For three years, a team of scientists kept a big secret: They had discovered a giant crater-shaped depression buried beneath about a kilometer of ice in northwestern Greenland. In November, the researchers revealed their find to the world.

They hadn’t set out to find a crater. But in 2015, glaciologists studying ice-penetrating radar images of Greenland’s ice sheet, part of an annual survey by NASA’s Operation IceBridge mission, noticed an oddly rounded shape right at the northern edge of Hiawatha Glacier. If the 31-kilometer-wide depression is confirmed to be the remnant of a meteorite impact — and the team has produced a wealth of evidence suggesting that it is (SN: 12/8/18, p. 6) — the discovery is exciting in and of itself. It’s rare to find a new crater, let alone one on land that has retained its perfect bowl shape.

“This is just a straight-up exciting discovery that starts with this wonderful element of serendipity,” says team member Joseph MacGregor, a glaciologist with Operation IceBridge.

But the crater — let’s call it that, for the sake of discussion — may have also reignited a debate over a controversial hypothesis about a mysterious cold snap known as the Younger Dryas. This cold period began abruptly about 12,800 years ago and ended just as abruptly about 11,700 years ago. For more than a decade, a small group of researchers, unconnected with the group behind the new discovery, has suggested that a cosmic impact triggered the cooling (SN: 7/7/18, p. 18).
Proponents of the Younger Dryas impact hypothesis say that the remnants of a comet exploded in Earth’s atmosphere and that the airbursts sparked wildfires across North America. Soot and other particles from the fires blocked out the sun, causing the cold snap, which has been blamed for everything from the extinction of the mammoths to the disappearance of a group of people known as the Clovis.

Most scientists reject that an impact was responsible, refuting the idea that there were vast wildfires at the time or that the Clovis people even disappeared. Another big objection: the lack of a smoking gun, a crater dating to the onset of the Younger Dryas.
The “mammoth in the room,” therefore, is whether the Greenland crater might be that smoking gun. But a large, recent impact would be extremely unlikely, given the rarity of such impacts on Earth, particularly on land, says planetary scientist Clark Chapman of the Southwest Research Institute in Boulder, Colo., who was not involved with the discovery.

Indeed, one sticking point is that there are no direct dates for the newly discovered crater, because it is still buried beneath all that ice. The radar data offer only tantalizing clues to the age, suggesting that the crater is between 2.6 million and 11,700 years old.

That’s a huge time range, but the proponents of the hypothesis are convinced that this crater is what they’ve been waiting for. “I think it’s transformational in terms of convincing a lot of skeptics,” says James Kennett, a geologist at the University of California, Santa Barbara.
There’s another big sticking point when it comes to linking this crater to the impact hypothesis: Instead of a fragment of a comet, the discoverers think the Hiawatha impactor was an iron meteorite. That determination is based on measurements of platinum and other elements in glacial outwash, sediments carried by meltwater from beneath the ice. An iron meteorite impact would probably not produce the kinds of explosive airbursts that could ignite continent-scale wildfires, says Michail Petaev, a geochemist at Harvard University.
Petaev and colleagues previously found a hint that an iron meteorite might have smacked into Greenland about 13,000 years ago. In 2013, his group examined Greenland ice cores and found a strange platinum anomaly dating to right before the Younger Dryas. The ratio of platinum to iridium measured in the ice cores points to an iron meteorite, the team reported.

Despite the platinum data, the impact hypothesis proponents hold firmly to the idea that the Hiawatha impactor was a comet. Because little is known about comet compositions, Kennett says, a comet might well have been the source for the platinum found in the glacial outwash and the ice cores. But Petaev maintains that the observed platinum ratios just wouldn’t occur in a comet, which is made of the primitive stuff of the universe. Instead, he says, those ratios require the cycles of melting and recrystallizing that form iron meteorites, the ancient cores of asteroids or planets.
Glaciologist Kurt Kjær of the University of Copenhagen, who led the team that identified the crater, and his colleagues don’t want to weigh in on the Younger Dryas debate. “We can’t prove it,” Kjær says. “But we can certainly not disprove it.”

Instead, the crater’s discoverers are planning to collect more sediments from the glacial outwash, and perhaps even drill directly into the crater to retrieve sediment cores that can be dated. And there may be other craters lurking beneath Greenland’s ice, or even Antarctica’s — perhaps more easily identifiable once you know what to look for, says MacGregor.

