These are wondrous times for space exploration. Just when you think exploring the cosmos couldn’t possibly get more fun, another discovery delivers a new “oh wow” moment.

Consider the asteroid Bennu. It’s an unprepossessing space rock that drew scientists’ curiosity because it is among the most pristine objects in our solar system, and it might provide clues to the origins of life. But checking out Bennu is no trip to Paris; it’s about 130 million kilometers from Earth. NASA launched its OSIRIS-REx probe to Bennu in 2016, and it didn’t arrive until last December. The spacecraft is currently orbiting its quarry in preparation for an attempt at gathering samples from the asteroid’s surface in 2020 and then toting them back to Earth. Estimated delivery date: September 24, 2023. Clearly, asteroid science is not a discipline for those with short attention spans.
So imagine scientists’ delight when OSIRIS-REx already had news to share: Bennu is squirting jets of dust into space. It’s an asteroid behavior no one had ever seen before. Astronomy writer Lisa Grossman learned all about Bennu’s surprise jets while attending the Lunar and Planetary Science Conference in March. She reports that the dusty fountains may be the work of volatile gases beneath Bennu’s surface. The presence of volatiles would suggest that the rock wandered into the inner solar system relatively recently. But astronomers still have a lot to figure out about Bennu’s history, and they couldn’t be happier.

In other surprising space rock news from the conference, astronomers analyzing the much-more-distant object dubbed Ultima Thule now think it’s an agglomeration of mini-worlds that stuck together in the early days of the solar system — as Grossman terms it, a “Frankenworld.” That’s just the latest unexpected news from this Kuiper Belt denizen. If you’re as space rock obsessed as we are, you may recall that the first fuzzy images from NASA’s New Horizons spacecraft, which flew by Ultima Thule on January 1, suggested that the rock looked like a bowling pin or a snowman spinning in space. More recent images reveal not a snowman, but instead two pancakes or hamburger patties glued end to end (SN: 3/16/19, p. 15). That has scientists scrambling to figure out what forces could create such an oddly shaped object.

We’ll be hearing more about Bennu, Ultima Thule and other residents of our solar system in the months to come. I’m particularly looking forward to news from the Parker Solar Probe, which is tightening its orbit around the sun. I’m the one who is going to have to be patient in this case, though that’s not an attribute typically associated with journalists. The spacecraft won’t make its closest encounter with the sun until 2024, before ending its mission the following year. But the probe will be reporting in, and we’ll be reporting, too, as it makes this historic journey (SN: 1/19/19, p. 7).

Open your Web browser or your trusty print magazine and join us for the adventure. We hope you’ll enjoy the journey as much as we do.

Unusual virus is valuable tool —

Viruses, which cannot reproduce on their own, infect cells and usurp their genetic machinery for use in making new viruses…. But just how viruses use the cell machinery is unknown.… Some answers may come from work with an unusual virus, called M13, that has a particularly compatible relationship with … [E. coli] bacteria. — Science News, April 5, 1969

Update
M13 did help unlock secrets of viral replication. Some bacteria-infecting viruses, called bacteriophages or simply phages, kill the host cell after hijacking the cell’s machinery to make copies of themselves. Other phages, including M13, leave the cell intact. Scientists are using phage replication to develop drugs and technologies, such as virus-powered batteries (SN: 4/25/09, p. 12). Adding genetic instructions to phage DNA for making certain molecules lets some phages produce antibodies against diseases such as lupus and cancer. The technique, called phage display, garnered an American-British duo the 2018 Nobel Prize in chemistry (SN: 10/27/18, p. 16).

My youngest child, now just over a year old, has started to talk. Even though I’ve experienced this process with my older two, it’s absolutely thrilling. He is putting words to the thoughts that swirl around in his sweet little head, making his mind a little less mysterious to the rest of us.

But these early words may not mean what we think they mean, a new study hints. Unsurprisingly, when 2-year-olds were asked a series of “this or that” questions, the toddlers showed strong preferences — but not for the reasons you’d think. Overwhelmingly, the toddlers answered the questions with the last choice given.
That bias, described in PLOS ONE on June 12, suggests that young children’s answers to these sorts of questions don’t actually reflect their desires. Instead, kids may simply be echoing the last thing they heard.

