Science News

The most ancient supermassive black hole is bafflingly big

Mon, 18 Jan 2021 13:00:00 GMT

The most ancient black hole ever discovered is so big it defies explanation.

This active supermassive black hole, or quasar, boasts a mass of 1.6 billion suns and lies at the heart of a galaxy more than 13 billion light-years from Earth. The quasar, dubbed J0313-1806, dates back to when the universe was just 670 million years old, or about 5 percent of the universe’s current age. That makes J0313-1806 two times heavier and 20 million years older than the last record-holder for earliest known black hole (SN: 12/6/17).

Finding such a huge supermassive black hole so early in the universe’s history challenges astronomers’ understanding of how these cosmic beasts first formed, researchers reported January 12 at a virtual meeting of the American Astronomical Society and in a paper posted at arXiv.org on January 8.

Supermassive black holes are thought to grow from smaller seed black holes that gobble up matter. But astronomer Feige Wang of the University of Arizona and colleagues calculated that even if J0313-1806’s seed formed right after the first stars in the universe and grew as fast as possible, it would have needed a starting mass of at least 10,000 suns. The normal way seed black holes form — through the collapse of massive stars — can only make black holes up to a few thousand times as massive as the sun.

A gargantuan seed black hole may have formed through the direct collapse of vast amounts of primordial hydrogen gas, says study coauthor Xiaohui Fan, also an astronomer at the University of Arizona in Tucson. Or perhaps J0313-1806’s seed started out small, forming through stellar collapse, and black holes can grow a lot faster than scientists think. “Both possibilities exist, but neither is proven,” Fan says. “We have to look much earlier [in the universe] and look for much less massive black holes to see how these things grow.”

The more contagious coronavirus variant may soon be the U.S.’s dominant strain

Fri, 15 Jan 2021 20:28:10 GMT

A highly contagious coronavirus variant will become the dominant version of the virus in the United States in March, emphasizing the need for more rapid vaccination, a new modeling study from the U.S. Centers for Disease Control and Prevention suggests.

The coronavirus variant was first identified in December in the United Kingdom (SN: 12/22/20). Called B.1.1.7, it has some mutations that may help the virus better spread among people, though the variant isn’t thought to cause more severe disease. It has so far been detected in 76 COVID-19 cases across 12 U.S. states. Because experts have analyzed the genetic fingerprints of only a small percentage of the millions of coronavirus infections in the United States, however, it’s unclear how widespread B.1.1.7 might be. Experts estimate that the variant currently causes less than half a percent of U.S. COVID-19 cases.

But while B.1.1.7 might be present at low levels now, it has the potential to drive a surge in U.S. cases and outpace the most prevalent viral variants currently infecting people in two months, researchers report January 15 in Morbidity and Mortality Weekly Report. Because B.1.1.7 is likely more transmissible, people must be more rigorous about following public health guidelines such as wearing masks to curb its spread, health officials say.

“These measures will be more effective if they are instituted sooner rather than later,” the researchers warn.

In the study, the team simulated how the variant might spread in the country from January to April 2021. Assuming that the variant is 50 percent more transmissible than other viral versions already spreading in the United States and that around 10 to 30 percent of people have immunity against any form of the virus from a previous bout of COVID-19, B.1.1.7 could cause most coronavirus cases in the country by March, the researchers found.

Vaccinating 1 million people a day, however, would help substantially reduce how many COVID-19 cases — and thus hospitalizations and deaths — caused by the new variant ultimately occur, though the variant would still dominate U.S. cases in March, the modeling study suggests. Since the rollout of vaccines in December, more than 10 million people have been inoculated against the coronavirus in the United States.

Reducing coronavirus transmission overall, including the spread of other variants, could also further reduce how much B.1.1.7 spreads, even after it becomes the dominant variant. More rigorous efforts to limit the spread of the virus — including more compliance with following public health guidelines like wearing masks and staying away from crowds — will slow the variant’s spread and give medical experts more time to vaccinate more people and build up community immunity, the team writes.

The Parker Solar Probe will have company on its next pass by the sun

Fri, 15 Jan 2021 15:28:42 GMT

The Parker Solar Probe is no stranger to the sun. On January 17, the NASA spacecraft will make its seventh close pass of our star, coming within 14 million kilometers of its scorching surface.

And this time, Parker will have plenty of company. A lucky celestial lineup means that dozens of other observatories will be trained on the sun at the same time. Together, these telescopes will provide unprecedented views of the sun, helping to solve some of the most enduring mysteries of our star.

“This next orbit is really an amazing one,” says mission project scientist Nour Raouafi of the Johns Hopkins Applied Physics Laboratory in Laurel, Md.

Chief among the spacecraft that will join the watch party is newcomer Solar Orbiter, which the European Space Agency launched in February 2020 (SN: 2/9/20). As Parker swings by our star this month, Solar Orbiter will be watching from the other side of the sun.

“This is partially luck,” solar physicist Timothy Horbury of Imperial College London said December 10 at a news briefing at the virtual meeting of the American Geophysical Union. “Nobody planned to have Parker Solar Probe and Solar Orbiter operating together; it’s just come out that way.”

Working together, the sungazers will tackle long-standing puzzles: how the sun creates and controls the solar wind, why solar activity changes over time and how to predict powerful solar outbursts.

“I think it genuinely is going to be a revolution,” Horbury said. “We’re all incredibly lucky to be doing this at this moment in time.”

Working in tandem

The Parker Solar Probe launched in 2018 and has already had six close encounters with the sun (SN: 7/5/18). During its nearly seven-year mission, the probe will eventually swing within 6 million kilometers of the sun — less than one-seventh the distance of Mercury from the sun — giving Parker’s heavily shielded instruments a better taste of the plasma and charged particles of the sun’s outer atmosphere, the corona (SN: 7/31/18).

Because Parker gets so close, its cameras cannot take direct pictures of the solar surface. Solar Orbiter, though, will get no closer than 42 million kilometers, letting it take the highest-resolution images of the sun ever. The mission’s official science phase won’t begin until November 2021, but the spacecraft has already snapped images revealing tiny “campfire” flares that might help heat the corona (SN: 7/16/20).

During Parker’s seventh close encounter, which runs January 12–23, Solar Orbiter will observe the sun from a vantage point almost opposite to Parker’s view. Half a dozen other observers will be watching as well, such as ESA’s BepiColombo spacecraft that is on its way to Mercury and NASA’s veteran sunwatcher STEREO-A. Both will flank Parker on either side of the sun. And telescopes on Earth will be watching from a vantage point about 135 million kilometers behind Parker, making a straight line from Earth to the spacecraft to the sun.

When the Parker Solar Probe makes its next close pass of the sun (shown in the black arc in the center of this diagram), a host of other spacecraft and telescopes on Earth will be watching too. This diagram shows the relative positions during the flyby of the sun, Earth, Parker, Solar Orbiter and two other spacecraft, BepiColombo and STEREO-A.JHU-APL

The situation is similar to Parker’s fourth flyby in January 2020, when nearly 50 observatories watched the sun in tandem with the probe, Raouafi says. Those observations led to a special issue of Astronomy & Astrophysics with more than 40 articles. One of the results was confirming that there is a region around the sun that is free of dust, which was predicted in 1929. “That was amazing,” Raouafi says. “We want to do a campaign that is that good or even better for this run.”

In the wind

At the AGU meeting, researchers presented new results from Parker’s second year of observations. The results deepen the mystery of magnetic kinks called “switchbacks” that Parker observed in the solar wind, a constant stream of charged particles flowing away from the sun (SN: 12/4/19), Raouafi says.

Some observations support the idea that the kinks originate at the base of the corona and are carried past Parker and beyond, like a wave traveling along a jump rope. Others suggest the switchbacks are created by turbulence within the solar wind itself.

Figuring out which idea is correct could help pinpoint how the sun produces the solar wind in the first place. “These [switchbacks] could be the key to explaining how the solar wind is heated and accelerated,” Raouafi said in a talk recorded for AGU.

Meanwhile, Solar Orbiter’s zoomed-in images plus simultaneous measurements of the solar wind may allow scientists to trace the wind’s energetic particles back to their birthplaces on the sun’s surface. Campfire flares — the “nanoflares” spotted by Solar Orbiter — might even explain the switchbacks, Horbury says.

“The goal is to connect tiny transient events like nanoflares to changes in the solar wind,” Horbury said in the news briefing.

Waking up with the sun

Parker and Solar Orbiter couldn’t have arrived at a better time. “The sun has been very quiet, in a deep solar minimum for the last several years,” Horbury said. “But the sun is just beginning to wake up now.”

Both spacecraft have seen solar activity building over the last year. During its sleepy period, the sun displays fewer sunspots and outbursts such as flares and coronal mass ejections, or CMEs. But as it wakes up, those signs of increasing magnetic activity become more common and more energetic.

On November 29, Parker observed the most powerful flare it had seen in the last three years, followed by a CME that ripped past the spacecraft at 1,400 kilometers per second.

“We got so much data from that,” Raouafi says. More CMEs should pass Parker when it’s even closer to the sun, which will tell scientists about how these outbursts are launched.

Solar Orbiter caught an outburst too. On April 19, a CME passed the spacecraft about 20 hours before its effects arrived at Earth. With existing spacecraft, observers on Earth get only about 40 minutes warning before a CME arrives.

Solar Orbiter detected a big burst of plasma called a coronal mass ejection in April, almost a day before signs of the eruption reached Earth. Observers on Earth typically get just 40 minutes of warning before such an eruption arrives.ESA

“We can see how that CME evolves as it travels away from the sun in a way we’ve never been able to do before,” Horbury said.

Strong CMEs can knock out satellites and power grids, so having as much forewarning as possible is important. A future spacecraft at Solar Orbiter’s distance from the sun could help give that warning.

Looking forward

This orbit is the first time that Parker Solar Probe and Solar Orbiter will watch the sun in tandem, but not the last. “There will be plenty of opportunities like this one,” Raouafi says.

He’s looking forward to one opportunity in particular: the solar eclipse of 2024. On April 8, 2024, a total eclipse will cross North America from Mexico to Newfoundland. Solar scientists plan to make observations from all along the path of totality, similar to how they watched the total eclipse of 2017.

During the eclipse, the Parker Solar Probe will be on its second-closest orbit, between 7 million and 8 million kilometers from the sun. Parker and Solar Orbiter will be “almost on top of each other,” Raouafi says — both spacecraft will be together off to one side of the sun as seen from Earth. Whatever prominences and other shapes in the corona are visible to observers on Earth will be headed right at the spacecraft.