Asked whether the team has actually identified any other round shapes of interest, he pauses. Then MacGregor says, cryptically, “stay tuned.”

Quantum physics has earned a reputation as a realm of science beyond human comprehension. It describes a microworld of perplexing, paradoxical phenomena. Its equations imply a multiplicity of possible realities; an observation seems to select one of those possibilities for accessibility to human perception. The rest either disappear, remain hidden or weren’t really there to begin with. Which of those explanations pertains is debated by competing interpretations of the quantum math, pursued in a field of study known as quantum foundations.

Numerous quantum interpretations have been proposed — and an even greater number of books have been written about them. Two of the latest such books offer very different perspectives.
Philip Ball, in Beyond Weird, argues that much of the famous quantum weirdness lies in the popular descriptions of it, rather than in the math itself. Adam Becker’s What is Real? insists that the traditional “Copenhagen interpretation” is misguided; he extols the work of several physicists who reject it. Becker writes with exuberance and self-assuredness, often focusing on the personal stories of the scientists he discusses. Ball’s approach is less personal but more conversational, although he does not try to evade the sticky technicalities that illustrate and partially explain the quantum mysteries.
Ball contends that many of the analogies and illustrations used by popularizers (and physicists) to convey the weirdness of quantum theory (like a particle being in two places at once) are actually misleading. With less flamboyant phrasing, in Ball’s view, quantum physics can seem less perplexing, even almost understandable.

Without fully endorsing it, Ball gives a fairly sound presentation of the Copenhagen interpretation, based on the ideas of the Danish physicist Niels Bohr. Bohr held that quantum reality cannot be described apart from the experiments designed to probe it. A particle has many possible locations before you experimentally observe it; once observed, the location is established and the other possibilities vanish. And an electron will seem to behave as a particle or wave, depending on what sort of experimental apparatus you use to observe it.

Bohr expressed these truths by a principle he called complementarity — mutually exclusive concepts (such as wave or particle) are required to explain reality, but both concepts cannot be observed in any individual experiment. Bohr’s elaborations on this idea are famously convoluted and expressed rather obscurely. (When asked what is complementary to truth, Bohr replied, “clarity.”)

Bohr’s lack of clarity has led to many misinterpretations of what he meant, and it is those misinterpretations that Becker criticizes, rather than Bohr’s actual views. Becker’s main argument insists that the Copenhagen interpretation embraces the philosophy known as positivism (roughly, nothing unobservable is real, and sensory perceptions are the realities on which science should be based), and then demonstrates positivism’s fallacies. He does a fine job of demolishing positivism. Unfortunately, the Copenhagen interpretation is not positivistic, as its advocates have often pointed out. Bohr’s colleague Werner Heisenberg said so quite clearly: “The Copenhagen interpretation of quantum theory is in no way positivistic,” he wrote. And the philosopher Henry Folse’s 1985 book on Bohr’s philosophy thoroughly dispelled the mistaken belief that Bohr’s view was positivistic or opposed to the existence of an underlying reality.

Becker’s book commits many other more specific errors. He says Heisenberg found his famous uncertainty principle “buried in the mathematics of [Erwin] Schrödinger’s wave mechanics.” But Heisenberg despised wave mechanics and did his work on uncertainty wholly within his own matrix mechanics. Becker claims that physicists Murray Gell-Mann and James Hartle “had long been convinced that the Copenhagen interpretation had to be wrong.” But Gell-Mann and Hartle are on record stating that the Copenhagen view is not wrong, merely limited to special cases and not general enough to tell the whole quantum story.

Becker’s book does offer engaging discussions of the physicists who have questioned Bohr’s ideas and proposed alternate ways of interpreting quantum physics. But he allows the opponents to frame Bohr’s position rather than devoting any effort of his own to examining the subtlety and depth of Bohr’s philosophy and arguments. And Becker fails to address the important point that every quantum experiment’s results, no matter how bizarre, are precisely what Bohr would have expected them to be.