This verbal quirk can be used by parents to great effect, as the researchers point out in the title of their paper: “Cake or broccoli?” More fundamentally, the results raise questions about what sort of information a verbal answer actually pulls out of a young child’s mind. This murkiness is especially troublesome when it comes to questions whose answers call for adult action, such as: “Did you hit your sister on purpose or on accident?”

In the first series of experiments, researchers led by Emily Sumner at the University of California, Irvine, asked 24 1- and 2-year-olds a bunch of two-choice questions, some of which involved a polar bear named Rori or a grizzly bear named Quinn. One question, for example, was, “Does Rori live in an igloo or a tepee?” Later, the researchers switched the bear and the order of the options, asking, for example, “Does Quinn live in a tepee or an igloo?”

The toddlers could answer either verbally or, for reluctant speakers, by pointing at one of two stickers that showed the choices. When the children answered the questions by pointing, they chose the second option about half the time, right around chance. But when the toddlers spoke their answers, they chose the second option 85 percent of the time, regardless of the bear.
SECOND BEST A toddler taking part in a study selects the second option in three either-or questions. This tendency, called the recency bias, may reflect kids’ inability to juggle several choices in their minds simultaneously. Credit: E. Sumner et al/PLOS ONE 2019

This abundance of second options selected — a habit known as the recency bias — might be due to the fact that young children have trouble holding the first option in mind, the researchers suspect. Other experiments showed that children’s tendency toward the second option got stronger when the words got longer.

Adults actually have the opposite tendency: We’re more inclined to choose the first option we’re given (the primacy bias). To see when this shift from last to first occurs, the researchers studied transcripts of conversations held between adults and children ages 1.5 to 4. In these natural conversations, 2-year-olds were more likely to choose the second option. But 3- and 4-year-olds didn’t show this bias, suggesting that the window closes around then.

The results hold a multitude of delightful parenting hacks: “Would you like to jump on the bed all night, or go to sleep?” But more importantly, the study serves as a reminder that the utterances of small children, while fascinating, may not carry the same meanings as those that come from more mature speakers. If you really want a straight answer, consider showing the two options to the toddler. But if you go that route, be prepared to hand over the cake.

For the first time, researchers have harnessed the body’s own chemistry to “grow” electrodes inside the tissues of living fish, blurring the boundary between biology and machines.

The technique uses the body’s sugars to turn an injected gel into a flexible electrode without damaging tissues, experiments show. Zebrafish with these electrodes grown in their brains, hearts and tail fins showed no signs of ill effects, and ones tested in leeches successfully stimulated a nerve, researchers report in the Feb. 24 Science.
Someday, these electrodes could be useful for applications ranging from studying how biological systems work to improving human-machine interfaces. They also could be used in “bioelectronic medicine,” such as brain stimulation therapies for depression, Parkinson’s disease and other conditions (SN: 2/10/19).

Soft electronics aim to bridge the gap between soft, curvy biology and electronic hardware. But these electronics typically still must carry certain parts that can be prone to cracks and other issues, and inserting these devices inevitably causes damage to tissues.

“All the devices we have made, even though we have made them flexible, to make them more soft, when we introduce them, there will still be a scar. It’s like sticking a knife into the organ,” says Magnus Berggren, a materials scientist at Linköping University in Sweden. That scarring and inflammation can degrade electrode performance over time.

Previous efforts to grow soft electronics inside tissues have drawbacks. One approach uses electrical or chemical signals to power the transformation from chemical soup to conducting electrodes, but these zaps also cause damage. A 2020 study got around this problem by genetically modifying cells in worms to produce an engineered enzyme that does the job, but the new method achieves its results without genetic alterations.

Berggren and colleagues’ electrodes instead exploit a natural energy source already present in the body: sugars. The gel cocktail contains molecules called oxidases that react with the sugars — glucose or lactate — to produce hydrogen peroxide. That then activates another ingredient in the cocktail, an enzyme called hydrogen peroxidase, which is the catalyst needed to transform the gel into a conducting electrode.

