These are the viruses that mRNA vaccines may take on next

Tiny molecules came up big in 2021. By year’s end, COVID-19 vaccines based on snippets of mRNA, or messenger RNA, proved to be safe and incredibly effective at preventing the worst outcomes of the disease.

mRNA vaccines tell our cells how to make a mimic of a viral protein, in this case the spike protein that the coronavirus uses to break into cells (SN Online: 12/16/21). The vaccine-generated protein then teaches the immune system what the real threat looks like should it later encounter that threat.

For decades, efforts to develop mRNA-based vaccines to fight infectious diseases like rabies have been on a slow and meandering road (SN Online: 6/29/21). But the urgency of the pandemic breathed new life into these attempts. The promise of mRNA technology now takes us well past this pandemic’s horizon. “We’re right at the beginning of a really exciting time,” says Anna Blakney, a bioengineer who studies RNA technology at the University of British Columbia in Vancouver.

The dreams are big: Fighting all sorts of infections. Attacking cancer cells. Restoring specific proteins to treat genetic diseases, such as cystic fibrosis.
“It’s a really amazing technology that’s been proven over the past year,” Blakney says. But it won’t be a panacea, she cautions. “It works really well for some things. It’s unknown how well it will work for other things.”

Those answers might come soon. Here’s a look at four research efforts that have been aided by the swift momentum for mRNA vaccines that COVID-19 generated.

Influenza
Our current flu vaccines aren’t so hot. In a given year, flu shots are between 40 percent and 60 percent effective at preventing the disease. mRNA might do better. Pfizer has begun enrolling about 600 people ages 65 to 85 to find out how mRNA vaccines stack up against traditional flu shots. Moderna has already dosed participants in its own trial of such a flu vaccine, slated to include 180 adults in the United States.

HIV
HIV is a slippery foe, able to evade the immune system by quickly mutating and disguising itself in a coat of human proteins and sugars (SN: 7/3/21 & 7/17/21, p. 14). But mRNA vaccines may be able to train the body’s immune system to detect HIV in its many permutations. That’s the premise of a new clinical trial in the works, sponsored by the International AIDS Vaccine Initiative and including scientists from Moderna.

Zika virus
There are no vaccines available to protect people against Zika virus, which can cause severe disabilities in children born to infected mothers (SN Online: 8/7/18). Scientists from Moderna are currently recruiting 800 adults for a clinical trial testing an mRNA vaccine for its safety and ability to prevent Zika infection.

CMV (cytomegalovirus)
CMV is a common and usually harmless virus. But it can be dangerous for newborn babies who get CMV from an infected mother before they are born. An early infection can lead to premature birth, hearing loss, seizures and developmental delays. Moderna has begun testing a CMV vaccine candidate — a combination of six different mRNAs that carry instructions for proteins on the surface of CMV. The clinical trial will include nearly 7,000 people.

The CDC recommends mRNA COVID-19 vaccines over J&J’s, citing fewer risks

People seeking a COVID-19 vaccine should choose an mRNA shot over Johnson & Johnson’s, the U.S. Centers for Disease Control and Prevention recommends.

The mRNA vaccines, made by Moderna and by Pfizer and its German partner BioNtech, are safer and more effective and are the preferred option, an advisory panel unanimously agreed on December 16. Shortly thereafter, the CDC signed off on the recommendation, which is similar to policies in other countries.

But people who have allergies to ingredients in the mRNA vaccines and those who want the single-dose vaccine can still opt to get J&J’s vaccine. The benefits of that shot, authorized for those 18 and older, still outweigh the risks. And as a single-shot vaccine, it’s been a crucial tool for getting vaccines to people who are incarcerated or transitory, such as the homeless.
The recommendation followed new data indicating that a blood-clotting side effect of J&J’s shot, while rare, affects more than just young women. Of the 14.1 million people in the United States who got the J&J jab from March 2 through August 31, 54 developed a blood-clotting condition known as thrombosis with thrombocytopenia, or TTS (SN: 4/23/21). Nine have died, including one person vaccinated after August 31. Blood clots following the vaccine are suspected in two other deaths as well.

