If signals from an alien civilization ever reach Earth, odds are the aliens will already be dead.

In an effort to update the 1961 Drake Equation, which estimates the number of detectable, intelligent civilizations in the Milky Way, physicist Claudio Grimaldi and colleagues calculated the area of the galaxy that should be filled with alien signals at a given time (SN Online: 11/1/09).

The team, which includes Frank Drake (now a professor emeritus at the SETI Institute in Mountain View, Calif., and the University of California, Santa Cruz), assumed technologically savvy civilizations are born and die at a constant rate. When a civilization dies out and stops broadcasting, the signals it had sent continue traveling like concentric ripples on a pond. Part of the Milky Way should be filled with these ghost signals.
If the civilization lasted less than 100,000 years — the time it takes light to cross the galaxy — then the odds of the signals reaching Earth while the civilization is still broadcasting are vanishingly small, the researchers report February 27 at arXiv.org. Humans, for example, have been transmitting radio waves for only about 80 years, so our radio waves cover less than 0.001 percent of the Milky Way.

“If the civilization emitted from the other side of the galaxy, when the signal arrives here, the civilization will already be gone,” says Grimaldi, of the Federal Polytechnical School of Lausanne in Switzerland.

Surprisingly, the team also calculated that the average number of E.T. signals crossing Earth at a given time should equal the number of civilizations currently transmitting — even if the civilizations we hear from aren’t the same ones presently broadcasting. Grimaldi is now working on a paper about what it means that we’ve found none so far.

THE WOODLANDS, Texas — It’s been six months since NASA’s Cassini spacecraft plunged to its doom in the atmosphere of Saturn, but scientists didn’t spend much time mourning. They got busy, analyzing the spacecraft’s final data.

The Cassini mission ended September 15, 2017, after more than 13 years orbiting Saturn (SN Online: 9/15/17). The spacecraft’s final 22 orbits, dubbed the Grand Finale, sent Cassini into the potentially dangerous region between the gas giant and its rings, and its final orbit sent it directly into Saturn’s atmosphere.
That perspective helped solve mysteries about the planet and its moons that could not be tackled any other way, scientists said March 19 at the Lunar and Planetary Science Conference in The Woodlands, Texas.

“In so many ways, the Grand Finale orbits provided information that was totally unexpected,” said Cassini project scientist Linda Spilker of NASA’s Jet Propulsion Laboratory in Pasadena, Calif. “So many of our models were not correct.”

Here are five things we now know and a few outstanding mysteries.

1. Saturn’s clouds go deep
   Those final daredevil orbits allowed Cassini to measure the gravity of Saturn and its rings independent of one another. Looking at the planet’s gravity field alone revealed that the swirling bands of clouds penetrate much deeper into the planet than expected.

Astronomers this month announced a similar discovery for an even larger gas giant, reporting that the Juno spacecraft, which is orbiting Jupiter, had found that the planet’s rotating cloud belts reach roughly 3,000 kilometers below the top of the atmosphere.

Saturn’s clouds reach a few times deeper than that. “This was an astonishing result,” Spilker said.

“People used to think that maybe Saturn was just a slightly smaller version of Jupiter, but it’s evident that that’s not the case,” says planetary scientist Paul Schenk of the Lunar and Planetary Institute in Houston, who was not involved in the gravity measurements. The difference speaks to how diverse planets are, he says. “Every place you look, everywhere we’ve been to, it’s just been so dramatically different and unique.”

2. Ring rain is eroding the innermost ring
   Grains of ice from the rings are raining down into Saturn’s atmosphere, Cassini’s final orbits confirmed. This “ring rain” idea has been suggested since the 1980s, but only by tasting the atmosphere and directly sampling the space between Saturn and the rings could Cassini confirm the rains are real.

In its last five full orbits, Cassini found a zoo of organic molecules in and just above Saturn’s atmosphere, said planetary scientist Kelly Miller of the Southwest Research Institute in San Antonio. The spacecraft found a lot of water, which wasn’t surprising — water makes up about 90 percent of the rings. But there were also a lot of hydrocarbons similar to propane, plus some methane and sulfur-bearing molecules.

The types of molecules became less well-mixed as the spacecraft looked deeper into Saturn’s atmosphere, which is what would happen if the particles came from the rings and sank at different speeds. The researchers think this material is especially raining from Saturn’s D ring, the thin innermost ring. Other Cassini data suggest this ring is losing mass.

“The D ring is slowly being eroded away and going into the planet,” Spilker said.

3. Organics could explain mysterious ring hues
   The organics in the ring rain could solve a debate about why Saturn’s rings appear reddish in some spots.

“We’ve had this debate going on for a couple of years now — are they red because of good old-fashioned rust like Mars, or because of the same kinds of organic materials … that make carrots and tomatoes and watermelon red?” said planetary scientist Jeff Cuzzi of NASA’s Ames Research Center in Moffett Field, Calif. “To me, this answers the question of what makes the rings red: It’s organics.”

It’s still not clear where the organics come from, though. They could be created within the rings, or they could come from cosmic dust from the tails of comets. Miller and her colleagues are comparing the ring rain molecules with data on comet 67P, which the Rosetta spacecraft observed, to see how well they match up (SN: 11/11/17, p. 32).