Becker does not engage deeply with the more recent body of work on quantum foundations, an area where Ball excels. Ball especially favors the perspective on quantum physics offered by the notion of quantum decoherence. Very roughly, the decoherence process dissipates various possible quantum realities into the environment, and only those versions of reality that are robustly recorded in the environment present themselves to observers. It’s of course much more complicated than that, and Ball admirably conveys those complications even at the occasional expense of clarity. Which puts his account closer to the truth.

Like a quantum version of a whirling top, protons have angular momentum, known as spin. But the source of the subatomic particles’ spin has confounded physicists. Now scientists have confirmed that some of that spin comes from a frothing sea of particles known as quarks and their antimatter partners, antiquarks, found inside the proton.

Surprisingly, a less common type of antiquark contributes more to a proton’s spin than a more plentiful variety, scientists with the STAR experiment report March 14 in Physical Review D.
Quarks come in an assortment of types, the most common of which are called up quarks and down quarks. Protons are made up of three main quarks: two up quarks and one down quark. But protons also have a “sea,” or an entourage of transient quarks and antiquarks of different types, including up, down and other varieties (SN: 4/29/17, p. 22).

Previous measurements suggested that the spins of the quarks within this sea contribute to a proton’s overall spin. The new result — made by slamming protons together at a particle accelerator called the Relativistic Heavy Ion Collider, or RHIC — clinches that idea, says physicist Elke-Caroline Aschenauer of Brookhaven National Lab in Upton, N.Y., where the RHIC is located.

A proton’s sea contains more down antiquarks than up antiquarks. But, counterintuitively, more of the proton’s spin comes from up than down antiquarks, the researchers found. In fact, the down antiquarks actually spin in the opposite direction, slightly subtracting from the proton’s total spin.

“Spin has surprises. Everybody thought it’s simple … and it turns out it’s much more complicated,” Aschenauer says.
Editor’s note: This story was updated April 3, 2019, to correct the subheadline to say that up antiquarks (not up quarks) add more angular momentum than do down antiquarks (not down quarks).

Life after shingles
In “With its burning grip, shingles can do lasting damage” (SN: 3/2/19, p. 22), Aimee Cunningham described the experience of Nora Fox, a woman whose bout with shingles nearly 15 years ago left her with a painful condition called postherpetic neuralgia. Fox hadn’t found any reliable treatments, Cunningham reported.

Fox praised Science News for our portrayal of shingles-related pain. “The cover is excellent and looks just like I felt,” she wrote.

As the story went to press, Fox had a surgery during which doctors placed electrodes under the skin near sites of pain. A device lets Fox control when stimulation is delivered to those areas. But the treatment, called peripheral nerve stimulation, may not work for all patients with postherpetic neuralgia. There are reports in scientific journals of individual patients experiencing relief from their neuropathic pain after the procedure, Cunningham says.
Fox’s husband, Denver C. Fox, sent Science News an update on her pain since the procedure: “There [has] been a significant change to the unbearable pain my wife has endured EVERY afternoon and evening for 14 years, despite trying every possible treatment the MDs knew of.” Shortly after the procedure, “her pain is greatly and markedly diminished.”
Stone Age throwback
Tests with replicas of a 300,000-year-old wooden spear suggest that Neandertals could have hunted from a distance, Bruce Bower reported in “Why modern javelin throwers hurled Neandertal spears at hay bales” (SN: 3/2/19, p. 14).

Reader Brenda Gray suggested that Neandertals’ spears could have been used for fighting instead of hunting.

The ancient spear found in Germany, on which the spear replicas were based, came from sediment that also contained stone tools and thousands of animal bones displaying marks made by stone tools, Bower says. “Such evidence indicates that the spears were used as hunting weapons. Neandertals could have used wooden spears in different ways, but there is no evidence that I know of for Neandertals using spears in warfare,” he says.

Young and restless
Earth’s inner core began hardening sometime after 565 million years ago, Carolyn Gramling reported in “Earth’s core may have hardened just in time to save its magnetic field” (SN: 3/2/19, p. 13). The core may have solidified just in time to strengthen the planet’s magnetic field, saving it from collapse.

Reader John Bunch thought that the timing of the inner core’s solidification “lines up nicely” with the Cambrian explosion, when life rapidly diversified about 542 million years ago. “It leads me to wonder if there may be some cause and effect or some other relationship between the two that’s going on here.”

