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SummaryThe rapid development of the global economy brings frequent artificial seismic events related to industrial activities. The identification of faults revealed by natural earthquakes, along with the temporal and spatial distribution of b-values derived from these seismic events, is influenced by their occurrence. Correcting identification of seismic events has significant influence on seismic risk assessment. In this paper, we present a tri-branch convolutional neural network (CNN) model, known as EQTypeNet, to automatically classify three classes of events (natural earthquakes, explosions, and collapses) in China, using waveform, spectrogram, and amplitude ratio features as inputs. The EQTypeNet has developed in two steps: 1. Binary classification: Mitigating data imbalance by supplementing non-natural events outside the test set area. In the classification of explosions and earthquakes, we obtained an individual station macroF1 of 0.99 and a classification accuracy of 98.7 per cent. In the classification of collapses and earthquakes, we obtained an individual station macroF1 of 0.99 and a classification accuracy of 99.5 per cent. 2. Ternary classification of natural earthquakes, explosions, and collapses: Enhancement of the model's classification in small areas by transfer learning. In the transfer learning of Shanxi and Northeast China, the F1-score of individual stations reached 0.98 and 0.97, with corresponding accuracies of 98.6 per cent and 96.8 per cent. The EQTypeNet applies to different magnitude ranges for seismic event discrimination and shows a satisfactory application performance in a large area. It will be expected to achieve higher performance in the ternary classification by further supplementing the training with suitable physical features.

SummaryIn February 2025, a strong seismic crisis occurred 35 km northeast of Santorini, an active volcano located in South Cyclades, Greece, a region of distributed extensional active faulting. The GNSS data shows an inflation of the volcano since August 2024. We model it with a magma source of 7.7 106 m3 located 3.1 km under the north-central floor of the caldera, near the inflation centre of 2011–2012. After 24 January 2025, the seismic activity, until then localised within the caldera, shifted offshore Santorini and increased with eight Mw ≥ 5 events and ground motion exceeding 5 mm at Syros at 110 km from the epicentres. The GNSS data is consistent with a model of dislocation involving a south-east dipping normal fault located between the Kolumbo submarine volcano and the Anydros islet, 18 km long, 12 km wide, with a tip at 7.5 km depth and ~3 m of slip. The ~17.5 1018 Nm corresponding seismic moment, much greater than the ~1.5 1018 Nm of the recorded earthquakes, reveals the probable occurrence of a slow-slip earthquake of equivalent magnitude 6.8. This event might have been triggered by a small dyke injected from the inferred source beneath Santorini. However, the subsidence recorded at Santorini and Anydros is incompatible with the hypothesis of a large dyke injected beneath Kolumbo-Anydros.

Melting glaciers may be silently setting the stage for more explosive and frequent volcanic eruptions in the future, according to research on six volcanoes in the Chilean Andes.

A joint project which saw two boreholes drilled in northern Singapore has revealed subsurface temperatures reaching up to 122°C at a depth of 1.76 km in Sembawang, significantly higher than earlier findings recorded in Admiralty, where 70°C was measured at a depth of 1.12 km.

A new study conducted at Reichman University's School of Sustainability presents an innovative tool to help decision-makers better understand the condition of streams and thereby advance their restoration and rehabilitation. The tool, called SESBI—the Stream Ecosystem Services and Biodiversity Index—is designed to measure what is called "stream health," meaning the degree to which a stream functions ecologically and contributes to public welfare.

Sea level on Earth has been rising and falling ever since there was water on the planet. Scientists were already able to use sediments and fossils to roughly reconstruct how sea levels changed over time steps of a million years or more.

Due to the radiative thermal conductivity of the mineral olivine, only oceanic plates over 60 million years old and subducting at more than 10 centimeters per year remain sufficiently cold to transport water into Earth's deep mantle. This was found by scientists from the University of Potsdam and from the Helmholtz Center for Geosciences (GFZ) Potsdam, together with international colleagues, by measuring the transparency of olivine under conditions in Earth's mantle for the first time. Their results are published in the journal Nature Communications.

A new autonomous underwater vehicle (AUV) imaged a previously unexplored portion of the seafloor in ultra-deep waters near the Mariana Trench. Operationalizing this technology for the first time was part of a mission led by the Ocean Exploration Cooperative Institute (OECI), based at the University of Rhode Island's Graduate School of Oceanography, with support from the National Oceanic and Atmospheric Administration (NOAA), the Bureau of Ocean Energy Management (BOEM), and the U.S. Geological Survey (USGS).