4. Titan’s “magic islands” aren’t islands, or bubbles
   Mysterious disappearing features in the lakes of Saturn’s moon Titan are caused by sunlight reflecting off giant waves, said planetary scientist Alexander Hayes of Cornell University.
   These features were named “magic islands” when they were first spotted in 2014. As recently as April 2017, planetary scientists thought they had the islands solved: They seemed to be the result of champagnelike bubbles of nitrogen burbling through the moon’s methane and ethane seas (SN Online: 4/18/17).

But Hayes presented newly analyzed data from August 2014, when Cassini looked at Kraken Mare, the moon’s largest northern sea, in radar and infrared wavelengths within two hours of each other. The radar images showed a magic island, and the infrared ones showed a peak in brightness at the same spot.

Because the observations were taken two hours apart, the island probably couldn’t have been due to bubbles, Hayes said — bubbles would pop or disperse too quickly. Instead, he thinks the brightening could be the glint of sunlight reflecting directly off of giant waves on the lake, like how the ocean ripples with gold at sunset. Simulations of Titan’s atmosphere suggest these waves could be raised by winds as slow as 0.5 meters per second, which would barely move a wind vane on Earth.

5. Enceladus’ plumes may brighten by the pull of another moon
   Saturn’s tiny moon Enceladus has plumes that may be driven by nudges from another moon.

The spurts of liquid water were discovered in 2006. Over the next six years, scientists noticed that the plumes varied in brightness (a proxy for how much material is gushing from the moon) on a daily cycle, probably driven by Saturn’s different positions in Enceladus’ sky.

Then, in 2015 some researchers noted that the plumes’ overall brightness had been decreasing since the beginning of the Cassini mission.

One possible explanation was that the plumes changed with Saturn’s seasons. Another was that ice built up in the vents, clogging them and decreasing the flow. But looking at the full 13-year dataset, planetary scientist Francis Nimmo found that the plumes grow brighter in a regular cycle every four and 11 years. The pattern is too coherent to be explained by clogged vents, said Nimmo, of the University of California, Santa Cruz. Oddly, the plume grew brighter in 2017, so the seasonal explanation doesn’t fit either.

The variations could be explained by a neighboring moon, Dione. Every time Dione and Enceladus line up, their gravitational stress on each other could force Enceladus’ vents open a bit more, causing the plumes to grow brighter.

Unsolved enigmas
So far, analyzing data from Cassini hasn’t answered all of scientists’ questions. Is Enceladus the only moon with plumes? Dione showed signs of activity, too, but Cassini wasn’t able to confirm it. How thick is Enceladus’ ice sheet? Why are Titan’s smaller lakes full of clear, pure methane, when scientists expected the lakes to be clogged with hydrocarbon silt?

Even though the spacecraft is gone, it left decades’ worth of data to sift through in search of answers. “Cassini is going to keep on giving as long as we keep looking,” Hayes said.

Editors’ note: This story was updated on March 21, 2018, to include the affiliations of Jeff Cuzzi and Francis Nimmo.

When the 2017 Great American Eclipse hit totality and the sky went dark, bees noticed.

Microphones in flower patches at 11 sites in the path of the eclipse picked up the buzzing sounds of bees flying among blooms before and after totality. But those sounds were noticeably absent during the full solar blackout, a new study finds.

Dimming light and some summer cooling during the onset of the eclipse didn’t appear to make a difference to the bees. But the deeper darkness of totality did, researchers report October 10 in the Annals of the Entomological Society of America. At the time of totality, the change in buzzing was abrupt, says study coauthor and ecologist Candace Galen of the University of Missouri in Columbia.
The recordings come from citizen scientists, mostly school classes, setting out small microphones at two spots in Oregon, one in Idaho and eight in Missouri. Often when bees went silent at the peak of the eclipse, Galen says, “you can hear the people in the background going ‘ooo,’ ‘ahh’ or clapping.”
There’s no entirely reliable way (yet) of telling what kinds of bees were doing the buzzing, based only on their sounds, Galen says. She estimates that the Missouri sites had a lot of bumblebees, while the western sites had more of the tinier, temperature-fussy Megachile bees.
More western samples, with the fussier bees, might have let researchers see an effect on the insects of temperatures dropping by at least 10 degrees Celsius during the eclipse. The temperature plunge in the Missouri summer just “made things feel a little more comfortable,” Galen says.

This study of buzz recordings gives the first formal data published on bees during a solar eclipse, as far as Galen knows. “Insects are remarkably neglected,” she says. “Everybody wants to know what their dog and cat are doing during the eclipse, but they don’t think about the flea.”

Vinita Surukan knew the mosquitoes were trouble. They attacked her in swarms, biting through her clothes as she worked to collect rubber tree sap near her village in Sabah, the northern state of Malaysia. The 30-year-old woman described the situation as nearly unbearable. But she needed the job.

There were few alternatives in her village surrounded by fragments of forest reserves and larger swaths of farms, oil palm plantations and rubber tree estates. So she endured until a week of high fever and vomiting forced her to stop.
The night of July 23, Surukan was trying to sleep off her fever when the clinic she visited earlier in the day called with results: Her blood was teeming with malaria parasites, about a million in each drop. Her family rushed her to the town hospital where she received intravenous antimalarial drugs before being transferred to a city hospital equipped to treat severe malaria. The drugs cleared most of the parasites, and the lucky woman was smiling by morning.

Malaria has terrorized humans for millennia, its fevers carved into our earliest writing on ancient Sumerian clay tablets from Mesopotamia. In 2016, four species of human malaria parasites, which are spread by mosquito from person to person, infected more than 210 million people worldwide, killing almost 450,000. The deadliest species, Plasmodium falciparum, causes most of the infections.