That extremely low-intensity magnetic field actually roughly lines up with the Avalon explosion, an earlier proliferation of new life forms called the Ediacaran biota, between about 575 million and 542 million years ago, Gramling says. It’s an intriguing coincidence that researchers noted.

Earth’s magnetic field helps protect the planet from radiation. So a weak magnetic field might somehow be linked with the Avalon explosion. One idea is that increased radiation reaching Earth’s surface hundreds of millions of years ago might have increased organisms’ mutation rates, Gramling says. But there just isn’t any evidence to support a causal link at the moment.

A week after two large earthquakes rattled southern California, scientists are scrambling to understand the sequence of events that led to the temblors and what it might tell us about future quakes.

A magnitude 6.4 quake struck July 4 near Ridgecrest — about 194 kilometers northeast of Los Angeles — followed by a magnitude 7.1 quake in the same region on July 5. Both quakes occurred not along the famous San Andreas Fault but in a region of crisscrossing faults in the state’s high desert area, known as the Eastern California Shear Zone.

The San Andreas Fault system, which stretches nearly 1,300 kilometers, generally takes center stage when it comes to California’s earthquake activity. That’s where, as the Pacific tectonic plate and the North American tectonic plate slowly grind past each other, sections of ground can lock together for a time, slowly building up strain until they suddenly release, producing powerful quakes.

For the last few tens of millions of years, the San Andreas has been the primary origin of massive earthquakes in the region. Now overdue for a massive earthquake, based on historical precedent, many people fear it’s only a matter of time before the “Big One” strikes.
But as the July 4 and July 5 quakes — and their many aftershocks — show, the San Andreas Fault system isn’t the only source of concern. The state is riddled with faults, says geophysicist Susan Hough of the U.S. Geological Survey in Pasadena, Calif. That’s because almost all of California is part of the general boundary between the plates. The Eastern California Shear Zone alone has been the source of several large quakes in the last few decades, including the magnitude 7.1 Hector Mine quake in 1999, the magnitude 6.7 Northridge quake in 1994 and the magnitude 7.3 Landers quake in 1992 (SN Online: 8/29/18).

Here are three questions scientists are trying to answer in the wake of the most recent quakes.

Which faults ruptured, and how?
The quakes appear to have occurred along previously unmapped faults within a part of the Eastern California Shear Zone known as the Little Lake Fault Zone, a broad bunch of cracks difficult to map, Hough says. “It’s not like the San Andreas, where you can go out and put your hand on a single fault,” she says. And, she adds, the zone also lies within a U.S. Navy base that isn’t generally accessible to geologists for mapping.

But preliminary data do offer some clues. The data suggest that the first rupture may actually have been a twofer: Instead of one fault rupturing, two connected faults, called conjugate faults, may have ruptured nearly simultaneously, producing the initial magnitude 6.4 quake.

It’s possible that the first quake didn’t fully release the strain on that fault, but the second, larger quake did. “My guess is that they will turn out to be complementary,” Hough says.

The jury is still out, though, says Wendy Bohon, a geologist at the Incorporated Research Institutions for Seismology in Washington, D.C. “What parts of the fault broke, and whether a part of the fault broke twice … I’m waiting to see what the scientific consensus is on that.”
And whether a simultaneous rupture of a conjugate fault is surprising, or may actually be common, isn’t yet clear, she says. “In nature, we see a lot of conjugate fault pairs. I don’t think they normally rupture at the same time — or maybe they do, and we haven’t had enough data to see that.”

Is the center of tectonic action moving away from the San Andreas Fault?
GPS data have revealed exactly how the ground is shifting in California as the giant tectonic plates slide past one another. The San Andreas Fault system bears the brunt of the strain, about 70 percent, those data show. But the Eastern California Shear Zone bears the other 30 percent. And the large quakes witnessed in that region over the last few decades raise a tantalizing possibility, Hough says: We may be witnessing the birth pangs of a new boundary.

“The plate boundary system has been evolving for a long time already,” Hough says. For the last 30 million years or so, the San Andreas Fault system has been the primary locus of action. But just north of Santa Barbara lies the “big bend,” a kink that separates the northern from the southern portion of the fault system. Where the fault bends, the Pacific and North American plates aren’t sliding sideways past one another but colliding.