The blood clotting problem is most common in women 30 to 49 years old, with about 10 cases and 2 deaths per million doses given. But men ages 40 to 49, and women 18 to 29 and 50 to 64 also develop about 4 to 5 cases for every million doses of the vaccine. The U.S. Food and Drug Administration had previously changed its guidance to say that anyone with a prior history of this kind of blood clot should not get the J&J shot.

In addition, a neurological side effect called Guillain-Barré syndrome is more common with the J&J vaccine than with mRNA vaccines. J&J’s single-shot vaccine is also less effective than the mRNA vaccines (SN: 10/19/21).

Taken together, the risks and benefits of the mRNA vaccines outweigh those of the J&J jab. For instance, for every million women 18 to 49 years old vaccinated with the J&J shot, 3,729 hospitalizations from COVID19 would be prevented. But nine cases of TTS and five cases of Guillain-Barré syndrome would be expected. The mRNA vaccines in women in that age group would avert 4,700 hospitalizations and produce two cases of myocarditis, a usually mild inflammation of the heart muscle (SN: 12/15/21).

A terrifying robot can thwart invasive mosquito fish

Invasive mosquito fish are often fearless.

Free from the predators of their native range, these mosquito fish run rampant, throwing naive ecosystems from Europe to Australia out of whack. To keep the problematic fish in check, scientists are trying to strike fear back into the hearts of these swimmers with a high-tech tool: robots.

In a laboratory experiment, a robotic fish designed to mimic one of mosquito fish’s natural predators increased fear and stress responses in mosquito fish, impairing their survival and reproduction, researchers report December 16 in iScience.

While robofish won’t be deployed in the wild anytime soon, the research highlights that there are “more creative ways of preventing unwanted behavior from a species” than simply killing them, says Michael Culshaw-Maurer, an ecologist at the University of Arizona in Tucson who wasn’t involved in the study. “It’s just wonderful seeing work in this area.”
Native to parts of the western and southeastern United States, mosquito fish (Gambusia spp.) were let loose in freshwater ecosystems around the globe last century in a foolhardy effort to control malaria. But instead of eating malaria-transmitting mosquito larvae, the mosquito fish mostly gobble up the eggs and gnaw at the tails of native fish and amphibians, making them one of the world’s most destructive invasive species, according to the International Union for Conservation of Nature.

Efforts to combat mosquito fish, and many other introduced, invasive species, usually rely on mass killing with traps, poison or other blunt methods, says Giovanni Polverino, a behavioral ecologist at the University of Western Australia in Perth. “For most of the invasive species considered problematic, this doesn’t work,” he says, and can often harm native species too.

The problem isn’t necessarily the presence of mosquito fish in these ecosystems, Polverino says, but their wanton behavior enabled by a lack of predators. While predation prevents prey numbers from ballooning, merely the fear of predators can influence prey behavior in ways that ripple throughout an ecosystem (SN: 5/5/19). Polverino and his colleagues wanted to see if a robotic fish crafted to mimic one of mosquito fish’s natural nemeses, the largemouth bass (Micropterus salmoides), could be just as scary and take some of the bite out of mosquito fish’s negative impact.

In the lab, researchers set up 12 tanks that each housed six mosquito fish (G. holbrooki) with six native Australian tadpoles (Litoria moorei) that are commonly harassed by mosquito fish. After a week of acclimatization, the team transferred each group to an experimental tank for one hour twice a week for five weeks. There, half of the groups faced a robotic predator designed to recognize and lunge at mosquito fish when they got too close to the tadpoles.

Fear of the robot altered the behavior, shape and fertility of the mosquito fish, both during exposure and weeks later. Mosquito fish facing the robot tended to cluster together and not explore the tank, while the tadpoles, free of harassment, ventured farther out. Even in the safety of their home aquariums, fish exposed to the robots were less active and more anxious — exhibited by seconds-longer freeze responses — than mosquito fish that weren’t exposed.

