A laser blast produces miniature diamonds from plain-old plastic. That’s right, the same kind used in soda bottles.

When squeezed to about a million times Earth’s atmospheric pressure and heated to thousands of degrees Celsius, polyethylene terephthalate, or PET, forms nanodiamonds, physicist Dominik Kraus and colleagues report September 2 in Science Advances.

Ice giant planets, such as Neptune and Uranus, have similar temperatures, pressures and combinations of chemical elements as the materials in the study, suggesting that diamonds may rain down in those planets’ interiors. What’s more, the researchers say, the new technique could be used to manufacture nanodiamonds for use in quantum devices and other applications.
In the new study, researchers trained lasers on samples of plastic. Each laser blast sent a shock wave careening through the plastic, amping up the pressure and temperature within. Probing the material with bursts of X-rays revealed that nanodiamonds had formed.

Previous studies had created diamonds by compressing compounds of hydrogen and carbon. But PET, which is commonly used in food and drink packaging, contains not just hydrogen and carbon but also oxygen. That makes it a better match to the composition of ice giant planets like Neptune and Uranus. The oxygen seems to assist the diamond formation, says Kraus, of the University of Rostock in Germany. “The oxygen sucks out the hydrogen,” he says, leaving behind carbon which can then form diamond.

Nanodiamonds are commonly produced using explosives, Kraus says, a process not easy to control. The new technique could create nanodiamonds that are more easily tailored for particular uses, such as quantum devices made using diamond with defects where, for example, nitrogen atoms replace some of the carbon atoms (SN: 7/6/18).

“The idea is quite cool. You take water bottle plastic; you zap it with a laser to make diamond. How practical it is, I don’t know,” says physicist Marius Millot of Lawrence Livermore National Laboratory in California, who was not involved with the new study. How easily the diamonds could be recovered is unclear, he says. But, “it’s pretty neat to think about the idea.”

In May 2021, Congo’s Mount Nyiragongo, one of the world’s most dangerous volcanoes, burst to life without warning. Lava erupted from fissures and flowed down the mountain toward cities below, leaving hundreds dead or missing and hundreds more injured.

Now, using data from monitoring stations installed near the volcano in 2015, researchers have pieced together how that eruption happened so suddenly. The data also suggest that the event could have been even deadlier — and highlight the urgent need to better understand this volcano’s particular hazards before the next eruption, volcanologist Delphine Smittarello and colleagues report in the Sept. 1 Nature.
“Nyiragongo is unique in that 1 million people are living just at the foot of the volcano,” says Smittarello, of the European Center for Geodynamics and Seismology in Luxembourg. The mountain sits near the eastern border of Congo, looming over both the Congolese city of Goma, population of about 700,000, and the Rwandan city of Gisenyi, population about 83,000 (SN: 12/2/14). “There are so many people so close to a very dangerous place.”

Nyiragongo’s last two eruptions, in 1977 and 2002, were both presaged by days of distinct seismic rumblings strong enough to be felt by people living nearby. But before the eruption on May 22, 2021, even the sensitive monitoring stations near the volcano seemed to detect no clear warning signs of magma on the move underground.

There was the large lake of molten lava burbling in the volcano’s summit crater: By 2021, that lake had risen to near the top of the crater. But typically lake level alone isn’t enough to indicate an imminent eruption, Smittarello says. Levels had intermittently risen and fallen over the years since 2002 as magma moved around the volcano’s deep plumbing. And in 2021, the lake was still 85 meters below its 2002 level.

So Smittarello and her colleagues took another look at the monitoring stations’ seismic and acoustic data. This time, the analysis identified a rumbling of small quakes that commenced just 40 minutes before the actual eruption. Half an hour later, just 10 minutes before the lava burst through, detections of acoustic signals — low-frequency “infrasound” waves — began to increase, a hint that the volcano was about to erupt (SN: 6/25/18).

The trigger for the actual eruption was probably a tiny rupture that formed in the volcanic cone due to the buildup of stress over time from the pressure and heat of the magma within, the researchers say. That would have been enough to allow the magma to push through.

The short lag time between the signals and the eruption was probably because that magma was already extremely close to the surface, the researchers suggest. “What we monitor is the magma moving, not the presence or absence of magma,” Smittarello says. Because the magma had very little distance to travel, there was also very little warning.