“They will be flying through the structure we will see from Earth during the solar eclipse,” Raouafi says. The combined observations will tell scientists how features on the sun evolve with time.

“I think it is a new era,” Horbury said. “The next few years is going to be a step change in the way we see the sun.”

‘The New Climate War’ exposes tactics of climate change ‘inactivists’

Fri, 15 Jan 2021 11:00:00 GMT

The New Climate War
Michael E. Mann
Public Affairs, $29

Sometime around the fifth century B.C., the Chinese general and military strategist Sun Tzu wrote in his highly quotable treatise The Art of War, “If you know the enemy and know yourself, you need not fear the result of a hundred battles.”

In The New Climate War, climate scientist Michael Mann channels Sun Tzu to demystify the myriad tactics of “the enemy” — in this case, “the fossil fuel companies, right-wing plutocrats and oil-funded governments” and other forces standing in the way of large-scale action to combat climate change. “Any plan for victory requires recognizing and defeating the tactics now being used by inactivists as they continue to wage war,” he writes.

Mann is a veteran of the climate wars of the 1990s and early 2000s, when the scientific evidence that the climate is changing due to human emissions of greenhouse gases was under attack. Now, with the effects of climate change all around us (SN: 12/21/20), we are in a new phase of those wars, he argues. Outright denial has morphed into “deception, distraction and delay.”

Such tactics, he says, are direct descendants of earlier public relations battles over whether producers or consumers must bear ultimate responsibility for, say, smoking-related deaths. When it comes to the climate, Mann warns, an overemphasis on individual actions could eclipse efforts to achieve the real prize: industrial-scale emissions reductions.

He pulls no punches, calling out sources of “friendly fire” from climate advocates who he says divide the climate community and play into the “enemy’s” hands. These advocates include climate purists who lambaste scientists for flying or eating meat; science communicators who push fatalistic visions of catastrophic futures; and idealistic technocrats who advocate for risky, pie-in-the-sky geoengineering ideas. All, Mann says, distract from what we can do in the here and now: regulate emissions and invest in renewable energy.

The New Climate War’s main focus is to combat psychological warfare, and on this front, the book is fascinating and often entertaining. It’s an engrossing mix of footnoted history, acerbic political commentary and personal anecdotes. As far as what readers can do to assist in the battle, Mann advocates four strategies: Disregard the doomsayers; get inspired by youth activists like Greta Thunberg; focus on educating the people who will listen; and don’t be fooled into thinking it’s too late to take action to change the political system.

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2020 and 2016 tie for the hottest years on record

Thu, 14 Jan 2021 22:35:42 GMT

2020 is in a “dead heat” with 2016 for the hottest year on record, scientists with NASA and the National Oceanic and Atmospheric Administration announced January 14.

Based on ocean temperature data from buoys, floats and ships, as well as temperatures measured over land at weather stations around the globe, the U.S. agencies conducted independent analyses and arrived at a similar conclusion.

NASA’s analysis showed 2020 to be slightly hotter, while NOAA’s showed that 2016 was still slightly ahead. But the differences in those assessments are within margins of error, “so it’s effectively a statistical tie,” said NASA climatologist Gavin Schmidt of the Goddard Institute for Space Studies in New York City at a Jan. 14 news conference.

NOAA climate scientist Russell Vose, who is also based in New York City, described in the news conference the extreme warmth that occurred over land last year, including a months-long heat wave in Siberia (SN: 12/21/20). Europe and Asia recorded their hottest average temperatures on record in 2020, with South America recording its second warmest.

It’s possible that 2020’s temperatures in some areas might have been even higher if not for massive wildfires. Vose noted that smoke lofted high into the stratosphere as a result of Australia’s intense fires in early 2020 may have slightly decreased temperatures in the Northern Hemisphere, though this is not yet known (SN: 12/15/20).

The ocean-climate pattern known as the El Niño Southern Oscillation can boost or decrease global temperatures, depending on whether it’s in an El Niño or La Niña phase, respectively, Schmidt said (SN: 5/2/16). The El Niño phase was waning at the start of 2020, and a La Niña was starting, so the overall impact of this pattern was muted for the year. 2016, on the other hand, got a large temperature boost from El Niño. Without that, “2020 would have been by far the warmest year on record,” he said.

But placed in the bigger picture, these rankings “don’t tell the whole story,” Vose said. “The last six to seven years really stand out above the rest of the record, suggesting the kind of rapid warming we’re seeing. [And] each of the past four decades was warmer than the one preceding it.”

Could delaying a second vaccine dose lead to more dangerous coronavirus strains?

Thu, 14 Jan 2021 21:03:34 GMT

Spiking COVID-19 cases, slow vaccine rollout and the emergence of more transmissible coronavirus variants in some countries have sparked debate among scientists over the best way to protect people with recently authorized vaccines.

One idea involves delaying when people receive the second of two required vaccine doses, so that more people can receive the doses that are currently available.

That’s happening in the United Kingdom, where researchers have raised concerns about a new coronavirus variant that appears to be more contagious than other versions. Officials there are opting to extend the time between each vaccine dose from three or four weeks to up to three months (SN: 12/22/20).

In the United States, on the other hand, officials strongly recommend that states stick to the regimen that the U.S. Food and Drug Administration authorized in December — two shots spaced three weeks apart for Pfizer-BioNTech’s vaccine and four weeks apart for Moderna’s.

On January 12, the Trump administration announced it was no longer holding back second shots of COVID-19 vaccines, several days after President-elect Joe Biden suggested he would release all the shots. While that may speed protection for more Americans, it also raises the possibility that people might not get their second doses on time, if manufacturing problems arise.

The possibility that second doses could be delayed has some experts concerned because it might lead to millions of people walking around with only partial immunity to the coronavirus, a condition that could be ripe for harmful mutations of the virus to arise.

Delaying the second shot is a gamble, says Ramón Lorenzo-Redondo, a virologist at Northwestern University Feinberg School of Medicine in Chicago, particularly without a lot of evidence suggesting how well one dose works. Officials “shouldn’t gamble [their] best tools” to fight the pandemic, he says. “We don’t want to fuel [potential viral evolution] by doing suboptimal immunization of the population.”

How that fueling of virus evolution could happen comes down to the immune system. If people have full immunity as a result of vaccination, their immune response is likely to be robust, spawning large numbers of neutralizing antibodies, for example, that stop viruses from getting into cells and heading off harmful mutations before they arise. But if people have partial immunity, that immune response is likely to be weaker.

It’s like when doctors encourage patients to finish a full course of antibiotics, Lorenzo-Redondo says. In that case, eliminating susceptible bacteria with a full course could help lower the chance that stragglers build up resistance.

For the COVID-19 vaccine, if people’s second doses are delayed long enough — akin to not finishing a full complement of antibiotics — it’s possible that low numbers of neutralizing antibodies triggered by only one dose may only partially fight an infection. That might provide more time for variants of the virus with immune-dodging mutations to arise and thrive and be transmitted to other people.

If immune-dodging variants do arise as a result of shot delays and spread to lots of people, that could deal a blow to vaccines’ effectiveness. For example, if mutations arose that prevented vaccine-induced antibodies from binding to the virus, or caused antibodies to bind less tightly, that virus variant may be more likely to infect cells than variants without the mutation and thus cause disease, Lorenzo-Redondo says. With cases surging in many places, including the United Kingdom and the United States, the coronavirus could have even more chances to accumulate vaccine-evading mutations than it would if case numbers were lower.

For now, it’s unclear how protected vaccinated people are after a single shot and for how long. Trial participants who received Pfizer-BioNTech’s vaccine had low levels of neutralizing antibodies 21 days after the first dose, researchers reported in the Dec. 17 New England Journal of Medicine. But clinical trial results from both the Pfizer-BioNTech and Moderna vaccines suggest that protection begins around two weeks after the first dose — Pfizer-BioNTech’s vaccine had an efficacy of around 50 percent after the first dose and Moderna’s had around 80 percent efficacy (SN: 12/18/20). It’s unknown how durable that protection might be, says Sarah Cobey, an epidemiologist and evolutionary biologist at the University of Chicago, but it would be weird to see it fade quickly.

Cobey is one of the scientists who isn’t worried about the risk of a long delay between shots. Instead, expanding how many people get the first dose could actually help control how much the coronavirus changes, she says. That’s because even the partial protection that people may get from a single dose “will almost certainly lower the prevalence of infection,” she says. Fewer infections overall would mean fewer coronavirus variants in general circulating among people. By virtue of numbers, the coronavirus then may not accumulate as many mutations that could help it evade immune systems.

And even if a virus accumulates mutations that help it dodge the immune response as a result of the dose delay, such changes might in turn damage essential viral functions like breaking into and hijacking a host cell. A virus that can escape immunity, for instance, might end up being less transmissible. For now, it’s unclear what might happen with the coronavirus, which in general mutates more slowly than other similar viruses thanks to a unique proofreading enzyme that acts as a spell-check for the letters that make up the coronavirus’s genetic blueprint (SN: 1/28/20).

What’s more, the immune responses that a person makes also don’t attack just one part of a virus. Antibodies, for instance, including those induced by vaccines, hit many different parts of viral proteins, making it harder for the virus to escape. And over time antibodies can get better at their job (SN: 11/24/20). So, most mutations are unlikely to render antibodies completely ineffective.

“You put that all together and it’s a pretty high barrier” for virus evolution to work around, says Adam Lauring, an infectious disease physician and virologist at the University of Michigan Medical School in Ann Arbor.

In lab experiments, for example, COVID-19 patient serum that harbors myriad coronavirus antibodies still stops the coronavirus from infecting cells in a dish, even if there are viral mutations, researchers reported in a preliminary study posted January 4 at bioRxiv.org. While a few mutations — including one present in a coronavirus variant now circulating in South Africa — made antibodies in the serum less effective at stopping viruses from infecting cells, the serum’s virus-halting activity didn’t outright disappear.

Still, that doesn’t mean potentially risky viral evolution as a result of delaying doses is not going to happen. “I think this is something we need to study and we need to look at for sure,” Lauring says. For now, “I’m not sure we know enough that we can really confidently say what one or other [vaccine-dosing] strategy is going to do.”

Some electric eels coordinate attacks to zap their prey

Thu, 14 Jan 2021 16:00:35 GMT

One Volta’s electric eel — able to subdue small fish with an 860-volt jolt — is scary enough. Now imagine over 100 eels swirling about, unleashing coordinated electric attacks.

