its electromagnetic waves rotated in time, changing the direction of the waves’ wiggles. If the electron escaped immediately, the laser would push it in one particular direction. But if tunneling took time, the laser’s direction would have rotated by the time the electron escaped, so the particle would be pushed in a different direction.

Comparing argon and krypton let the scientists cancel out experimental errors, leading to a more sensitive measurement that was able to distinguish between the two theories. The data matched predictions based on the theory that tunneling takes time.
The conclusion jibes with some physicists’ expectations. “I’m pretty sure that the tunneling time cannot be instantaneous, because at the end, in physics, nothing can be instantaneous,” says physicist Ursula Keller of ETH Zurich. The result, she says, agrees with an earlier experiment carried out by her team.

Other scientists still think instantaneous tunneling is possible. Physicist Olga Smirnova of the Max Born Institute in Berlin notes that Keitel and colleagues’ conclusions contradict previous research. In theoretical calculations of tunneling in very simple systems, Smirnova and colleagues found no evidence of tunneling time. The complexity of the atoms studied in the new experiment may have led to the discrepancy, Smirnova says. Still, the experiment is “very accurate and done with great care.”

Although quantum tunneling may seem an esoteric concept, scientists have harnessed it for practical purposes. Scanning tunneling microscopes, for instance, use tunneling electrons to image individual atoms. For such an important fundamental process, Keller says, physicists really have to be certain they understand it. “I don’t think we can close the chapter on the discussion yet,” she says.

Discoveries about the molecular ups and downs of fruit flies’ daily lives have won Jeffrey C. Hall, Michael Rosbash and Michael W. Young the Nobel Prize in physiology or medicine.

These three Americans were honored October 2 by the Nobel Assembly at the Karolinska Institute in Stockholm for their work in discovering important gears in the circadian clocks of animals. The trio will equally split the 9 million Swedish kronor prize — each taking home the equivalent of $367,000.
The researchers did their work in fruit flies. But “an awful lot of what was subsequently found out in the fruit flies turns out also to be true and of huge relevance to humans,” says John O’Neill, a circadian cell biologist at the MRC Laboratory of Molecular Biology in Cambridge, England. Mammals, humans included, have circadian clocks that work with the same logic and many of the same gears found in fruit flies, say Jennifer Loros and Jay Dunlap, geneticists at the Geisel School of Medicine at Dartmouth College.
Circadian clocks are networks of genes and proteins that govern daily rhythms and cycles such as sleep, the release of hormones, the rise and fall of body temperature and blood pressure, as well as other body processes. Circadian rhythms help organisms, including humans, anticipate and adapt to cyclic changes of light, dark and temperature caused by Earth’s rotation. When circadian rhythms are thrown out of whack, jet lag results. Shift workers and people with chronic sleep deprivation experience long-term jet lag that has been linked to serious health consequences including cancer, diabetes, heart disease, obesity and depression.
Before the laureates did their work, other scientists had established that plants and animals have circadian rhythms. In 1971, Seymour Benzer and Ronald Konopka (both now deceased and ineligible for the Nobel Prize) found that fruit flies with mutations in a single gene called period had disrupted circadian rhythms, which caused the flies to move around at different times of day than normal.

“But then people got stuck,” says chronobiologist Erik Herzog of Washington University in St. Louis. “We couldn’t figure out what that gene was or how that gene worked.”
At Brandeis University in Waltham, Mass., Hall, a geneticist, teamed up with molecular biologist Rosbash to identify the period gene at the molecular level in 1984. Young of the Rockefeller University in New York City simultaneously deciphered the gene’s DNA makeup. “In the beginning, we didn’t even know the other group was working on it, until we all showed up at a conference together and discovered we were working on the same thing,” says Young. “We said, ‘Well, let’s forge ahead. Best of luck.’”
It wasn’t immediately apparent how the gene regulated fruit fly activity. In 1990, Hall and Rosbash determined that levels of period’s messenger RNA — an intermediate step between DNA and protein — fell as levels of period’s protein, called PER, rose. That finding indicated that PER protein shuts down its own gene’s activity.

A clock, however, isn’t composed of just one gear, Young says. He discovered in 1994 another gene called timeless. That gene’s protein, called TIM, works with PER to drive the clock. Young also discovered other circadian clockworks, including doubletime and its protein DBT, which set the clock’s pace. Rosbash and Hall discovered yet more gears and the two groups competed and collaborated with each other. “This whole thing would not have turned out nearly as nicely if we’d been the only ones working on it, or they had,” Young says.

Since those discoveries, researchers have found that nearly every cell in the body contains a circadian clock, and almost every gene follows circadian rhythms in at least one type of cell. Some genes may have rhythm in the liver, but not the skin cells, for instance. “It’s normal to oscillate,” Herzog says.
Trouble arises when those clocks get out of sync with each other, says neuroscientist Joseph Takahashi at the University of Texas Southwestern Medical Center in Dallas. For instance, genes such as cMyc and p53 help control cell growth and division. Scientists now know they are governed, in part, by the circadian clock. Disrupting the circadian clock’s smooth running could lead to cancer-promoting mistakes.

But while bad timing might lead to diseases, there’s also a potential upside. Scientists have also realized that giving drugs at the right time might make them more effective, Herzog says.

Rosbash joked during a news conference that his own circadian rhythms had been disrupted by the Nobel committee’s early morning phone call. When he heard the news that he’d won the prize, “I was shocked, breathless really. Literally. My wife said, ‘Start breathing,’” he told an interviewer from the Nobel committee.