The eruption itself lasted about six hours, but in its aftermath, there was plenty of seismic activity lasting another 10 days, suggesting the magma was now on the move. Those data, monitored in real time, indicated something troubling — the magma was moving underground, away from the summit, snaking beneath the city of Goma and nearby Lake Kivu.

As the magma migrated, scientists and local citizens worked together to trace the formation of cracks in the ground, which can indicate propagating dikes, lateral pathways through which magma is moving beneath the surface. Similar lateral pathways formed during the eruption of Kilauea in Hawaii, Smittarello says. In that case, the magma migrated to a neighborhood along the volcano’s lower east rift zone before erupting (SN: 7/6/18).

Based on the possible path of the magma, Goma city officials issued evacuation orders for tens of thousands of people who were potentially in the magma’s path. Meanwhile, scientists anxiously watched for signs of a potential “limnic eruption” at Lake Kivu — a rare type of disaster in which a noxious cloud of dissolved gases like carbon dioxide and methane suddenly erupts from deep lakes, suffocating living creatures nearby (SN: 4/2/94). Gas-rich magma seeping into the lake’s bottom could have triggered such an eruption. In either case, “if [the magma] finds a path to the surface, it’s a catastrophe,” Smittarello says.

Neither catastrophe occurred, thankfully, Smittarello says. “It was a lucky situation. But we don’t know why.”

It was especially lucky given the fact that the magma was closer to the surface than thought at the time, the team reports in the new study. That means the residents above were even closer to greater disaster than had been realized.

Reanalysis of posteruptive seismic data let the researchers determine the actual position of the underground dikes. The team found that one dike beneath Goma was as shallow as 450 meters deep. That’s particularly surprising because such a shallow magma channel would be expected to emit a telltale cocktail of volcanic gases from the ground cracks.
It’s not unheard-of for volcanic dikes to give no gassy indicators of their presence, says geophysicist Michael Poland of the U.S. Geological Survey, who is based in Vancouver, Wash., and leads the Yellowstone Volcano Observatory. The magma may have lost a lot of its gases as it circulated up into the summit lava lake; by the time it pushed into underground channels, it was potentially already degassed.

But that scenario is worrisome because there’s one fewer warning signal of possible danger to the communities above, says Poland, who was not involved in the new study. It also raises new questions — such as how such gas-poor magma might interact with Lake Kivu if it does flow into the lake.

What the 2021 eruption makes clear is that scientists need to investigate such questions to get a better understanding of the peculiarities of Nyiragongo — and to tailor monitoring and hazard warnings accordingly, Poland adds.

All volcanoes have their own personalities, and scientists need to develop a better appreciation for any warning signs that might exist. In this case, for example, that might include the lava lake level, he says. “The traditional approach is less reliable at Nyiragongo.”

At the start of another school year, I’ve been thinking about the differences between 2021 and 2022. Last year, many schools had mask mandates, testing programs and quarantine rules (SN: 3/15/22). This year, masking is optional and testing and quarantines are out (SN: 8/19/22).

We’ve shed measures that stop the spread of the coronavirus and help prevent excessive disruptions to in-person learning. Without them, and with the absence of nearly any controls in place elsewhere in society, we’re inviting the virus to keep spreading, to find new ways to thwart immunity and to continue to derail plans and routines. And it’s not just a risk to our day-to-day lives, but to our future health. As much as we want to put the pandemic in the rearview mirror, evidence continues to emerge that the coronavirus’s impact will be a recurring, unwelcome feature of many tomorrows.

Scientists predict COVID-19 cases will rise this fall and winter in the United States, as more of life heads indoors during colder weather. The Biden Administration has said there could be 100 million new cases. We have a new aid in the face of a possible surge: a revamped COVID-19 shot targeting the omicron variant, from both Pfizer (for 12 years and up) and Moderna (for 18 years and up), is now available (SN: 9/2/22). Meant as a booster shot, the tweaked vaccine is the original version with added protection against the BA.4 and BA.5 variants. The BA.5 variant is dominant in the United States, accounting for 89 percent of cases at the beginning of September.
Public health officials would like to get as many boosters in arms as possible this fall to temper a rise in cases. We know the original vaccine has done an outstanding job protecting people from severe illness and death. The vaccine has also helped reduced transmission, although this benefit can wane quickly. Overall, the COVID-19 vaccine is a crucial tool to protect public health. But it alone can’t shoulder the entire burden of keeping the virus at bay. Controlling the coronavirus takes a team approach, the vaccine together with masks, ventilation improvements and crowd control (SN: 4/4/22).

