Jupiter was an early bloomer. New measurements of meteorite ages suggest that the giant planet’s core must have formed within the solar system’s first million years. If so, Jupiter’s presence could help explain why the inner planets are so small — and possibly even be responsible for Earth’s existence.

Previously, astronomers’ best constraints on Jupiter’s age came from simulations of how solar systems form in general. Gas giants like Jupiter grow by accreting gas from spinning disks of gas and dust around a young star. Those disks typically don’t last more than 10 million years, so astronomers inferred that Jupiter formed by the time that disk dissipated.
“Now we can use actual data from the solar system to show Jupiter formed even earlier,” says Thomas Kruijer, who did the research while at the University of Münster in Germany. Kruijer, now at Lawrence Livermore National Laboratory in California, and his team report Jupiter’s new age in the Proceedings of the National Academy of Sciences the week of June 12.

To study one of the biggest objects in the solar system, Kruijer and colleagues turned to some of the smallest: meteorites. Most meteorites come from the asteroid belt currently located between Mars and Jupiter but probably were born elsewhere.

Luckily, meteorites carry a signature of their birthplaces. The gas and dust disk that the planets formed from had different neighborhoods. Each had its own “zip code,” areas enriched in certain isotopes, or different masses of the same elements. Careful measurements of a meteorite’s isotopes can point to its home.

Kruijer and colleagues selected 19 samples of rare iron meteorites from the Natural History Museum in London and the Field Museum in Chicago. These rocks represent the metal cores of the first asteroid-like bodies to congeal as the solar system was forming.

The team dissolved about a gram of each sample in a solution of nitric acid and hydrochloric acid. “It smells terrible,” Kruijer says.
Then the researchers separated out the elements tungsten — a good tracer of both a meteorite’s age and birthplace — and molybdenum, another tracer of a meteorite’s home.

By measuring the relative amounts of molybdenum-94, molybdenum-95, tungsten-182 and tungsten-183, Kruijer and his team identified two distinct groups of meteorites. One group formed closer to the sun than Jupiter is today; the other formed farther from the sun.

The tungsten isotopes also showed that both groups existed at the same time, between about 1 million and 4 million years after the start of the solar system about 4.57 billion years ago (SN Online: 8/23/10). That means something must have kept them separated.

The most likely candidate is Jupiter, Kruijer says. His team’s calculations suggest that Jupiter’s core had probably grown to about 20 times the mass of the Earth in the solar system’s first million years, making it the oldest planet. Its presence would have created a gravitational barrier that kept the two meteorite neighborhoods segregated. Jupiter would then have continued growing at a slower rate for the next few billion years.

“I have high confidence that their data is excellent,” says cosmochemist Meenakshi Wadhwa of Arizona State University in Tempe. The suggestion that Jupiter held the different meteorites apart is “a little more speculative, but I buy it,” she adds.

Jupiter’s early entrance could also explain why the inner solar system lacks any planets larger than Earth. Many extrasolar planetary systems have large close-in planets, from rocky super-Earths (about two to 10 times the mass of Earth) to gassy mini-Neptunes or hot Jupiters. Astronomers have puzzled over why our solar system looks so different.

An early Jupiter’s gravity could have kept most of the planet-forming disk away from the sun, meaning there was less raw material for the inner planets. This picture is consistent with other work suggesting a young Jupiter wandered through the inner solar system and swept it clean (SN: 4/2/16, p.7), Kruijer says.

“Without Jupiter, we could have had Neptune where Earth is,” Kruijer says. “And if that’s the case, there would probably be no Earth.”

Get a grip. A new robotic gripping tool based on gecko feet can grab hold of floating objects in microgravity. The grippers could one day help robots move dangerous space junk to safer orbits or climb around the outside of space stations.

Most strategies for sticking don’t work in space. Chemical adhesives can’t withstand the wide range of temperatures, and suction doesn’t work in a vacuum.

Adhesives inspired by gecko feet — which use van der Waals forces to cling without feeling sticky (SN Online: 11/18/14) — could fit the bill, says Mark Cutkosky of Stanford University, whose team has been designing such stickers for more than a decade. Now his team has built robotic gripper “hands” that can grapple objects many times their size without pushing them away, the researchers report June 28 in Science Robotics.
The team first tested the grippers in the Robo-Dome, a giant air hockey table at NASA’s Jet Propulsion Laboratory in Pasadena, Calif., where two 370-kilogram robots gently pushed each other around using a small square of gecko gripper.