The cumulative stress taxed the fishes’ bodies too. Exposed fish lost energy reserves, becoming slightly smaller than nonexposed fish. Exposed males became more streamlined, potentially to quicken escape behaviors, the researchers say. And the sperm count of scared fish decreased by about half, on average.

“Instead of investing in reproduction, they’re investing in reshaping their body to escape better after only six weeks,” Polverino says. “Overall, they became less healthy and less fertile.”

The long-term impact that such robotic predators would have on wild mosquito fish and their neighbors remains unclear. That’s beside the point for Polverino, who says the main contribution of this study is showing that fear has significant consequences that may reduce the survival and reproduction of invasive species.

“Our plan is not to release hundreds of thousands of these robots in the wild and pretend they will solve the problem,” Polverino says. But there may be more than one way to scare a mosquito fish. Giving the fish a whiff of their predator, for example, might induce similar changes.

“These are not invincible animals,” he says. “They have weaknesses that we can take advantage of that don’t involve killing animals one by one.”

‘Penis worms’ may have been the original hermits

Hermit crabs have been taking shelter in abandoned shells for millions of years, but scientists now have evidence suggesting that the “hermit” lifestyle has existed far longer than that.

Besides hermit crabs, a few modern-day species of crustaceans and worms inhabit the cast-off shells of other marine creatures, mostly for protection against predators, says Martin Smith, a paleontologist at Durham University in England. Until recently, the oldest known fossils suggesting hermiting behavior were about 170 million years old, he says.

Now, Smith and his colleagues say that they have unearthed fossils of hermiting creatures almost three times that age, from a geologic period dubbed the Cambrian.

Remains of the ancient squatters were preserved in rocks laid down as seafloor sediments about 500 million years ago in what is now southern China. The cone-shaped shells that seem to hold the occupants probably had belonged to hyoliths, a once-common group of ancient marine invertebrates that died out more than 250 million years ago (SN: 1/11/17).

The marine creatures that then took shelter in those vacant shells, the researchers say, belong to a group called priapulid worms — commonly known as penis worms, thanks to their suggestive body shape. The Chinese rocks contain dozens of empty shells, Smith says. But four of those shells appear to have been inhabited by penis worms, he and his colleagues report November 8 in Current Biology. Because there were no free-ranging priapulids preserved in the ancient sediments, the researchers propose that the worms were living inside the shells.

A relatively consistent ratio between the size of a worm and the shell it was preserved within suggests that the animals picked a shell based on its size and then moved to another when they outgrew their adopted home, Smith says. Modern-day hermit crabs use the same strategy, though none of the 20 species of penis worms around today have this hermiting behavior.

The researchers “have made some good observations to support their claims” that the association between the shells and the penis worms isn’t merely fortuitous, says Jakob Vinther, a paleontologist at the University of Bristol in England who wasn’t involved in the research. It’s not clear, however, whether the priapulids carried the shells from place to place, like hermit crabs do, or whether the animals merely lived inside them, he says.

A great variety of creatures — including most of the major groups of animals alive today and a proliferation of predators — evolved rapidly during the Cambrian Period, which began about 542 million years ago (SN: 3/21/19). As a result, many researchers refer to that explosion of diversity as “life’s Big Bang.”

“Perhaps it’s not a surprise that some priapulids became hermits when you think about what this predatory arms race was all about: eating, ducking and hiding,” Vinther says.

Ancient giant orangutans evolved smaller bodies surprisingly slowly

Giant orangutans that once dwelled in mainland Southeast Asian forests belonged to a single species that gradually shrank in size over nearly 2 million years, a study suggests.

Today, orangutans are found only on the islands of Sumatra and Borneo. But their ancient, super-size kin roamed forests in what’s now southern China and northern Vietnam. Fragmentary Asian fossils of uncertain age have long indicated that these massive, now-extinct orangutans shrank over time. And biological anthropologist Terry Harrison of New York University suspected — based on a small number of fossils from widely different time periods — that the apes rapidly evolved from a larger-bodied species to a different, smaller-bodied species roughly 400,000 years ago as the climate cooled.