“The approach leverages elegant chemistry to overcome many of the technical challenges,” says biomedical engineer Christopher Bettinger of Carnegie Mellon University in Pittsburgh, who was not involved in the study.

To test the technique, the researchers injected the cocktail into the brains, hearts and tail fins of transparent zebrafish. The gel turns blue when it becomes conductive, giving a visual readout of its success.
“The beautiful thing is you can see it: The zebrafishes’ tail changes color, and we know that blue indicates a conducting polymer,” says materials scientist Xenofon Strakosas, also of Linköping University. “The first time I saw it, I thought ‘Wow, it’s really working!’”

The fish appeared to suffer no ill effects, and the researchers saw no evidence of tissue damage. In partially dissected leeches, the team showed that delivering a current to a nerve via a soft electrode could induce muscle contractions. Ultimately, devices like this could be paired with various wireless technologies in development.

Long-term implant performance remains to be determined, however. “The demonstrations are impressive,” Bettinger says. “What remains to be seen is the stability of the electrode.” Over time, substances in the body could react with the electrode materials, degrading it or even producing toxic substances.

The team still needs to refine how precisely the electrodes can stimulate nerves, says chemical engineer Zhenan Bao of Stanford University, who was not involved in the work. She and colleagues developed the way to “grow” electrical components using genetic modifications. Ensuring stimulation is concentrated where it’s needed for a treatment, while preventing the leakage of current to unwanted regions will be important, she says.

In the new study, the relative abundance of different sugars in different tissues determines exactly where electrodes form. But in the future, a component of the main ingredient could be swapped out for elements that attach to specific bits of biology to make targeting much more precise, Berggren says. “We’re conducting experiments right now where we’re trying to bind these materials directly on individual cells.” Notes Strakosas: “There are some applications where precision is really important; that’s where we have to invest effort.”

The best shot we have at minimizing the future impacts of climate change is to limit global warming to 1.5 degrees Celsius. Since the Industrial Revolution began, humankind has already raised the average global temperature by about 1.1 degrees. If we continue to emit greenhouse gases at the current rate, the world will probably surpass the 1.5-degree threshold by the end of the decade.

That sobering fact makes clear that climate change isn’t just a problem to solve someday soon; it’s an emergency to respond to now. And yet, most people don’t act like we’re in the midst of the greatest crisis humans have ever faced — not politicians, not the media, not your neighbor, not myself, if I’m honest. That’s what I realized after finishing The Climate Book by Greta Thunberg.

The urgency to act now, to kick the addiction to fossil fuels, practically jumps off the page to punch you in the gut. So while not a pleasant read — it’s quite stressful — it’s a book I can’t recommend enough. The book’s aim is not to convince skeptics that climate change is real. We’re well past that. Instead, it’s a wake-up call for anyone concerned about the future.

A collection of bite-size essays, The Climate Book provides an encyclopedic overview of all aspects of the climate crisis, including the basic science, the history of denialism and inaction, and what to do next. Thunberg, who became the face of climate activism after starting the Fridays For Future protests as a teenager (SN: 12/16/19), assembles an all-star roster of experts to write the essays.

The first two sections of the book lay out how a small amount of warming can have major, far-reaching effects. For some readers, this will be familiar territory. But as each essay builds on the next, it becomes clear just how delicate Earth’s climate system is. What also becomes clear is the significance of 1.5 degrees (SN: 12/17/18). Beyond this point, scientists fear, various aspects of the natural world might reach tipping points that usher in irreversible changes, even if greenhouse gas emissions are later brought under control. Ice sheets could melt, raise sea levels and drown coastal areas. The Amazon rainforest could become a dry grassland.

The cumulative effect would be a complete transformation of the climate. Our health and the livelihood of other species and entire ecosystems would be in danger, the book shows. Not surprisingly, essay after essay ends with the same message: We must cut greenhouse gas emissions, now and quickly.