Such a sight was assumed to be only the stuff of nightmares, at least for prey. Researchers have long thought that these eels, a type of knifefish, are solitary, nocturnal hunters that use their electric sense to find smaller fish as they sleep (SN: 12/4/14). But in a remote region of the Amazon, groups of over 100 electric eels (Electrophorus voltai) hunt together, corralling thousands of smaller fish together to concentrate, shock and devour the prey, researchers report January 14 in Ecology and Evolution.

“This is hugely unexpected,” says Raimundo Nonato Mendes-Júnior, a biologist at the Chico Mendes Institute for Biodiversity Conservation in Brasilia, Brazil who wasn’t involved in the study. “It goes to show how very, very little we know about how electric eels behave in the wild.”

Volta’s electric eels sometimes hunt as a group (pictured), using their numbers to corral shoals of smaller fish into shallow areas where they can easily be picked off.Douglas Bastos

Group hunting is quite rare in fishes, says Carlos David de Santana, an evolutionary biologist at the Smithsonian’s National Museum of Natural History in Washington, D.C. “I’d never even seen more than 12 electric eels together in the field,” he says. That’s why he was stunned in 2012 when his colleague Douglas Bastos, now a biologist at the National Institute of Amazonian Research in Manaus, Brazil, reported seeing more than 100 eels congregating and seemingly hunting together in a small lake in northern Brazil.

Two years later, de Santana’s team returned to the lake to make more detailed observations. The nearly 2-meter-long eels lethargically lay in deeper waters during much of the day, the researchers found. But at dusk and dawn, these long streaks of black come together, swirling in unison to form a writhing circle over 100 strong that herds thousands of smaller fish into shallower waters.

Volta’s electric eels can gather in groups, working together to corral smaller fish in shallower waters, a new study finds. Then, groups of about 10 eels attack in unison, shocking the fish out of the water and into a stupor so that they can easily be eaten.

After corralling the prey, smaller groups of about 10 eels unleash coordinated electric attacks that can send shocked fish flying from the water. The researchers haven’t yet measured the combined voltage of such attacks, but 10 Volta’s eels firing together could, in theory, power something like 100 light bulbs, de Santana says. The then helpless, floating prey make easy pickings for the mass of eels. The whole ordeal lasts about two hours.

So far, such aggregations have been observed in only this one lake. But de Santana suspects that group hunting may be advantageous in other lakes and rivers with large shoals of small fish. Much of the eels’ range remains underexplored by scientists, so de Santana and colleagues are launching a citizen science project with Indigenous communities to identify more spots where many eels live together, he explains. “There is still so much we don’t know about these organisms.”

Drones could help create a quantum internet

Thu, 14 Jan 2021 11:00:00 GMT

The quantum internet may be coming to you via drone.

Scientists have now used drones to transmit particles of light, or photons, that share the quantum linkage called entanglement. The photons were sent to two locations a kilometer apart, researchers from Nanjing University in China report in a study to appear in Physical Review Letters.

Entangled quantum particles can retain their interconnected properties even when separated by long distances. Such counterintuitive behavior can be harnessed to allow new types of communication. Eventually, scientists aim to build a global quantum internet that relies on transmitting quantum particles to enable ultrasecure communications by using the particles to create secret codes to encrypt messages. A quantum internet could also allow distant quantum computers to work together, or perform experiments that test the limits of quantum physics.

Quantum networks made with fiber-optic cables are already beginning to be used (SN: 9/28/20). And a quantum satellite can transmit photons across China (SN: 6/15/17). Drones could serve as another technology for such networks, with the advantages of being easily movable as well as relatively quick and cheap to deploy.

The researchers used two drones to transmit the photons. One drone created pairs of entangled particles, sending one particle to a station on the ground while relaying the other to the second drone. That machine then transmitted the particle it received to a second ground station a kilometer away from the first. In the future, fleets of drones could work together to send entangled particles to recipients in a variety of locations.

One of the oldest known cave paintings has been found in Indonesia

Wed, 13 Jan 2021 19:00:53 GMT

Inside a cave on the Indonesian island of Sulawesi, scientists have found one of the oldest known artistic depictions of a real-world object or organism. It’s a painting of a warty pig, an animal still found on Sulawesi, that was rendered on the cave’s back wall at least 45,500 years ago, researchers report January 13 in Science Advances.

The discovery adds to evidence that “the first modern human cave art traditions did not emerge in Ice Age Europe, as long supposed, but perhaps earlier in Asia or even in Africa, where our species evolved,” says study author Adam Brumm, an archaeologist at Griffith University in Brisbane, Australia.

At least two, and possibly three, other partially preserved pig paintings appear on the cave wall near the newly dated figure. All of the painted pigs in the Sulawesi cave appear to be confronting each other in a scene of some sort, says archaeologist Iain Davidson of the University of New England in Armidale, Australia. Similarly positioned, painted animals dating to roughly 30,000 years ago or more appear in scenes in France’s Chauvet Cave, says Davidson, who did not participate in the new study.

On the ceiling of a small chamber in another Sulawesi cave, the researchers found a large pig painting — like the others, executed in red or dark red and purple mineral pigments — that dates to between 32,000 and 73,400 years ago. At least two other poorly preserved paintings of unidentified animals are located on the chamber’s ceiling and wall.

The team considers it likely that Homo sapiens, rather than a closely related species such as Homo floresiensis (SN: 6/8/16), painted on the Sulawesi cave walls.

Like a painted hunting scene from at least 43,900 years ago previously found in a separate Sulawesi cave (SN: 12/11/19), minimum age estimates for the pig paintings are based on measures of radioactive uranium’s decay in cauliflower-like mineral growths that formed in thin layers over and underneath parts of the depictions.

Uranium-based dating of ancient cave art has drawn criticism (SN: 10/28/19). For instance, Brumm’s group dated three mineral layers partly covering one of the pig paintings to estimate its minimum age. The layer closest to the painting was slightly younger than the two layers above it, the opposite of what would be expected if the layers had formed one after the other. Those topsy-turvy dates raise doubts about the accuracy of the painting’s minimum age, says archaeologist João Zilhão of the University of Barcelona.

A mix of slightly older and younger age estimates can result from gaps that form in successive mineral layers, Brumm’s team says. Averaging the dates of multiple layers provides a reasonable, possibly understated minimum age estimate for the underlying art, the researchers contend.

Ultimately, cave art such as the pigs on islands in Southeast Asia and Australia, and probably Sulawesi as well, may be shown to date to as early as around 60,000 to 70,000 years ago, says archaeologist Peter Veth of the University of Western Australia in Perth. That’s when H. sapiens first settled the region, probably bringing mainland cave art traditions with them rather than suddenly inventing the practice on isolated islands, he suggests.

Marie Tharp’s groundbreaking maps brought the seafloor to the world

Wed, 13 Jan 2021 16:00:00 GMT

Walk the halls of an academic earth sciences department, and you’ll likely find displayed on a wall somewhere a strikingly beautiful map of the world’s ocean floors. Completed in 1977, the map represents the culmination of the unlikely, and underappreciated, career of Marie Tharp. Her three decades of work as a geologist and cartographer at Columbia University gave scientists and the public alike their first glimpse of what the seafloor looks like.

In the middle of the 20th century, when many American scientists were in revolt against continental drift — the controversial idea that the continents are not fixed in place — Tharp’s groundbreaking maps helped tilt the scientific view toward acceptance and clear a path for the emerging theory of plate tectonics.

Tharp was the right person in the right place at the right time to make the first detailed maps of the seafloor. Specifically, she was the right woman. Her gender meant certain professional avenues were essentially off-limits. But she was able to take advantage of doors cracked open by historical circumstances, becoming uniquely qualified to make significant contributions to both science and cartography. Without her, the maps may never have come to be.

“It was a once-in-a-lifetime — a once-in-the-history-of-the-world — opportunity for anyone, but especially for a woman in the 1940s,” Tharp recalled in a 1999 perspective. “The nature of the times, the state of the science, and events large and small, logical and illogical, combined to make it all happen.”

With funding from the U.S. Navy, Marie Tharp and Bruce Heezen produced this 1977 map with Austrian painter Heinrich Berann. It has become iconic among cartographers and earth scientists.Library of Congress, Geography and Map Division

Tharp’s cartographic roots ran deep. She was born in Michigan in 1920 and as a young girl would accompany her father on field trips to survey land and make maps for the U.S. Department of Agriculture’s Bureau of Soils, a job that kept the family on the move. “By the time I finished high school I had attended nearly two dozen schools and I had seen a lot of different landscapes,” Tharp recalled. “I guess I had map-making in my blood, though I hadn’t planned to follow in my father’s footsteps.”

Tharp was a student at the University of Ohio in 1941 when the attack on Pearl Harbor emptied campuses of young men, who were joining the military in droves. This sudden scarcity of male students prompted the University of Michigan’s geology department to open its doors to women. Tharp had taken a couple of geology classes and jumped at the opportunity. “There were 10 or 12 of us that appeared from all over the United States, girls. With a sense of adventure,” she recalled in an oral history interview in 1994. Tharp earned a master’s degree in 1943, completing a summer field course in geologic mapping and working as a part-time draftsperson for the U.S. Geological Survey along the way. Upon graduating she took a job with an oil company in Oklahoma but was bored by work that involved neither fieldwork nor research. So she enrolled in night classes to earn a second master’s degree in mathematics from the University of Tulsa.

To celebrate our upcoming 100th anniversary, we’re launching a series that highlights some of the biggest advances in science over the last century. For more on the story of plate tectonics, visit Century of Science: Shaking up Earth.

Looking for more excitement, she moved to New York City in 1948. When she walked into the Columbia University geology department looking for a job, her advanced degrees got her an interview, but the only position available to a woman was that of a draftsperson assisting male graduate students working toward a degree in geology that she had already earned. Still, it seemed more promising than the other job she had inquired about — studying fossils at the American Museum of Natural History — so she took it.

The following year Tharp became one of the first women employed by Columbia’s newly founded Lamont Geological Observatory and soon was working exclusively with geologist Bruce Heezen, a newly minted Ph.D. Like many of the male scientists at Lamont, Heezen was primarily occupied with collecting ocean data, which Tharp would then analyze, plot and map — work she was more than qualified to do.

“These men considered it glamorous and pleasurable to go to sea, far more so than staying at home to analyze [the data],” writes science historian Naomi Oreskes of Harvard University in her forthcoming book Science on a Mission: How Military Funding Shaped What We Do and Don’t Know About the Ocean. “This is one reason data analysis was often left to women.” In fact, women often weren’t allowed on the research ships at all.