We are going back 55 million years. That was when Greenland and Norway began to drift apart, causing the Atlantic Ocean to open up. The Earth's crust between them became thinner and thinner, and enormous amounts of lava poured forth.

Peak water flows in parts of India's largest river basin have been falling by more than one-sixth every decade, according to a study published in npj Natural Hazards that highlights a similar trend across the country, impacting irrigation, domestic water, and hydropower in the world's most populous nation.

Solar Maximum 2025 is the expected peak of solar activity in Solar Cycle 25, characterized by heightened sunspots, solar flares, and coronal mass ejections. This peak is anticipated around mid to late 2025, coinciding with the sun's magnetic field flip. Such solar activity may influence Canadian climate patterns by potentially affecting weather systems.

New research from a Southampton scientist has identified the causes of changes affecting river deltas around the world—warning of an urgent need to tackle them through climate adaptation.

Earth formed about 4.6 billion years ago, during the geological eon known as the Hadean. The name "Hadean" comes from the Greek god of the underworld, reflecting the extreme heat that likely characterized the planet at the time.

Research involving the University of Liverpool has discovered a trend of increasing surface meltwater in East Antarctica. In an ambitious new study, they produced the first Antarctic-wide, high-resolution monthly dataset of surface meltwater using satellite images.

Scientists have discovered hundreds of giant sand bodies beneath the North Sea that appear to defy fundamental geological principles and could have important implications for energy and carbon storage.

Takao Doi’s dream is to go to the Moon and plant a tree. The former astronaut is inspired by ancient wooden shrines and temples in Kyoto, Japan, that have lasted more than a thousand years.

“If we can use wood in space, we might be able to have sustainable space development forever,” said Doi, a professor at Ryukoku University.

The idea of a wooden space age gained traction last year with the launch of LignoSat, the world’s first wooden satellite to reach orbit. LignoSat, developed by Doi, a group of Kyoto University scientists, and logging company Sumitomo Forestry, is a CubeSat—a type of minisatellite that is relatively inexpensive and easy to construct. LignoSat’s structure is meant to reduce its environmental impact because wood is a renewable material and creates less pollution when it burns up on reentry into Earth’s atmosphere.

“We think wooden satellites orbiting around the Earth are the future.”

LignoSat was deployed from the International Space Station (ISS) last year by the Japan Aerospace Exploration Agency (JAXA) and stayed in space for 116 days.

Doi and his colleagues are using what they learned to develop LignoSat-2, which they expect to launch in 2028. And they’re not alone—at least one other group is also developing a wooden satellite.

“We think wooden satellites orbiting around the Earth are the future,” Doi said.

Raphaela Günther, an aerospace engineering Ph.D. student at Technische Universität Dresden in Germany who is not involved in the LignoSat project, said she considers the work from the Kyoto University team to be a “small breakthrough” in renewable space materials research.

Lessons Learned

The first LignoSat was a 10-centimeter cube made of magnolia wood panels assembled with traditional wooden joinery. An aluminum frame reinforced the structure.

LignoSat used a traditional joinery method called the blind miter dovetail joint. Credit: Kyoto University

The LignoSat mission had five goals: to measure strain on the wooden structure, to measure temperature inside the satellite, to demonstrate how permeable wood is to magnetic fields in space, to analyze the effects of space radiation on wood, and to establish two-way communication with scientists on the ground.

After the satellite was deployed from the ISS on 9 December 2024, though, scientists in Kyoto weren’t able to communicate with it.

Orbital data from the U.S. Department of Defense show the satellite stayed in one piece during its time in space, proving wooden satellites can work, Doi said. But without the ability to communicate with the satellite, the other four missions weren’t able to be completed, either.

“Unfortunately, we didn’t receive any of the information we wanted to know about,” Doi said.

An analysis indicated that the loss of communication could have been caused by two failures: First, any or all of the three switches needed to activate the satellite system and deploy its antenna may not have turned on, and second, the computer program used in the system may not have started up as expected, Doi said. “We are still analyzing what happened, but we now have two reasons to further investigate.”

Despite the lack of communication, Doi recognized two achievements in the LignoSat mission. First, it demonstrated that a wooden satellite can exist in orbit without falling apart. Second, it streamlined the review process for wooden spacecraft. NASA must complete a safety review of all satellites that head to the ISS, he explained, and now that such a review was completed for LignoSat, reviews for subsequent wooden satellites will be simpler.

