GRAPEVINE, TEXAS — A mysterious, recurring blast of cosmic radio waves finally has a home address. For the first time, astronomers have definitively traced a fast radio burst back to its source: a faint galaxy about 2.5 billion light-years away. The finding confirms a decade-long suspicion that these outbursts originate well outside our galaxy, although the mystery as to what’s causing them remains unsolved.

“Now with the first proven distance, we can see how remote and how bright the source must be,” Sarah Burke-Spolaor, an astrophysicist at West Virginia University, said January 4 at a meeting of the American Astronomical Society. For roughly five milliseconds, the burst outshined all the stars in its own galaxy and rivaled the luminosity of blazing disks of gas that swirl around supermassive black holes, said Burke-Spolaor, one of the researchers involved with the project.
Fast radio bursts have stumped astronomers since the first one was reported in 2007 (SN: 8/9/14, p. 22). Since then, 17 more bursts have been detected by several radio telescopes around the world. In nearly every case, the outburst lasted just a few milliseconds and was never seen again. Only one, first detected at the Arecibo Observatory in Puerto Rico in 2012, has been seen multiple times (SN Online: 12/21/16).

Most radio telescopes can provide only a fuzzy idea of where on the sky a burst comes from. But the repetitive nature of this burst, dubbed FRB 121102, gave astronomers a heads up of where to point the Very Large Array, a network of radio dishes near Socorro, N.M., which could provide a sharper image.

“We have imaged the burst itself with the VLA and pinpointed where it is on the sky,” said Shami Chatterjee, an astrophysicist at Cornell University. Over the span of six months, the VLA detected nine outbursts coming from the same direction as previous repetitions. A persistent glow of radio waves also comes from the same spot. Further observations with the Gemini telescope in Hawaii revealed that the radio outbursts coincide with a faint galaxy. By measuring how much the expansion of the universe has stretched the light coming from the galaxy, the researchers were able to measure the distance to the source of the burst.
The findings appear in a paper in the Jan. 5 Nature and two papers in the Jan. 10 Astrophysical Journal Letters.
“Without a doubt, this is a landmark event,” said Duncan Lorimer, an astrophysicist at West Virginia University who was not involved with these studies but did discover the first radio burst roughly a decade ago. “There’s no question about the validity of the result.”

The host galaxy is tiny. “We’re barely able to distinguish it from a star,” said project member Shriharsh Tendulkar, an astrophysicist at McGill University in Montreal. It has roughly one one-thousandth of the stars as the Milky Way and is less than one-tenth as wide. “That’s weird,” he said. One favored explanation for fast radio bursts is that they come from neutron stars, the dense cores left behind after a massive star explodes. But if neutron stars are responsible, then astronomers expect to find bursts in places with lots of stars, Tendulkar said.

Tracing FRB 121102 back to a dwarf galaxy doesn’t rule out neutron stars as a source. The gas in dwarf galaxies is more pristine than in other locales such as the Milky Way — with relatively low amounts of elements heavier than helium. Such gas makes it easier for massive stars to form. More heavyweight stars lead to more neutron stars, which could lead to more radio bursts.

Some of the new data, however, also suggest that the source sits near a supermassive black hole, indicating that perhaps the radio blast is somehow connected to gas and dust swirling down the black hole’s gravitational throat.

“We’ve made this huge breakthrough in getting the distance, and it still doesn’t want to let its identity be known,” Lorimer said.

With a host galaxy in hand, astronomers can now point telescopes covering a broad range of the electromagnetic spectrum — from radio waves to gamma rays — at the galaxy to learn more about the burst’s home. One thing that researchers will look for is whether or not the bursts have a steady beat; all the detections so far have appeared randomly. If the signal has a regular period, then something that is spinning (like a neutron star) might be the culprit. Pinpointing more radio bursts and seeing if they originate in dwarf galaxies could also help researchers figure out if this object is unusual or typical of all radio bursts.

For dinosaurs, the end of the world began in fire.

The space rock that stamped a Vermont-sized crater into the Earth 66 million years ago packed a powerful punch. Any animal living within about a thousand miles of the impact zone was probably vaporized, says paleontologist Stephen Brusatte of the University of Edinburgh in Scotland.

“Everything would have been toast.”