Then last summer, Aaron Parness and Christine Fuller, of the Jet Propulsion Lab, and Hao Jiang of Stanford took the full gripper hand, which includes several patches of gripping material in a specific arrangement, on a microgravity flight in NASA’s Weightless Wonder aircraft. The team used the hand to grab and release a cube, cylinder and beach ball, which represented satellites, spent rockets or fuel tanks, and pressure vessels.

Gripper hands could be used to repair or move dead satellites, or help miniature satellites called CubeSats stick to larger spacecraft like barnacles, Parness says.

Hominid hubbub
In “Hominid roots may go back to Europe” (SN: 6/24/17, p. 9), Bruce Bower reported that the teeth of Graecopithecus, a chimp-sized primate that lived in southeastern Europe 7 million years ago, suggest it was a member of the human evolutionary family.

“Is it appropriate to use the terms ‘hominid’ and ‘ape’ as if the two are mutually exclusive categories?” asked online reader Tim Cliffe. “The distinction being made is between our clade in particular and all other apes. It seems to me that ‘hominids’ should be described as a subset of apes, not a separate category,” he wrote.
“Yes, hominids are apes,” Bower says. “The terminology gets pretty thick in evolutionary studies, so researchers (and journalists) use some shortcuts.”

Fossils of many ancient apes dating to between 25 million and 5 million years ago have been found, but the interest in this case is in a key transition to a particular kind of ape that walked upright and displayed various skeletal traits similar to traits unique to the human evolutionary family. “That’s why one source in the story, Bernard Wood, wonders whether Graecopithecus was an apelike hominid or a hominid-like ape,” Bower says. “But it’s important to remember that hominids diverged from other, ancestral apes. So did chimps.”

Science News defines “hominid” as a member of the human evolutionary family.

Laser, camera, action
The world’s fastest video camera films 5 trillion frames every second, Ashley Yeager reported in “A different kind of camera captures speedy actions” (SN: 6/24/17, p. 5). The camera works by flashing a laser at a subject and using a computer program to combine the still images into a video. Researchers tested the device by filming particles of light as the particles traveled a short distance.

Online reader JHoughton1 wondered if the researchers really filmed a light particle in their tests. “I thought light ‘sometimes behaves like a wave, sometimes like a particle,’ but that there isn’t really any particle that’s a particle in the usual sense. Is this really a picture of a ‘particle’ of light? A photon-as-ball-of-stuff?”

The camera captured the forward progression of a laser pulse, which is an ensemble of photons, Yeager says.

Photons themselves aren’t “balls of stuff” on quantum scales, says physics writer Emily Conover. All particles, including photons, are spread out in space, propagating like waves. “Only when scientists measure or observe a photon or any other particle do they find it in one place, like the ball of stuff that people typically imagine. I think in that sense, photons are about as tangible as any other quantum particle,” Conover says.

Bringing down the mucus house
Little-known sea animals called giant larvaceans can catch a lot of carbon in disposable mucus casings called “houses,” Susan Milius reported in “ ‘Mucus houses’ catch sea carbon fast” (SN: 6/10/17, p. 13).

Online reader Robert Stenton wondered what happens to mucus houses as they fall to the bottom of the ocean.

What happens to discarded houses isn’t yet clear, Milius says, though researchers have proposed that the houses might carry substantial portions of carbon to life on the sea bottom. And if bits of a house fall fast enough to reach great depths, the carbon could get trapped in water masses that move around the planet for centuries before surfacing. Bits drifting down slowly may be intercepted by microbes and other debris feeders and would not end up sequestered.

Correction
In “Human noises invade wilderness” (SN: 6/10/17, p. 14), Science News incorrectly reported that official wilderness areas in the United States do not allow livestock grazing. Grazing is permitted in protected wilderness areas at preprotection levels under the Wilderness Act of 1964, which created the National Preservation System.

Our view of the earliest flowers just bloomed. A new reconstruction, the most detailed to date, suggests the flowers were bisexual, with more than five female reproductive organs, or carpels, and more than 10 male reproductive organs, or stamen. Petallike structures, grouped in sets of three, surrounded the sex organs, researchers report August 1 in Nature Communications.

Flowering plants comprise roughly 90 percent of plants on Earth. Researchers think they evolved from a common ancestor that lived about 140 million years ago. But it has been hard to reconstruct the structure of such ancient blooms because so few fossils have been found.