But Surukan’s malaria was different. Hers was not a human malaria parasite. She had P. knowlesi, which infects several monkey species. The same parasite had recently infected two other people in Surukan’s village — a man who hunts in the forest and a teenager. Surukan suspects that her parasites came from the monkeys that live in the forest bordering the rubber tree estate where she worked. Some villagers quit working there after hearing of Surukan’s illness.

Monkey malaria, discovered in the early 1900s, became a public health concern only in the last 15 years. Before that, scientists thought it was extremely rare for monkey malaria parasites, of which there are at least 30 species, to infect humans.
Yet since 2008, Malaysia has reported more than 15,000 cases of P. knowlesi infection and about 50 deaths. Infections in 2017 alone hit 3,600.
People infected with monkey malaria are found across Southeast Asia near forests with wild monkeys. In 2017, another species of monkey malaria parasite, P. cynomolgi, was found in five Malaysians and 13 Cambodians. And by 2018, at least 19 travelers to the region, mostly Europeans, had brought monkey malaria back to their home countries.

The rise of monkey malaria in Malaysia is closely tied to rapid deforestation, says Kimberly Fornace, an epidemiologist at the London School of Hygiene and Tropical Medicine. After testing blood samples of nearly 2,000 people from areas in Sabah with various levels of deforestation, she found that people staying or working near cut forests were more likely than people living away from forests to have P. knowlesi infections, she and colleagues reported in June in PLOS Neglected Tropical Diseases. Stepping over felled trees, humans move closer to the monkeys and the parasite-carrying mosquitoes that thrive in cleared forests.
It’s out there
There’s no feasible way to treat wild monkeys for an infection that they show no signs of. “That’s the problem with P. knowlesi,” says Singapore-based infectious disease specialist Fe Espino, a director of the Asia Pacific Malaria Elimination Network.

In 2015, the World Health Organization set a goal for 2030: to stop malaria transmission in at least 35 of the 91 malaria-endemic countries. WHO targets the four human malaria parasites: P. falciparum, P. vivax, P. malariae and P. ovale. Monkey malaria is excluded from the campaign because the agency regards it as an animal disease that has not been shown to transmit among humans.

But as countries reduce human malaria, they will eventually have to deal with monkey malaria, Espino says, echoing an opinion widely shared by monkey malaria scientists.

“Something nasty” could emerge from the pool of malaria parasites in monkeys, says malariologist Richard Culleton of Nagasaki University in Japan. Culleton studies the genetics of human and monkey malaria. Malaria parasites can mutate quickly — possibly into new types that can more easily infect humans (SN: 9/6/14, p. 9). To Culleton, the monkey malaria reservoir “is like a black box. Things come flying out of it occasionally and you don’t know what’s coming next.”
Malaysia is very close to reaching the WHO target of human malaria elimination. In 2017, only 85 people there were infected with human malaria. But that success feels hollow as monkey malaria gains a foothold. And while monkey malaria has swelled into a public health threat only in Malaysia, the same could happen in other parts of Southeast Asia and beyond. Even in southeastern Brazil, where human malaria was eliminated 50 years ago, the P. simium malaria parasite that resides in howler monkeys caused outbreaks in humans in 2015 and 2016.

From tool to threat
In the late 1800s, scientists discovered the Plasmodium parasite and its Anopheles mosquito carriers. Humans retaliated by draining marshes to stop mosquito breeding and spraying insecticides over whole communities. Governments and militaries pursued antimalarial drugs as the disease claimed countless soldiers during the two World Wars.

Scientists soon found malaria parasites in birds, rodents, apes and monkeys. To the researchers, the parasites found in monkeys were a tool for testing antimalarial drugs, not a threat. An accident, however, showed otherwise.
In 1960, biologist Don Eyles had been studying the monkey malaria P. cynomolgi at a National Institutes of Health lab in Memphis, Tenn., when he fell ill with malarial fevers. He had been infected with the parasites found in his research monkeys. His team quickly confirmed that the malaria parasites in his monkeys could be carried by mosquitoes to humans. Suddenly, monkey malaria was not just a tool; it was an animal disease that could naturally infect humans.
The news shook WHO, McWilson Warren said in a 2005 interview recorded by the Office of NIH History. Warren, a parasitologist, had been Eyles’ colleague. Five years before Eyles became infected, WHO had launched the Global Malaria Eradication Programme. Banking on insecticides and antimalarial drugs, the agency had aimed to end all malaria transmissions outside of Africa. A monkey malaria that easily infects humans would sink the program because there would be no way to treat all the monkeys.

A team of American scientists, including Eyles and Warren, traveled to Malaysia — then the Federation of Malaya — where the P. cynomolgi parasites that infected Eyles came from. Funded by NIH, the scientists worked with colleagues from the Institute of Medical Research in Kuala Lumpur, established in 1900 by the British to study tropical diseases.

From 1961 to 1965, the researchers discovered five new species of monkey malaria parasites and about two dozen mosquito species that carry the parasites. But the researchers did not find any human infections. Then, in 1965, an American surveyor became infected with P. knowlesi after spending several nights camping on a hill about 160 kilometers inland from Kuala Lumpur.

Warren surveyed the forested area where the infected American had camped. The hill sat beside a meandering river. Monkeys and gibbons, a type of ape, lived on the hill and in adjacent forests. The closest house was about two kilometers away. Warren sampled the blood of four monkeys and more than 1,100 villagers around the hill; he collected mosquitoes too.