Repetition is found elsewhere in the book. Numerous essays offer overlapping scientific explanations, stats about emissions, historical notes and thoughts about the future. Rather than being tedious, the repetition reinforces the message that we know what the climate change threat is, we know how to tackle it and we’ve known for a long time.
Thunberg’s anger and frustration over the decades of inaction, false starts and broken pledges are palpable in her own essays that run throughout the book. The world has known about human-caused climate change for decades, yet about half of all human-related carbon dioxide emissions ever released have occurred since 1990. That’s the year the Intergovernmental Panel on Climate Change released its first report and just two years before world leaders met in Rio de Janeiro in 1992 to sign the first international treaty to curb emissions (SN: 6/23/90).

Perversely, the people who will bear the brunt of the extreme storms, heat waves, rising seas and other impacts of climate change are those who are least culpable. The richest 10 percent of the world’s population accounts for half of all carbon dioxide emissions while the top 1 percent emits more than twice as much as the bottom half. But because of a lack of resources, poorer populations are the least equipped to deal with the fallout. “Humankind has not created this crisis,” Thunberg writes, “it was created by those in power.”

That injustice must be confronted and accounted for as the world addresses climate change, perhaps even through reparations, Olúfẹ́mi O. Táíwò, a philosopher at Georgetown University, argues in one essay.

So what is the path forward? Thunberg and many of her coauthors are generally skeptical that new tech alone will be our savior. Carbon capture and storage, or CCS, for example, has been heralded as one way to curb emissions. But less than a third of the roughly 150 planned CCS projects that were supposed to be operational by 2020 are up and running.

Progress has been impeded by expenses and technology fails, science writer Ketan Joshi explains. An alternative might be “rewilding,” restoring damaged mangrove forests, seagrass meadows and other ecosystems that naturally suck CO2 out of the air (SN: 9/14/22), suggest environmental activists George Monbiot and Rebecca Wrigley.

Fixing the climate problem will not only require transforming our energy and transportation systems, which often get the most attention, but also our economies (endless growth is not sustainable), political systems and connection to nature and with each other, the book’s authors argue.

The last fifth of the book lays out how we could meet this daunting challenge. What’s needed is a critical mass of individuals who are willing to make lifestyle changes and be heard. This could trigger a social movement strong enough to force politicians to listen and create systemic and structural change. In other words, it’s time to start acting like we’re in a crisis. Thunberg doesn’t end the book by offering hope. Instead, she argues we each have to make our own hope.

“To me, hope is not something that is given to you, it is something you have to earn, to create,” she writes. “It cannot be gained passively, through standing by and waiting for someone else to do something. Hope is taking action.”

Modern birds evolved from dinosaurs, but it’s not clear how well birds’ ancient dino ancestors could fly (SN: 10/28/16). Now, a look at the fossilized feet of one nonavian dinosaur suggests that it may have hunted on the wing, like some hawks today.

The crow-sized Microraptor had toe pads very similar to those of modern raptors that can hunt in the air, researchers report December 20 in Nature Communications. That means the feathered, four-winged dinosaur probably used its feet to catch flying prey too, paleobiologist Michael Pittman of the Chinese University of Hong Kong and colleagues say (SN: 7/16/20).
Other researchers caution that toe pads alone aren’t enough to declare Microraptor an aerial hunter. But if the claim holds up, such a hunting style would reinforce a debated hypothesis that powered flight evolved multiple times among dinosaurs, a feat once attributed solely to birds.

Toe pads are bundles of scale-covered flesh on the undersides of dinosaur feet, similar to “toe beans” on dogs and cats. Because the pads are points where the living animal interacted with surfaces, toe pads give paleontologists a “sense of where the rubber meets the road,” says Alexander Dececchi, a paleontologist at Mount Marty University in Yankton, S.D., who was not involved in the new study.

These contact points can paint a clearer picture of an animal’s behavior by providing “details that the skeleton itself wouldn’t show,” says Thomas Holtz Jr., a dinosaur paleobiologist at the University of Maryland in College Park, who was also not involved in the study.