But outside of the impact zone, amid the smoking ruins of the battered planet, some survivors emerged.
Life there was no picnic. Wave after wave of life-threatening disasters pummeled the animals that remained, says paleontologist Nicholas Longrich of the University of Bath in England. Earthquakes. Wildfires. Volcanoes. Acid rain. Dust and gunk in the air, blotting out the sun. “It’s this series of biblical plagues,” Longrich says.

With little light, much plant life perished, and entire food webs collapsed. Life would have been like an ancient Hunger Games, with all living creatures as contestants. The odds were not in their favor. From sea to land to lake to sky, animals suffered incredible losses.

“You’re basically losing all the big herbivores, all the big carnivores, apex predators in the oceans, entire guilds — wiped out overnight,” Longrich says. On land, he adds, anything bigger than a beaver went extinct. Just a few places in North America offer a fossil record of the early years after the extinction, he says, but “there’s no evidence for anything over 10 kilos surviving.”

Tyrannosaurus rex, Triceratops, Ankylosaurus and all other nonavian dinosaurs gone.

A lucky few animals managed to cope with the dramatic changes reshaping their environment, Brusatte says. But why exactly some animal groups survived and others bit the dust is still one of paleontology’s biggest mysteries.
New fossil research is now helping scientists peer back through time, offering glimmers of what might have been: How some animals made it through one of the worst extinction events the planet has ever seen — and how mammals, in particular, came to dominate.

Sussing out animals’ survival strategies could offer hints about how animals today might handle a changing climate, Brusatte says. It might even expose the evolutionary drivers that shaped modern life. After the extinction, evolution went wild, he says. The survivors “had a new world to play in — a new world to conquer.”

Cretaceous catastrophe
Near the very end of the Late Cretaceous Epoch, right before the world blew up, one of the largest mammals in North America may have been noshing on bones.

Didelphodon vorax, a honey badger–looking creature with oddly bulbous teeth, was petite by today’s standards — weighing just about five kilograms. But it was no lightweight. “Pound for pound, it had the greatest bite force of any mammal we’ve ever measured,” says paleontologist Gregory Wilson of the University of Washington in Seattle.
Wilson and colleagues estimated Didelphodon’s bite force from the shape of its fossilized skull. The mammal could snap its jaws together with about 50 pounds of force — enough to crush bones and crack shells, the team reported December 8 in Nature Communications.

This fearsome skill wasn’t enough to save it: After the asteroid hit and global disasters descended, Didelphodon went extinct — just like duck-billed dinosaurs and Pteranodon.

The colossal wipeout of Didelphodon and so many others is plain to see in the fossil record. In Montana’s badlands, where Wilson and colleagues hunt for ancient teeth and bones, tributaries of the Missouri River carve steep bluffs into the earth, exposing slabs of sandstone and siltstone rock. Montana is part of the Western Interior, an ancient seaway that once cut a wide aisle through North America from the Gulf of Mexico to the Arctic.

Much of what scientists know about the dino-killing event, called the Cretaceous–Paleogene, or K–Pg, extinction, traces back to this sweeping tract of land. The area has rocks with fossils from before and after the extinction event. “We haven’t found many places in the world like it,” Wilson says. Spain, France and Romania hold a few dinosaur and mammalian fossils from this time period (and a handful of underexplored spots in India and South America may offer more). But so far, the Western Interior is home to the best land-based record scientists have.

In Montana, the rocks capture a snapshot of time from about 2 million years before the extinction to roughly 1.5 million years after. A thin layer of reddish-brown clay marks the before and after of the asteroid’s impact. “It’s a line in the sand, almost literally,” Brusatte says. Within the clay, here and elsewhere in the world, scientists find elevated levels of iridium, a silvery-white metal carried to Earth via asteroid. Though not visible by eye (scientists need chemical tests to spot it), the metallic dust marks a memory of the impact known as Chicxulub.

All around the globe, Brusatte says, scientists see “a knife-edge separation in the rock” before and after Chicxulub hit. “For over 150 million years you have tons and tons of dinosaur bones, and then literally — Bam! There’s nothing.”

Dinosaurs were among the animal groups hit hardest by the extinction. Others suffered fewer casualties. In what is now northeastern Montana, about half of fish species survived, Wilson reported at an Origins Project workshop at Arizona State University in 2015. Turtles and salamanders seemed to fare the best, losing only roughly a quarter of their species, Wilson and colleagues reported in a series of studies in 2014.