But an analysis of 600 ancient orangutan teeth unearthed in 10 caves in southern China supports a different evolutionary scenario, Harrison and colleagues report in the December Journal of Human Evolution.

From around 2 million to 111,000 years ago, the shapes of the teeth remained largely the same, suggesting all were from a single orangutan species. But tooth sizes progressively declined. Using tooth measurements, Harrison, paleoanthropologist Yingqi Zhang of the Chinese Academy of Sciences in Beijing and colleagues estimate that the ancient orangutans’ average body mass started out around 96 kilograms, close to double that of orangutans today.

By around 111,000 years ago, the ancient apes’ average body mass was almost 80 kilograms, which still exceeded that of modern orangutans by nearly 25 kilograms.

Fossils of other ancient Asian animals, including rhinos and monkeys, also show declines in body size over the same period. Cooler, drier conditions that reduced available food starting around 400,000 years ago may have spurred a trend toward smaller bodies, Harrison says.

It’s not clear when orangutans on mainland Asia died out. But climate change and possibly the arrival of humans in the region more than 60,000 years ago contributed to their demise, Harrison speculates.

This tiny, sizzling exoplanet could be made of molten iron

A newly discovered exoplanet is really making astronomers prove their mettle. Planet GJ 367b is smaller than Earth, denser than iron and hot enough to melt, researchers report in the Dec. 3 Science.

“We think the surface of this exoplanet could be molten,” says astronomer Kristine Wei Fun Lam of the Institute of Planetary Research at the German Aerospace Center in Berlin.

Signals of the planet were first spotted in data from NASA’s TESS telescope in 2019. The small world swung around its host star every 7.7 hours.

Using data from TESS and the ground-based HARPS spectrograph at the European Southern Observatory in Chile, Lam and her colleagues measured the planet’s radius and mass. GJ 367b clocked in at about 0.72 times Earth’s radius and 0.55 times its mass. That makes it the first ultrashort-period planet — a class of worlds with years shorter than one Earth day and with mysterious origins — known to be smaller and lighter than Earth.

Using those measurements, the team then calculated the planet’s density: about 8.1 grams per cubic centimeter, or slightly denser than iron. A computer analysis of the planet’s interior structure suggests that 86 percent of it could comprise an iron core, with only a sliver of rock left on top.

Mercury has a similarly large core, Lam notes (SN: 4/22/19). Scientists think that’s a result of a giant impact with another planet that stripped away most of its outer layers. GJ 367b could have formed after a similar collision. It could also have once been a gaseous planet whose atmosphere was blasted off by radiation from its star (SN: 7/1/20).

Whatever its origins, GJ 367b is so close to its star that it’s almost certainly covered in melted metallic lava now. “At 1400° Celsius, I don’t think it would be very nice to stand on it,” Lam says.

Merck’s COVID-19 pill may soon be here. How well will it work?

Hopes for an easy pill that could combat COVID-19 before people land in the hospital have dimmed a bit. New data about an antiviral pill made by Merck with its partner Ridgeback Pharmaceuticals show it’s not as stellar as first believed. And the drug has drawbacks that could outweigh its potential to fight the coronavirus and keep people out of the hospital.

The U.S. Food and Drug Administration is now weighing whether to grant emergency use authorization for the drug, called molnupiravir, after the agency’s advisory panel narrowly voted to recommend it on November 30. The drug was authorized for use in the United Kingdom on November 4. If the FDA follows suit, it could wind up being just a stopgap: Some advisers already have urged the agency to be ready to withdraw that authorization as soon as something better comes along.

Finding an early treatment hasn’t been easy, so many experts initially hailed the development of molnupiravir as a potential game changer for the pandemic: A pill that could be given to people early in the infection might help keep health care systems from being overwhelmed, and spare people at high risk from the most severe complications (SN: 7/27/21).