In the new study, Hervé Sauquet of the Université Paris-Sud in Orsay, France, and colleagues combined models of flower evolution with a database of features for 792 species of flowering plants, and data from the fossil record. The new picture of ancient flowers suggests some blossoms lost their bisexuality with time. Also, modern blooms lost some of their whorls, the concentric layers of different flower parts. In some flowers, whorls dropped from at least four to two in petals and the leaflike structures at the base of a bloom, and from four to one in stamen, the team concludes. The finding suggests that natural selection pushed the plants to a less complex floral plan over time.

Physicists often ponder small things, but probably not the ones on Kerwyn Casey “KC” Huang’s mind. He wants to know what it’s like to be a bacterium.

“My motivating questions are about understanding the physical challenges bacterial cells face,” he says. Bacteria are the dominant life-forms on Earth. They affect the health of plants and animals, including humans, for good and bad. Yet scientists know very little about the rules the microbes live by. Even questions as basic as how bacteria determine their shape are still up in the air, says Huang, of Stanford University.

Huang, 38, is out to change that. He and colleagues have determined what gives cholera bacteria their curved shape and whether it matters (a polymer protein, and it does matter; the curve makes it easier for cholera to cause disease), how different wavelengths of light affect movement of photosynthetic bacteria (red and green wavelengths encourage movement; blue light stops the microbes in their tracks), how bacteria coordinate cell division machinery and how photosynthetic bacteria’s growth changes in light and dark.

All four of these findings and more were published in just the first three months of this year.
Huang also looks for ways to use tools and techniques his team develops to solve problems unrelated to bacteria. Computer programs that measure changes in bacterial cell shape can also track cells in plant roots and in developing zebrafish embryos. He’s even helped determine how a protein’s activity and stability contribute to a human genetic disease.

A physicist by training, Huang delves into biology, biochemistry, microbial ecology, genetics, engineering, computer science and more, partnering with a variety of scientists from across those fields. He’s even teamed up with his statistician sister. He’s an “all-in-one scientist,” says longtime collaborator Ned Wingreen, a biophysicist at Princeton University.

When Huang started his lab at Stanford in 2008, after getting his Ph.D. at MIT and spending time at Princeton as a postdoctoral fellow, his background was purely theoretical. He designed and ran the computer simulations and then his collaborators carried out the experiments. But soon, he wanted to do hands-on research too, to learn why cells are the way they are.
Such a leap “is not trivial,” says Christine Jacobs-Wagner, a microbiologist at Yale University who also studies bacterial cell shape. But Huang is “a really, really good experimentalist,” she says.

Jacobs-Wagner was particularly impressed with a “brilliant microfluidics experiment” Huang did to test a well-established truism about how bacteria grow. Researchers used to think that turgor pressure — water pressure inside a cell that pushes the outer membrane against the cell wall — controlled bacterial growth, just like it does in plants. But abolishing turgor pressure didn’t change E. coli’s growth rate, Huang and colleagues reported in 2014 in Proceedings of the National Academy of Sciences. “This result blew my mind away,” Jacobs-Wagner says. The finding “crumbled the foundation” of what scientists thought about bacterial growth.

“He uses clever experiments to challenge old paradigms,” Jacobs-Wagner says. “More than once he has come up with a new trick to address a tough question.”
Sometimes Huang’s tricks require breaking things. Zemer Gitai, a microbiologist at Princeton, remembers talking with Huang and Wingreen about a question that microbiologists were stuck on: How are molecules oriented in bacterial cell walls? Researchers knew that the walls are made of rigid sugar strands connected by flexible proteins, like a chain link fence held together by rubber bands. What they didn’t know was whether the rubber bands circled the bacteria like the hoops on a wine barrel, ran in stripes down the length of the cell or stuck out like hairs.

If bacteria were put under pressure, the cells would crack along the weak rubber band–like links, Huang and Wingreen reasoned. If the cells split like hot dogs on a grill, it would mean the links ran the length of the cells. If they opened like a Slinky, it would suggest a wine-barrel configuration. The researchers reported the results — opened like a Slinky — in 2008. Another group, using improved microscope techniques, got the same result.

Huang teamed up with other researchers to do microfluidics experiments, growing bacteria in tiny chambers and tracking individual cells to learn how photosynthetic bacteria grow in light and dark.