“Most people think that mammals did awesome,” Wilson says. But at least 75 percent of mammals were snuffed out, according to his analysis, which compared fossils present before and after the extinction. Longrich and colleagues put the number even higher: Of 59 mammalian species living in North America during the Late Cretaceous Epoch, about 93 percent died out after the asteroid hit. Those calculations appeared in the Journal of Evolutionary Biology in August 2016.

Still, some species found a way to endure.

Survival strategies
A small body. An aquatic lifestyle. Night vision. An unfussy palate. Any one of these features could have helped survivors withstand the relentless undoing of their ecosystems.

It makes sense. Small animals would have required less food than large ones and may have had an easier time finding shelter. Animals that lived in water could have been buffered from dramatic temperature swings.

Nocturnal animals would have been able to hunt for food when debris-filled skies wrapped the world in gloom. The right diet, in fact, could have been one of the biggest tickets to survival. Among insects, for instance, the difference between survival and demise depended on dietary diversity.

Some insects are adventurous eaters: They feed on lots of different kinds of plants. Other insects are pickier. Leaf miners, for example, typically dine on just one plant species, or a few closely related ones, which made it hard to survive the cataclysm.
These insects burrow through leaves, leaving behind a distinctive trail. Cataloging the trails and other damage patterns on fossil leaves can give researchers a rough idea of the kinds of insects that went extinct — or survived, says Penn State paleontologist Michael Donovan. It’s like a calling card stamped into stone.

Donovan examined 3,646 fossil leaves found in Patagonia, Argentina, from slices of time bracketing the Chicxulub impact. The leaf-mining patterns seen before the impact vanished after the asteroid hit, he and colleagues reported in Nature Ecology & Evolution in 2016.

That suggests a major extinction of leaf-mining insects, a find echoed in previous results from North Dakota. (Though not all perished. Donovan saw new leaf-mining patterns after the extinction.) Other types of leaf damage did persist through the extinction event — damage made by insects that eat many plant species. Unlike leaf miners, these insects took what they could get in the dark days after the impact. “That’s probably a good way to survive,” Donovan says.

This type of strategy may have helped some species adapt to their new habitat, Longrich says, which after the K–Pg extinction “happened to be this post-apocalyptic wasteland world.” It’s like Mad Max of the movies, he says. “A guy who’s super versatile — good at many different things,” Longrich says, “that’s who’s likely to live through an apocalypse.”

Some animals may have already been plugged into the right food chain. When dinosaurs began dying and leaves fell from trees, the bodies and detritus would have littered the ground and washed into rivers and lakes. That would have been a bonanza for the garbage disposal crew. Decaying matter could feed microbes and fish and insects, which could then feed larger animals, like crocodiles and mammals.

Birdlike dinosaurs with beaks could have cracked into another Cretaceous leftover: seeds. The calorie-rich food could have lasted for decades, says paleontologist Derek Larson of the Philip J. Currie Dinosaur Museum in Alberta and the University of Toronto. Other birdlike dinosaurs, with sharp teeth but no beaks, would have had trouble eating seeds. That might explain why they succumbed, while their close relatives — ancestors of modern birds — survived, he and colleagues suggested last year in Current Biology (SN: 5/14/16, p. 11).

Making it as a mammal
Mammals seemed to capitalize on the detritus-based food chain too, Wilson says. He and University of Washington student Stephanie Smith studied fossils found in northeastern Montana from a 1.2-million-year window after the impact. “Fossil mammals are mostly just teeth,” Smith said at the 2016 Society of Vertebrate Paleontology meeting in Salt Lake City. “Luckily, teeth contain a lot of information.”
Smith compared the intricate details of fossil teeth with those from living mammals to learn about the ancient animals’ diets. In Montana, at least, mammals that lived during the first 200,000 years after the extinction event tended to have teeth that were good for crunching insects — “sharp and pointy,” Wilson says. These animals would have had a reliable source of supper. But plant eaters, which have teeth with big basins for grinding and crushing, would have seen their food supplies wither.
For some mammals, a sharp sense of smell could also have offered a competitive edge. Onychodectes tisonensis, a bull dog–sized mammal that lived about 350,000 years after the extinction, had one of the largest olfactory bulbs of any mammal (relative to the cerebrum) — bigger than those found in even expert sniffers like modern dogs and pigs. The smell organs look like two almonds sticking out from the front of the brain, says James Napoli of Brown University in Providence, R.I., who reported the results at the paleontology meeting last year. He and colleagues built a digital model based on a CT scan of an Onychodectes skull unearthed in New Mexico in 1892.