“The plates are trying to move, but the San Andreas is actually not well aligned with that motion,” she says. But the Eastern California Shear Zone is. And, Hough says, there’s some speculation that it’s a new plate boundary in the making. “But it would happen over millions of years,” she adds. “It’s not going to be in anyone’s lifetime.”

Will these quakes trigger the Big One on the San Andreas?
Such large quakes inevitably raise these fears. Historically, the San Andreas Fault system has produced a massive quake about every 150 years. But “for whatever reason, it has been pretty quiet in the San Andreas since 1906,” when an estimated magnitude 7.9 quake along the northern portion of the fault devastated San Francisco, Hough says. And the southern portion of San Andreas is even more overdue for a massive quake; its last major event was the estimated magnitude 7.9 Fort Tejon quake in 1857, she says.

The recent quakes aren’t likely to change that situation. Subsurface shifting from a large earthquake can affect strain on nearby faults. But it’s unlikely that the quakes either relieved stress or will ultimately trigger another earthquake along the San Andreas Fault system, essentially because they were too far away, Hough says. “The disruption [from one earthquake] of other faults decreases really quickly with distance,” she says (SN Online: 3/28/11).

Some preliminary data do suggest that the magnitude 7.1 earthquake produced some slippage, also known as creep, along at least one shallow fault in the southern part of the San Andreas system. But such slow, shallow slips don’t produce earthquakes, Hough says.

However, the quakes could have more significantly perturbed much closer faults, such as the Garlock Fault, which runs roughly west to east along the northern edge of the Mojave Desert. That’s not unprecedented: The 1992 Landers quake may have triggered a magnitude 5.7 quake two weeks later along the Garlock Fault.

“Generations of graduate students are going to be studying these events — the geometry of the faults, how the ground moved,” even how the visible evidence of the rupture, scarring the land surface, erodes over time and obscures its traces, Bohon says.

At the moment, scientists are eagerly trading ideas on social media sites. “It’s the equivalent of listening in on scientists shouting down the hallway: ‘Here’s my data — what do you have?’ ” she says. Those preliminary ideas and explanations will almost certainly evolve as more information comes in, she adds. “It’s early days yet.”

The James Webb Space Telescope’s first peek at the distant universe unveiled galaxies that appear too big to exist.

Six galaxies that formed in the universe’s first 700 million years seem to be up to 100 times more massive than standard cosmological theories predict, astronomer Ivo Labbé and colleagues report February 22 in Nature. “Adding up the stars in those galaxies, it would exceed the total amount of mass available in the universe at that time,” says Labbé, of the Swinburne University of Technology in Melbourne, Australia. “So you know that something is afoot.”
The telescope, also called JWST, released its first view of the early cosmos in July 2022 (SN: 7/11/22). Within days, Labbé and his colleagues had spotted about a dozen objects that looked particularly bright and red, a sign that they could be massive and far away.

“They stand out immediately, you see them as soon as you look at these images,” says astrophysicist Erica Nelson of the University of Colorado Boulder.

Measuring the amount of light each object emits in various wavelengths can give astronomers an idea of how far away each galaxy is, and how many stars it must have to emit all that light. Six of the objects that Nelson, Labbé and colleagues identified look like their light comes from no later than about 700 million years after the Big Bang. Those galaxies appear to hold up to 10 billion times the mass of our sun in stars. One of them might contain the mass of 100 billion suns.

“You shouldn’t have had time to make things that have as many stars as the Milky Way that fast,” Nelson says. Our galaxy contains about 60 billion suns’ worth of stars — and it’s had more than 13 billion years to grow them. “It’s just crazy that these things seem to exist.”

In the standard theories of cosmology, matter in the universe clumped together slowly, with small structures gradually merging to form larger ones. “If there are all these massive galaxies at early times, that’s just not happening,” Nelson says.

One possible explanation is that there’s another, unknown way to form galaxies, Labbé says. “It seems like there’s a channel that’s a fast track, and the fast track creates monsters.”

But it could also be that some of these galaxies host supermassive black holes in their cores, says astronomer Emma Curtis-Lake of the University of Hertfordshire in England, who was not part of the new study. What looks like starlight could instead be light from the gas and dust those black holes are devouring. JWST has already seen a candidate for an active supermassive black hole even earlier in the universe’s history than these galaxies are, she says, so it’s not impossible.
Finding a lot of supermassive black holes at such an early era would also be challenging to explain (SN: 3/16/18). But it wouldn’t require rewriting the standard model of cosmology the way extra-massive galaxies would.