To generate the seafloor maps, Marie Tharp started with two-dimensional ocean profiles (top) and then used her extensive geologic knowledge to decipher landforms and fill in the blank spaces (bottom).B.C. Heezen, M. Tharp, and M. Ewing/Lamont-Doherty Earth Observatory/Geological Society of America Special Paper 1965

Barred from ocean expeditions, Tharp poured all of her energy into mapping the seafloor starting with the North Atlantic, work that would lead to two important discoveries. To make a map, she first translated the echo soundings gathered by ships crossing the ocean into depths and then created two-dimensional vertical slices of the terrain beneath the ships’ tracks. These ocean-floor profiles showed a broad ridge running down the middle of the Atlantic. Though the feature had been roughly mapped in the 19th century, Tharp noticed a notch near the top of the ridge in each of the profiles. She believed the notches represented a continuous, deep valley running down the center of the mid-ocean ridge. If she was right, the valley might be a rift where molten material came up from below, forming new crust and pushing the ocean floor apart — evidence that could support continental drift.

The idea that the continents were not fixed in place had gained traction in Europe, but Heezen, like most U.S. scientists at the time, “considered it to be almost a form of scientific heresy,” Tharp later wrote in Natural History magazine. It took her a year or so to convince Heezen that the rift was real, and it took the two several more years to finish their first map of the North Atlantic in 1957.

In order to publish that first map and share their work with other scientists, Tharp and Heezen had to get around the U.S. Navy’s Cold War–inspired decision to classify detailed topographic maps that used contour lines to indicate depths. This was one of the reasons the pair chose to adapt a relatively new cartographic style known as a physiographic diagram, a sort of three-dimensional sketch of terrain as if seen from an airplane window. To do this, Tharp had to use her training as a geologist and experience with mapping on land — knowledge and skills that a typical research assistant or draftsperson wouldn’t have had.

Physiographic maps had previously been used to represent continental landforms with standardized symbols. Each type of mountain, valley, plain and desert was sketched in a specific way. Tharp and Heezen were the first to use the technique to show what unknown, unseeable terrain might look like. Tharp first sketched a strip of seafloor along each profile, deciphering what type of landform each bump and dip was likely to be. Then she identified patterns to fill in the blank spaces between the profiles.

Bruce Heezen and Marie Tharp’s physiographic maps, this one of the North Atlantic first published in 1957 and again in 1959, gave scientists a compelling visual comparison to continental landforms they understood.Physiographic Diagram of the North Atlantic Ocean (1959) by Heezen and Tharp; reproduced by permission of Marie Tharp Maps LLC and the Lamont-Doherty Earth Observatory

“The amount of work involved in taking it from just from those soundings and being able to create that is just amazing,” says historian Judith Tyner, author of Women in American Cartography.

As Tharp was creating her map, an unrelated project was taking shape on the drafting table next to hers. Heezen had hired a recent art school graduate to plot thousands of earthquake epicenters in the Atlantic Ocean to help Bell Labs find the safest places to lay transoceanic cables. The epicenters he was plotting lined up with Tharp’s rift valley. The correlation lent weight to the idea that the rift was where the crust was pulling apart, and gave Tharp a way to accurately locate the rift between the ship tracks.

Heezen and Tharp’s 1957 diagram of the north Atlantic Ocean was by far the most exhaustive seafloor map ever produced.

“The marvelous thing about that map is how comprehensive it looked on rather limited data,” says science historian Ronald Doel of Florida State University in Tallahassee. “But the earthquake data also helped to make clear just where the ridges are oriented and where the associated geological features are.”

The American scientific community was initially skeptical, wary of the speculative nature of their map. But as the pair continued mapping the rest of the Atlantic and moved on to other oceans, evidence accumulated for a continuous ridge, with a rift valley at its center, stretching for some 60,000 kilometers across the globe.

Tharp and Heezen’s innovative use of the physiographic method gave scientists a compelling visual comparison to continental landforms they understood. This helped convince them that just as the East African Rift was splitting that continent, the submarine rift valley marked where the continents on either side of the Atlantic had pulled away from each other.

“That’s why her map is so powerful,” says historian of geology David Spanagel of Worcester Polytechnic Institute in Worcester, Mass. “It allows people to see the bottom of the ocean as if it were a piece of land, and then reason about it. That’s a transformative thing that she’s able to accomplish.”

National Geographic also took notice of the maps and invited Heezen and Tharp to collaborate on some ocean illustrations with the Austrian painter Heinrich Berann, who would become famous for his mountain panoramas. The gorgeous ocean-floor depictions were included as poster-sized supplements in issues of National Geographic magazine between 1967 and 1971. The magazine had a circulation of 6 million or 7 million at the time, giving a sizable swathe of the public a window into the ocean.

In 1973, Heezen and Tharp received a grant from the U.S. Navy to work with Berann on a complete map of the world’s ocean floors. It took the trio four years to create their iconic cartographic masterpiece, an unparalleled, panoramic visualization that continues to shape how both scientists and the public think about the seafloor.

The map was finished just weeks before Heezen died of a heart attack at age 53, while in a submarine exploring the mid-ocean ridge near Iceland. His death left Tharp without a source of funding and data, essentially ending her remarkable career. It would be decades before her contributions were fully recognized. But unlike many other unsung figures in the history of science, the accolades began rolling in before she died of cancer in 2006. During the last decade of her life, Tharp received prestigious awards from several institutions including Lamont — now known as the Lamont-Doherty Earth Observatory — and the Library of Congress, which named her one of the four greatest cartographers of the 20th century.

“Can you imagine what heights she would have risen to in her profession,” says Tyner, “if she’d been a man?”

Though hers was always the second name, after Heezen’s, on the maps they made, and doesn’t appear at all on many of the papers her work contributed to, Tharp never expressed any regrets about her path. “I thought I was lucky to have a job that was so interesting,” she recalled in 1999. “Establishing the rift valley and the mid-ocean ridge that went all the way around the world for 40,000 miles — that was something important… You can’t find anything bigger than that, at least on this planet.”

How the Earth-shaking theory of plate tectonics was born

Wed, 13 Jan 2021 16:00:00 GMT

Some great ideas shake up the world. For centuries, the outermost layer of Earth was thought to be static, rigid, locked in place. But the theory of plate tectonics has rocked this picture of the planet to its core. Plate tectonics reveals how Earth’s surface is constantly in motion, and how its features — volcanoes, earthquakes, ocean basins and mountains — are intrinsically linked to its hot interior. The planet’s familiar landscapes, we now know, are products of an eons-long cycle in which the planet constantly remakes itself.

When plate tectonics emerged in the 1960s it became a unifying theory, “the first global theory ever to be generally accepted in the entire history of earth science,” writes Harvard University science historian Naomi Oreskes, in the introduction to Plate Tectonics: An Insider’s History of the Modern Theory of the Earth. In 1969, geophysicist J. Tuzo Wilson compared the impact of this intellectual revolution in earth science to Einstein’s general theory of relativity, which had produced a similar upending of thought about the nature of the universe.

This article is an excerpt from a series celebrating some of the biggest advances in science over the last century. For an expanded version of the story of plate tectonics, visit Century of Science: Shaking up Earth.

Plate tectonics describes how Earth’s entire, 100-kilometer-thick outermost layer, called the lithosphere, is broken into a jigsaw puzzle of plates — slabs of rock bearing both continents and seafloor — that slide atop a hot, slowly swirling inner layer. Moving at rates between 2 and 10 centimeters each year, some plates collide, some diverge and some grind past one another. New seafloor is created at the center of the oceans and lost as plates sink back into the planet’s interior. This cycle gives rise to many of Earth’s geologic wonders, as well as its natural hazards.

“It’s amazing how it tied the pieces together: seafloor spreading, magnetic stripes on the seafloor … where earthquakes form, where mountain ranges form,” says Bradford Foley, a geodynamicist at Penn State. “Pretty much everything falls into place.”

With so many lines of evidence now known, the theory feels obvious, almost inevitable. But the conceptual journey from fixed landmasses to a churning, restless Earth was long and circuitous, punctuated by moments of pure insight and guided by decades of dogged data collection.

Continents adrift

In 1912, German meteorologist Alfred Wegener proposed at a meeting of Frankfurt’s Geological Association that Earth’s landmasses might be on the move. At the time, the prevailing idea held that mountains formed like wrinkles on the planet as it slowly lost the heat of formation and its surface contracted. Instead, Wegener suggested, mountains form when continents collide as they drift across the planet’s surface. Although now far-flung, the continents were once joined together as a supercontinent Wegener dubbed Pangaea, or “all-Earth.” This would explain why rocks of the same type and age, as well as identical fossils, are found on either side of the Atlantic Ocean, for example.

The San Andreas Fault (shown) is the boundary between the Pacific and North American plates.KEVIN SCHAFER/ALAMY

In 1989, a slip of the San Andreas Fault triggered a magnitude 6.9 earthquake that rocked the San Francisco Bay area, causing 63 deaths and billions of dollars in damage (shown).David Weintraub/Science Source

This idea of drifting continents intrigued some scientists. Many others, particularly geologists, were unimpressed, hostile, even horrified. Wegener’s idea, detractors thought, was too speculative, not grounded enough in prevailing geologic principles such as uniformitarianism, which holds that the same slow-moving geologic forces at work on Earth today must also have been at work in the past. The principle was thought to demand that the continents be fixed in place.

German geologist Max Semper disdainfully wrote in 1917 that Wegener’s idea “was established with a superficial use of scientific methods, ignoring the various fields of geology,” adding that he hoped Wegener would turn his attention to other fields of science and leave geology alone.“O holy Saint Florian, protect this house but burn down the others!” he wrote sardonically.

The debate between “mobilists” and “fixists” raged on through the 1920s, picking up steam as it percolated into English-speaking circles. In 1926, at a meeting in New York City of the American Association of Petroleum Geologists, geologist Rollin T. Chamberlin dismissed Wegener’s hypothesis as a mishmash of unrelated observations. The idea, Chamberlin said, “is of the foot-loose type, in that it takes considerable liberty with our globe, and is less bound by restrictions or tied down by awkward, ugly facts than most of its rival theories.”

One of the most persistent sticking points for Wegener’s idea, now called continental drift, was that it couldn’t explain how the continents moved. In 1928, English geologist Arthur Holmes came up with a potential explanation for that movement. He proposed that the continents might be floating like rafts atop a layer of viscous, partially molten rocks deep inside Earth. Heat from the decay of radioactive materials, he suggested, sets this layer to a slow boil, creating large circulating currents within the molten rock that in turn slowly shift the continents about.

Holmes admitted he had no data to back up the idea, and the geology community remained largely unconvinced of continental drift. Geologists turned to other matters, such as developing a magnitude scale for earthquake strength and devising a method to precisely date organic materials using the radioactive form of carbon, carbon-14.

