爱上海龙凤

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).

A new type of implantable bandage could help mend broken hearts.

Each bandage is a thin film that oozes a cocktail of molecules to heal tissue damaged during a heart attack. In experiments with rats and pigs, these patches helped minimize scarring and preserve the heart’s ability to pump blood, researchers report online November 28 in Science Advances. Such devices could someday curb heart attack survivors’ risk of heart failure.

The base of each heart-healing film is a polymer sheet studded with tiny needles — similar to other microneedle patches that deliver vaccines but designed to stick to a patient’s heart rather than her skin (SN: 8/5/17, p. 8). The surface of the polymer opposite the array of microneedles is coated in a gel containing cardiac stromal cells. These cells secrete molecules, such as proteins and tiny pieces of genetic material known as microRNAs, that support the growth of heart muscle cells.
“We’re treating [the patch cells] as little pharmacies,” says study coauthor Ke Cheng, a biological engineer at North Carolina State University in Raleigh. When a patch is attached to the heart, the microneedles funnel curative molecules from the cardiac stromal cells directly into the damaged tissue.

In rats, Cheng’s team tested how well the microneedle patches promoted healthy tissue growth and mitigated scarring. Three weeks after researchers induced rats to have heart attacks, the animals with microneedle patches had roughly 40 percent healthy tissue in the regions of their hearts affected by the heart attack, whereas as untreated rats had only about 10 percent.
For the pigs, the researchers tracked heart health by measuring how much blood was pumped from the animal’s left ventricle to the rest of its body with each heartbeat. Four hours after a heart attack, each heartbeat released about 56 to 57 percent of all the blood in the left ventricle, in both treated and untreated pigs. But 48 hours after the attack, the results began to diverge: Hearts treated with microneedle patches pumped about 60 percent of the left ventricle’s volume, while untreated hearts pumped about 50 percent.
The new microneedle design “is a very interesting and exciting” idea, but researchers need to investigate how animals implanted with these patches fare over longer periods, says Tamer Mohamed, a cardiovascular researcher at the University of Louisville in Kentucky not involved in the work.
Before these microneedle patches are used to treat humans, Cheng’s team plans to swap out the polymer used in this study for a material that gradually dissolves inside the body. The researchers are also exploring less invasive ways to implant patches than open-heart surgery, Cheng says.

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.

In 2018, we saw just how much power science has to make a real impact.

Science News’ top stories of the year include a literal impact — the hidden contours of what appears to be a massive crater created when a meteorite slammed into Greenland long ago. That discovery ranks among our Top 10 partly because it’s just cool, but also because it raises the tantalizing prospect of solving a scientific mystery: Did the impact kick the planet into a roughly 1,000-year cold snap, called the Younger Dryas, almost 13,000 years ago?
The mammoths and other species that died out by the end of that period didn’t see climate change coming. But we can. That’s why human-driven climate change is our top story of the year. The rising tide of attribution studies shows that climbing temperatures are already turning extreme events, such as Hurricane Florence, more extreme. This year’s barrage of climate reports gave us a clearer picture of how climate change will affect Earth in the near future — fueling wildfires, sparking heat waves, raising sea levels —and how human actions to curb warming can have an impact.

2018 is also the year a Chinese researcher made the startling claim that he had created the first babies to be born with an edited gene. The ensuing uproar over the controversial birth of twin girls in China, whose genes were allegedly tweaked to reduce their risk of contracting HIV, is sure to have a lasting impact on the future of gene-editing technology.

Two other genetics stories made our Top 10. Genetic genealogy is shaking up the field of forensics, ID’ing suspects in cold cases while raising privacy issues. And in a lab experiment, a gene drive — a genetic tool designed to be inherited by 100 percent of offspring — wiped out a population of mosquitoes. That feat ushers in the enticing but perilous possibility of both eliminating certain diseases and deliberately driving a species to extinction.