In a clinical trial, the drug showed early signs of preventing hospitalization and death from COVID-19 in people at high risk of severe disease (SN: 10/1/21). In fact, the results were so promising — a 48 percent reduction in the relative risk of hospitalization or death — that the trial was stopped so that the drug might potentially reach the public earlier.
But on November 26, Merck announced in a news release that when all the available data from the trial was in, the reduction in relative risk fell to 30 percent against hospitalization and death compared with a placebo. The shift stemmed from an unexplained decrease in severe disease among people in the placebo group in the last part of the trial.

In data collected from May 7 through August 5, 53 of 377 people (or 14.1 percent) in the placebo group were hospitalized and eight died (2.1 percent). In the molnupiravir group, 28 of 385 people (7.3 percent) were hospitalized and none died.

But an FDA analysis of subsequent data showed that from August 6 through October 2, 15 of the 322 people (4.7 percent) in the placebo group were hospitalized and one died (less than 1 percent). Of the 324 people who got molnupiravir during that time period, 20 (6.2 percent) were hospitalized and one died (less than 1 percent), making molnupiravir appear to produce worse outcomes than placebo.

Overall, among the 709 people in the molnupiravir group, there were 48 hospitalizations and one death compared with 68 hospitalizations and nine deaths among the 699 people who got a placebo, dropping the effectiveness from the initial 48 percent to 30 percent.

Split support
Taking that lower-than-expected efficacy into account, the FDA’s antimicrobial drugs advisory committee came to a split 13–10 decision about whether the antiviral drug should be granted emergency use authorization, with experts on each side of the vote often agreeing with points made by the opposing side. The debate and vote reflected a storm of uncertainty about the drug’s efficacy and who should use it — the list of people who would not be eligible is far longer than those most experts would give the drug to. The panel also queried whether the drug could lead to even more dangerous versions of the coronavirus, whether it can cause growth delays in children or mutations in human DNA, and other unanswered questions.
Virologist John Coffin of Tufts University in Boston said during the FDA meeting that he’s dreamed of a small molecule drug that could effectively treat viral infections. “I’m not sure [molnupiravir] is the one we’ve been waiting for, but it’s all we’ve got at the moment.” He voted in favor of the drug but was among those urging the FDA to reconsider if better options become available.

Something better might already be on the horizon if an antiviral pill made by Pfizer lives up to its early promise of an 89 percent decrease in hospitalization and death compared with placebo if taken within three days of symptom onset. That drug works differently than molnupiravir and may not have the same safety concerns.

Another early treatment, lab-made monoclonal antibodies, is already authorized for use in nonhospitalized COVID-19 patients (SN: 9/22/20). But that treatment has to be given intravenously, requiring a trip to an infusion center. Many people don’t have ready access to such a facility. Some new variants of the coronavirus can also evade some of these antibodies.

Drug drawbacks
Among the worries about authorizing molnupiravir is the possibility that the antiviral could spur evolution of more dangerous versions of the coronavirus. The antiviral pill works by making mutations in viral RNA so that viruses are rendered noninfectious and eventually stop replicating. Such mutations happen throughout the virus’s genetic instruction book, or genome.

Some of those mutations could land in the spike protein, which helps the coronavirus break into cells, or other proteins and make the virus more transmissible or more evasive to vaccines. That’s especially a fear if people don’t finish the full five-day course of the drug needed to render the virus inoperable, leading potentially to highly mutated new forms of the virus that could infect others.

“The potential for this drug to drive some very challenging variants into the public is of major, major concern,” said James Hildreth, an immunologist and president of Meharry Medical College in Nashville.

Merck representatives said that possibility is unlikely, because after five days of taking even a half dose of the drug, infectious viruses were no longer detectable among study participants tested. In one study, the company found seven patients who had changes in the coronavirus’s spike protein after taking molnupiravir, but there was no evidence that the viruses spread to other people or affected the patient’s health (none were hospitalized or died).