He found P. knowlesi parasites in the monkeys, but none among the villagers. Only one mosquito species, A. maculatus, appeared capable of transmitting malaria between monkeys and humans, but Warren deemed its numbers too low to matter. He concluded that monkey malaria stayed in the forests and rarely ever spilled into humans.

With those results, NIH ended the monkey malaria project, Warren said, and the Institute of Medical Research in Kuala Lumpur returned to its primary focus: human malaria, dengue and other mosquito-borne diseases. Monkey malaria was struck off the list of public health concerns.

Wake-up call
P. knowlesi landed back in the spotlight in 2004, with a report in the Lancet by malariologist Balbir Singh and his team. The group had found 120 people infected over two years in southern Malaysian Borneo. The patients were mostly indigenous people who lived near forests. Clinicians initially had checked the patients’ blood samples under microscopes — the standard test — and diagnosed the parasites as human malaria. But when Singh, of Universiti Malaysia Sarawak, applied molecular tools that identify parasite species by their DNA, he revealed that all the samples were P. knowlesi. Monkey malaria was breaking out of the diminishing forests.

By 2018, P. knowlesi had infected humans in all Southeast Asian countries except for East Timor. Singapore, declared malaria free in 1982, reported that six soldiers were infected with P. knowlesi from wild monkeys in a forest reserve. The parasite also turned up in almost 380 out of 3,700 visitors to health clinics in North Sumatra, Indonesia, an area that is close to being deemed free of human malaria.
Many scientists now recognize P. knowlesi as the fifth malaria parasite species that can naturally infect humans. It is also the only one to multiply in the blood every 24 hours, and it can kill if treatment is delayed. People pick up P. knowlesi parasites from long-tailed macaques, pig-tailed macaques and Mitred leaf monkeys. These monkeys range across Southeast Asia. So far, malaria parasites have been found in monkeys near or in forests, but rarely in monkeys in towns or cities.

Scientists propose several reasons for the recent rise in monkey malaria infections, but two stand out: improvement in malaria detection and forest loss.

Malaysia, for instance, finds more monkey malaria cases than other Southeast Asian countries because it added molecular diagnostic tools in 2009. Other countries use only microscopy for detection, says Rose Nani Mudin, who heads the vectorborne disease sector at Malaysia’s Ministry of Health. Since 2008, annual monkey malaria cases in Malaysia have climbed tenfold, even as human malaria cases have plummeted. “Maybe there is a genuine increase in [monkey malaria] cases. But with strengthening of surveillance, of course you would detect more cases,” she says.

Data collected by Malaysia’s malaria surveillance system have also revealed strong links between infection risk and deforestation. Fornace, the epidemiologist, examined the underlying drivers of monkey malaria in Surukan’s home state of Sabah. Fornace mapped monkey malaria cases in 405 villages, based on patient records from 2008 to 2012. Satellite data showed changes in forested areas around those villages. The villages most likely to report monkey malaria infections were those that had cut more than 8 percent of their surrounding forests within the last five years, she and colleagues reported in 2016 in Emerging Infectious Diseases.
Fornace’s team went into the field for a follow-up study, published in June in PLOS Neglected Tropical Diseases. The team collected blood samples from almost 2,000 people in two areas in Sabah and checked for current and past malaria infection. People who farmed or worked in plantations near forests had at least a 63 percent higher risk of P. knowlesi infection, and — like in the 2016 study — forests and cleared areas escalated risk of infection.

“It feels almost like P. knowlesi follows deforestation,” Fornace says. Several years after a forest is cut back, nearby communities “get a peak of P. knowlesi.”

Today, the hill where the American surveyor camped in 1965 is a small island in a sea of oil palm estates. From 2000 to 2012, Malaysia cleared a total amount of forest equaling 14.4 percent of its land area, more than any other country, according to a study published in 2013 in Science. A study in 2013 in PLOS ONE used satellite images to show that in 2009, only one-fifth of Malaysian Borneo was intact forest. Almost one-fourth of all forest there had been logged, regrown and logged many times over.

Since 2008, oil palm acreage in Malaysian Borneo has increased from 2.08 million hectares to 3.1 million, according to the Malaysian Palm Oil Board. In Malaysia, the four states hit hardest by deforestation — Sabah, Sarawak, Kelantan and Pahang — report 95 percent of the country’s P. knowlesi cases.
Fornace thinks deforestation and the ecological changes that come with it are the main drivers of monkey malaria’s rise in Malaysia. She has seen long-tailed macaques spend more time in farms and near houses after their home forests were being logged. Macaques thrive near human communities where food is abundant and predators stay out. Parasite-carrying mosquitoes breed in puddles made by farming and logging vehicles.

Where monkeys go, mosquitoes follow. Indra Vythilingam, a parasitologist at University of Malaya in Kuala Lumpur, studied human malaria in indigenous communities in the early 1990s. Back then, she rarely found A. cracens, the mosquito species that carries monkey malaria in Peninsular Malaysia. But in 2007, that species made up over 60 percent of mosquitoes collected at forest edges and in orchards, she reported in 2012 in Malaria Journal. “It’s so much easier to find them” now, she says.

As Fornace points out, “P. knowlesi is a really good example of how a disease can emerge and change” as land use changes. She recommends that when big projects are evaluated for their impact on the economy and the environment, human health should be considered as well.