Having big olfactory bulbs means the animal would have been good at nosing out meals, a valuable skill when food is scarce, Napoli says.

Onychodectes belongs to a weird group of mammals called taeniodonts, says study coauthor Thomas Williamson of the New Mexico Museum of Natural History and Science in Albuquerque. “They have bizarre-looking skulls, enlarged forearms, big claws,” he says. The animals may have survived by digging up and eating tough roots and tubers. “We call them the pigs of the Paleocene.”

Paleontologists don’t know for sure if this group of animals lived through the asteroid crash, or if they arose afterward. There’s just one reported taeniodont fossil from the Late Cretaceous — a partial skull from Alberta, Canada.

If taeniodonts did make it through the impact and its aftermath, an aptitude for rooting out hidden food caches would have been useful. If, instead, the animal group emerged later, Onychodectes could have been one of the early examples of mammalian experimentation.

For more than 150 million years, mammals had been “kept under the thumb of the dinosaurs,” Wilson says. After the extinction, with dinosaurs out of the picture, the “Age of Mammals” could begin.

Boomtime for mammals
In the years after the impact, the world was like a school playground that had banished the big kids.

The animals that survived the early hard years gave rise to a slew of new species able to fill the niches left behind by dinosaurs — and all the other creatures that didn’t make it. Before the impact, humans’ ancestors mostly scurried along the ground. But afterward, with fewer predators and competitors, they were free to try out new lifestyles, like living in trees and gliding.

Placental mammals, a group that includes humans, elephants and most mammals living today, experienced a big evolutionary boom, says Thomas Halliday, a paleobiologist at University College London. “Diversification exploded.”

Without dinosaurs breathing down their necks and with fewer competitors, placental mammals had “freedom to evolve in a variety of new directions,” Halliday says. It’s like they were “exploring almost every aspect of the ways of being a mammal.”

When exactly these mammals arose and how much dinosaurs were holding them back remains controversial: Molecular evidence places their origin tens of millions of years before the dinosaurs died. Fossil evidence puts it closer to the K–Pg extinction.
In a series of papers published in 2015 and 2016, Halliday and colleagues analyzed mammalian fossils to sketch out a clearer picture of placental mammals’ history. First, the team built a family tree focused on placental mammals that lived in the Paleocene, the 10-million-year epoch immediately following the extinction. That’s no easy feat, Halliday says, because these animals tend to lack the kind of standout features that would clearly label them as members of one group or another.

So he and colleagues created an exhaustive catalog of 680 body features (such as skull length, tooth number and molar shape) in 177 genera of extinct and living placental mammals and their close relatives. Presumably, animals that shared features were more closely related than those that didn’t. With so many species, the web of potential relationships was astronomical, Halliday says. “There were more possible arrangements … than there are hydrogen atoms in the universe.” The team plugged the data into a computer, which chugged through all the possibilities and came up with the most likely family tree.

Then, the researchers used the tree to calculate rates of evolution. Placental mammals, they found, probably did originate in the Late Cretaceous, but they evolved three times faster after the extinction event than in the 80 million years before it. “We’re talking about new anatomical innovations,” Halliday says: molars good for grinding leaves, limbs adapted for climbing or swimming.

One of these early innovators was Periptychus carinidens, a muscular animal that walked like a bear and had five toes with “weird little hooves,” says University of Edinburgh paleontologist Sarah Shelley. “It’s not like anything alive today.”

Shelley, Williamson and Brusatte described Periptychus fossils found in New Mexico’s San Juan Basin at the 2016 paleontology meeting. “They have really strange cheek teeth,” Williamson says. The teeth are enlarged and conical with big ridges that run from the base to the tip. He thinks Periptychus used its weird chompers to eat hard objects — seeds, perhaps, or unripe fruit.
Periptychus was among the first plant-eating placental mammals to emerge after the extinction — and for a few million years it flourished. Fossils of the animal have been found from West Texas to eastern Montana, Williamson says. “It must have been a highly successful mammal.” But Periptychus couldn’t cope with changes that came later — it died out about 60 million years ago. The animals “were early experiments,” he says, “but they were ultimately dead ends.”