But in nature, bacteria don’t live alone. So Huang has also worked with Stanford colleague Justin Sonnenburg to answer a basic question: “Where and when are bacteria in the gut growing? No one knows,” Huang says. “How can we not know that? It’s totally fundamental.” Without that information, it’s impossible to know, for example, how antibiotics affect the microbial community in the intestines, he says.

Stripping fiber from a mouse’s diet not only changes the mix of microbes in the gut, it alters where in the intestines the microbes grow, the researchers discovered. Bacteria deprived of fiber’s complex sugars began to munch on the protective mucus lining the intestines, bumping against the intestinal lining and sparking inflammation, Huang, Sonnenburg and colleagues reported in Cell Host & Microbe in 2015.

Huang’s breadth of research — from deciphering the nanoscale twists of proteins to mapping whole microbial communities — is sure to lead to many more discoveries. “He’s capable of making contributions to any field,” Jacobs-Wagner says, “or any research question that he’s interested in.”

Over the last 40 years, the number of kids and teens with obesity has skyrocketed worldwide. In 1975, an estimated 5 million girls and 6 million boys were obese. By 2016, those numbers had risen to an estimated 50 million girls and 74 million boys, according to a report published online October 10 in the Lancet. While the increase in childhood obesity has slowed or leveled off in many high-income countries, it continues to grow in other parts of the world, especially in Asia.

Using the body mass index, a ratio of weight to height, of more than 30 million 5- to 19-year-olds, researchers tracked trends from 1975 to 2016 in five weight categories: moderate to severe underweight, mild underweight, healthy weight, overweight and obesity. The researchers defined obesity as having a BMI around 19 or higher for a 5-year-old up to around 30 or higher for a 19-year-old.

Globally, more kids and teens — an estimated 117 million boys and 75 million girls — were moderately or severely underweight in 2016 than were obese. But the total number of obese children is expected to overtake the moderately or severely underweight total by 2022, the researchers say.

The globalization of poor diet and inactivity is part of the problem, says William Dietz, a pediatrician at George Washington University in Washington D.C., who wrote a commentary that accompanies the study. Processed foods and sugary drinks have become widely available around the world. And urbanization, which also increased in the last four decades, tends to reduce physical activity, Dietz says.

While obesity rates for kids and teens have largely leveled off in most wealthy countries, those numbers continue to increase for adults. The findings in children are consistent with evidence showing a drop in the consumption of fast food among children and adults in the United States over the last decade, Dietz says. “Children are going to be much more susceptible to changes in caloric intake than adults.”

Off the Kohala coast on the Big Island of Hawaii, Christine Gabriele spots whale 875. The familiar propeller scar on its left side and the shape of its dorsal fin are like a telltale fingerprint. Gabriele, a marine biologist with the Hawaii Marine Mammal Consortium, confirms the whale’s identity against her extensive photo catalog. Both Gabriele and this male humpback have migrated to this Pacific Island from Southeastern Alaska.

In those Alaska summer feeding grounds, Gabriele sees the same 300 or so whales “again and again.” But winter brings more than 10,000 whales to the waters of Hawaii from all over the North Pacific. Spotting 875 is like finding a needle in a haystack.
Gabriele is here today to focus on the slew of worrisome bumps on the familiar traveler’s flank. The bumps are separate from the usual ones bulging from the head of a humpback ( Megaptera novaeangliae ). Those iconic oversize hair follicles are thought to be part of the sensory system. The smaller body bumps look more like bad acne or an allergic reaction. Noted on rare occasions in the 1970s, the condition called nodular dermatitis has become much more prevalent. These days, Gabriele and colleagues see these skin lesions on over 75 percent of Hawaii’s humpback visitors.
The bumps coincide with other suggestions of declining health in the whales. In the nearly three decades that Gabriele has been studying whales, she would not describe the animals as skinny. Now, often “you can see their shoulder blades,” she says. “They look angular rather than round.”
Gabriele’s team is trying to figure out the cause of the bumps, comparing tissue samples from bumpy and nonbumpy whales. Several times per week, a small team sets out on the water, research permits in hand. Once a whale pod is spotted, Gabriele’s colleague Suzanne Yin zooms in with a camera and volunteer Kim New enlarges the image on her iPad, examining skin on the whale’s flanks and behind the blowhole to confirm if it’s bumpy or not. Gabriele carefully steers the boat so that Yin can shoot a biopsy dart from a crossbow.
The dart “takes a little plug of skin and blubber … about the size of a pencil eraser,” Gabriele says. The dart bounces off the whale and floats until the researchers can grab it. When darted, some whales dive; others show no reaction at all.