What to expect
While P. knowlesi cases are climbing in Malaysia, scientists have found no evidence that P. knowlesi transmits directly from human to mosquito to human (though many suspect it happens, albeit inefficiently).
Following a review by experts in 2017, WHO continues to exclude P. knowlesi from its malaria elimination efforts. Rabindra Abeyasinghe, a tropical medicine specialist who coordinates WHO malaria control in the western Pacific region, says the agency will reconsider P. knowlesi as human malaria if there is new evidence to show that the parasite transmits within human communities.

In Malaysia last year, only one person died from human malaria, but P. knowlesi killed 11. “We don’t want that to happen, which is why [P. knowlesi] is our priority even though it is not in the elimination program,” says Rose Nani Mudin from the country’s Ministry of Health.

Unable to do much with the monkeys in the trees, Malaysian health officers focus on the people most likely to be infected with P. knowlesi. Programs raise awareness of monkey malaria and aim to reduce mosquitoes around houses. New mosquito-control methods are needed, however, because conventional methods like insecticide-treated bed nets do not work for monkey malaria mosquitoes that bite outdoors around dusk.

Fighting malaria is like playing chess against an opponent that counters every good move we make, says Culleton in Japan. Malaria parasites can mutate quickly and “go away and hide in places and come out again.” Against malaria, he says, “we can never let our guard down.”

This article appears in the November 10, 2018 Science News with the headline, “The Next Malaria Menace: Deforestation brings monkeys and humans close enough to share an age-old disease.”

Editor’s note: This story was updated on November 6, 2018 to correct the WHO’s position on monkey malaria. The agency excludes monkey malaria parasites from its malaria eradication goals, not because those particular parasites rarely infect humans, but because the parasites have not been shown to transmit among humans.

The United States is poised to take a powerful economic hit from climate change over the next century. Heat waves, wildfires, extreme weather events and rising sea levels could cost the country hundreds of billions of dollars in lost labor, reduced crop yields, health problems and crumbling infrastructure.

A report authored by hundreds of U.S. climate scientists from 13 federal agencies presents a stark picture of the country’s fate due to climate change. The Fourth National Climate Assessment, released November 23, predicts the U.S. economy will shrink by as much as 10 percent by the end of the century if global warming continues apace.
A separate report released November 27 by the United Nations Environment Programme reveals that in 2017, global emissions of carbon dioxide — a major driver of warming — rose for the first time in three years. That suggests that the nations that promised to curb emissions as part of the historic 2015 Paris agreement are falling short (SN: 1/9/16, p. 6).

It’s unclear what effect, if any, the reports will have on the U.S. government’s strategy on dealing with climate change and its consequences. President Donald Trump has previously announced he would withdraw the United States from the Paris agreement (SN Online: 6/1/17). And on November 26, Trump told reporters that he had read “some of” his scientists’ report. “It’s fine,” he said. But when it comes to the dire predictions of economic losses, he added, “I don’t believe it.”

The National Climate Assessments are mandated by Congress and produced every four years, focusing on the risks of climate change specifically to the United States. What’s different about the new report compared with previous editions is its precision about the risks to different parts of the U.S. economy, putting a price tag on the potential losses in agriculture, trade and energy generation.

To put a dollar value on bad air quality or worsening heat waves, for instance, scientists try to assess the measurable impacts of those issues — for example, the number of days of work or school missed, or the number of doctors’ visits triggered (SN Online: 10/14/18).
The more-than-1,600-page report includes detailed examinations of the effects of climate change on the country’s different regions. People living in the northeastern United States, for example, will be among the hardest hit by deaths due to poor air quality and temperature extremes by the end of the century. Labor losses in the southeastern United States are the highest of all regions, as are projected damages to roads and bridges, the report found.

Meanwhile, the Midwest will see the highest increase in premature deaths from increased amounts of ozone. And the Southwest, which includes California in these analyses, will suffer from extreme heat, drought and an increase in future cases of the mosquito-borne West Nile virus.

The report estimates that cumulatively the country will spend $23 billion responding to wildfires by the end of the century, even if greenhouse gas emissions are modestly reduced. The Southwest will bear the brunt of that impact, spending $13 billion dollars.

The report also details the many ways in which climate change is already hurting the country economically. For example, three storms that made landfall during the 2017 Atlantic hurricane season — Harvey, Irma and Maria — together cost the United States at least $265 billion, according to the National Oceanic and Atmospheric Administration.

By continuing on its current trajectory of greenhouse gas emissions, the “business-as-usual” scenario, the United States will see the greatest losses, the assessments concludes. However, the report also considers climate impacts in an alternate future, in which the world has taken modest actions to curb greenhouse emissions, including using more carbon-neutral fuels and the growth of technological innovations to remove carbon dioxide from the atmosphere (SN Online: 10/20/18).

Earth’s heart may have a secret chamber. The planet’s inner core isn’t just a solid ball of nickel and iron, researchers say, but contains two layers of its own: a distinct central region nestled within an outer shell.

Scientists say they have confirmed the existence of this innermost inner core using a type of previously undescribed seismic wave that not only travels through Earth’s core but also bounces back and forth through the interior, collecting invaluable data about the core’s structure along the way.
Focusing on earthquakes of magnitude 6 or larger that struck in the last decade, the researchers combined data on these quakes that were collected at seismic stations around the world. Combining these signals made it possible to detect even very faint reflections of the seismic waves. Of the 200 or so quakes analyzed, 16 events spawned seismic waves that detectably bounced through the inner core multiple times.

The origin, structure and fate of Earth’s core is of intense interest because the core generates the planet’s magnetic field, which shields the Earth from charged particles ejected by the sun and helps keep the planet’s denizens safe from too much radiation.

