Climate change amped up the rains that pounded southeastern Africa and killed hundreds of people during two powerful storms in early 2022.
But a dearth of regional data made it difficult to pinpoint just how large of a role climate change played, scientists said April 11 at a news conference.
The findings were described in a study, published online April 11, by a consortium of climate scientists and disaster experts called the World Weather Attribution network.
A series of tropical storms and heavy rain events battered southeast Africa in quick succession from January through March. For this study, the researchers focused on two events: Tropical Storm Ana, which led to flooding in northern Madagascar, Malawi and Mozambique in January and killed at least 70 people; and Cyclone Batsirai, which inundated southern Madagascar in February and caused hundreds more deaths. To search for the fingerprints of climate change, the team first selected a three-day period of heavy rain for each storm. Then the researchers tried to amass observational data from the region to reconstruct historical daily rainfall records from 1981 to 2022.
Only four weather stations, all in Mozambique, had consistent, high-quality data spanning those decades. But, using the data on hand, the team was able to construct simulations for the region that represented climate with and without human-caused greenhouse gas emissions.
The aggregate of those simulations revealed that climate change did play a role in intensifying the rains, Izidine Pinto, a climatologist at the University of Cape Town in South Africa, said at the news event. But with insufficient historical rainfall data, the team “could not quantify the precise contribution” of climate change, Pinto said.
The study highlights how information on extreme weather events “is very much biased toward the Global North … [whereas] there are big gaps in the Global South,” said climate scientist Friedericke Otto of Imperial College London.
That’s an issue also highlighted by the Intergovernmental Panel on Climate Change. The IPCC cites insufficient Southern Hemisphere data as a barrier to assessing the likelihood of increasing frequency and intensity of tropical cyclones beyond the North Atlantic Ocean (SN: 8/9/21).
Europa’s frozen surface is covered with distinctive pairs of ridges that straddle troughs of ice. These double ridges are the most common features on the Jovian moon. But scientists don’t yet have a clear idea of how the oddities are created.
Now, an analysis of images of a similar set of ridges on Greenland’s ice sheet suggests that relatively shallow water within Europa’s thick icy shell may be behind their formation, scientists report April 19 in Nature Communications. If so, that could mean that Europa has much more shallow liquid water than scientists have thought.
Europa’s double ridge systems, which can stretch for hundreds of kilometers, include some of the oldest features on the moon, says Riley Culberg, a geophysicist at Stanford University. Some researchers have proposed that the flexing of the moon’s icy shell due to tides in an underlying liquid water ocean plays a role in the ridges’ formation (SN: 8/6/20). Yet others have suggested that water erupted from deep within the icy moon — a process known as cryovolcanism — to create the ridges. Without a closer look, though, it’s been hard to nail down a more solid explanation. But Culberg and his colleagues seem to have caught a break. Data gathered by NASA’s ICESat-2 satellite in March 2016 showed an 800-meter-long double ridge system in northwestern Greenland. So the team looked back at other images to see when the ridge system first appeared and to assess how it grew. The researchers found that the ridges appeared in images taken as early as July 2013 and are still there today.
When the ridges — which lie on either side of a trough, like those on Europa — reached full size, they averaged only 2.1 meters high. That’s a lot smaller than the ridges on Europa, which can rise 300 meters or more from the moon’s surface. But surface gravity is much lower on Europa, so ridges can grow much larger there, Culberg says. When he and his colleagues considered the difference between Earth’s gravity and Europa’s in their calculations, they found that the proportions of the two ridge systems are consistent. Scientists will never get a perfect analog of Europa on Earth, but the ridges in Greenland “look just like the Europan ridges,” says Laurent Montési, a geophysicist at the University of Maryland in College Park who was not involved in the study.
Data from airplane-mounted radar gathered in March 2016 show that a water-filled layer of snow about 10 to 15 meters below the surface underlies the Greenland ridges, Culberg and his team say. That water comes from surface meltwater that sinks into and is then collected in the buried snow, which in turn sits atop an impermeable layer of ice.
Repeated freeze-thaw cycles of water in that layer of snow would squeeze water toward the surface, the researchers propose. In the first phase of refreezing, a solid plug of ice forms. Then, as more water freezes, it expands and is forced toward the surface on either side of that plug, pushing material upward and producing the double ridges at the surface.