Molnupiravir might also create mutations in human DNA, researchers say. The drug is a nucleoside analog — an artificial RNA building block that can mimic the bases cytosine and uracil. Some enzymes in human cells might convert those RNA subunits to a DNA building block, which may lead to mutations in human DNA, especially in rapidly reproducing cells, such as blood cells. How likely that is is an open question.

Lab tests with bacteria and cells grown in lab dishes suggested that the drug might cause such DNA mutations under certain circumstances. But tests in animals suggested that the risk of such mutations actually happening in the body is low. To reduce the chance of such mutations happening, people would be able to take molnupiravir for no more than five days. That should be long enough to eliminate the virus but short enough not to cause lasting harm.

Limited eligibility
Animal studies have also indicated that molnupiravir might interfere with bone growth, so the drug probably would not be given to pregnant women or to children or adolescents. For three months, researchers gave rats doses of the drug nine to 15 times higher than people would receive. Those young rats had trouble converting cartilage at growth plates — tissue at the end of long bones that determines the bone’s future length and shape — into bone. But the problem wasn’t seen if rats were dosed for one month or if they got a dose similar to what people would get.

Such bone problems would not be an issue for adults, but more data are needed before giving the drug to kids or to pregnant women, experts say.

It’s also unclear whether the drug will help vaccinated people, or be effective against the delta variant. It’s efficacy also varied depending on a patient’s high-risk health condition. It was good at keeping people with obesity out of the hospital, but more people with diabetes ended up hospitalized while taking the drug than in the placebo group.

Filling a need
Still, there are no good remedies for people with mild to moderate COVID-19. Yet as of November 30, more than 82,000 people in the United States are being diagnosed with COVID-19 each day and more than 800 die. Those numbers are expected to increase as case counts surge in some parts of the country. The new omicron variant might add fuel to that fire if it proves more contagious than the currently dominant delta variant (SN: 12/1/21).

So even with all of molnupiravir’s drawbacks, federal regulators might decide a 30 percent reduction in hospitalizations and deaths is worth giving the drug temporary authorization.

The drug might be helpful for “the right patient population, the right virus at the right time,” said Lindsey Baden, an infectious diseases doctor at Brigham and Women’s Hospital in Boston who chaired the FDA’s advisory committee. “To me that at least suggests there are populations where there may be benefit.”

But more studies need to be done to address concerns about the drug, he said. “It’s the absence of data that makes many of us uncomfortable.”

President Joe Biden said December 2 during remarks laying out a plan to combat the omicron variant that the government has secured a supply of the drugs and, if authorized, will distribute them similarly to vaccines.

The Southern Ocean is still swallowing large amounts of humans’ carbon dioxide emissions

The Southern Ocean is still busily absorbing large amounts of the carbon dioxide emitted by humans’ fossil fuel burning, a study based on airborne observations of the gas suggests. The new results counter a 2018 report that had found that the ocean surrounding Antarctica might not be taking up as much of the emissions as previously thought, and in some regions may actually be adding CO₂ back to the atmosphere.

It’s not exactly a relief to say that the oceans, which are already becoming more acidic and storing record-breaking amounts of heat due to global warming, might be able to bear a little more of the climate change burden (SN: 4/28/17; SN: 1/13/21). But “in many ways, [the conclusion] was reassuring,” says Matthew Long, an oceanographer at the National Center for Atmospheric Research in Boulder, Colo.

That’s because the Southern Ocean alone has been thought to be responsible for nearly half of the global ocean uptake of humans’ CO₂ emissions each year. That means it plays an outsize role in modulating some of the immediate impacts of those emissions. However, the float-based estimates had suggested that, over the course of a year, the Southern Ocean was actually a net source of carbon dioxide rather than a sink, ultimately emitting about 0.3 billion metric tons of the gas back to the atmosphere each year.