Without these additional measures, people will keep getting sick. Claire Taylor, a physician in the United Kingdom, tweeted about her experience having COVID-19 three times this year, in March, June and August, as the omicron family of variants moved through her country. “How can it be sustainable, sensible, bearable even, to get a virus that floors you in the same way multiple times a year?” she wrote.

It doesn’t seem sustainable, sensible or bearable. Not with what the virus can do in the midst of infection, and not with the harms that can linger after an infection subsides. Adults, for example, can face health issues throughout the body after a bout of COVID-19. A study of health records from the U.S. Department of Veterans Affairs reported that, compared with those who haven’t had COVID-19, those who have — whether hospitalized or not — face higher risks of a variety of cardiovascular diseases beyond the initial 30 days post-infection. Other research has found an increased risk of neurological and psychiatric illnesses for two years after a SARS-CoV-2 infection, compared with other respiratory infections.
On top of the risks from COVID-19 itself is the expected health effects of the pandemic’s disruptions to medical care. A study of a large health care system in Massachusetts found a drop in expected hospitalizations for urgent heart issues during the first year of the pandemic. Breast and ovarian cancer screenings in the United States decreased in 2020 compared with 2018. These delayed and lost health care opportunities may reverberate for years.

And then there is long COVID. Each surge of infections adds to the pool of people suffering from a range of debilitating symptoms that they just can’t shake, from extreme fatigue to brain fog to shortness of breath (SN: 9/1/22). Because it takes time to identify people who develop long COVID, we don’t yet know the toll from the omicron surge earlier this year. But the spike in cases was so large, “I suspect there will be millions of people who acquire long COVID after omicron infection,” immunobiologist Akiko Iwasaki told Liz Szabo of Kaiser Health News on August 26.

Long COVID can leave people unable to work, which is a threat to their ability to support themselves and maintain health insurance, as well as a looming crisis for the economy. There are already an estimated 16.3 million working-age Americans, meaning those 18 to 65 years old, who have long COVID; 2 million to 4 million of them are out of work because of their illness, a new Brookings Metro report finds. The annual cost of the wages lost is around $170 billion and may be as high as $230 billion.

There are also health impacts from grieving the loss of so many lives during the pandemic (SN: 10/27/21). Already 1 million people have died worldwide this year from COVID-19; close to 6.5 million in total have lost their lives to the disease during the pandemic.

Those deaths have included a devastating number of children’s parents and caregivers. Approximately 7.5 million children have lost one or both parents to COVID-19 as of May 2022, researchers report in JAMA Pediatrics on September 6. An estimated 10.5 million children have become orphans or lost caregivers. These deaths put children’s education, health and well-being at risk, deficits that cannot be overcome without dedicated societal support (SN: 2/24/22).

Like adults, children who’ve had COVID-19 are at higher risk for various health issues compared with children who haven’t had the illness, including heart inflammation and blood clots, researchers reported in Morbidity and Mortality Weekly Report on August 5. Children also develop long COVID. And kids and teens have suffered mental health harms from the pandemic, with many experiencing increased anxiety and depression. The subsequent demand for mental health services hasn’t been met.

We’re just beginning to learn about other health issues that could stem from the virus or the circumstances of the pandemic. A recent U.S. study found an alarming rise in youth-onset type 2 diabetes during the first year of the pandemic compared with the average of the prior two years. New cases jumped by 77 percent in 2020. It’s not clear if the increase is due to COVID-19 infection, shifts in diet or activity or stressors from the pandemic, but the rise has strained existing health services for children with diabetes, the researchers wrote.
The pandemic has also disrupted vital health services for children around the world. A study of 18 low- and lower-middle–income countries found a decline in doctor visits and the delivery of maternal and child health care from March 2020 to June 2021. The lost care is estimated to have led to more than 110,000 excess deaths among children under 5 and more than 3,000 excess deaths among mothers, a threat to recent progress in reducing child and maternal mortality, researchers report August 30 in PLOS Medicine. The pandemic has also interfered with vaccination campaigns, leaving children worldwide vulnerable to vaccine-preventable diseases.

Even newborns may face worsened health as a result of the pandemic. Research on prenatal exposures to maternal infection during the 1918 influenza pandemic has found health issues much later in life for the babies born, including higher rates of cardiovascular disease, kidney disease and diabetes.