To investigate dinosaur toe pads, Pittman and colleagues turned to the Shandong Tianyu Museum of Nature in Linyi, China. It “has arguably the largest collection of feathered dinosaurs in the world, and, importantly, they haven’t been prepared extensively,” Pittman says. Many of these dinosaur skeletons are still surrounded by rock, which is where soft tissues can be preserved. Such a specimen “gives us the best chance of finding this wonderful soft tissue information,” he says.
Using special lasers that cause the otherwise nearly invisible soft tissue in the fossils to fluoresce, the team found 12 specimens with exceptionally well-preserved toe pads among the thousands examined (SN: 3/20/17).

The team compared the fossil toe pads with those of 36 types of modern birds, whose toe pads vary with their lifestyle. Predatory birds, for example, have protruding toe pads with spiky scales for grasping prey, while ground birds that spend their time walking and running have flatter toe pads. The analysis showed that Microraptor’s toe pads and other aspects of the feet, like the shape of the toe joints and claws, are most like those of modern hawks. That similarity suggests that the dinosaur could hunt prey midair and on the ground like hawks do, the team says.

Other dinosaurs, like the feathered Anchiornis, had flatter toe pads and straighter claws, suggesting a terrestrial lifestyle. That’s in line with ideas about this dinosaur being a poor flier, Pittman says.
The idea that Microraptor hunted like a hawk is consistent with other fossil evidence. One Microraptor fossil has been found with a bird in its stomach, and Microraptor‘s skeletal and soft tissue anatomy suggest some powered flight capability.

There’s still more work to do to figure out how well the dinosaur may have flown. “Microraptor is not a bird, but a close relative. Just because it has feet like a predatory bird doesn’t necessarily mean it must be catching prey in the exact same way,” Pittman says. But Microraptor’s hawklike lifestyle “is a strong possibility,” he adds.
Flight could have been useful to Microraptor when hunting, even if it couldn’t stack up to today’s fliers. Dececchi speculates that Microraptor’s anatomy probably prevented it from outflying birds, but may have helped it surprise otherwise out-of-reach prey, including flying and gliding animals.

“You only have to be fast or aerobatic enough to catch other things in your environment,” Holtz says. “So, it’s not improbable that [Microraptor was] catching things in the air on occasion.”

Other paleontologists are more skeptical that Microraptor hunted on the wing. “It would be a bit of a stretch to me to suggest that Microraptor was pursuing prey in an aerial context,” says Albert Chen, a paleobiologist at the University of Cambridge. The new findings inform only “what the foot was used for.”

Alternative hypotheses, such as a completely or partially terrestrial hunting style, could fit the data too, Holtz says, but the “feet are definitely playing a major role in their prey capture,” whether on the ground or in the air.

For now, the picture of Microraptor’s ecology remains fuzzy, but as lasers continue to increase the picture’s resolution, our understanding of dinosaur flight may reach new heights.

Turns out there is rest for the wicked: Sleepy mosquitoes are more likely to catch up on missed z’s than drink blood, a new study finds.

Most people are familiar with the aftermath of a poor night’s sleep. Insects also suffer; for instance, drowsy honeybees struggle to perform their signature waggle dance, and weary fruit flies show signs of memory loss. In the case of sleep-deprived mosquitoes, they give up valuable time for feeding in favor of sleeping overtime, researchers report June 1 in Journal of Experimental Biology.
The preference for dozing over dining is surprising given that “we know that mosquitoes love blood a lot,” says Oluwaseun Ajayi, a disease ecologist at the University of Cincinnati.

Scientists have long been interested in mosquitoes’ circadian rhythms, the internal clock that determines their sleep and awake times (SN: 10/2/17). Knowing when a mosquito is awake — and biting — is important for understanding and limiting disease transmission. For instance, malaria, often transmitted by nocturnal mosquitoes, is kept under control by slinging netting around beds. But new research suggests that mosquitoes that feed during the day may also spread the disease.

It’s challenging to study sleeping bloodsuckers in the lab. That’s partly because awake mosquitoes are aroused by the presence of a meal — the experimenter. And when mosquitoes do fall asleep, they look rather similar to peers that are merely resting to conserve energy.

That’s the tricky — and often species-specific — question: “How can you tell [when] an insect is sleeping?” says Samuel Rund, a mosquito circadian biologist at the University of Notre Dame in Indiana who was not involved in the research.