Collaborators from the National Institute of Standards and Technology’s Hollings Marine Laboratory in Charleston, S.C., are analyzing the skin for trace elements. National Marine Fisheries Service lab staff are studying the blubber for organic pollutants like PCBs and flame retardants. Preliminary results suggest that bumpy whales differ from nonbumpy in levels of manganese and a few other trace elements. Gabriele eagerly awaits the full analyses to make sense of what she’s seeing among the migratory creatures.

A chicken eggshell has a tricky job: It must protect a developing chick, but then ultimately let the chick break free. The secret to its success lies in its complex nanostructure — and how that structure changes as the egg incubates.

Chicken eggshells are about 95 percent calcium carbonate by mass. But they also contain hundreds of different kinds of proteins that influence how that calcium carbonate crystalizes. The interaction between the mineral crystals and the proteins yields an eggshell that’s initially crack-resistant, while making nanoscale adjustments over time that ultimately let a chick peck its way out, researchers report online March 30 in Science Advances.
Researchers used a beam of ions to cut thin cross sections in chicken eggshells. They then analyzed the shells with electron microscopy and other high-resolution imaging techniques. The team found that proteins disrupt the crystallization of calcium carbonate, so that what seems at low resolution to be neatly aligned crystals is actually a more fragmented jumble. This misalignment can make materials more resilient: Instead of spreading unimpeded, a crack must zig and zag through scrambled crystals.
Lab tests back up that finding: The researchers added a key shell-building protein called osteopontin to calcium carbonate to yield crystals like those seen in the eggshells. The presence of that protein makes calcium carbonate crystals form in a nanostructured pattern, rather than smooth and even crystal, study coauthor Marc McKee, a biomineralization researcher at McGill University in Montreal, and colleagues found.

The team also found structural variation on a minute scale throughout the eggshell, though it’s only about a third of a millimeter thick. Inner layers have less osteopontin, leading to bigger nanostructures. That may make the inner shell less resilient than the outer shell, which makes sense, McKee says­­. The outer shell needs to be hard enough to protect the chick, while the inner shell nourishes the developing chick.

Over time, the inner layers of the shell dissolve through a chemical reaction, releasing calcium to build a chick’s developing bones. The eggshell undergoes structural changes to facilitate that process, McKee and his colleagues found.

The researchers compared fertilized eggs incubated for 15 days to nonfertilized eggs. Over time, the nanostructures toward the inner shell became smaller in fertilized eggs, but remained the same in the nonfertilized eggs. The change gives the inside of the eggshell a bumpier texture, and by extension, more surface area. That provides more space for that shell-dissolving chemical reaction to take place, the researchers propose. The reaction also thins the shell overall, making it easier for a chick to break through from the inside when it’s time to hatch.

Advances in imaging technology are helping scientists find new details like this even in objects as familiar as a chicken eggshell, says Lara Estroff, a materials scientist at Cornell University who wasn’t part of the research. In connecting the eggshell’s functionality with its fine-grain structure, the new study could provide inspiration for designing new kinds of materials with specific properties.

Your brain might make new nerve cells well into old age.

Healthy people in their 70s have just as many young nerve cells, or neurons, in a memory-related part of the brain as do teenagers and young adults, researchers report in the April 5 Cell Stem Cell. The discovery suggests that the hippocampus keeps generating new neurons throughout a person’s life.

The finding contradicts a study published in March, which suggested that neurogenesis in the hippocampus stops in childhood (SN Online: 3/8/18). But the new research fits with a larger pile of evidence showing that adult human brains can, to some extent, make new neurons. While those studies indicate that the process tapers off over time, the new study proposes almost no decline at all.
Understanding how healthy brains change over time is important for researchers untangling the ways that conditions like depression, stress and memory loss affect older brains.

When it comes to studying neurogenesis in humans, “the devil is in the details,” says Jonas Frisén, a neuroscientist at the Karolinska Institute in Stockholm who was not involved in the new research. Small differences in methodology — such as the way brains are preserved or how neurons are counted — can have a big impact on the results, which could explain the conflicting findings. The new paper “is the most rigorous study yet,” he says.