In a piece on why studies across the life span of children born to mothers who’ve had COVID-19 are needed, the authors discuss the hypothesis that maternal infections during different trimesters may put the fetal organs developing at the time at risk. For example, the heart develops in the first trimester, the kidneys in the third, so infections in those periods could mean a higher risk later in life of cardiovascular disease or kidney disease, respectively.

This is just a preview of the pandemic’s reach; we’re going to continue to learn of ways COVID-19 will shape our health and our lives going forward. It’s enough to keep me in a mask, and though reasons for donning one undoubtedly vary, I’m far from alone: 31 percent of Americans are masking most or all of the time, while 26 percent are some of the time, according to a poll from late August by The Economist/YouGov.

Considering what we know so far, and with an expected rise in COVID-19 cases on the horizon, reinstating masking and implementing other control measures indoors in the coming months seems prudent. It’s a guard against infections now and may contribute to a healthier tomorrow.

In the wake of the dinosaurs’ demise, a bizarre beast that some researchers have nicknamed “ManBearPig” lived life in the fast lane. This sheep-sized mammal — which sported five-fingered hands, a bearlike face and the stocky build of a pig — gave birth to highly developed young. And those young grew up much faster than expected for an animal as massive as ManBearPig, new fossil analyses show.

That combination of long gestation and quick aging may have led to many rapid generations of bigger and bigger babies, researchers report online August 31 in Nature. Such an approach to life could help explain how some mammals took over the world after the dinosaur doomsday.
During the age of the dinosaurs, mammals “only got as large as a domestic cat, maybe, or a badger,” says Gregory Funston, a paleontologist at the Royal Ontario Museum in Toronto. But after an asteroid wiped out all nonbird dinosaurs about 66 million years ago, “we see this huge explosion in mammal diversity, where mammals start to get really big,” Funston says.

In particular, placental mammals got really big. Those are mammals whose babies develop mainly in the womb while fed by a placenta — unlike egg-laying platypuses or marsupials, whose tiny newborns do much of their development in their mother’s pouch. Today, placentals are the most diverse group of mammals and include some of the world’s largest animals such as whales, elephants and giraffes.

Paleontologists have long wondered why placentals rose to dominance. Researchers suspected that the long gestation period of this mammal lineage was an important factor. But it was unclear how long ago such long gestation evolved.

For clues, Funston and colleagues turned to what they call ManBearPig, or Pantolambda bathmodon. This ancient herbivore, which lived about 62 million years ago, was one of the first large mammals to appear after the dinosaur apocalypse. The team examined fossils from the San Juan Basin in New Mexico, including two partial skeletons and scattered teeth from several other individuals.

Daily and annual growth lines in the teeth sketched out a timeline of each animal’s life. On that timeline, chemical signatures recorded when the creature underwent major life changes. The physical stress of being born left a deposit of zinc on the tooth enamel. Barium in the enamel spiked while an animal was nursing. Other details of the teeth and bones revealed how fast P. bathmodon grew throughout its life and each animal’s age at death.
P. bathmodon stayed in the womb for about seven months, nursed for just a month or two, reached adulthood within a year and lived at most about 11 years, the team found. A female’s pregnancy was much longer than the weeks-long gestation seen in modern marsupials and platypuses, but similar to the months-long pregnancies typical of modern placentals.

“It was reproducing like the most extreme placentals do today,” Funston says, such as giraffes and wildebeests — which are on their feet within minutes of birth. P. bathmodon gave birth to “probably just one baby in each litter, and that baby had a full set of teeth already in the mouth when it was born, and that means it was probably born with fur in place and with open eyes.”
The rest of P. bathmodon’s life trajectory, however, was markedly different from modern mammals. This species weaned and reached adulthood faster than expected for an animal of its size. Most died between two and five years old, with the oldest one studied dead at age 11 — only about half of the 20-year lifespan expected for an animal as big as ManBearPig.

That “live fast, die young” lifestyle may have helped placental mammals fill giant dinos’ empty shoes, says Graham Slater, a paleobiologist at the University of Chicago who was not involved in the study. “These things are going to be kicking out new generations every year and a half,” he says, “and because they’re having that rapid generation time … evolution can just act faster.”

Longer gestation could have led to bigger babies, which grew into bigger adults that had bigger babies themselves. With many such generations passing in quick succession, Slater says, “you’re going to get bigger and bigger animals very, very quickly.”