In contrast, the new findings, published in the Dec. 3 Science, suggest that from 2009 through 2018, the Southern Ocean was still a net sink, taking up a total of about 0.55 billion metric tons of carbon dioxide each year.
The 2018 study had used newly deployed deep-diving ocean floats, now numbering almost 200, that are part of a project called Southern Ocean Carbon and Climate Observations and Modeling, or SOCCOM. Calculations based on data collected from 2014 through 2017 by 35 of the floats suggested that parts of the ocean were actually releasing a great deal of carbon dioxide back into the atmosphere during winter (SN: 6/2/19). That sparked concerns that the Southern Ocean’s role in buffering the impacts of climate change on Earth might not be so robust as once thought.

Long says he and other researchers were somewhat skeptical about that takeaway, however. The floats measure temperature, salinity and pH in the water down to about 2,000 meters, and scientists use those data to calculate the carbon dioxide concentration in the water. But those calculations rest on several assumptions about the ocean water properties, as actual data are still very scarce. That may be skewing the data a bit, leading to calculations of higher carbon dioxide emitted from the water than is actually occurring, Long suggests.

Another way to measure how much carbon dioxide is moving between air and sea is by taking airborne measurements. In the new study, the team amassed previously collected carbon dioxide data over large swaths of the Southern Ocean during three separate series of aircraft flights — one series lasting from 2009 to 2011, one in the winter of 2016 and a third in several periods from 2016 to 2018 (SN: 9/8/11). Then, the researchers used those data to create simulations of how much carbon dioxide could possibly be moving between ocean and atmosphere each year.

The float-based and aircraft-based studies estimate different overall amounts of carbon dioxide moving out of the ocean, but both identified a seasonal pattern of less carbon dioxide absorbed by the ocean during winter. That indicates that both types of data are picking up a real trend, says Ken Johnson, an ocean chemist at the Monterey Bay Aquarium Research Institute in Moss Landing, Calif., who was not involved in the research. “We all go up and down together.”

It’s not yet clear whether the SOCCOM data were off. But to better understand what sorts of biases might affect the pH calculations, researchers must compare direct measurements of carbon dioxide in the water taken from ships with pH-based estimates at the same location. Such studies are under way right now off the coast of California, Johnson says.

The big takeaway, Johnson says, is that both datasets — as well as direct shipboard measurements in the Southern Ocean, which are few and far between — are going to be essential for understanding what role these waters play in the planet’s carbon cycle. While the airborne studies can help constrain the big picture of carbon dioxide emissions data from the Southern Ocean, the floats are much more widely distributed, and so are able to identify local and regional variability in carbon dioxide, which the atmospheric data can’t do.

“The Southern Ocean is the flywheel of the climate system,” the part of an engine’s machinery that keeps things chugging smoothly along, Johnson says. “If we don’t get our understanding of the Southern Ocean right, we don’t have much hope for understanding the rest of the world.”

Explainer: Earth — layer by layer

Mountain ranges tower to the sky. Oceans plummet to impossible depths. Earth’s surface is an amazing place to behold. Yet even the deepest canyon is but a tiny scratch on the planet. To really understand Earth, you need to travel 6,400 kilometers (3,977 miles) beneath our feet.

Starting at the center, Earth is composed of four distinct layers. They are, from deepest to shallowest, the inner core, the outer core, the mantle and the crust. Except for the crust, no one has ever explored these layers in person. In fact, the deepest humans have ever drilled is just over 12 kilometers (7.6 miles). And even that took 20 years!

Still, scientists know a great deal about Earth’s inner structure. They’ve plumbed it by studying how earthquake waves travel through the planet. The speed and behavior of these waves change as they encounter layers of different densities. Scientists — including Isaac Newton, three centuries ago — have also learned about the core and mantle from calculations of Earth’s total density, gravitational pull and magnetic field.