One way to tell is by tracking the insect’s behavior. So Ajayi and colleagues watched mosquitoes sleep. The team focused on three species known to carry diseases, including malaria: Aedes aegypti, which are active during the day; Culex pipiens, which prefer dusk; and the nocturnal Anopheles stephensi. The mosquitoes were left alone in a room in small enclosures, where the team used cameras and infrared sensors to spy on them.

After about two hours, the mosquitoes appeared to nod off. Their abdomens lowered to the ground and their hind legs drooped, the footage showed. As time went on, C. pipiens and A. aegypti showed a reduced response when the experimenter walked in the room, suggesting a tasty smell was less likely to wake those species when in a deep sleep. Taken together, the change in posture, periods of inactivity and lower arousal were determined to identify a snoozing mosquito.

What started as a relaxing experiment for the mosquitoes quickly changed gears. The insects were placed in clear tubes that received vibration pulses every few minutes, preventing them from falling into deep sleep. After four to 12 hours of this sleep deprivation, the team mimicked the presence of a host with a pad of heated artificial sweat. In another experiment, a plucky human volunteer offered up a leg to be fed on for five minutes by sleep-deprived and well-rested A. aegypti in batches of 10 insects.

In both cases, the mosquitoes that had had a full night’s rest were much more likely to land on the host than those that had been deprived of sleep. And the leg exposed to sleepy mosquitoes fared much better than when it was exposed to the control group: In eight tests, on average 77 percent of the well-rested mosquitoes went for a blood meal, compared with only 23 percent of sleepy mosquitoes.

The findings, Rund says, open avenues for research into controlling mosquito populations and reducing disease using the insects’ circadian rhythms.

The fading of a once-vibrant yellow rose reveals how the ravages of time and chemical alteration can dampen the visual power of a painting.

Most of the flowers in Abraham Mignon’s 17th century painting Still Life with Flowers and a Watch seem to leap off the canvas. But one yellow rose, painted with arsenic sulfide–based orpiment pigment, is a flat, jarring element. That wasn’t Mignon’s intention: The rose lost its luster due to the chemical transformation of some of its original bright pigment into colorless lead arsenates, researchers report June 8 in Science Advances.
Paintings conservator Nouchka De Keyser of the Rijksmuseum in Amsterdam and colleagues analyzed the rose using noninvasive techniques including X-ray fluorescence imaging and X-ray powder diffraction (SN: 10/1/21). The team first mapped the lingering traces of arsenic, lead, calcium and other chemical elements in the layers of paint to reveal how Mignon carefully layered paint to create a nearly three-dimensional rose out of light and shadow.

The analyses also revealed two newer crystals on the rose containing both lead and arsenic. Called mimetite and schultenite, the crystals are the product of a series of chemical reactions. First, the reaction of orpiment with light created a highly mobile type of arsenic called arsenolite. That mobilized arsenolite then found its way to an underlying layer of lead white paint and chemically reacted with it to produce the mimetite and schultenite. The crystals lack the bright color of the orpiment — instead, they are colorless and flatten the flower’s appearance.
Science can’t turn back the clock on the chemical transformation to restore the rose’s erstwhile glory — that’s a one-way street. But digital reconstructions made using similar techniques as in the new study could offer several benefits and not just to scientists and art historians, De Keyser says. Not only can such reconstructions reveal now-faded elements in other paintings — they might also appear in museums, allowing visitors a ghostly glimpse of a painting’s true past.

The undoing of toxic “forever chemicals” may be found in products in your pantry.

Perfluoroalkyl and polyfluoroalkyl substances, also known as PFAS, can persist in the environment for centuries. While the health impacts of only a fraction of the thousands of different types of PFAS have been studied, research has linked exposure to high levels of some of these widespread, humanmade chemicals to health issues such as cancer and reproductive problems.

Now, a study shows that the combination of ultraviolet light and a couple of common chemicals can break down nearly all the PFAS in a concentrated solution in just hours. The process involves blasting UV radiation at a solution containing PFAS and iodide, which is often added to table salt, and sulfite, a common food preservative, researchers report in the March 15 Environmental Science & Technology.
“They show that when [iodide and sulfite] are combined, the system becomes a lot more efficient,” says Garrett McKay, an environmental chemist at Texas A&M University in College Station who was not involved in the study. “It’s a big step forward.”