“Understanding how the magnetic field evolves is extremely important for the life on Earth’s surface,” says Hrvoje Tkalčić, a seismologist at the Australian National University in Canberra.

The entire core, about 6,600 kilometers across, consists of two main parts: a liquid outer core and a solid inner core (SN: 1/23/23). As iron-rich fluid circulates in the outer core, some of the material cools and crystallizes, sinking to form a solid center. That interplay generates Earth’s magnetic field.

When this swirling dance first began isn’t certain, but some studies suggest it was as recent as 565 million years ago, just a fraction of Earth’s 4.6-billion-year-long life span (SN: 1/28/19). That dance has faltered from time to time, its stuttering steps preserved in tiny magnetic grains in rocks. These data suggest the planet’s magnetic poles have flip-flopped many times over the years, temporarily weakening the magnetic field (SN: 2/18/21). As more and more crystals cool, the dance will eventually slow and stop, shutting off the planet’s magnetic field millions or billions of years from now.

Different types and structures of minerals, as well as different amounts of liquid in the subsurface, can change the speed of seismic waves traveling through Earth, offering clues to the makeup of the interior. In 2002, researchers noted that seismic waves traveling through the innermost part of Earth move slightly slower in one direction relative to the planet’s poles than in other directions. That suggests there’s some oddity there — a difference in crystal structure, perhaps. That hidden heart, the team suggested, might be a kind of fossil: a long-preserved remnant of the core’s early formation.

Since that observation, Tkalčić and others have pored over seismic data, finding independent lines of evidence that help support the idea of an innermost inner core. The reverberating seismic waves, described February 21 in Nature Communications, also show a slowdown, and are the strongest evidence yet that this hidden heart exists.
Using that seismic data, Tkalčić and seismologist Thanh-Son Phạm, also of the Australian National University, estimate that this inner heart is roughly 600 kilometers across, or about half the diameter of the full inner core. And the pair was able to assess the direction of the slowest waves at about 50 degrees relative to the Earth’s rotation axis, providing more insight into the region.

The exact source of the wave slowdown isn’t clear, Tkalčić says. The phenomenon might be related to the structure of the iron crystals, which may be packed together differently farther into the center. Or it could be from a different crystal alignment caused by some long-ago global event that changed how inner core crystals solidified out of the outer core.

The inner core holds many other mysteries too. Lighter elements present in small amounts in the core — hydrogen, carbon, oxygen — may flow around the solid iron in a liquidlike “superionic” state, further complicating the seismic picture (SN: 2/9/22).

By identifying and reporting seismic waves that bounced back and forth through the planet’s interior multiple times, the researchers have made an invaluable contribution that will help researchers study the core in new ways, says seismologist Paul Richards of Columbia University’s Lamont-Doherty Earth Observatory in Palisades, N.Y.

Still, the team’s interpretation of the inner core’s structure from those waves “is probably more iffy,” says Richards, who wasn’t involved in the work.

One reason for this uncertainty is that as the waves bounce back and forth, they can become weaker and more difficult to see in the data, he says. “Many further observations will help decide” what these new data can reveal about the heart of the planet.

Future therapy patients may spend a lot more time exploring virtual environments than sitting on sofas.

In a clinical trial of a new virtual reality treatment for fear of heights, participants reported being much less afraid after using the program for just two weeks. Unlike other VR therapies, which required that a real-life therapist guide patients through treatment, the new system uses an animated avatar to coach patients through ascending a virtual high-rise. This kind of fully automated counseling system, described online July 11 in the Lancet Psychiatry, may make psychological treatments for phobias and other disorders far more accessible.
This is “a huge step forward” for therapeutic VR, says Jennifer Hames, a clinical psychologist at the University of Notre Dame in Indiana, who wasn’t involved in the work. By bringing expert therapy out of the counselor’s office and into primary care clinics — or even people’s homes — the new system could help those who aren’t comfortable or don’t have the means to speak with a therapist face-to-face, she says.
Users immerse themselves in this virtual reality program using a VR headset, handheld controllers and headphones. An animated counselor guides the user through a virtual 10-story office complex, where upper floors overlook a ground-level atrium. On every floor, the user performs tasks designed to test their fear responses and help them learn that they’re safer than they might think. The tasks start out relatively easy — like standing close to a drop-off where a safety barrier gradually lowers — and progress to more difficult challenges — like riding a moving platform out into the open space over the atrium.
By working through these activities, “the person builds up memories that being around heights is safe, and this counteracts the old fear beliefs,” says Daniel Freeman, a clinical psychologist at the University of Oxford.

To test their program’s effectiveness, Freeman and colleagues recruited 100 adult volunteers who were moderately to severely afraid of heights. The researchers randomly assigned 49 people to undergo VR treatment, which involved using the program for about six 30-minute sessions over two weeks, while the other 51 participants received no treatment.

Participants filled out a questionnaire that rated their fear of heights from 16 to 80 (with 80 being most severe), before treatment, immediately afterward, and two weeks later. People who underwent VR treatment dropped about 25 points on average on the questionnaire’s scale, while patients who received no treatment remained stable. Participants who used the VR program found they “could go to places that they wouldn’t have imagined possible,” Freeman says, like steep mountains, rope bridges or simply escalators in shopping malls.

“When I’ve always got anxious about an edge, I could feel the adrenaline in my legs, that fight/flight thing; that’s not happening as much now,” one participant said. “I’m still getting a bit of a reaction to it, both in VR and outside as well, but it’s much more brief, and I can then feel my thighs soften up as I’m not bracing up against that edge.”