Other stories rounding out our Top 10 examine issues close to home (how to sort through conflicting advice about drinking alcohol) and very far away (tracing a high-energy neutrino back to its source in a distant galaxy). We’ll be watching these stories to see what happens in 2019 and beyond.
— Macon Morehouse, News Director
hurricane flooding
SN TOP 10
1
Can half a degree save us?
This is the year we learned that the 2015 Paris Agreement on global warming won’t be enough to forestall significant impacts of climate change. And a new field of research explicitly attributed some extreme weather events to human-caused climate change. This one-two punch made it clear that climate change isn’t just something to worry about in the coming decades. It’s already here. FULL STORY
Jiankui He
SN TOP 10
2
Gene-edited babies
A Chinese scientist surprised the world in late November by claiming he had created the first gene-edited babies. Many researchers and ethicists say implanting gene-edited embryos to create babies is premature and exposes the children to unnecessary health risks. Critics also fear the creation of “designer babies.” FULL STORY
Sacramento sheriff and Golden State killer
SN TOP 10
3
Genealogy solves crimes
In 2018, criminal investigators in the United States embraced genetic genealogy, a forensic technique for tracking down suspects through their family trees, to solve decades-old cold cases and some fresh crimes. But this new type of DNA-based detective work has raised questions about genetic privacy and police procedures. FULL STORY
IceCube detector
SN TOP 10
4
A neutrino’s distant source
Mysterious particles called neutrinos constantly barrel down on Earth from space. No one has known where, exactly, the highest-energy neutrinos come from. This year, scientists finally put a finger on one likely source: a brilliant cosmic beacon called a blazar. The discovery could kick-start a new field of astronomy that combines information gleaned from neutrinos and light. FULL STORY
Greenland crater illustration
SN TOP 10
5
Impact crater unearthed
For three years, a team of scientists kept a big secret: They had discovered a giant crater-shaped depression buried beneath about a kilometer of ice in northwestern Greenland. In November, the researchers revealed their find to the world. The crater may have reignited a debate over a controversial hypothesis about a mysterious cold snap known as the Younger Dryas. FULL STORY
Anopheles gambiae mosquitoes
SN TOP 10
6
The end of mosquitoes?
For the first time, humans have built a set of pushy, destructive genes that infiltrated small populations of mosquitoes and drove them to extinction. This test and other news from 2018 feed one of humankind’s most persistent dreams: wiping mosquitoes off the face of the Earth. FULL STORY
person covering wine glass
SN TOP 10
7
Health risks of alcohol
For people who enjoy an occasional cocktail, 2018 was a sobering year. Headlines delivered the news with stone-cold certainty: Alcohol — in any amount — is bad for your health. “The safest level of drinking is none,” a group of scientists concluded. FULL STORY
Mars south pole
SN TOP 10
8
Mars’ ice-covered lake
Researchers reported this year that they found a wide lake of standing liquid near the Red Planet’s south pole, buried beneath 1.5 kilometers of ice. The purported polar pool is the largest volume of liquid water ever claimed to currently exist on Mars, and has probably been around for a long time. Both of those features raise hopes that life could survive on Mars today. FULL STORY
Gert-Jan Oskam walking with crutches
SN TOP 10
9
Progress against paralysis
Intensive rehabilitation paired with electric stimulation of the spinal cord allowed six paralyzed people to walk or take steps years after their injuries, three small studies published this year showed. More importantly, they show that the spinal cord can make a comeback. FULL STORY
painting on cave walls in Spain
SN TOP 10
10
Origins of human smarts
Archaeological discoveries reported this year broadened the scope of what scientists know about Stone Age ingenuity. These finds move the roots of innovative behavior ever closer to the origins of the human genus. FULL STORY

Behavioral ecologist Anna Holzner recalls first seeing a southern pig-tail macaque munching on a headless rat. These monkeys were known to eat fruits, insects and even dirt, but nobody had reported them eating rats. “It was funny,” says Holzner, “and disgusting.”

This unexpected act occurred dozens of times from March to August 2016 as Holzner, of the University of Leipzig in Germany, and colleagues recorded what the macaques ate on oil palm plantations in northwest Peninsular Malaysia. To planters there, the macaques are pests.

Holzner did the work as part of the Macaca Nemestrina Project led by primate ecologist Nadine Ruppert of Universiti Sains Malaysia, in Penang. She presented the results on July 2 at the annual meeting of the Association of Tropical Biology and Conservation in Kuching, Malaysia.

While pig-tail macaques, Macaca nemestrina, spend most of their time in the forest, they visit adjacent plantations daily to forage, report Ruppert, Holzner and others in a related study in the April 4 International Journal of Primatology.

Holzner’s new study shows that in the plantations, pig-tail macaques ate mostly oil palm fruits, spending only 1 percent of their meal times on rats. But the monkeys would peel open the bark on oil palm trunks to expose rats hiding within. The researchers estimate that a group of 30 macaques might eat as many as 2,080 rats in a year. Holzner’s team counted fewer rats wherever they located macaques.