That’s how it goes with evolution, Halliday says. After the dinosaurs died and mammals tested out different modes of life, some found success and others fizzled. “The most successful strategies are honed and the less successful ones are pared away,” he says.

What’s left is what we have today: more than 5,400 different mammal species spread across the world. But descending from an evolutionary winner doesn’t guarantee a safe future. As species carve out an ever more ideal niche, they become more and more vulnerable to extinction, Halliday says. Animals built for a narrow mode of living tend to have a hard time handling disruptions to their environment. And as the climate changes, some species have already begun to suffer. “In the metaphorical sense, we are in the middle of the asteroid strike right now,” he says.

Already, a changing climate has erased pockets of plants and animals across the globe, John Wiens of the University of Arizona in Tucson reported in December 2016 in PLOS Biology. Further warming in coming decades could ramp up extinctions, he warns.

That’s why studying life and death 66 million years ago is still relevant today, Brusatte says. “It’s not just storytelling about the ancient past,” he says. “It can help us understand our modern world,” and maybe even influence conservation strategies to mitigate some of the changes that are happening now.

Fancy flight tricks are a breeze for a new flying robot. Call it an acrobat.

Bat Bot, a lightweight flier with thin silicone wings stretched over a carbon fiber skeleton, can cruise, dive and bank turn just like its namesake, researchers report February 1 in Science Robotics.

Such a maneuverable machine could one day soar up the towering structures of a construction site, flying in and out of steel beams to help keep track of a building’s progress, study coauthor Seth Hutchinson, a roboticist at the University of Illinois at Urbana-Champaign, said in a news briefing January 31.
Other aerial robots, like some drones, aren’t so agile, relying on four whirling rotor blades to lift off the ground, Hutchinson said. These bots also have trouble flying in the wind, because they can exert force in only one direction, he said. Bat Bot’s flexible wings could make it a more versatile flier.

“Bat flight is the holy grail of aerial robotics,” said study coauthor Soon-Jo Chung, a Caltech aerospace engineer. Bats have more than 40 joints in their wings, which give the animals exquisite control over their flight maneuvers. Chung and colleagues re-created nine of the key joints, so their robot could flap its wings in sync, fold each wing independently and move each of its hind legs up and down. At 93 grams, with a wingspan of 47 centimeters, Bat Bot is roughly the size of an Egyptian fruit bat, Chung said.

An onboard computer and sensors let Bat Bot adjust its movements in midair. But the bot still needs a net to land: A crash could bust its electronics. Sticking the landing is the next step, the researchers said. They want Bat Bot to be able to perch — both right-side up and upside down.

High-energy ion collisions have produced the swirliest fluid ever discovered, in a state of matter that mimics the early universe.

To create the überwhirly liquid, scientists slammed gold ions together at velocities approaching the speed of light at Brookhaven National Laboratory in Upton, N.Y. Such collisions, performed in Brookhaven’s Relativistic Heavy Ion Collider, cook up an ultrahot fluid, re-creating the state of the universe millionths of a second after the Big Bang, before protons and neutrons had formed. In this fluid, known as a quark-gluon plasma, the constituents of protons and neutrons — quarks and gluons — intermingle freely (SN: 12/10/16, p. 9).

Scientists already knew that this fluid is the hottest ever produced in a laboratory, and that it has almost no viscosity. Now, physicists can add one more unusual property to the list. The quark-gluon plasma created in such collisions has an average vorticity — or swirliness — of about 9 billion trillion radians per second, researchers from the STAR Collaboration report online January 23 at arXiv.org. That’s vastly more than other known fluids. Even the core of a supercell tornado has a vorticity of only 0.1 radians per second.

To measure vorticity, the scientists studied a quantum mechanical property called spin from particles produced in the collision known as lambda baryons. The spin, an intrinsic type of angular momentum, tends to align with the vorticity of the fluid, providing a window into the plasma’s gyrations.

African penguins have used biological cues in the ocean for centuries to find their favorite fish. Now these cues are trapping juvenile penguins in areas with hardly any food, scientists report February 9 in Current Biology.