While the clinical trial results provide strong evidence that the new VR program mitigates fear better than no treatment at all, researchers still need to investigate how VR therapy stacks up against sessions with a therapist, Hames says. And since Freeman’s team only tracked treatment effects up to a couple of weeks after their experiment, it remains to be seen how long the effects of this therapy last — although previous research on therapist-led VR treatment have shown lasting impacts for at least a year.

While fully automated VR therapy may be good news for people who fear heights, it’s not clear how well this type of system could address more complex mental health issues, says Mark Hayward, a clinical psychologist at the University of Sussex in England whose commentary on the study appears in the same issue of the Lancet Psychiatry. Virtual environments may be well suited for helping people who fear everyday situations, like those who suffer from common phobias, social anxiety or paranoia, Hayward says. But when it comes to helping people with more severe symptoms, like psychosis, VR probably won’t stand in for trained therapists any time soon.

“We can’t get carried away and say we can automate all [mental health] treatment,” says Albert Rizzo, a clinical virtual reality developer at the University of Southern California in Playa Vista not involved in the work. But the new standalone system for curbing fear of heights is “an excellent first effort.”

Just a few powerful storms in Antarctica can have an outsized effect on how much snow parts of the southernmost continent get. Those ephemeral storms, preserved in ice cores, might give a skewed view of how quickly the continent’s ice sheet has grown or shrunk over time.

Relatively rare extreme precipitation events are responsible for more than 40 percent of the total annual snowfall across most of the continent — and in some places, as much as 60 percent, researchers report March 22 in Geophysical Research Letters.
Climatologist John Turner of the British Antarctic Survey in Cambridge and his colleagues used regional climate simulations to estimate daily precipitation across the continent from 1979 to 2016. Then, the team zoomed in on 10 locations — representing different climates from the dry interior desert to the often snowy coasts and the open ocean — to determine regional differences in snowfall.

While snowfall amounts vary greatly by location, extreme events packed the biggest wallop along Antarctica’s coasts, especially on the floating ice shelves, the researchers found. For instance, the Amery ice shelf in East Antarctica gets roughly half of its annual precipitation — which typically totals about half a meter of snow — in just 10 days, on average. In 1994, the ice shelf got 44 percent of its entire annual precipitation on a single day in September.

Ice cores aren’t just a window into the past; they are also used to predict the continent’s future in a warming world. So characterizing these coastal regions is crucial for understanding Antarctica’s ice sheet — and its potential future contribution to sea level rise.
Editor’s note: This story was updated April 5, 2019, to correct that the results were reported March 22 (not March 25).

We live in a sea of neutrinos. Every second, trillions of them pass through our bodies. They come from the sun, nuclear reactors, collisions of cosmic rays hitting Earth’s atmosphere, even the Big Bang. Among fundamental particles, only photons are more numerous. Yet because neutrinos barely interact with matter, they are notoriously difficult to detect.

The existence of the neutrino was first proposed in the 1930s and then verified in the 1950s (SN: 2/13/54). Decades later, much about the neutrino — named in part because it has no electric charge — remains a mystery, including how many varieties of neutrinos exist, how much mass they have, where that mass comes from and whether they have any magnetic properties.
These mysteries are at the heart of Ghost Particle by physicist Alan Chodos and science journalist James Riordon. The book is an informative, easy-to-follow introduction to the perplexing particle. Chodos and Riordon guide readers through how the neutrino was discovered, what we know — and don’t know — about it, and the ongoing and future experiments that (fingers crossed) will provide the answers.

It’s not just neutrino physicists who await those answers. Neutrinos, Riordon says, “are incredibly important both for understanding the universe and our existence in it.” Unmasking the neutrino could be key to unlocking the nature of dark matter, for instance. Or it could clear up the universe’s matter conundrum: The Big Bang should have produced equal amounts of matter and antimatter, the oppositely charged counterparts of electrons, protons and so on. When matter and antimatter come into contact, they annihilate each other. So in theory, the universe today should be empty — yet it’s not (SN: 9/22/22). It’s filled with matter and, for some reason, very little antimatter.

Science News spoke with Riordon, a frequent contributor to the magazine, about these puzzles and how neutrinos could act as a tool to observe the cosmos or even see into our own planet. The following conversation has been edited for length and clarity.

SN: In the first chapter, you list eight unanswered questions about neutrinos. Which is the most pressing to answer?

Riordon: Whether they’re their own antiparticles is probably one of the grandest. The proposal that neutrinos are their own antiparticles is an elegant solution to all sorts of problems, including the existence of this residue of matter we live in. Another one is figuring out how neutrinos fit in the standard model [of particle physics]. It’s one of the most successful theories there is, but it can’t explain the fact that neutrinos have mass.
SN: Why is now a good time to write a book about neutrinos?

Riordon: All of these questions about neutrinos are sort of coming to a head right now — the hints that neutrinos may be their own antiparticles, the issues of neutrinos not quite fitting the standard model, whether there are sterile neutrinos [a hypothetical neutrino that is a candidate for dark matter]. In the next few years, a decade or so, there will be a lot of experiments that will [help answer these questions,] and the resolution either way will be exciting.

SN: Neutrinos could also be used to help scientists observe a range of phenomena. What are some of the most interesting questions neutrinos could help with?