“The formation and growth of black holes at these early times is really not well understood,” she says. “There’s not a tension with cosmology there, just new physics to be understood of how they can form and grow, and we just never had the data before.”

To know for sure what these distant objects are, Curtis-Lake says, astronomers need to confirm the galaxies’ distances and masses using spectra, more precise measurements of the galaxies’ light across many wavelengths (SN: 12/16/22).

JWST has taken spectra for a few of these galaxies already, and more should be coming, Labbé says. “With luck, a year from now, we’ll know a lot more.”

Blurry vision sounds like a reason to visit an eye doctor. But visual fuzziness might actually help some animals catch dinner. Out-of-focus areas created by vertically elongated pupils help predators triangulate the distance to objects, scientists propose August 7 in Science Advances. Prey animals may gain different visual advantages from pupil shapes that provide panoramic views.

Cats, foxes and many other predators that ambush prey have vertical pupils. Through these narrow slits, vertical objects appear sharp over great distances, the scientists report. Horizontal shapes are clear over a more limited distance, quickly going out of focus as an object moves farther away. This rapidly blurring vision should make it easy to detect even subtle changes in distance, the researchers say. That makes blur a good estimate of distance, says study author Martin Banks, a vision scientist at the University of California, Berkeley. A stalking predator might rely upon an object’s fuzziness to judge its location.
The benefits of this mix of visual cues make good sense, says Michael Land, a neurobiologist at the University of Sussex in Brighton, England. A predator that must pounce on its dinner needs to be able to accurately judge distances, he says.
Many herbivores, like horses and deer, have horizontal, rectangular pupils, rather than vertical slits. The authors don’t think these pupils help with depth perception. But rectangular pupils probably have their own advantages, the authors report, including better panoramic vision and shielding of potentially blinding overhead light. These benefits could help grazing prey spot – and flee from – an approaching slit-eyed hunter.
These visual benefits could explain why predators and prey evolved their pupil shapes, Banks’ team says. But vision scientist Ronald Kröger of Lund University in Sweden warns against assuming that an animal’s habits caused the evolution of a certain pupil shape. Counterexamples exist of predators without slit pupils and herbivores with them, he says. Additionally, many predators and prey animals, including most birds – which were excluded from the study’s analysis – have circular pupils.

But evolution is complex, and the new hypotheses about the advantages of pupil shape only address one aspect of the evolution of vision, Banks says. “There are multiple forces that push the eye to evolve in multiple ways.”

The photosynthesizing plankton Emiliania huxleyi has a dramatic relationship with its bacterial frenemies. These duplicitous bugs help E. huxleyi in exchange for nutrients until it becomes more convenient to murder and eat their hosts. Now, scientists have figured out how these treacherous bacteria decide to turn from friend to foe.

One species of these bacteria appears to keep tabs on health-related chemicals produced by E. huxleyi, researchers report January 24 in eLife. The bacteria maintain their friendly facade until their hosts age and weaken, striking as soon as the vulnerable algae can’t afford to keep bribing them with nutrients. The finding could help explain how massive algal blooms come to an end.
The bacteria is “first establishing what we call the ‘first handshake,’” says marine microbiologist Assaf Vardi of the Weizmann Institute of Science in Rehovot, Israel. “Then it will shift into a pathogen.”

E. huxleyi’s partnership with these bacteria, which belong to a group called Roseobacter, might be best described as a love-hate relationship. The single-celled alga can’t produce the B vitamins it needs on its own, so it offers up nutrients to lure in Roseobacter that can (SN: 7/8/16). The trade is win-win — at least until the bacteria decide they’d be better off slaying and devouring their algal hosts than sticking around in peaceful coexistence.

Sometimes called the “Jekyll-and-Hyde” trait, this kind of bacterial backstabbery shows up everywhere from animal guts to the open seas. But it wasn’t clear before how Roseobacter decide it’s the right moment to murder E. huxleyi.

Vardi’s team exposed a type of Roseobacter that lives with E. huxleyi to chemicals taken from algae that were either young and growing or old and stagnant. The team also introduced the bacteria to extra doses of a certain health-signaling algal chemical.Looking at which genes the bacteria activated in the different experiments revealed how and why they switched from friend to foe.