It’s the first known ocean “ecological trap,” which occurs when a once-reliable environmental cue instead, often because of human interference, prompts an animal to do something harmful.

When juvenile Spheniscus demersus penguins off the Western Cape of South Africa leave the nest for their maiden voyage at sea, they head for prime penguin hunting grounds. But the fish are no longer there, says Richard Sherley, a marine ecologist with the University of Exeter Environment and Sustainability Institute. Increased ocean temperatures, changes in salinity and overfishing have driven the fish eastward.
Penguins are doing what they’ve evolved to do, following signs in the water to historically prosperous habitats. “But humans have broken the system,” Sherley says, and there’s no longer enough fish to support the seabirds.

Sherley estimates that only about 20 percent of these African penguins survive their first year, partly because they can fall into this ecological trap.
Ecological traps have been documented on land for decades. There has been a lot of speculation about traps in the ocean, but this study is the best evidence so far, says Rob Hale, an ecologist with the University of Melbourne.
“Hopefully the study will generate more interest in examining ecological traps in the ocean so we can better understand when and why traps arise, how they are likely to affect animals, and how we can go about managing their effects,” Hale says.

This trap may have occurred because of how penguins find their food. Researchers think penguins can sense a stress chemical that phytoplankton release when being eaten. Penguins eat sardines, which eat phytoplankton. Usually the chemical, dimethyl sulfide, signals to penguins where the fish are feasting on phytoplankton. But phytoplankton can release the compound in other situations, like in rough water. The signal is still sent, but there are no fish.

“You have a cue that used to signal high quality in an environment, but that environment has been modified by human action to some extent,” Sherley says. “The animals are tricked or trapped into selecting a lower quality habitat because the cue still exists, even though there’s high quality habitat available.”

Adult penguins have adapted to the trap and shifted their hunting patterns to follow the fish east. Sherley says they’re not sure how adults learned to avoid the problem, but that there must be a way that juveniles who survive to adulthood also adapt.

Researchers also tracked juvenile penguins from the Namibia and Eastern Cape of South Africa breeding regions. The eastern penguins have been unaffected by the trap because the fish have moved closer to them. The Namibia population is being barely sustained by the goby, a junk food fish that appears to be taking over the areas previously inhabited by sardines and anchovies.

The Western Cape penguins have been most affected. The population has declined 80 percent in the last 15 years — from 40,000 breeding pairs to 5,000 or 6,000, Sherley says. He estimates that if juvenile penguins hadn’t been falling victim to this trap, the Western Cape population would be double its current levels.

If the loss of fish off the Western Cape of South Africa can’t be reversed, Sherley speculates the two most likely outcomes are an African penguin extinction or an ecosystem shift. Current penguin conservation efforts protect penguin breeding areas, but the study suggests that the protections may be insufficient because the ecological trap is far from the breeding grounds.

Short bouts of suffocating conditions can desolate swaths of seafloor for decades, new research suggests. That devastation could spread in the future, as rising temperatures and agricultural runoff enlarge oxygen-poor dead zones in the world’s oceans.

Monitoring sections of the Black Sea, researchers discovered that even days-long periods of low oxygen drove out animals and altered microbial communities. Those ecosystem changes slow decomposition that normally recycles plant and animal matter back into the ecosystem after organisms die, resulting in more organic matter accumulating in seafloor sediments, the researchers report February 10 in Science Advances.
Carbon is included among that organic matter. Over a long enough period of time, the increased carbon burial could help offset a small fraction of carbon emitted by human activities such as fossil fuel burning, says study coauthor Antje Boetius, a marine biologist at the Max Planck Institute for Marine Microbiology in Bremen, Germany. That silver lining comes at a cost, though. “It means your ecosystem is fully declining,” she says.