On Europa, the process works the same way, the researchers suggest. But because there is no known meltwater or precipitation at the moon’s surface, near-surface water there probably would have to come from the ocean thought to be trapped beneath the moon’s icy shell (5/14/18). Once that water rose toward the surface through cracks, it could pool in thick layers of ice shattered by tidal flexing or the impacts of meteorites.
“There’s a general consensus that these ridges grow from cracks in the ice,” says William McKinnon, a planetary scientist at Washington University in Saint Louis who was not involved in the study. “But how do they do it is the question.”
The answer to that question may not be long in coming, McKinnon says. NASA’s Europa Clipper mission is scheduled to launch in late 2024. If all goes well, the orbiter will arrive at Jupiter in April 2030. “If there’s anything like what has happened in Greenland going on at Europa, we’ll be able to see it,” he says.
Researchers will also be interested to see if the mission can ascertain what sort of materials might have been brought to Europa’s surface from the ocean deep below, because the moon is considered to be one of the best places in the solar system to look for extraterrestrial life (SN: 4/8/20).
Inside Egypt’s Great Pyramid of Giza lies a mysterious cavity, its void unseen by any living human, its surface untouched by modern hands. But luckily, scientists are no longer limited by human senses.
To feel out the contours of the pyramid’s unexplored interior, scientists followed the paths of tiny subatomic particles called muons. Those particles, born high in Earth’s atmosphere, hurtled toward the surface and burrowed through the pyramid. Some of the particles imprinted hints of what they encountered on sensitive detectors in and around the pyramid. The particles’ paths revealed the surprising presence of the hidden chamber, announced in 2017 (SN: 11/25/17, p. 6).
That stunning discovery sparked plans among physicists to use muons to explore other archaeological structures. And some researchers are using the technique, called muography, to map out volcanoes’ plumbing. “You can see inside the volcano, really,” says geophysicist Giovanni Leone of Universidad de Atacama in Copiapó, Chile. That internal view could give scientists more information about how and when a volcano is likely to erupt. Muons are everywhere on Earth’s surface. They’re produced when high-energy particles from space, known as cosmic rays, crash into Earth’s atmosphere. Muons continuously shower down through the atmosphere at various angles. When they reach Earth’s surface, the particles tickle the insides of large structures like pyramids. They penetrate smaller stuff too: Your thumbnail is pierced by a muon about once a minute. Measuring how many of the particles are absorbed as they pass through a structure can reveal the density of an object, and expose any hidden gaps within.
The technique is reminiscent of taking an enormous X-ray image, says Mariaelena D’Errico, a particle physicist at the National Institute for Nuclear Physics in Naples, Italy, who studies Mount Vesuvius with muons. But “instead of X-rays, we use … a natural source of particles,” the Earth’s very own, never-ending supply of muons.
Physicists have typically studied cosmic rays to better understand the universe from whence they came. But muography turns this tradition on its head, using these cosmic particles to learn more about previously unknowable parts of our world. For the most part, says particle physicist Hiroyuki Tanaka of the University of Tokyo, “particles arriving from the universe have not been applied to our regular lives.” Tanaka and others are trying to change that. No particle like it Awkward cousins of electrons, muons may seem like an unnecessary oddity of physics. When the particle’s identity was first revealed, physicists wondered why the strange particle existed at all. While electrons play a crucial role in atoms, the heavier muons serve no such purpose.
But muons turn out to be ideal for making images of the interiors of large objects. A muon’s mass is about 207 times as large as an electron’s. That extra bulk means muons can traverse hundreds of meters of rock or more. The difference between an electron and a muon passing through matter is like the difference between a bullet and a cannonball, says particle physicist Cristina Cârloganu. A wall may stop a bullet, while a cannonball passes through.
Muons are plentiful, so there’s no need to create artificial beams of radiation, as required for taking X-ray images of broken bones in the doctor’s office, for example. Muons “are for free,” says Cârloganu, of CNRS and the National Institute of Nuclear and Particle Physics in Aubière, France. Another crucial upside of muons: “They’re also very easy to detect,” says nuclear physicist Richard Kouzes of the Pacific Northwest National Laboratory in Richland, Wash. A simple detector made of strips of plastic and light sensors will do the trick. Other muon detectors require little more than a specialized version of photographic film. There’s no other particle like it, Kouzes says.