A PFAS molecule contains a chain of carbon atoms that are bonded to fluorine atoms. The carbon-fluorine bond is one the strongest known chemical bonds. This sticky bond makes PFAS useful for many applications, such as water- and oil-repellant coatings, firefighting foams and cosmetics (SN: 6/4/19; SN: 6/15/21). Owing to their widespread use and longevity, PFAS have been detected in soils, food and even drinking water. The U.S. Environmental Protection Agency sets healthy advisory levels for PFOA and PFOS — two common types of PFAS — at 70 parts per trillion.

Treatment facilities can filter PFAS out of water using technologies such as activated carbon filters or ion exchange resins. But these removal processes concentrate PFAS into a waste that requires a lot of energy and resources to destroy, says study coauthor Jinyong Liu, an environmental chemist at the University of California, Riverside. “If we don’t [destroy this waste], there will be secondary contamination concerns.”

One of the most well-studied ways to degrade PFAS involves mixing them into a solution with sulfite and then blasting the mixture with UV rays. The radiation rips electrons from the sulfite, which then move around, snipping the stubborn carbon-fluorine bonds and thereby breaking down the molecules.

But some PFAS, such as a type known as PFBS, have proven difficult to degrade this way. Liu and his colleagues irradiated a solution containing PFBS and sulfite for an entire day, only to find that less than half of the pollutant in the solution had broken down. Achieving higher levels of degradation required more time and additional sulfite to be poured in at spaced intervals.

The researchers knew that iodide exposed to UV radiation produces more bond-cutting electrons than sulfite. And previous research has demonstrated that UV irradiation paired with iodide alone could be used to degrade PFAS chemicals.

So Liu and his colleagues blasted UV rays at a solution containing PFBS, iodide and sulfite. To the researchers’ surprise, after 24 hours of irradiation, less than 1 percent of the stubborn PFBS remained.

What’s more, the researchers showed that the process destroyed other types of PFAS with similar efficiency and was also effective when PFAS concentrations were 10 times that which UV light and sulfite alone could degrade. And by adding iodide the researchers found that they could speed up the reaction, Liu says, making the process that much more energy efficient.

In the solution, iodide and sulfite worked together to sustain the destruction of PFAS molecules, Liu explains. When UV rays release an electron from iodide, that iodide is converted into a reactive molecule which may then recapture freed electrons. But here sulfite can step in and bond with these reactive molecules and with electron-scavenging oxygen in the solution. This sulfite “trap” helps keep the released electrons free to cut apart PFAS molecules for eight times longer than if sulfite wasn’t there, the researchers report.

It’s surprising that no one had demonstrated the effectiveness of using sulfite with iodide to degrade PFAS before, McKay says.

Liu and his colleagues are now collaborating with an engineering company, using their new process to treat PFAS in a concentrated waste stream. The pilot test will conclude in about two years.

For weeks, I have been watching coronavirus cases drop across the United States. At the same time, cases were heading skyward in many places in Europe, Asia and Oceania. Those surges may have peaked in some places and seem to be on a downward trajectory again, according to Our World in Data.

Much of the rise in cases has been attributed to the omicron variant’s more transmissible sibling BA.2 clawing its way to prominence. But many public health officials have pointed out that the surges coincide with relaxing of COVID-19 mitigation measures.

People around the world are shedding their masks and gathering in public. Immunity from vaccines and prior infections have helped limit deaths in wealthier countries, but the omicron siblings are very good at evading immune defenses, leading to breakthrough infections and reinfections. Even so, at the end of February, the U.S. Centers for Disease Control and Prevention posted new guidelines for masking, more than doubling the number of cases needed per 100,000 people before officials recommended a return to the face coverings (SN: 3/3/22).