Data flood in

Rekindled interest in continental drift came in the 1950s from evidence from an unexpected source — the bottom of the oceans. World War II had brought the rapid development of submarines and sonar, and scientists soon put the new technologies to work studying the seafloor. Using sonar, which pings the seafloor with sound waves and listens for a return pulse, researchers mapped out the extent of a continuous and branching underwater mountain chain with a long crack running right down its center. This worldwide rift system snakes for over 72,000 kilometers around the globe, cutting through the centers of the world’s oceans.

Armed with magnetometers for measuring magnetic fields, researchers also mapped out the magnetic orientation of seafloor rocks — how their iron-bearing minerals are oriented relative to Earth’s field. Teams discovered that the seafloor rocks have a peculiar “zebra stripe” pattern: Bands of normal polarity, whose magnetic orientation corresponds to Earth’s current magnetic field, alternate with bands of reversed polarity. This finding suggests that each of the bands formed at different times.

The Pacific Ocean’s Mariana Trench is the deepest known subduction zone, where a tectonic plate sinks back into Earth’s interior. Here, the Deep Discoverer explores the trench at a depth of 6,000 meters in 2016.NOAA OFFICE OF OCEAN EXPLORATION AND RESEARCH

Meanwhile, growing support for the detection and banning of underground nuclear testing also created an opportunity for seismologists: the chance to create a global, standardized network of seismograph stations. By the end of the 1960s, about 120 different stations were installed in 60 different countries, from the mountains of Ethiopia’s Addis Ababa to the halls of Georgetown University in Washington, D.C., to the frozen South Pole. Thanks to the resulting flood of high-quality seismic data, scientists discovered and mapped rumbles along the mid-ocean rift system, now called mid-ocean ridges, and beneath the trenches. The quakes near very deep ocean trenches were particularly curious: They originated much deeper underground than scientists had thought possible. And the ridges were very hot compared with the surrounding seafloor, scientists learned by using thin steel probes inserted into cores drilled from shipboard into the seafloor.

In the early 1960s, two researchers working independently, geologist Harry Hess and geophysicist Robert S. Dietz, put the disparate clues together — and added in Holmes’ old idea of an underlying layer of circulating currents within the hot rock. The mid-ocean ridges, each asserted, might be where circulation pushes hot rock toward the surface. The powerful forces drive pieces of Earth’s lithosphere apart. Into the gap, lava burbles up — and new seafloor is born. As the pieces of lithosphere move apart, new seafloor continues to form between them, called “seafloor spreading.”

Research suggests that volcanic island chains form as plates move over upwellings of magma. But the origin of the Hawaiian Islands (Kilauea volcano shown) and other similar chains remains something of a geologic puzzle.ART WOLFE/GETTY IMAGES

The momentum culminated in a two-day gathering of perhaps just 100 earth scientists in 1966, held at the Goddard Institute for Space Studies in New York. “It was quite clear, at this conference in New York, that everything was going to change,” University of Cambridge geophysicist Dan McKenzie told the Geological Society of London in 2017 in a reflection on the meeting.

But going in, “no one had any idea” that this meeting would become a pivotal moment for the earth sciences, says seismologist Lynn Sykes of Columbia University. Sykes, then a newly minted Ph.D., was one of the invitees; he had just discovered a distinct pattern in the earthquakes at mid-ocean ridges. This pattern showed that the seafloor on either side of the ridges was pulling apart, a pivotal piece of evidence for plate tectonics.

At the meeting, talk after talk piled data on top of data to support seafloor spreading, including Sykes’ earthquake data and those symmetrical patterns of zebra stripes. It soon became clear that these findings were building toward one unified narrative: Mid-ocean ridges were the birthplaces of new seafloor, and deep ocean trenches were graves where old lithosphere was reabsorbed into the interior. This cycle of birth and death had opened and closed the oceans over and over again, bringing the continents together and then splitting them apart.

The evidence was overwhelming, and it was during this conference “that the victory of mobilism was clearly established,” geophysicist Xavier Le Pichon, previously a skeptic of seafloor spreading, wrote in 2001 in his retrospective essay “My conversion to plate tectonics,” included in Oreskes’ book.

Plate tectonics emerges

The whole earth science community became aware of these findings the following spring, at the American Geophysical Union’s annual meeting. Wilson laid out the various lines of evidence for this new view of the world to a much larger audience in Washington, D.C. By then, there was remarkably little pushback from the community, Sykes says: “Right away, they accepted it, which was surprising.”

Scientists now knew that Earth’s seafloor and continents were in motion, and that ridges and trenches marked the edges of large blocks of lithosphere. But how were these blocks moving, all in concert, around the planet? To plot out the choreography of this complex dance, two separate groups seized upon a theorem devised by mathematician Leonhard Euler way back in the 18th century. The theorem showed that a rigid body moves around a sphere as though it is rotating around an axis. McKenzie and geophysicist Robert Parker used this theorem to calculate the dance of the lithospheric blocks — the plates. Unbeknownst to them, geophysicist W. Jason Morgan independently came up with a similar solution.

Shifting landmasses — such as the opening of the Drake Passage between South America and Antarctica (icebergs around Elephant Island shown) — can alter currents, and climates.NASA IMAGE BY JEFF SCHMALTZ, LANCE/EOSDIS RAPID RESPONSE

With this last piece, the unifying theory of plate tectonics was born. The hoary wrangling over continental drift now seemed not only antiquated, but also “a sobering antidote to human self-confidence,” physicist Egon Orowan told Science News in 1970.

People have benefited greatly from this clearer vision of Earth’s workings, including being able to better prepare for earthquakes, tsunamis and volcanoes. Plate tectonics has also shaped new research across the sciences, offering crucial information about how the climate changes and about the evolution of life on Earth.

And yet there’s still so much we don’t understand, such as when and how the restless shifting of Earth’s surface began — and when it might end. Equally puzzling is why plate tectonics doesn’t appear to happen elsewhere in the solar system, says Lindy Elkins-Tanton, a planetary scientist at Arizona State University in Tempe. “How can something be a complete intellectual revolution and also inexplicable at the same time?”

Jupiter’s frozen moon Europa (shown) has its own form of icy plate tectonics.NASA, JPL-Caltech, SETI Institute

Crucible of life

Earth is the only known world with plate tectonics. It’s also the only one known to harbor life.

Planetary scientists puzzle over whether and how these two facts might be related — and what it means for just how unusual Earth really is, says Lindy Elkins-Tanton, a planetary scientist at Arizona State University in Tempe. “Nobody knows how plate tectonics began on Earth, and why it didn’t begin elsewhere,” she adds. “It’s a mystery that connects to a lot of other mysteries, and one of those is habitability.”

We know plate tectonics plays a powerful role in keeping Earth habitable, primarily by moving carbon around. “It’s responsible for mediating the climate on long geological time scales, making sure the climate is more or less temperate for life,” says Roger Fu, a geophysicist at Harvard University.

When two tectonic plates collide, one can slide beneath the other, carrying rocks bearing carbon deep into the planet’s interior. The subducting plate begins to melt, and volcanoes bloom on the overlying plate, belching carbon dioxide and other gases into the atmosphere. As carbon dioxide builds up, it warms the planet through the greenhouse effect.

This warmer atmosphere then speeds up weathering of rocks on Earth’s surface, by boosting the chemical reaction between carbon dioxide–rich rainwater and the rocks. Those reactions draw the gas out of the atmosphere to form new carbon minerals. The minerals wash into the ocean, where tiny ocean creatures use the carbon to build their calcium carbonate shells. Ultimately those creatures die, their shells sinking to the ocean floor and becoming carbonate rocks themselves. As more and more carbon dioxide gets sequestered away from the atmosphere in this way, the planet cools — until, eventually, the slow grind of plate tectonics carries the carbonate into the planet’s interior with a subducting plate.

Signs of plate tectonics are clearly visible on Earth’s surface (Piqiang Fault in China’s Xinjiang Province shown). Scientists wonder whether similar features on other planets could be clues to habitability.NASA

This cycle, playing out over many millions of years, doesn’t just keep temperatures mild. The churning also keeps oxygen, nitrogen, phosphorus and other nutrients cycling through the atmosphere, oceans and rocks — and chemically transforms them into forms that living organisms can use.

“That’s not to say that life wouldn’t happen without plate tectonics,” Fu says. “But it would be very different.”

In fact, the first life on Earth may predate the onset of plate tectonics. The planet’s ancient rocks bear traces of life dating to at least 3.4 billion years ago, several hundred million years before the earliest known evidence for any plate motions, in the form of fossilized stromatolites, layered structures made of microbes and minerals. Similar microbial communities exist in modern times at hot springs, such as those of Yellowstone National Park. Some scientists to speculate that hot springs — which contain the biochemical recipe for life, including chemical elements, water and energy — may have set the stage for Earth’s earliest life.

It’s certainly theoretically possible for planets without plate tectonics — like the early Earth — to have livable atmospheres and liquid water, as well as abundant heat, says Bradford Foley, a geodynamicist at Penn State. Foley has simulated how much carbon dioxide could seep out from the interior of “stagnant lid” planets — planets like Mars and Mercury that have a single, continuous piece of lithosphere that sits like a cold, heavy lid over the hot interior. Even on these planets, Foley says, “we still have volcanism,” because there’s still hot rock circulating beneath that heavy lid. Those eruptions release carbon dioxide to the atmosphere and produce fresh new rock for weathering.

Mars shows signs of volcanic activity (Olympus Mons shown) but no known plate tectonics.JPL, NASA

Volcanism on a climate-altering scale might not last as long as it does when plate tectonics keeps things churning along, but it theoretically could persist for 1 billion or 2 billion years, Foley says. That means that some stagnant lid planets could create an atmosphere and even have temperate climates with liquid water, at least for a time.

Then there’s Europa, Jupiter’s icy moon. The surface of the moon is broken into a mosaic of plates of ice that slide past and over and under one another, much like those on Earth. “Instead of subduction, it’s referred to as subsumption,” Fu says. But the result of this icy cycle may be similar to the hard-rock recycling on Earth, moving nutrients between surface ice and liquid ocean below, which in turn could help support life on the moon.

“What exactly plate tectonics is isn’t an answered question,” Fu says. The term, he says, has become a catchall that encompasses numerous physical features on Earth — mid-ocean ridges, subduction, moving continents — as well as geochemical processes like nutrient cycling. “But there’s no guarantee they always have to happen together.”

Scientists instinctively turn to Earth as a template for studying other worlds, and as an example of what to look for in the search for habitability, Elkins-Tanton says. “So many of the things we try to explain in the natural sciences relies on us being in the middle of the bell curve,” she says. “If it turns out we’re unusual, we’re a bit of an outlier, then explaining things is much harder.”