Young’s sleep was untroubled by the call from Sweden. His home phone is the kitchen, and he didn’t hear it ring, so the committee was unable to reach him before making the announcement. “The rest of the world knew, but I didn’t,” he says. Rockefeller University president Richard Lifton called him on his cell phone and shared the news, throwing Young’s timing off, too. “This really did take me surprise,” Young said during a news conference. “I had trouble even putting my shoes on this morning. I’d go pick up the shoes and realize I needed the socks. And then ‘I should put my pants on first.’”

THE WOODLANDS, Texas — Mars’ missing magnetic field may have drowned in the planet’s core.

An excess of hydrogen, split off from water molecules and stored in the Martian mantle, could have shut down convection, switching the magnetic field off forever, planetary scientist Joseph O’Rourke proposed March 21 at the Lunar and Planetary Science Conference.

Planetary scientists think magnetic fields are produced by the churning of a planet’s molten iron core. Convection relies on denser materials sinking into the core, and lighter stuff rising to the surface. The movement of iron, which can carry a charge, generates a strong magnetic field that can protect a planet’s atmosphere from being ravaged by solar wind (SN Online: 8/18/17).
But if lighter material, like hydrogen, settles close to the iron core, it could block dense material from sinking deep enough to keep convection going, said O’Rourke, of Arizona State University in Tempe.

“Too much hydrogen and you can shut down convection entirely,” he said. “Hydrogen is a heartless killer.”

O’Rourke and his ASU colleague S.-H. Dan Shim suggested the hydrogen could come from water locked up in Martian minerals. Near the hot core, water would split into hydrogen and oxygen. The oxygen would form compounds with other elements and stay high in the mantle, but the hydrogen could sit atop the core and effectively suffocate the dynamo.
The question is whether Mars’ minerals would have had what it took to deliver the hydrogen at the right time. Mars’ crust is rich in the mineral olivine, which does not bond well with water and so is relatively dry.

In the planet’s interior, pressure forces olivine to transform into the minerals wadsleyite and ringwoodite, which hold more water. Deeper still, the mineral turns into bridgmanite and becomes dry again. For a time, that bridgmanite layer could act as a buffer against water, allowing the core to keep convecting. But as the mantle cooled, the bridgmanite layer would shrink and eventually disappear, O’Rourke’s study suggests.

Whether Mars’ interior ever had that saving layer of bridgmanite depends on how big its core is — a property that may be tested by NASA’s InSight Mars lander, launching on May 5, O’Rourke said. Mars did have a magnetic field more than 4 billion years ago. Scientists have struggled to explain how it vanished, leaving the planet vulnerable to solar winds, which probably stripped away its atmosphere and surface water (SN: 12/12/15, p. 31).

If hydrogen shut down the planet’s generator, it would have had to act fast. Previous observations suggest the magnetic field disappeared relatively rapidly, over 100 million years.

Another theory by James Roberts of the Johns Hopkins Applied Physics Lab in Laurel, Md., suggests a large impact could have shut down the dynamo by heating the outermost core, which would have kept it from sinking.

“It’s actually a similar idea to O’Rourke’s,” Roberts says. It may take many more sophisticated Mars missions to figure out what really happened.

Honeybee royal jelly is food meant to be eaten on the ceiling. And it might also be glue that keeps a royal baby in an upside-down cradle.

These bees raise their queens in cells that can stay open at the bottom for days. A big blob of royal jelly, abundantly resupplied by worker bees, surrounds the larva at the ceiling. Before the food is deposited in the cell, it receives a last-minute jolt of acidity that triggers its proteins to thicken into goo, says Anja Buttstedt, a protein biochemist at Technische Universität Dresden in Germany. Basic larva-gripping tests suggest the jelly’s protein chemistry helps keep future queens from dropping out of their cells, Buttstedt and colleagues propose March 15 in Current Biology.
Suspecting the stickiness of royal jelly might serve some function, researchers tweaked its acidity. They then filled small cups with royal jelly with different pH levels and gently turned the cups upside down. At a natural royal jelly acidity of about pH 4.0, all 10 larvae dangled from their gooey blobs upside down overnight. But in jelly boosted to pH 4.8 (and thinned in the process), four of the 10 larvae dropped from the cups. At pH 5.9, all of them dropped.

Honeybees build several forms of royally oversized cells for raising a queen. Those for queens who will swarm with their workers to a new home hang from the rim of an array of regular cells. A hole stays open at the bottom of the cell until the larva nears pupation from her fat grub shape into a queen with wings. That hole at the bottom is big enough for a royal larva to fall through, confirms insect physiologist Steven Cook at the honeybee research lab in Beltsville, Md., run by the U.S. Department of Agriculture’s Agricultural Research Service.

Buttstedt and colleagues propose that the stickiness of royal jelly may be what keeps the larva in place. The team worked out how the jelly’s proteins change as it is made, and how those changes affect its consistency.

Royal jelly is secreted as a brew of proteins from the glands above a worker bee’s brain. At that point, it has a neutral pH, around 7, like water’s. The worker bee then adds fatty acids from glands in her mouthparts, which take the pH to around 4.
“It has a quite sour smell,” Buttstedt says. As for taste? “Really weird.” A steady diet of this jelly is what turns a larvae into a queen instead of a worker.

At pH 4, the jelly’s most common protein, MRJP1, goes complicated. When the protein leaves the glands above the brain, it’s clustered in groups of four along with smaller proteins called apisimins, the team found. When the acidity shifts, the MRJP1 foursomes and the apisimins hook together in slender fibers and get gluey.

“The most puzzling question,” Buttstedt says, is “why build upside-down queen cells in the first place?”