Researchers studied hippocampi from the autopsied brains of 17 men and 11 women ranging in age from 14 to 79. In contrast to past studies that have often relied on donations from patients without a detailed medical history, the researchers knew that none of the donors had a history of psychiatric illness or chronic illness. And none of the brains tested positive for drugs or alcohol, says Maura Boldrini, a psychiatrist at Columbia University. Boldrini and her colleagues also had access to whole hippocampi, rather than just a few slices, allowing the team to make more accurate estimates of the number of neurons, she says.
To look for signs of neurogenesis, the researchers hunted for specific proteins produced by neurons at particular stages of development. Proteins such as GFAP and SOX2, for example, are made in abundance by stem cells that eventually turn into neurons, while newborn neurons make more of proteins such as Ki-67. In all of the brains, the researchers found evidence of newborn neurons in the dentate gyrus, the part of the hippocampus where neurons are born.

Although the number of neural stem cells was a bit lower in people in their 70s compared with people in their 20s, the older brains still had thousands of these cells. The number of young neurons in intermediate to advanced stages of development was the same across people of all ages.

Still, the healthy older brains did show some signs of decline. Researchers found less evidence for the formation of new blood vessels and fewer protein markers that signal neuroplasticity, or the brain’s ability to make new connections between neurons. But it’s too soon to say what these findings mean for brain function, Boldrini says. Studies on autopsied brains can look at structure but not activity.

Not all neuroscientists are convinced by the findings. “We don’t think that what they are identifying as young neurons actually are,” says Arturo Alvarez-Buylla of the University of California, San Francisco, who coauthored the recent paper that found no signs of neurogenesis in adult brains. In his study, some of the cells his team initially flagged as young neurons turned out to be mature cells upon further investigation.

But others say the new findings are sound. “They use very sophisticated methodology,” Frisén says, and control for factors that Alvarez-Buylla’s study didn’t, such as the type of preservative used on the brains.

Composting waste is heralded as being good for the environment. But it turns out that compost collected from homes and grocery stores is a previously unknown source of microplastic pollution, a new study April 4 in Science Advances reports.

This plastic gets spread over fields, where it may be eaten by worms and enter the food web, make its way into waterways or perhaps break down further and become airborne, says Christian Laforsch, an ecologist at the University of Bayreuth in Germany. Once the plastic is spread across fields, “we don’t know its fate,” he says.
That fate and the effects of plastic pollution on land and in freshwater has received little research attention compared with marine plastic pollution, says ecologist Chelsea Rochman of the University of Toronto. Ocean microplastics have gained notoriety thanks in part to coverage of the floating hulk of debris called the great Pacific garbage patch (SN Online: 3/22/18).

But current evidence suggests that plastic pollution is as prevalent in land and freshwater ecosystems as it is in the oceans, where it’s found “from the equator to the poles,” says Rochman, author of a separate commentary on the state of plastic pollution research published in the April 6 Science. Plastic “is seen in the high Arctic, where we suspect it comes down in rain. We know it’s in drinking water, in our seafood and spread on our agricultural fields,” she says.

Laforsch and his colleagues looked at several different kinds of biowaste that’s composted and spread on farmland in Germany, including household compost and grass clippings, supermarket waste and grain silage leftover from biogas production.

Compost samples taken from supermarket waste contained the greatest amount of plastic particles, with 895 pieces larger than 1 millimeter found per kilogram of dry weight. Household compost in contrast contained 20 and 24 particles per kg of dry weight, depending on the size of the sieves used to sift the compost. The detritus included bits of polyester and a lot of styrene-based polymers, commonly used in food packaging. Almost no particles were found in samples of silage from biogas production.
“I never thought about plastic in compost ending up as fertilizer. But when you think about it, it makes sense,” says environmental scientist Ad Ragas of Radboud University in Nijmegen, The Netherlands, who wasn’t involved in the work. A crate of rotting cucumbers wrapped in plastic that gets chucked, those stickers on every tomato in a bunch — that packaging doesn’t disappear.

Ragas says compost probably doesn’t contribute as much plastic to the environment as other sources, such as sewage treatment plant sludge, which contains polyester debris from clothes washers, and runoff from streets, which can be loaded with particles of synthetic rubber used in tires. But the compost contribution deserves investigation, Ragas says. “This triggers a lot of questions we haven’t studied yet.”

Those questions include possible effects on different organisms, from plants to earthworms to birds to people, Rochman says. Those effects will likely differ depending on the kind of plastic, which varies depending on its starting polymer and the additives used to impart certain qualities such as flexibility, sturdiness or durability under ultraviolet light.

“We are not saying we should get rid of all plastics,” Rochman says. “But we do need to start thinking of plastics as a persistent global pollutant.”