It may be that each world has its own eclectic history, she says. Earth’s happens to include the powerful cycle of plate tectonics. But life elsewhere might have found another way. — Carolyn Gramling

Earth’s oceans are storing record-breaking amounts of heat

Wed, 13 Jan 2021 09:00:00 GMT

Pandemic-related shutdowns may have spared Earth’s atmosphere some greenhouse gas emissions last year, but the world continued to warm.

Water temperature measurements from around the globe indicate that the total amount of heat stored in the upper oceans in 2020 was higher than any other year on record dating back to 1955, researchers report online January 13 in Advances in Atmospheric Sciences. Tracking ocean temperature is important because warmer water melts more ice off the edges of Greenland and Antarctica, which raises sea levels (SN: 4/30/20) and supercharges tropical storms (SN: 11/11/20).

Researchers estimated the total heat energy stored in the upper 2,000 meters of Earth’s oceans using temperature data from moored sensors, drifting probes called Argo floats, underwater robots and other instruments (SN: 5/19/10). The team found that upper ocean waters contained 234 sextillion, or 10²¹, joules more heat energy in 2020 than the annual average from 1981 to 2010. Heat energy storage was up about 20 sextillion joules from 2019 — suggesting that in 2020, Earth’s oceans absorbed about enough heat to boil 1.3 billion kettles of water.

This analysis may overestimate how much the oceans warmed last year, says study coauthor Kevin Trenberth, a climate scientist with the U.S. National Center for Atmospheric Research who is currently based in Auckland, New Zealand. So the researchers also crunched ocean temperature data using a second, more conservative method for estimating total annual ocean heat and found that the jump from 2019 to 2020 could be as low as 1 sextillion joules. That’s still 65 million kettles brought to boil.

The three other warmest years on record for the world’s oceans were 2017, 2018 and 2019. “What we’re seeing here is a variant on the movie Groundhog Day,” says study coauthor Michael Mann, a climate scientist at Penn State. “Groundhog Day has a happy ending. This won’t if we don’t act now to dramatically reduce carbon emissions.”

Rats with poisonous hairdos live surprisingly sociable private lives

Tue, 12 Jan 2021 17:30:22 GMT

Crested rats don’t just chew tree bark that’s poisonous enough to kill an elephant. The rabbit-sized rodents dribble and lick the toxic drool into their long rat fluff for a weaponized hairdo. Yet these dangerous rats, which scientists assumed were loners, turn out to have a close and cuddly family life. They even purr.

Chewing on bark or other parts of East Africa’s arrow poison trees gives the rats toxic saliva to apply to specialized zones of fur. The toxins sink in to porous, easily detached hairs on the rat’s flanks. Any predator foolish enough to bite a Lophiomys imhausi gets a hairy mouthful of bitter toxins that human poachers use on arrows for hunting big game.

The rats “have the personality of something poisonous,” says ecologist Sara Weinstein, who studied them during a Smithsonian fellowship at the Mpala Research Center in Kenya. “They can run quickly if they feel like it, but they don’t typically.” The rats are more likely to jog away from trouble or stand their ground, hissing, growling and grunting.

Trapping crested rats took some experimenting, says ecologist Katrina Nyawira, who worked on the project with Weinstein before moving to Oxford Brookes University in England. “Sometimes we’d set traps for about two weeks and just get one individual and, trust me, that would be a win.”

Sara B. Weinstein (left), Katrina Nyawira (right) stand at an African arrow poison tree, which provides defensive toxins for crested rats.Stephanie Higgins

Researchers set traps in a weird variety of locations, from remote spots in the Kenyan savanna to behind somebody’s bedroom door, Nyawira and Weinstein realized that the common success factor was access to arrow poison trees (Acokanthera schimperi).

With glossy, green leaves shaped like fat teardrops, this widespread shade tree is a cousin of the North American milkweeds that give monarch butterfly caterpillars their defensive toxins. From roots to shoots, the arrow poison tree carries potent cardenolides that can give would-be predators a heart attack.

When Weinstein and Nyawira had trapped a crested rat for a few days of video observation, the researchers tucked some shreds of the deadly tree bark and roots in the temporary cages. Cameras occasionally caught a nocturnal rat touching up its poison hairs. Rather than luxuriate in grooming, the animals got the poison-handling over with in 10 minutes.

Weinstein wondered if the 25 animals they caught paid some price for licking toxins: “Do they get sick and have to take a nap to sleep it off?” The videos, however, overall showed no extra naps, no sluggishness or other noticeable changes in behavior after hair care. For crested rats, poison really may be just mousse.

How these rats withstand the stuff is an ongoing mystery, with lots of speculation. This species’ stomach, for instance, has chambers more “like a cow…than your typical pizza rat’s,” says Weinstein, now at the University of Utah in Salt Lake City.

She hadn’t planned to study crested rat home life, but one why-not whim changed that. Weinstein once reset a trap in the same place she had just caught a crested rat. She’d heard that the rats were solitary, so her first catch should have emptied the territory. Yet she quickly caught a second rat in the same spot.

“We put the two rats sort of next to each other,” says Weinstein, “They start purring — this vocalization that we’ve never heard before.”

“They very much looked as if they wanted to be together,” she recalls. One was male, the other female. When Weinstein allowed the rats into the same cage, the two started grooming each other. One began following the other around, and the couple eventually retired to the cage’s private retreat, a nest box.

Over the course of several months, Weinstein and Nyawira eventually caught four more male-female pairs. Two pairs had youngsters, and each family snuggled together when reunited in captivity. In videos, pair members stayed close, spending about half of their waking time within just 15 centimeters of each other, the researchers reported online November 17 in the Journal of Mammalogy.

Videos inside the nest box looked especially cozy. Pairs bundled together in nose-to-tail swathes of fluff “like a big scarf,” Nyawira says. Their hair is “really soft, like cat’s fur.” Or as Weinstein puts it: “They’re super cute.”

The unusual crested rats of East Africa are not the feisty loners that scientist expected. The rats are best known for chewing up bark or other parts of a poisonous tree and dribbling the toxic saliva onto their fur. Any would-be predator foolish enough to take a bite gets a potentially deadly mouthful of detachable fluff that can induce a heart attack. But the rats with these dangerous hairdos have a snuggly domestic side. Cameras reveal they stick close to a mate and snuggle up to sleep in a mutual cloud of fluff.

Newborn megalodon sharks were larger than most adult humans

Tue, 12 Jan 2021 16:42:20 GMT

“Baby shark” has taken on a whole new meaning. Newborn megalodon sharks were supersized fish larger than most adult humans, a new study suggests.

An analysis of the growth rates of the ancient ocean predators, which lived between about 23 million and 2.5 million years ago, estimates that the sharks started life at about 2 meters long, researchers report January 11 in Historical Biology.

Otodus megalodon is right up there with Tyrannosaurus rex in the pantheon of scary extinct predators, but little is actually known about the shark’s biology (SN: 8/10/18). Its skeleton was made of difficult-to-fossilize cartilage, so what scientists do know mostly comes from fossilized teeth. For example, paleobiologist Kenshu Shimada of DePaul University in Chicago and colleagues previously used megalodon teeth, as well as those of other ancient and modern sharks, to estimate a total adult body length for the fish of at least 14 meters (SN: 10/5/20).

In the new study, Shimada and colleagues had an extra, rare piece of evidence: megalodon vertebrae. Although shark skeletons are made of cartilage, the animals’ backbones can become hardened and strengthened by deposits of calcium salts, which can then be fossilized. These vertebrae also preserve annual growth bands, like the rings of a tree, showing how the fish grew.

The researchers used an imaging technique called micro-computed tomography to study three well-preserved vertebrae from one shark. Those images revealed 46 growth bands, suggesting that this shark lived to the ripe old age of 46. The creature is estimated to have been about 9 meters long at its death, and the size of the bands hints that the animal grew at a rate of about 16 centimeters each year. That means that the shark would have been about 2 meters long at birth — large enough for even a newborn to be a fearsome foe in the seas, the scientists conclude.

Shimada’s team has previously suggested that while in utero, megalodon sharks, like some of their modern cousins, might have fed on unhatched eggs in the womb. That practice may have helped the giant fish to gain such a large size even before entering the world.

Mice may ‘catch’ each other’s pain — and pain relief

Tue, 12 Jan 2021 11:00:00 GMT

In pain and pain relief, mice may feel for each other.

Research has shown that mice can “catch” the emotions of an injured or fearful fellow. When some mice are injured, other healthy mice living alongside them behave as though in pain. Now, a study suggests that not only can pain be passed along, but also pain relief is contagious too.

In the last decade, researchers have done a lot of work showing that animals can pick up and share each other’s emotions, particularly fear (SN: 5/20/19), says Monique Smith, a neuroscientist at Stanford University. She and colleagues published their new findings on pain and relief in the Jan. 8 Science. Investigating these building blocks of empathy in animals can help researchers understand human empathy, Smith says, and may someday lead to treatments for disorders that affect the ability to be sensitive to the feelings and experiences of other people.

“Pain isn’t just a physical experience,” Smith says. “It’s an emotional experience” as well.

In experiments on pairs of mice, one mouse received an injection that caused arthritis-like inflammation in one hind paw while the other mouse was unharmed. After hanging out together for an hour, “the bystander has it worse than the mouse that got the injection,” says Jeffrey Mogil, a neuroscientist at McGill University in Montreal who was not part of the work.

Injected mice acted as though one paw is in pain, as expected, showing extra sensitivity to being prodded there with a plastic wire. Their uninjured companions also showed heightened sensitivity, and in both hind paws. Those mice act as though they’re in the same amount of pain and in more places, Mogil says. “The behavior is astounding.”

In another set of experiments, both mice received the irritating injection, but one also got a dose of soothing morphine. For hours after these mice mingled, the second mouse behaved as though it also got the drug. “You’ve actually relieved pain in this animal simply by letting it hang out with another animal whose pain was relieved,” says Robert Malenka, a neuroscientist also at Stanford University. In a control group where both mice partners experienced inflammation, the animals’ sensitivity didn’t change after their time together.

To understand how these mice pick up on each other’s feelings, Smith, Malenka and their colleague neuroscientist Naoyuki Asada watched which brain regions were active after the mice spent time together. The team saw nerve cells, or neurons, firing in the anterior cingulate cortex, an area important in human empathy and part of the brain region responsible for memory and cognition.