“We need to pay more attention to the bottom of the ocean,” says Lisa Levin, a biological oceanographer at the Scripps Institution of Oceanography in La Jolla, Calif. “There’s a lot happening down there.” The new work shows that scientists need to consider oxygen conditions when tracking how carbon moves around the environment, says Levin, who was not involved in the research.
Some oxygen-poor, or hypoxic, waters form naturally, such as the suffocating conditions caused by a lack of churning in the deep realms of the Black Sea (SN Online: 10/9/15). Other regions lose their oxygen to human activities; fertilizer washing in from farms nourishes algal blooms, for example, and the bacteria that later decompose that algal influx suck up oxygen. Rising sea-surface temperatures could worsen these problems by decreasing the amount of dissolved oxygen that water can hold and making it harder for ocean layers to mix, as warmer waters remain on top (SN: 3/5/16, p. 11).
Scientists have noticed increased carbon burial in hypoxic waters before. The mechanism behind that increase was unclear, though. Boetius and colleagues headed out to the Black Sea, the world’s largest oxygen-poor body of water, and studied sites along a 40-kilometer-long stretch of seafloor. (Military activities in the region following Russia’s annexation of Crimea limited where the researchers could study, Boetius says.) Some sites were always flush with oxygen, some occasionally suffered a few days of low oxygen, and others were permanently oxygen-free.

The ecological difference between the sites was stark. In oxygen-rich waters, animals such as fish and starfish flourished, and little organic matter was deposited on the seafloor. In areas with perpetually or sporadically low oxygen, the researchers reported that oxygen-dependent animals were nowhere to be seen, and organic matter burial rates were 50 percent higher.

Bottom-dwelling animals are particularly important, the researchers observed, helping recycle organic matter by eating larger bits of debris sinking from the surface ocean and by mixing oxygen into sediments during scavenging. What’s more, the researchers found that the microbial community in oxygen-poor waters shifted toward those microbes that don’t depend on oxygen to live. Such microbes further limit decomposition by producing sulfur-bearing compounds that make organic matter harder to break down.

Depending on the size of the area affected, animals could take years or decades to return to previously hypoxic waters, Boetius says. Some of the studied sites experienced low-oxygen conditions for only a few days a year yet remained barren even when oxygen returned. The absence of animals prolongs the effects of hypoxic conditions beyond the times when oxygen is scarce, she says.

BOSTON — For the first time since the Viking missions to Mars in the 1970s, NASA is making the search for evidence of life on another world the primary science goal of a space mission. The target world is Jupiter’s moon Europa, considered possibly habitable because of its subsurface ocean.

The proposed mission, which could be operational in the next two decades, calls for a lander with room for roughly 43 kilograms of science instruments. They include a robotic arm to scoop samples and others to analyze the chemistry of the Jovian moon’s icy surface (SN: 5/17/14, p. 20). “It’s the first time in human history that we have the ability to design instruments to detect life within our own solar system’s backyard in the next 20 years,” astrobiologist and planetary scientist Kevin Hand said February 17 at the annual meeting of the American Association for the Advancement of Science. Hand’s team submitted a 264-page report describing the potential mission to NASA on February 8. The report is now open for review by the scientific community.

A major concern is taking precautions to prevent contamination of Europa by microbes from Earth. “These are important for protecting Europa for Europans,” said Hand, who works out of NASA’s Jet Propulsion Laboratory in Pasadena, Calif. His team proposes baking the spacecraft to kill as many microorganisms clinging to the exterior of the lander as possible.

Decontamination precautions are important not only for protecting the life that’s on the world being explored, notes biologist Norine Noonan of the University of South Florida St. Petersburg. They are also important for the science goals of the potential mission. “You don’t want to send a $2 billion spacecraft somewhere to discover E. coli,” Noonan says.

From deep in the gold mines of South Africa’s Orange Free State has come evidence that there was some form of biologic activity on Earth at least 2.15 billion years ago. Polymerized hydrocarbon “chemo-fossils” found in the gold ores … [probably] were originally part of a rich bacterial and algal life in the Witwatersrand basin. Since the rock layers from which they come have been dated to about 2.15 billion years ago, it seems likely that photosynthesis existed on Earth before then. — Science News, March 18, 1967

UPDATE
Scientists still debate when early photo­synthesizing organisms called cyanobacteria began pumping oxygen into Earth’s atmosphere. Recent evidence suggests the microbes existed some 3.2 billion years ago (SN Online: 9/8/15), even though a larger oxygen surge didn’t happen until about 2.4 billion years ago (SN: 3/4/17 p. 9). Those tiny bacteria left an outsized impact on our planet, releasing extra oxygen into the atmosphere that paved the way for complex multicellular life like plants and animals.

Catch sight of someone scratching and out of nowhere comes an itch, too. Now, it turns out mice suffer the same strange phenomenon.