Muons have a negative electric charge, like an electron. Their antiparticles, antimuons, which also shower down on Earth, have a positive charge. Muon detectors capture tracks of both negatively and positively charged varieties. When these particles pass through material, they lose energy in various ways, for example, by colliding with electrons and knocking them loose from their atoms.
With that energy loss, muons slow down, sometimes enough to stop. The denser the material, the fewer muons will make it through to a detector placed underneath or to the side of the material. So large, dense objects such as volcanoes or pyramids cast a muon shadow. And any gaps within those structures will appear as bright spots within that shadow, because more muons can slip through. Interpreting such dappled shadows can open a vista into hidden worlds.
Probing pyramids Muography proved itself in a pyramid. One of the first uses of the technique was in the 1960s, when physicist Luis Alvarez and colleagues looked for hidden chambers in Khafre’s pyramid in Giza, a slightly smaller neighbor of the Great Pyramid. Detectors found no hint of unexpected rooms, but proved that the technique worked.
Still, the idea took time to take off, because muon detectors of the era tended to be bulky and worked best in well-controlled laboratory conditions. To spot the muons, Alvarez’s team used detectors called spark chambers. Spark chambers are filled with gas and metal plates under high voltage, so that charged particles passing through create trails of sparks.
Now, thanks to advances in particle physics technologies, spark chambers have largely been replaced. “We can make very compact, very sturdy detectors,” says nuclear physicist Edmundo Garcia-Solis of Chicago State University. Those detectors can be designed to work outside a carefully controlled lab.
One type of resilient detector is built with plastic containing a chemical called scintillator, which releases light when a muon or other charged particle passes through (SN Online: 8/5/21). The light is then captured and measured by electronics. Later this year, physicists will use these detectors to take another look at Khafre’s pyramid, Kouzes and colleagues reported February 23 in the Journal for Advanced Instrumentation in Science. Compact enough to fit within two large carrying cases, the detector “can be carried into the pyramid and then operated with a laptop and that’s all,” Kouzes says. A different but particularly low-maintenance type of detector, called a nuclear emulsion film, was crucial to uncovering the Great Pyramid’s hidden void in 2017. Nuclear emulsions record particle tracks in a special type of photographic film. The detectors are left in place for a period of time, then brought back to a lab for analysis of the tracks imprinted in them.
Particle physicist Kunihiro Morishima of Nagoya University in Japan helped discover the secret chamber through work on an international project called ScanPyramids. “Nuclear emulsions are lightweight, compact and do not require a power supply,” he explains. That meant that multiple detectors could be placed in prime viewing locations in one of the pyramid’s rooms, the Queen’s Chamber, and a small niche next to it. The detectors’ measurements were supplemented with plastic scintillator detectors inside the Queen’s Chamber, and gas-based detectors outside the pyramid. Since the discovery of the void, Morishima and colleagues have been taking additional measurements to better sketch out its properties. The team placed emulsion detectors in 20 locations in the pyramid, as well as gas detectors in several different spots. Using their new array of instruments, the researchers determined that the void is over 40 meters long. Its purpose is still unknown.
A more extensive survey of the Great Pyramid, placing much larger detectors outside the pyramid, is being planned by another team of researchers. The detectors will be periodically moved to measure muons from multiple angles, the team reported March 6 in the Journal for Advanced Instrumentation in Science. The result, says coauthor and particle physicist Alan Bross of Fermilab in Batavia, Ill., will offer a 3-D view of what’s inside (SN: 12/18/21 & 1/1/22, p. 44).
Pyramids in other parts of the world are also getting closer scrutiny. Garcia-Solis and colleagues are now planning muography of the Maya pyramid known as El Castillo at Chichén Itzá in Mexico. Morishima and colleagues, as well, are planning work on Maya pyramids.
Scientists hope such studies might reveal new chambers, or features not visible with other techniques for peering inside of objects. Ultrasound, ground-penetrating radar or X-rays, for example, can only penetrate a short distance from the surface, Bross explains. Muons, on the other hand, give an in-depth picture. For studying pyramids, Bross says, “muons really are ideal.”
Peering inside a volcano Vesuvius is a known menace in Naples and the surrounding municipalities that snuggle up against the volcano’s flanks. Infamous for destroying the ancient city of Pompeii in A.D. 79, the volcano has been quiescent since 1944, when a major eruption destroyed several nearby villages (SN: 2/29/20, p. 5). But if it erupted, it would endanger the lives of roughly 600,000 people who live closest to it, and many others in the vicinity.