But no single species can tell the story of how mammals took over the world (SN: 6/7/22). Future studies should investigate whether other mammals that lived around this time had a similar life cycle, Slater says.

Once is apparently enough for male dark fishing spiders. After delivering only half of their available sperm to a single female, males curl up and wait for death.

In the considerable annals of spider sex ending badly, male Dolomedes tenebrosus suffer a fate not described before, says behavioral ecologist Steven K. Schwartz of the University of Nebraska-Lincoln. Males of this widespread North American species prepare sperm for two matings but spontaneously fall into a spidery version of a coma during the first one. Their legs crumple and their bodies hang terminally motionless without any sign of the female having injured them, Schwartz and his colleagues report June 18 in Biology Letters.
Male spiders deliver sperm via a pair of boxing-glove shaped projections, or pedipalps. Male dark fishing spiders load both pedipalps with sperm, but in lab and outdoor matings, males used only one before curling into a deathlike posture. Even when protected from any female attack, males’ hearts stopped beating about two hours after mating, Schwartz says.

If females eat the inert male, his death may gain him especially abundant or healthy offspring, Schwartz speculates. Or a recently fed female may be less likely to mate with the next suitor that comes along.

As dark male fishing spiders prepare to mate, the male (smaller than the female) rocks the female’s body. When he finally inserts one of his sperm-delivery organs into one of her reproductive openings, he suddenly collapses. He no longer responds when researchers pick up or poke at him.
Credit: S.K. Schwartz

A mysterious gap in a star’s dusty shell of debris could be the signature of a young planet circling its sun at twice the distance of Pluto’s orbit. If it does exist, the far-flung planet’s birth may be hard for astronomers to explain.

“If this is a planet, it is extremely challenging for existing planet formation theories,” says Katherine Kretke, an astronomer at the Southwest Research Institute in Boulder, Colo.

Most planets are thought to begin their lives as small clumps of hot, rapidly moving dust and gas within vast disks of debris that orbit newborn stars. As a planet grows it behaves like a snow plow, scooping up some material to bulk up while flinging other material away, until it has cleared a smooth orbital path.
John Debes, an astronomer at the Space Telescope Science Institute in Baltimore, used the Hubble Space Telescope to study a disk around TW Hydrae, a 10-million-year-old star located about 176 light-years from Earth.

Hubble images revealed an unmistakable gap 12 billion kilometers from the star, 80 times farther than Earth is from the sun. “It’s very striking,” says Phil Armitage, an astrophysicist at the University of Colorado Boulder. “It looks like what you’d expect from a forming planet.”

If the planet’s existence is confirmed, astronomers have their work cut out for them explaining how it got there. Compared with particles in tighter orbits, ones near that gap are less densely packed and move much more slowly, Kretke says. As a result, it would be difficult for a potential planet to accrue enough material to clear its own orbit.

An alternative theory of planet formation posits that clumps of gas within a disk can rapidly collapse together in a process similar to the one that forms stars. That could account for the outer bulky planets recently discovered around the star HR 8799 (SN Online: 12/3/10). But Kretke says that process is capable only of building worlds more massive than Jupiter, while this potential planet would be the size of Neptune or a large Earth.

“No matter how you look at it, if there’s a planet there it’s going to change theories of how planets form,” Debes says. His team’s results appear June 14 in the Astrophysical Journal.

The next step is to find the planet, Debes says, which will be no easy task. Just identifying the gap in TW Hydrae’s disk was akin to seeing a groove in an LP record from six kilometers away; now astronomers hope to find a speck hidden within that groove.

Debes notes that the Hubble photos were taken by a nearly 20-year-old instrument; he is confident that next-generation telescopes will see the planet if it exists.

Two drugs already on the market for other purposes can halt Ebola virus in mice. The findings open the way for further testing of the drugs, clomiphene and toremifene, against the deadly virus.

Scientists screened more than 2,000 drugs against Ebola, a process that required the highest level of safety precautions because the virus is so lethal. Several drugs called selective estrogen receptor modulators showed promise, including clomiphene, marketed as Clomid and prescribed to treat infertility, and toremifene, used to treat advanced breast cancer.
In the June 19 Science Translational Medicine, researchers report that each drug prevented Ebola virus from commandeering cells in lab-dish experiments. The researchers also injected mice with one form of the Ebola virus, and nine of 10 mice given clomiphene one hour after exposure survived a month-long observation period. Five of 10 mice getting toremifene died within 10 days, but the other five survived the month. All mice given the virus without the drugs died within a week.