The team found neurons connecting this area to other parts of the brain, including the nucleus accumbens, an area that deals with motivation and social behavior. When the scientists disrupted that particular neural connection, “the animals no longer were able to manifest empathy” for pain or pain relief, Malenka says.

The transfer of other emotions between mice may rely on different brain connections. The researchers also examined how mice feel each other’s fear in experiments where mice saw other mice receive an electric shock. The team found that fear transfer relied on connections from the cortex to part of the amygdala, a region known to respond to fear. That suggests that different processes in the brain are involved in different types of empathy. But the differences may also be linked to how mice sense their fellows’ emotions, Mogil says. In the pain and pain relief experiments, mice spend time together sniffing each other, and odors can contain clues to the animals’ feelings. But in the tests on fear, visual cues conveyed animal emotions.

“Not surprisingly, the circuits that they’re looking at are remarkably similar to some of these processes in humans,” says Jules Panksepp, a social neuroscientist at the University of Wisconsin–Madison who was not part of the study. Both mice and humans share a connectedness with their compatriots in emotional situations, he says, and research points to a shared evolutionary basis for empathy.

If scientists can home in on the neurochemicals that foster empathic processes, Panksepp says, they may be able to design drugs to treat conditions, such as psychopathy or social personality disorders, that cause empathy to go awry.

Brown tree snakes use their tails as lassos to climb wide trees

Mon, 11 Jan 2021 16:00:56 GMT

Snakes do a lot more than slither. Some swim, while others sidewind across sand (SN: 10/9/14). Some snakes even fly (SN: 6/29/20). But no one has ever seen a snake move the way that brown tree snakes do when they climb certain trees. By wrapping its tail around a tree or pole in a lasso-like grip and wriggling to propel itself, a brown tree snake can shimmy up structures that would otherwise be too wide to climb.

Better understanding how brown tree snakes (Boiga irregularis) get around could inform strategies to control their population in Guam, where the snakes are an invasive species. The reptiles are infamous for having wiped out almost all of the native forest birds on Guam and frequently cause power outages by clambering up utility poles.

The discovery of brown tree snakes’ lasso climbing method, reported online January 11 in Current Biology, was somewhat serendipitous. Julie Savidge, an ecologist at Colorado State University in Ft. Collins, and colleagues were investigating ways to keep these tree-climbing snakes away from Guam’s Micronesian starlings — one of only two native forest birds left on the island.

One of these ways involved tests to see whether a wide pipe, or baffle, around a pole could prevent predators from reaching a starling nest box at the top. In reviewing hours of footage of the baffle to monitor how well it deterred brown tree snakes, the team saw one snake do something wholly unexpected: The snake lassoed itself around the baffle and began scooting upward.

“We were in total shock,” says study coauthor Thomas Seibert, also an ecologist at Colorado State. “This isn’t something that a snake is supposed to do.”

Footage of a brown tree snake, caught with an infrared camera at night, reveals the unique way that this species climbs: The snake lassos itself around a pole and wriggles the loop of its tail to propel itself upward. The technique allows the reptile to shimmy up structures that would otherwise be too wide to climb.

Brown tree snakes and other snakes typically climb trees that are too smooth to slither up by coiling around a trunk multiple times. A snake wraps the front of its body around the trunk and then coils its back end around the tree in another loop to get a second grip. The snake then stretches its neck up and repeats the process to inch upward. But wrapping around a tree multiple times limits the width of a tree that a snake can scale. Using a single, large, lasso-like grip allows the brown tree snake to climb wider trees — or baffles, explains study coauthor Bruce Jayne, a biologist at the University of Cincinnati in Ohio.

In later lab experiments, the researchers observed several brown tree snakes using this lasso-like posture when placed inside an enclosure with a wide pole topped with a dead mouse for bait. But the lasso climbing method is not very efficient. Five brown tree snakes, ranging from about 1.1 to 1.7 meters long, climbed less than a millimeter per second, on average.

“This was extremely strenuous [for the snakes]. You could see them breathing heavily, and they’d take frequent breaks,” Seibert says. As a result, the snakes probably use the lasso-like motion only on the rare occasions that they encounter trees or poles too wide and smooth to be scaled any other way.

Using infrared cameras to watch nocturnal brown tree snakes at night, researchers observed the reptiles using a bizarre technique to climb wide poles: The snakes (one pictured) used their tails as lassos to grip a pole and wriggle their way upward.J. Savidge et al/Current Biology 2020

It’s “kind of whacky” to see a snake move like this, says Gregory Byrnes, a biologist at Siena College in Loudonville, N.Y., who was not involved in the work. But Byrnes is not entirely surprised that brown tree snakes have devised a way to deal with wide trees or baffles. These snakes are notoriously agile climbers that can bridge large gaps, slide up steep surfaces and traverse thin wires. “They have so much control over their bodies that if they’re given a challenge … they figure out a way to [overcome] it,” he says.

Testing the limits of brown tree snake agility could help design new baffles or other tools to protect endangered birds on Guam, Savidge says. Already, after the researchers placed several bird boxes on utility poles on the island that were too wide for brown tree snakes to lasso their way up, “the birds adopted these birdhouses and have done very, very well,” she says.

Better understanding snakes’ repertoire of climbing techniques could also make for better robots, says Henry Astley, a biologist at the University of Akron in Ohio who was not involved in the work.

Astley and others are interested in building snakelike robots to navigate terrains that are too difficult for robots with legs or wheels to traverse (SN: 11/16/12). He envisions snake bots slithering through earthquake rubble to search for survivors or wriggling inside large machinery to perform inspections. Discovering new, clever ways in which real snakes exploit their incredible flexibility could help engineers make better use of serpentine machines.

Ocean acidification may make some species glow brighter

Mon, 11 Jan 2021 13:00:00 GMT

A more acidic ocean could give some species a glow-up.

As the pH of the ocean decreases as a result of climate change, some bioluminescent organisms might get brighter, while others see their lights dim, scientists report January 2 at the virtual annual meeting of the Society for Integrative and Comparative Biology.

Bioluminescence is de rigueur in parts of the ocean (SN: 5/19/20). The ability to light the dark has evolved more than 90 times in different species. As a result, the chemical structures that create bioluminescence vary wildly — from single chains of atoms to massive ringed complexes.

With such variability, changes in pH could have unpredictable effects on creatures’ ability to glow (SN: 7/6/10). If fossil fuel emissions continue as they are, average ocean pH is expected to drop from 8.1 to 7.7 by 2100. To find out how bioluminescence might be affected by that decrease, sensory biologist Tom Iwanicki and colleagues at the University of Hawaii at Manoa gathered 49 studies on bioluminescence across nine different phyla. The team then analyzed data from those studies to see how the brightness of the creatures’ bioluminescent compounds varied at pH levels from 8.1 to 7.7.

As pH drops, the bioluminescent chemicals in some species, such as the sea pansy (Renilla reniformis), increase light production twofold, the data showed. Other compounds, such as those in the sea firefly (Vargula hilgendorfii), have modest increases of only about 20 percent. And some species, like the firefly squid (Watasenia scintillans), actually appear to have a 70 percent decrease in light production.

For the sea firefly — which uses glowing trails to attract mates — a small increase could give it a sexy advantage. But for the firefly squid — which also uses luminescence for communication — low pH and less light might not be a good thing.

Because the work was an analysis of previously published research, “I’m interpreting this as a first step, not a definitive result,” says Karen Chan, a marine biologist at Swarthmore College in Pennsylvania who wasn’t involved in the study. It “provides [a] testable hypothesis that we should … look into.”

The next step is definitely testing, Iwanicki agrees. Most of the analyzed studies took the luminescing chemicals out of an organism to test them. Finding out how the compounds function in creatures in the ocean will be key. “Throughout our oceans, upward of 75 percent of visible critters are capable of bioluminescence,” Iwanicki says. “When we’re wholescale changing the conditions in which they can use that [ability] … that’ll have a world of impacts.”

Reawakened Yellowstone geyser isn’t a sign of imminent explosion

Mon, 11 Jan 2021 11:00:00 GMT

A recent reawakening of the tallest geyser in the world is not a harbinger of an imminent volcanic eruption, a new study reports. And it isn’t likely to portend a dangerous hydrothermal explosion either, which can occur when superheated water turns to steam and bursts violently out of the confining rock, researchers report in the Jan. 12 Proceedings of the National Academy of Sciences.

The reason for the sudden restart of Steamboat Geyser, found at Yellowstone National Park in Wyoming, remains a mystery, the scientists say. But the study, which examines a wealth of seismic, environmental and other data from the Yellowstone region, is helping scientists better understand what makes Steamboat, and other geysers, tick.

After over three years of dormancy, Steamboat abruptly shot a towering stream of hot water into the sky on March 15, 2018. That event kicked off a new active phase for the geyser, one of Yellowstone’s most famous features — and made some park watchers wonder if the sudden eruption warned of greater dangers yet to come.

When it comes to potential threats at Yellowstone, the supervolcano itself gets most of the attention (SN: 1/2/18). But its deep reservoir of magma also heats groundwater that circulates underground or pools on the surface — and those boiling waters pose a far more immediate threat to park visitors. “Probably the biggest hazard in Yellowstone is people going off trail and falling in the boiling water. But there’s always a risk of hydrothermal explosions,” says Michael Manga, a geologist at the University of California, Berkeley.

Such explosions are little understood and therefore difficult to anticipate. But they can be deadly: In December 2019, for example, a sudden hydrothermal explosion at Whakaari, or White Island, in New Zealand killed 22 people.

So after Steamboat reawakened, scientists thought it was “perfectly reasonable to consider the possibility that maybe even more violent activity might be coming along,” Manga says. To assess that potential threat, he and colleagues collected a wide range of data from Steamboat — which erupted another 109 times between March 2018 and July 2020 — as well as from other geysers in the region and from the surrounding environment.

Those data included seismic records going back to 2003; GPS-determined changes in the shape of the ground that might be linked to moving magma; changes in temperature underground as well as in how much heat was emitted to the air over the geyser basin; and changes in the volume and chemistry of the water erupting out of Steamboat.

The data revealed that, just before Steamboat’s 2018 reactivation, seismic activity in the region was slightly heightened, the land rose very slightly and the heat emanating to the atmosphere from the geyser basin increased — all of which might point to some sort of magmatic movement. But no other dormant geyser in the region awoke, and temperatures underground didn’t change. The team also found no other correlations between subsequent Steamboat eruptions and seismic activity, land deformation or thermal emissions.

Steamboat also seemed to show a seasonal eruption cycle, bursting forth more often during the summer than in the winter. That pattern suggests a possible relationship between eruption frequency and an increase in river flow due to melting snow, the study suggests.