The study has local plantation owners reconsidering the monkeys, which may not be pests after all, but agents of rat control, Holzner says. But as macaques adapt to the encroaching plantations and their numbers grow, they can reduce birds and other creatures living in adjacent forests, warns ecologist Matthew Luskin at the Nanyang Technological University in Singapore.

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.”

Saturn’s rings are painting its innermost moons.

Data from NASA’s now-defunct Cassini spacecraft show that five odd-shaped moons embedded in Saturn’s rings are different colors, and that the hues come from the rings themselves, researchers report. That observation could help scientists figure out how the moons were born.

“The ring moons and the rings themselves are kind of one and the same,” says planetary scientist Bonnie Buratti of NASA’s Jet Propulsion Laboratory in Pasadena, Calif. “For as long as the moons have existed, they’ve been accreting particles from the rings.”
Saturn has more than 60 moons, but those nearest to the planet interact closely with its main band of rings. Between December 2016 and April 2017, Cassini passed close to five of these ring-dwelling moons: ravioli-shaped Pan and Atlas (SN Online: 3/10/17), ring-sculpting Daphnis and Pandora (SN: 9/2/17, p. 16) and potato-shaped Epimetheus. The flybys brought Cassini between two and 10 times closer to the moons than it had ever been, before the spacecraft deliberately crashed into Saturn in September 2017 (SN Online: 9/15/17).

Examining those close-ups, Buratti and her colleagues noticed that the moons’ colors vary depending on the objects’ distances from Saturn. And the moon hues are similar to the colors of the rings that the objects are closest to, the team reports online March 28 in Science.
Close-in Pan was the reddest moon, while the farthest-out Epimetheus was the bluest. The researchers think the red material comes from Saturn’s dense main rings, and mostly consists of organics and iron (SN Online: 10/4/18). The blue material is probably water ice from Saturn’s more distant E ring, which is created by plumes erupting from the larger, icy moon Enceladus.
The team thinks that the rings are continually depositing material onto the moons. “It’s an ongoing process,” Buratti says. She notes that “skirts” of material at Atlas and Pan’s equators are probably made of accreted ring debris, too.

The overall similarity between the moons and rings led the researchers to conclude that these small moons are leftover shards of a destructive event that created the rings in the first place. But it’s unknown whether that event was a collision between long-gone, larger moons, the shredding of one moon by Saturn’s gravity, or some other occurrence (SN: 1/20/18, p. 7).

Saturn, its rings and its moons are “very dynamic,” says planetary scientist Matija Ćuk of the SETI Institute in Mountain View, Calif. The idea that the rings are still shedding material onto the moons today “sounds perfectly reasonable.” He isn’t sure the moons formed at the same time as the rings, though. It’s possible “they formed from the rings since that catastrophic event,” he says.

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.

In the classic fairy tale, Hansel and Gretel dropped bread crumbs while walking through a treacherous forest so they wouldn’t lose their way. Rovers may one day use a similar trick to traverse other planets without losing their data.

Typically, if a rover permanently loses communication during a mission, all the information that it has gathered is lost. To avoid this, researchers suggest using a multi-rover system in which a smaller rover piggybacks on a larger “mother rover.” The smaller rover would then venture into any especially uncertain territory, such as a cave or lava tubes, deploying sensors the size of an AirPods case like bread crumbs as it goes.
The sensors could then communicate with each other via a wireless network and funnel any collected data back to the mother rover, theoretical physicist Wolfgang Fink and colleagues propose February 11 in Advances in Space Research. As proof of concept, the team built prototype sensors that communicate via Wi-Fi.

It’s not that the smaller rover would be following the “bread crumbs” back the way it came. Instead, “we use [the sensors] for the data to find its way communication-wise out of the cave to the mother rover,” says Fink, of the University of Arizona in Tucson.

The technology could also be useful here on Earth, especially after a natural disaster such as an earthquake. A rover could be sent with the deployable sensors into rubble where it’s too dangerous for people to perform search-and-rescue missions (SN: 12/3/14).

The bread crumb–like communication network could allow researchers to “cater to the essence of scientific exploration,” Fink says, by allowing rovers to overcome some of the constraints posed by tricky terrain. “To get to the real exciting science, you most of the time have to go to exotic places, hard-to-get-to places.”