The drugs bottled up Ebola in a cell compartment called an endosome, which the virus uses as a way station when it invades a cell. How the drugs thwart the virus there is unclear, says study coauthor Gene Olinger, a virologist at the U.S. Army Medical Research Institute of Infectious Diseases in Frederick, Md. But the results suggest that the drugs might stop other versions of the Ebola virus and the related Marburg virus, another deadly pathogen. In theory, the drugs would be given to patients and health care workers in an outbreak, he says.

“This is an interesting study, and it’s the way one wants to go with these viruses,” says Stephan Becker, a virologist at Philipps University in Marburg, Germany. Ebola burst on the scene in 1976 with deadly outbreaks in Zaire and Sudan. But it has been a sporadic menace, racking up about 2,300 victims worldwide. Despite a stunning mortality rate, Becker says, the small numbers suggest that the best strategy against Ebola is to repurpose drugs already cleared for other uses.

While testing an established drug for a new use is faster than starting from scratch, Olinger says, approval of these drugs for Ebola might still take five to 10 years. There is currently no cure for an Ebola infection.

Stone Age people may have carried land snails on a voyage from the Pyrenees to Ireland, an examination of the snails’ DNA reveals.

Scientists have struggled to explain why Ireland shares some plant and animal species with the Iberian Peninsula, but not with the rest of Europe or the British Isles. For example, Cepaea nemoralis land snails on Ireland’s western coast and in the southern Pyrenees share unique white-lipped shells.

To find out if the two populations of white-lipped snails are related, Angus Davison and Adele Grindon of the University of Nottingham in England took DNA samples from the species all over Europe. The researchers found that snails in Ireland and the Pyrenees share a variation in one gene that distinguishes them from other European specimens.

The simplest explanation, Davison and Grindon report June 19 in PLOS ONE, is that humans journeying to Ireland about 8,000 years ago brought along escargot as a food source. “Other explanations get quite convoluted,” Davison says.

A new, deadly respiratory virus spreads easily in hospital settings, a team of investigators has found.

The virus, called the Middle East respiratory syndrome coronavirus, or MERS, reminds Johns Hopkins University epidemiologist Trish Perl of SARS. “The cases are eerily similar,” she says. Perl and two colleagues investigated a SARS outbreak in Toronto 10 years ago. This spring, they helped unravel the chain of infection of a MERS outbreak in Saudi Arabia.

By examining medical records and carefully tracking where patients and hospital personnel had been, Perl’s team discovered that dialysis clinics played an important role in the outbreak. One man, designated Patient C, infected seven others, six of whom had undergone dialysis at the same time he did, the team reports June 19 in the New England Journal of Medicine. Patient C caught MERS from patient A, who was staying in the hospital room next door. Patient A ended up transmitting the virus to three people in total.
Once a person has been infected, it takes an average of 5.2 days for symptoms to appear and 7.6 days for MERS to spread to the next victim, the researchers calculate. MERS seems to spread earlier in the infection than SARS did. It is also more deadly.

SARS infected 8,098 people and killed 9.5 percent of them, or 774 people, between November 2002 and July 2003. To date, MERS has infected 64 people worldwide, killing 38, or about 59 percent. In the Saudi outbreak, 65 percent of the 23 people confirmed to have caught the virus died; most were elderly and had other health problems.

Laser pulses beamed from a low-flying airplane into northwestern Cambodia’s dense jungles have revealed ancient remnants of extensive, carefully planned settlements of rice farmers. These settlements were part of Angkor, the capital of the region’s Khmer empire.

Angkor flourished from around 900 to 1500, but forests now obscure much of the city’s urban sprawl. Laser technology called lidar has now seen through the jungle to the ground. It shows that, starting around 1100, roadways and canals formed rectangular grids — much like modern city blocks — around Angkor’s central temples and royal palaces, say archaeologist Damian Evans of the University of Sydney and his colleagues. Similar grids containing villages, ponds and small temples spread out far into the countryside over the next few centuries, covering as many as 1,000 square kilometers, the researchers report June 17 in the Proceedings of the National Academy of Sciences.

New probes of Angkor’s landscape support an increasingly popular idea: The city grew so large that its canals and reservoirs could not provide enough water when severe droughts hit around 1400. Residents may have gradually abandoned Angkor for cities built near rivers, in the region of today’s Phnom Penh.