“Vesuvius always scared me,” D’Errico says. “I was born and I live under this volcano.” Now, as part of the Muon Radiography of Vesuvius experiment, or MURAVES, she seeks to better understand the volcano and its dangers. Using muon detectors 1.5 kilometers from the volcano’s crater, the team is mapping out muon densities — and thus rock densities — at the top of Vesuvius’ cone. In a paper posted February 24 at arXiv.org, the researchers presented preliminary hints of density differences between the volcano’s northwestern and southeastern halves. MURAVES is still collecting data; future observations should help scientists understand finer details of the volcano’s internal structure, which is thought to be layered due to repeated eruptions.
Information about a volcano’s structure can help scientists predict what hazards to expect in an eventual eruption, such as where landslides might occur. And that could help scientists know what steps to take to reduce risks to people living nearby, says Cârloganu, who studied the dormant volcano Puy de Dôme near Clermont-Ferrand, France, with muography and is now working to image the aptly named island of Vulcano in Italy.
When Mount St. Helens in Washington erupted in 1980, for example, an entire flank of the volcano collapsed. The disaster killed 57 people and caused widespread damage. Knowing where a volcano’s structural weaknesses lie could help scientists better predict how an eruption might play out, and what areas sit inside the danger zone, Cârloganu says.
Cârloganu thinks muons will be useful for pointing out structural weaknesses, but not for giving a warning when the volcano is going to blow. Other researchers are more optimistic about muons’ capability for giving timely forewarnings.
Muography is ripe for inclusion in volcano early-warning systems, Leone, Tanaka and colleagues wrote last November in Proceedings of the Royal Society A. But more work needs to be done to integrate muography with other established methods that help warn of an upcoming eruption, Leone says. These methods include seismic measurements, as well as observations of ground deformation and volcanic gas emissions.
Tanaka and colleagues are studying Sakurajima, one of the most active volcanoes in the world, near Kagoshima, Japan. One of the volcano’s craters, the Showa crater, erupted frequently until 2017 when the activity abruptly shifted to another crater, Minamidake. Comparing muography data taken before and after this shift revealed that a new, dense region had formed below the Showa crater, Tanaka and colleagues reported in 2019 in Geophysical Research Letters. That hints at the reason Showa’s eruptions stopped: It was clogged with a dense plug of solidified magma, Tanaka says. These results suggest that scientists can use muography to help predict volcanic eruptions, Tanaka says. In fact, using deep learning techniques on the muography data from Sakurajima, Tanaka and colleagues reported in Scientific Reports in 2020 that they were able to predict whether the volcano would erupt the next day, by analyzing the previous week’s data. The technique correctly predicted eruption days of the volcano more than 72 percent of the time, and correctly predicted non-eruption days more than 85 percent of the time.
Just as the discovery of X-rays unveiled a whole new way of seeing the world, harnessing muons could change our perspective on our surroundings. Attitudes toward a particle once thought to be unnecessary — unwanted and unloved by physicists — have been transformed. One day, perhaps, muons could save lives.
From cylindrical nanotubes to the hollow spheres known as buckyballs, carbon is famous for forming tiny, complex nanostructures (SN: 8/15/19). Now, scientists have added a new geometry to the list: a twisted strip called a Möbius carbon nanobelt.
Möbius strips are twisted bands that are famous in mathematics for their weird properties. A rubber band, for example, has an inside and an outside. But if you cut the rubber band crosswise, twist one end and glue it back together, you get a Möbius strip, which has only one face (SN: 7/24/07).
In 2017, researchers created carbon nanobelts, thin loops of carbon that are like tiny slices of a carbon nanotube. That feat suggested it might be possible to create a nanobelt with a twist, a Möbius carbon nanobelt. To make the itsy-bitsy twisty carbon, some of the same researchers stitched together individual smaller molecules using a series of 14 chemical reactions, chemist Yasutomo Segawa of the Institute for Molecular Science in Okazaki, Japan, and colleagues report May 19 in Nature Synthesis.
While carbon nanotubes can be used to make new types of computer chips and added to textiles to create fabric with unusual properties, scientists don’t yet know of any practical applications for the twisty nanobelts (SN: 8/28/19; SN: 2/8/19). But, Segawa says, the work improves scientists’ ability to make tiny carbon structures, especially complicated ones.