The bacteria kill their algal pals when exposed to high concentrations of a sulfur-containing chemical called DMSP, the researchers found. E. huxleyi leaks more and more DMSP as it ages. This eventually cues its duplicitous microbial partners to go rogue, kill their aging host, and kick their genes for nutrient-grabbing proteins and flagella — whiplike tails used to swim — into overdrive.

It’s an “eat-and-run strategy,” says Noa Barak-Gavish, a microbiologist at ETH Zurich. “You eat up whatever you can and then swim away to avoid competition … [and] to find alternative hosts.”

DMSP isn’t the only figure in this deadly chemical calculus. E. huxleyi can sate its companion’s bloodlust with a bribe of benzoate, a nutrient that Roseobacter can use but most bacteria can’t.

While it’s clearer now what drives the bacteria to kill their hosts, their murder weapon remains a mystery. Vardi says his group has some hunches to follow up on.

This kind of frenemies relationship could be a key factor in controlling the boom and bust of massive algal blooms if other phytoplankton and bacteria have a similar dynamic, says Mary Ann Moran of the University of Georgia in Athens, who was not involved in the study. Algal blooms can be toxic (SN: 8/28/18). But they also “fix” enormous amounts of carbon dioxide into biomass and are a major source of organic carbon to the ocean.
“Phytoplankton fix half of all the carbon on the planet, and probably 20 percent to 50 percent of what they fix … actually goes right to bacteria,” she says. So if this kind of relationship controls how carbon flows through the ocean, “that is something that we would really like to understand.”

Vikings brought horses and dogs to the British Isles from Scandinavia, a new study suggests.

A chemical analysis of bone fragments from a cemetery in England provides the first solid scientific evidence of animals traveling with Vikings across the North Sea, scientists report February 1 in PLOS ONE.

In the 1990s, researchers unearthed the cremated remains of a human adult and child as well as of a dog, horse and probable pig from a burial mound in a Viking cemetery in Derbyshire, England. In previous work, radiocarbon dating of femur, skull and rib fragments revealed that the inhabitants all died sometime between the eighth and 10th centuries. That date was narrowed down to the year 873, thanks to the ninth-century Anglo-Saxon Chronicle, which records that a Viking army wintered near the site that year.
Where the animals came from has been a mystery. Norse raiders are known to have stolen horses from people in England around the time. And researchers have generally thought that Viking boats at the time were too small to allow for much transport of animals from Scandinavia to the British Isles. One entry in the Anglo-Saxon Chronicle describes Vikings moving from France to England along with their horses in the year 892, but no physical evidence of such activity had been found before.

In the new work, Tessi Löffelmann and colleagues turned to certain forms, or isotopes, of strontium to unravel the individuals’ provenance. The element accumulates in bones over time through diet, leaving a distinct signature of where an individual has lived (SN: 4/2/19).
Strontium ratios in the child’s remains matched those of shrubs growing at the burial site, suggesting the child spent most, if not all, of its life in England. The ratios of the adult and three animals, on the other hand, differed substantially from the local fauna, the team found. That suggests the individuals hadn’t spent much time in the country before they died. Instead, their ratios were similar to ones found in the Baltic Shield region in Norway, central and northern Sweden and Finland, suggesting a Scandinavian origin.

“One of the joys of isotope analysis is that you are able to really pinpoint things that previously we could discuss endlessly,” says Marianne Moen, an archeologist at the University of Oslo who was not involved in the study. Using strontium to analyze more cremated remains, which can elude common forms of isotope analysis including carbon and nitrogen, “is the next logical chapter for understanding prehistoric mobility.”

Isotope analysis helped reveal where these individuals lived and when they died, but it couldn’t answer why the dog, horse and pig made the journey to England in the first place. That’s where historical records can help, says Löffelmann, of Durham University in England and Vrije Universiteit Brussel in Belgium.

For Löffelmann, the small sizes of early Norse ships combined with the fact that the animals and people were buried together suggest Vikings may have initially brought animals with them for companionship, not just function.

“It could have only been selected animals that made that journey,” she says. “They were important to what the person was.… They went through life together, and now they’re going through death.”