Riordon: There are some observations that simply have to be done with neutrinos, that there are no other technological alternatives for. There’s a problem with using light-based telescopes to look back in history. We have this really amazing James Webb Space Telescope that can see really far back in history. But at some point, when you go far enough back, the universe is basically opaque to light; you can’t see into it. Once we narrow down how to detect and how to measure the cosmic neutrino background [neutrinos that formed less than a second after the Big Bang], it will be a way to look back at the very beginning. Other than with gravitational waves, you can’t see back that far with anything else. So it’ll give us sort of a telescope back to the beginning of the universe.

The other thing is, when a supernova happens, all kinds of really cool stuff happens inside, and you can see it with neutrinos because neutrinos come out immediately in a burst. We call it the “cosmic neutrino bomb,” but you can track the supernova as it’s going along. With light, it takes a while for it to get out [of the stellar explosion]. We’re due for a [nearby] supernova. We haven’t had one since 1987. It was the last visible supernova in the sky and was a boon for research. Now that we have neutrino detectors around the world, this next one is going to be even better [for research], even more exciting.

And if we develop better instrumentation, we could use neutrinos to understand what’s going on in the center of the Earth. There’s no other way that you could probe the center of the Earth. We use seismic waves, but the resolution is really low. So we could resolve a lot of questions about what the planet is made of with neutrinos.

SN: Do you have a favorite “character” in the story of neutrinos?

Riordon: I’m certainly very fond of my grandfather Clyde Cowan [he and Frederick Reines were the first physicists to detect neutrinos]. But Reines is a riveting character. He was poetic. He was a singer. He really was this creative force. I mentioned [in the book] that they put this “SNEWS” sign on their detector for “supernova early warning system,” which sort of echoed the ballistic missile early warning systems at the time [during the Cold War]. That’s so ripe.

When you’re stressed and anxious, you might feel your heart race. Is your heart racing because you’re afraid? Or does your speeding heart itself contribute to your anxiety? Both could be true, a new study in mice suggests.

By artificially increasing the heart rates of mice, scientists were able to increase anxiety-like behaviors — ones that the team then calmed by turning off a particular part of the brain. The study, published in the March 9 Nature, shows that in high-risk contexts, a racing heart could go to your head and increase anxiety. The findings could offer a new angle for studying and, potentially, treating anxiety disorders.
The idea that body sensations might contribute to emotions in the brain goes back at least to one of the founders of psychology, William James, says Karl Deisseroth, a neuroscientist at Stanford University. In James’ 1890 book The Principles of Psychology, he put forward the idea that emotion follows what the body experiences. “We feel sorry because we cry, angry because we strike, afraid because we tremble,” James wrote.

The brain certainly can sense internal body signals, a phenomenon called interoception. But whether those sensations — like a racing heart — can contribute to emotion is difficult to prove, says Anna Beyeler, a neuroscientist at the French National Institute of Health and Medical Research in Bordeaux. She studies brain circuitry related to emotion and wrote a commentary on the new study but was not involved in the research. “I’m sure a lot of people have thought of doing these experiments, but no one really had the tools,” she says.

Deisseroth has spent his career developing those tools. He is one of the scientists who developed optogenetics — a technique that uses viruses to modify the genes of specific cells to respond to bursts of light (SN: 6/18/21; SN: 1/15/10). Scientists can use the flip of a light switch to activate or suppress the activity of those cells.
In the new study, Deisseroth and his colleagues used a light attached to a tiny vest over a mouse’s genetically engineered heart to change the animal’s heart rate. When the light was off, a mouse’s heart pumped at about 600 beats per minute. But when the team turned on a light that flashed at 900 beats per minutes, the mouse’s heartbeat followed suit. “It’s a nice reasonable acceleration, [one a mouse] would encounter in a time of stress or fear,” Deisseroth explains.

When the mice felt their hearts racing, they showed anxiety-like behavior. In risky scenarios — like open areas where a little mouse might be someone’s lunch — the rodents slunk along the walls and lurked in darker corners. When pressing a lever for water that could sometimes be coupled with a mild shock, mice with normal heart rates still pressed without hesitation. But mice with racing hearts decided they’d rather go thirsty.

“Everybody was expecting that, but it’s the first time that it has been clearly demonstrated,” Beyeler says.
The researchers also scanned the animals’ brains to find areas that might be processing the increased heart rate. One of the biggest signals, Deisseroth says, came from the posterior insula (SN: 4/25/16). “The insula was interesting because it’s highly connected with interoceptive circuitry,” he explains. “When we saw that signal, [our] interest was definitely piqued.”

Using more optogenetics, the team reduced activity in the posterior insula, which decreased the mice’s anxiety-like behaviors. The animals’ hearts still raced, but they behaved more normally, spending some time in open areas of mazes and pressing levers for water without fear.
A lot of people are very excited about the work, says Wen Chen, the branch chief of basic medicine research for complementary and integrative health at the National Center for Complementary and Integrative Health in Bethesda, Md. “No matter what kind of meetings I go into, in the last two days, everybody brought up this paper,” says Chen, who wasn’t involved in the research.

The next step, Deisseroth says, is to look at other parts of the body that might affect anxiety. “We can feel it in our gut sometimes, or we can feel it in our neck or shoulders,” he says. Using optogenetics to tense a mouse’s muscles, or give them tummy butterflies, might reveal other pathways that produce fearful or anxiety-like behaviors.

Understanding the link between heart and head could eventually factor into how doctors treat panic and anxiety, Beyeler says. But the path between the lab and the clinic, she notes, is much more convoluted than that of the heart to the head.