Not everyone has ditched their masks. I have observed some regional trends. The majority of people I see at my grocery store and other places in my community in Maryland are still wearing masks. But on road trips to the Midwest and back, even during the height of the omicron surge, most of the faces I saw in public were bare. Meanwhile, I was wearing my N95 mask even when I was the only person doing so. I reasoned that I was protecting myself from infection as best I could. I was also protecting my loved ones and other people around me from me should I have unwittingly contracted the virus.

But I will tell you a secret. I don’t really like wearing masks. They can be hot and uncomfortable. They leave lines on my face. And sometimes masks make it hard to breathe. At the same time, I know that wearing a good quality, well-fitting mask greatly reduces the chance of testing positive for the coronavirus (SN: 2/12/21). In one study, N95 or KN95 masks reduced the chance of testing positive by 83 percent, researchers reported in the February 11 Morbidity and Mortality Weekly Report. And school districts with mask mandates had about a quarter of the number of in-school infections as districts where masks weren’t required (SN: 3/15/22).

With those data in mind, I am not ready to go barefaced. And I’m not alone. Nearly 36 percent of the 1,916 respondents to a Science News Twitter poll said that they still wear masks everywhere in public. Another 28 percent said they mask in indoor crowds, and 23 percent said they mask only where it’s mandatory. Only about 12 percent have ditched masks entirely.

Some poll respondents left comments clarifying their answers, but most people’s reasons for masking aren’t clear. Maybe they live in the parts of the country or world where transmission levels are high and hospitals are at risk of being overrun. Maybe they are parents of children too young for vaccination. Perhaps they or other loved ones are unvaccinated or have weakened immune systems that put them at risk for severe disease. Maybe, like me, they just don’t want to get sick — with anything.

Before the pandemic, I caught several colds a year and had to deal with seasonal allergies. Since I started wearing a mask, I haven’t had a single respiratory illness, though allergies still irritate my eyes and make my nose run. I’ve also got some health conditions that raise my risk of severe illness. I’m fully vaccinated and boosted, so I probably won’t die if I catch the virus that causes COVID-19, but I don’t want to test it (SN: 11/8/21). Right now, I just feel safer wearing a mask when I’m indoors in public places.

I’ve been thinking a lot about what would convince me that it was safe to go maskless. What is the number or metric that will mark the boundary of my comfort zone?

The CDC now recommends using its COVID-19 Community Levels map for determining when mask use is needed. That metric is mostly concerned with keeping hospitals and other health care systems from becoming overwhelmed. By that measure, most of the country has the green light to go maskless. I’m probably more cautious than the average person, but the levels of transmission in that metric that would trigger mask wearing — 200 or more cases per 100,000 population — seem high to me, particularly since CDC’s prior recommendations urged masking at a quarter of that level.

The metric is designed for communities, not individuals. So what numbers should I, as an individual, go by? There’s always the CDC’s COVID-19 Integrated County View that tracks case rates and test positivity rates — the percentage of tests that have a positive result. Cases in my county have been ticking up in the last few days, with 391 people having gotten COVID-19 in the last week — that’s about 37 out of every 100,000 people. That seems like relatively low odds of coming into contact with a contagious person. But those are only the cases we know about officially. There may be many more cases that were never reported as people take rapid antigen tests at home or decide not to test. There’s no way to know exactly how much COVID-19 is out there.

And the proportion of cases caused by BA.2 is on the rise, with the more infectious omicron variant accounting for about 35 percent of cases nationwide in the week ending March 19. In the mid-Atlantic states where I live, about 30 percent of cases are now caused by BA.2. But in some parts of the Northeast, that variant now causes more than half of cases. The increase is unsettling but doesn’t necessarily mean the United States will experience another wave of infections as Europe has. Or maybe we will. That uncertainty makes me uncomfortable removing my mask indoors in public right now.

Maybe in a few weeks, if there’s no new surge in infections, I’ll feel comfortable walking around in public with my nose and mouth exposed. Or maybe I’ll wait until the number of cases in my county is in single digits. I’m pretty sure there will come a day when I won’t feel the need to filter every breath, but for me, it’s not that time yet. And I truthfully can’t tell you what my magic number will be.

Here’s what I do know: Even if I do decide to have an unmasked summer, I will be strapping my mask back on if COVID-19 cases begin to rise again.