Tests with mice that watched itchy neighbors, or even just videos of scratching mice, provide the first clear evidence of contagious scratching spreading mouse-to-mouse, says neuroscientist Zhou-Feng Chen of Washington University School of Medicine in St. Louis. The quirk opens new possibilities for exploring the neuroscience behind the spread of contagious behaviors.
For the ghostly itch, experiments trace scratching to a peptide nicknamed GRP and areas of the mouse brain better known for keeping the beat of circadian rhythms, Chen and colleagues found. They report the results in the March 10 Science.

In discovering this, “there were lots of surprises,” Chen says. One was that mice, nocturnal animals that mostly sniff and whisker-brush their way through the dark, would be sensitive to the sight of another mouse scratching. Yet Chen had his own irresistible itch to test the “crazy idea,” he says.

Researchers housed mice that didn’t scratch any more than normal within sight of mice that flicked and thumped their paws frequently at itchy skin. Videos recorded instances of normal mice looking at an itch-prone mouse mid-scratch and, shortly after, scratching themselves. In comparison, mice with not-very-itchy neighbors looked at those neighbors at about the same frequency but rarely scratched immediately afterward.
Videos of scratching mice produced the same result. More audience itching and scratching followed a film of a mouse with itchy skin than one of a mouse poking about on other rodent business.
Next, researchers looked at how contagious itching plays out in the mouse nervous system. Brains of mice recently struck by contagious urges to scratch showed heightened activity in several spots, including, surprisingly, a pair of nerve cell clusters called the suprachiasmatic nuclei, or SCN. People have these clusters, too, deep in the brain roughly behind the eyes.

Other tests linked the contagious itching with GRP, previously identified as transmitting itch information elsewhere in the mouse nervous system. Mice didn’t succumb to contagious itching if they had no working genes for producing GRP or the molecule that detects it. Yet these mice still scratched when researchers irritated their skin. Also, in normal mice, a dose of GRP injected to the SCN brain regions brought on scratching without the sight of an itchy neighbor, but a dose of plain saline solution to same spots failed to set off much pawing.

It’s fine work, says dermatologist Gil Yosipovitch, who studies itching at the University of Miami. But he wonders how the mouse discovery might apply to people. So far, brain imagery in his own work has not turned up evidence for an SCN role in human contagious itching, he says.

SCN is better known as a circadian timekeeper, responding to cues in light. It’s unclear how the nerve cell clusters might orchestrate behavior based on seeing a scratching mouse, “a very specific and rich visual stimulus,” says psychologist and neuroscientist Henning Holle of the University of Hull in England. Other research suggests different brain regions are involved in contagious itching in people.

Tracking down the mechanisms behind the phenomenon is more than an intriguing science puzzle, Yosipovitch says. People troubled with strong, persistent itching are often unusually susceptible to contagious scratching, and new ideas for easing their misery would be welcome.

NEW ORLEANS — In a primordial soup on ancient Earth, droplets of chemicals may have paved the way for the first cells. Shape-shifting droplets split, grow and split again in new computer simulations. The result indicates that simple chemical blobs can exhibit replication, one of the most basic properties of life, physicist Rabea Seyboldt of the Max Planck Institute for the Physics of Complex Systems in Dresden, Germany, reported March 16 at a meeting of the American Physical Society.

Within a liquid, small droplets of particular chemicals can separate out, like beads of oil in water. Such globules typically remain spherical, growing as they merge with other drops. But in simulations, Seyboldt and colleagues found that droplets might behave in a counterintuitive way under certain conditions, elongating and eventually dividing into two.
If additional droplet material is continuously produced in reactions in the primordial soup, chemicals will accumulate on either end of a droplet, causing it to elongate, the simulations show. Meanwhile, waste products from the droplet are eliminated from the middle, causing the droplet to pinch in and eventually split. The resulting pair of droplets would then grow and split again to create a new generation. In addition to the above reactions, the process requires an energy source, such as heat or chemicals from a hydrothermal vent, to get reactions going.

The study, which was also described in Nature Physics in December, is theoretical — the researchers didn’t select particular chemicals for study but simply showed that certain types of reactions could cause droplets to split.

How such droplets would have evolved into vastly more complicated cells is unknown. “This is really a minimal scenario that’s supposed to give the very first indications of something that goes towards life, but if you look at living cells today, they’re infinitely more complex,” Seyboldt said.