But the ultimate trigger for Steamboat’s reawakening is still unknown, says U.S. Geological Survey geophysicist Michael Poland, who is also the scientist-in-charge at the Yellowstone Volcano Observatory in Vancouver, Wash. The authors “did a really nice job of taking every possible variable that they could and ruling them out,” Poland says. “And even though the answer is we don’t see any reason why Steamboat became active, that’s still valuable information.”

The study also gives some insight into these mysterious, and sometimes deadly, hot-water fountains. “Most geysers don’t behave in a predictable way,” Poland says. “Old Faithful is very unusual” in that it erupts on a regular schedule. One of the most fundamental questions about geysers is why they erupt to certain heights, he adds — and why, for example, Steamboat can shoot water over 100 meters into the air, while Old Faithful’s fountain is perhaps a third as high.

The new study gives a possible answer, by noting that the reservoir of hot water that feeds Steamboat is much deeper than other geysers. Water stored deeper underground is under higher pressure and can also get to higher temperatures — and that extra energy may drive those taller eruptions (SN: 3/21/16).

A new polio vaccine joins the fight to vanquish the paralyzing disease

Fri, 08 Jan 2021 13:00:00 GMT

After decades of work and mass vaccination campaigns that have spared millions of children from paralysis, the world is close to wiping out polio.

But a small number of outbreaks that have simmered in areas of low vaccination remain. And some happened after weakened virus in the oral polio vaccine, over time, moved around a community and regained the ability to cause disease. No other vaccines made with weakened live viruses have caused outbreaks of disease.

To stamp out vaccine-derived polio outbreaks, the World Health Organization has granted emergency use for a new polio vaccine. The oral vaccine got the go-ahead on November 13.

“We are very, very enthusiastically looking forward to using this new vaccine,” says medical epidemiologist Chima Ohuabunwo of Morehouse School of Medicine in Atlanta, who has worked on polio eradication in Africa for more than two decades. Along with continuing the crucial work of improving vaccination coverage in places where it is low, the new vaccine will “hopefully … take us to the finishing line of polio eradication.”

Eight years after the WHO’s 1980 declaration that the world was free of smallpox, the Global Polio Eradication Initiative launched to tackle polio. The disease was a promising candidate for eradication. An effective, easily administered and cheap vaccine was available. And poliovirus, which naturally infects only humans, doesn’t hang around in other animals in between outbreaks.

Most people who become infected with poliovirus don’t feel sick, while some have flu-like symptoms. But about one in 200 become paralyzed for life. Although not a routine threat in the United States since the early 1950s (SN: 9/12/19), polio has continued to harm people, especially children, around the world.

In the late 1980s, wild poliovirus paralyzed more than 1,000 children each day, according to the Global Polio Eradication Initiative. Since then, thanks to widespread vaccination campaigns, cases have plummeted by more than 99 percent, and two of the three types of wild poliovirus have been eradicated. The last cases from type 2 and type 3 were reported in 1999 and 2012, respectively. Only wild poliovirus type 1 remains, and only in two countries: As of December 30, 56 cases were reported in Afghanistan and 83 in Pakistan caused by type 1, in 2020.

Much of this progress has been possible because of the oral polio vaccine. “It’s been the workhorse of the eradication campaign,” says virologist and infectious disease physician Adam Lauring of the University of Michigan School of Medicine in Ann Arbor. Immunization with the oral vaccine has prevented more than 13 million cases of polio since 2000, according to WHO.

A big advantage of the oral vaccine, which is made of live but weakened poliovirus, is that it not only protects against paralysis — it also can stop wild poliovirus from spreading in a community. Poliovirus moves from person to person when someone ingests water or food contaminated with virus-containing stool. The oral vaccine prevents wild poliovirus from multiplying in the gut and being passed on. (There is another, more expensive, injected polio vaccine with killed virus that prevents paralysis but not viral spread.)

While the oral vaccine has nearly wiped out wild poliovirus, it has a vulnerability. Weakened poliovirus in the vaccine has genetic changes that keep it from causing disease. As vaccine virus multiplies in the gut, it can lose key genetic changes, bringing it closer to behaving like wild poliovirus. And altered vaccine virus “can be spread to others and establish community transmission,” says biologist Raul Andino of the University of California, San Francisco School of Medicine. That can be a problem if not enough people have been immunized against polio.

A doctor examines a child in Nigeria in 2013 suspected of being paralyzed by polio. Nigeria’s last wild poliovirus case was reported in 2016, clearing the way for Africa to be certified free of wild poliovirus in August of 2020.Rebecca Martin/CDC

More than 80 percent of children need to be vaccinated to keep poliovirus from spreading in a community. The first vaccine-derived polio outbreak to be detected occurred in the Dominican Republic and Haiti two decades ago, in areas with low vaccination. That allowed altered vaccine virus, shed in the stool of the immunized, to spread largely unchecked and, over time, return to a form that causes paralysis (SN: 8/10/04). The full process of vaccine virus reverting to disease-causing virus is rare and takes many months of moving around a community.

Today, vaccine-derived outbreaks are primarily found in Afghanistan, Pakistan and countries in Africa. Most of these outbreaks — which have been responsible for more polio cases in the last few years than the remaining type of wild poliovirus — are linked to vaccine virus type 2. Vaccination campaigns, which had used an oral vaccine containing weakened versions of all three types of poliovirus, switched to using a formulation with just types 1 and 3 in 2016.

However, the way to stop a type 2 vaccine-derived outbreak is with an oral vaccine containing only the weakened type 2 virus. And that has sparked new outbreaks, researchers reported in Science in April. “It is this vicious circle,” Lauring says. As of December 22, in 2020 there were 854 polio cases linked to the type 2 vaccine virus.

Hence the quest for a new and improved poliovirus type 2 oral vaccine, one that kept the good parts of the original but with tweaks to try to prevent problematic genetic changes. “It’s a wonderful vaccine, so we didn’t want to change the characteristics” that induce the body’s immune response, Andino says. “The only thing we wanted to do is prevent the reversion” to a disease-causing virus.

Andino and colleagues modified the type 2 vaccine virus in several places. The researchers altered a part of the virus’s genetic instruction book, or genome, to make the virus less likely to develop a “gatekeeper” change: a first, critical step along the road to regaining the ability to cause disease.

Poliovirus can swap pieces of its genome with related viruses called enteroviruses. So the researchers moved a string of genetic letters the virus needs to make more copies of itself close to the “gatekeeper” modification. That way, if the vaccine virus was able to ditch that modification by way of a swap, it would lose this necessary string of genetic letters too, and die out.

Finally, the team tinkered with an enzyme that RNA viruses, including poliovirus, use to help replicate themselves. The enzyme is sloppy and can introduce a lot of genetic changes, Andino says. That’s advantageous for the viruses, which “are continuously trying to adapt to a new environment,” he says. Andino and colleagues modified this enzyme in the vaccine virus to introduce fewer mistakes, “so the virus cannot evolve so quickly.” The researchers described their improved oral polio vaccine in a study in Cell Host & Microbe in May.

The new oral polio vaccine was shown to be safe and to produce an immune response similar to that seen with the original vaccine in infants and children, researchers reported online December 9 in the Lancet. The hope is that the modifications will slow the evolution of the new vaccine virus such that it can end the existing outbreaks without creating new ones.

The vaccine-derived outbreaks are a significant, yet surmountable hurdle to polio eradication, says Ohuabunwo, and “science is helping.” But the key to ending polio is “very high vaccination coverage.” Obstacles including war, migrating populations, difficult terrain and lack of vaccine acceptance have created pockets of inaccessible children, he says.

Reaching all children requires engaging community leaders, providing culturally sensitive information and finding out how to meet other community needs, says Ohuabunwo. For example, while working in Nigeria, he and his colleagues made progress with nomadic populations. It meant “sometimes combining vaccinating their children with vaccinating their animals.” The nomads’ cattle would be immunized against brucellosis and anthrax bacterial infections. Protecting the animals also protected the nomads from these infections, he says, and motivated their cooperation towards having their children receive polio vaccine: “a win-win.”

Polio eradication has been a long journey, “but we’re getting close,” Ohuabunwo says. The new oral polio vaccine “is another light in the tunnel.”

‘The Light Ages’ illuminates the science of the so-called Dark Ages

Fri, 08 Jan 2021 11:00:00 GMT

The Light Ages
Seb Falk
W.W. Norton & Co., $30

A long-standing myth about medieval history is that the Middle Ages were intellectually dark. Science supposedly took a hiatus between the demise of Rome and the rise of Copernican astronomy and Galileo’s physics, some superficial accounts suggest.

“The medieval reality, however, is a Light Age of scientific interest and inquiry,” historian Seb Falk writes in The Light Ages. Historians have long known that medieval monasteries and universities hosted many deep thinkers engaged in sophisticated intellectual enterprises. In particular, Falk emphasizes, the medieval era produced high-level technical achievements in the realm of scientific instrument making.

Falk tells his story from the perspective of John Westwyk, a monk at St. Albans Abbey in England in the 14th century. Little is known about Westwyk, but Falk re-creates his life through an account of the life events and duties of monks at that time. Westwyk is known to have produced two important astronomical manuscripts, both about scientific instruments.

Most noteworthy among the instruments of the day was the astrolabe, a contraption containing movable disks to measure and represent the positions of astronomical objects. If you ever wondered how astrolabes worked, down to the last detail, this is the book for you. And if you’re curious about the medieval obsession with astrology — a prime motivation for building astrolabes — your appetite will be sufficiently satisfied.

If you desire more detail about medieval science, though, other books offer more. Falk mentions only in passing the accomplishments of some of the era’s many serious science-minded scholars, such as Robert Grosseteste, Roger Bacon, Albert the Great and Nicole Oresme. There is virtually no discussion about the science of mechanics during the Middle Ages, which, while falling short of modern understanding, still provided a foundation for later achievements.

Nonetheless, Falk’s book offers an illuminating antidote to the “Dark Ages” myth. It’s thoroughly documented, richly illustrated and engagingly written (although with occasional slower sledding through the details of some of those astronomical mechanisms and the casting of horoscopes).

Falk says he “sought to tell the story of medieval science … as an integral part of medieval life and culture,” and he succeeds in embedding scientific pursuits within the culture of medieval religious life. Science and religion were not generally at odds, as sometimes assumed, but rather were dual attempts to grasp the workings of God’s creation. True, theologians sometimes clashed with natural philosophers, but everyone operated within the understanding that the study of nature was the study of God’s work.

Falk’s account is not the whole story of all the ways that medieval science was light rather than dark. But it is still an important part of that story.

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