Here’s a primer on Earth’s layers, starting with a journey to the center of the planet.
The inner core
This solid metal ball has a radius of 1,220 kilometers (758 miles), or about three-quarters that of the moon. It’s located some 6,400 to 5,180 kilometers (4,000 to 3,220 miles) beneath Earth’s surface. Extremely dense, it’s made mostly of iron and nickel. The inner core spins a bit faster than the rest of the planet. It’s also intensely hot: Temperatures sizzle at 5,400° Celsius (9,800° Fahrenheit). That’s almost as hot as the surface of the sun. Pressures here are immense: well over 3 million times greater than on Earth’s surface. Some research suggests there may also be an inner, inner core. It would likely consist almost entirely of iron.

The outer core
This part of the core is also made from iron and nickel, just in liquid form. It sits some 5,180 to 2,880 kilometers (3,220 to 1,790 miles) below the surface. Heated largely by the radioactive decay of the elements uranium and thorium, this liquid churns in huge, turbulent currents. That motion generates electrical currents. They, in turn, generate Earth’s magnetic field. For reasons somehow related to the outer core, Earth’s magnetic field reverses about every 200,000 to 300,000 years. Scientists are still working to understand how that happens.

The mantle
At close to 3,000 kilometers (1,865 miles) thick, this is Earth’s thickest layer. It starts a mere 30 kilometers (18.6 miles) beneath the surface. Made mostly of iron, magnesium and silicon, it is dense, hot and semi-solid (think caramel candy). Like the layer below it, this one also circulates. It just does so far more slowly.
Near its upper edges, somewhere between about 100 and 200 kilometers (62 to 124 miles) underground, the mantle’s temperature reaches the melting point of rock. Indeed, it forms a layer of partially melted rock known as the asthenosphere (As-THEEN-oh-sfeer). Geologists believe this weak, hot, slippery part of the mantle is what Earth’s tectonic plates ride upon and slide across.

Diamonds are tiny pieces of the mantle we can actually touch. Most form at depths above 200 kilometers (124 miles). But rare “super-deep” diamonds may have formed as far down as 700 kilometers (435 miles) below the surface. These crystals are then brought to the surface in volcanic rock known as kimberlite.

The mantle’s outermost zone is relatively cool and rigid. It behaves more like the crust above it. Together, this uppermost part of the mantle layer and the crust are known as the lithosphere.
The crust
Earth’s crust is like the shell of a hard-boiled egg. It is extremely thin, cold and brittle compared to what lies below it. The crust is made of relatively light elements, especially silica, aluminum and oxygen. It’s also highly variable in its thickness. Under the oceans (and Hawaiian Islands), it may be as little as 5 kilometers (3.1 miles) thick. Beneath the continents, the crust may be 30 to 70 kilometers (18.6 to 43.5 miles) thick.

Along with the upper zone of the mantle, the crust is broken into big pieces, like a gigantic jigsaw puzzle. These are known as tectonic plates. These move slowly — at just 3 to 5 centimeters (1.2 to 2 inches) per year. What drives the motion of tectonic plates is still not fully understood. It may be related to heat-driven convection currents in the mantle below. Some scientists think it’s caused by the tug from slabs of crust of different densities, something called “slab pull.” In time, these plates will converge, pull apart or slide past each other. Those actions cause most earthquakes and volcanoes. It’s a slow ride, but it makes for exciting times here on Earth’s surface.

Scientists Say: Avalanche

Avalanche (noun, “AV-uh-lanch”)
An avalanche is any large mass of material that is tumbling downhill. But the word usually refers to snow cascading down a mountainside. A snow avalanche is triggered when snow high on a mountain is disturbed. Falling rocks and earthquakes can destabilize snow. People can also set off avalanches by walking or skiing in the wrong place at the wrong time. Sometimes people will use explosives to cause an avalanche before someone can accidentally set one off and get hurt.

As snow slides downhill, it picks up speed, snow and other debris. Smaller spills of powdery snow are called sluffs. More dangerous avalanches occur when huge slabs of snow break loose from a mountainside. The snow in an avalanche can plunge downward at hundreds of kilometers (miles) per hour. And if someone is buried, it can be nearly impossible to dig out without help. An average of 27 people in the United States alone die in avalanches each year.