LignoSat-2 will have both an external antenna and an internal antenna and will be twice the size of the first LignoSat. Credit: Kyoto University

The Kyoto University team plans to build LignoSat-2 to be twice the size of LignoSat, with two communication systems (one inside the structure and another attached to its surface). Installing the antenna inside the satellite body reduces the drag of the structure as it orbits Earth, Doi said.

“Even if the antenna is not deployed, which might have been the cause of LignoSat 1’s communication problems, we may be able to use this second communication system to communicate with [LignoSat-2],” Doi said.

Finnish space technology company Arctic Astronautics is also thinking about wood in space. In 2021, they and Finnish company UPM Plywood developed the WISA Woodsat, a 10-centimeter birch plywood CubeSat. The satellite contains a suite of sensors meant to gather information about how outer space affects wooden spacecraft. It has a deployable camera, a “selfie stick” meant to take photos of itself in space and allow the team on the ground to monitor it visually.

The WISA Woodsat contains a suite of sensors meant to measure how outer space will affect its materials. It also has a selfie stick. Credit: Arctic Astronautics/Flickr, CC BY 2.0

“There is a niche for these kinds of satellites, and the basic research is extremely interesting,” said Jari Mäkinen, cofounder of Arctic Astronautics and initiator of the WISA Woodsat project. “It’s totally possible that when we see these satellites flying, we realize important information [about how plywood acts in space].”

The WISA Woodsat itself is nearly ready for launch, Mäkinen said, but Arctic Astronautics still needs permitting from Finnish space authorities to proceed. He’s hopeful the launch will take place next year. “We will fly as soon as possible,” he said.

A Sustainable Space Industry

For Doi, the wooden CubeSats are just the beginning. “Let’s create a space timber industry” reads the translation of the bio of the research team’s X (formerly Twitter) account. Doi said he imagines a future where wood overtakes aluminum as the primary material for satellites.

Wood is cheaper, easier to use, and lighter than conventional spacecraft materials. Its use as a potential material could both push the space industry toward using more wood and make space development more accessible to countries with fewer resources, Günther said.

A wooden space age could shrink the environmental footprint of the space industry, too. When aluminum satellites fall back into Earth’s atmosphere, they burn, creating aluminum oxide particles. These particles, sometimes smaller than 1 micrometer, may destroy ozone, disrupt atmospheric processes, and even alter Earth’s magnetic field, some scientists suggest. When wood burns, it generates only carbon dioxide, biodegradable ash, and water vapor.

And though scientists don’t fully understand all the possible ways that particles from decomposing metal or wooden spacecraft interact with the upper atmosphere, the decomposition products of wood are easier to assess because they are already major drivers of atmospheric processes, Günther said.

“It’s not a question if we do or if we don’t” begin to use more sustainable spacecraft materials, she said. “I think we have to.”

With a few hundred tracked objects returning to Earth each year, reentering metal spacecraft are not currently a major environmental problem. But as the space industry quickly grows, it’s crucial to look for more ecofriendly materials, Doi said. Replacing even a small portion of parts on future satellites with wood could significantly reduce pollution, Mäkinen said.

Wood poses challenges for spacecraft engineers, too. Because it’s grown naturally, it has defects and doesn’t behave homogeneously, meaning “the behavior of the material in three different directions is not the same,” Günther said. Her own research is working to create spacecraft materials made of wood fibers and binding material that behave more consistently.

“It’s not a question if we do or if we don’t” begin to use more sustainable spacecraft materials, she said. “I think we have to.”

Mäkinen agreed that wood provides many environmental and technical advantages but said large space companies have likely invested enough in their current manufacturing processes that a large-scale shift to wood as a satellite material is unlikely without pressure from space authorities. “I hope that I’m wrong,” he said.

—Grace van Deelen (@gvd.bsky.social), Staff Writer

Citation: van Deelen, G. (2025), A new satellite material comes out of the woodwork, Eos, 106, https://doi.org/10.1029/2025EO250241. Published on 7 July 2025. Text © 2025. AGU. CC BY-NC-ND 3.0
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Some species of fig trees store calcium carbonate in their trunks—essentially turning themselves (partially) into stone, new research has found. The team of Kenyan, U.S., Austrian, and Swiss scientists found that the trees could draw carbon dioxide (CO2) from the atmosphere and store it as calcium carbonate 'rocks' in the surrounding soil.

Author(s): Koji Kikuchi and Hiroshi Akatsuka

Nonequilibrium plasma has attracted significant attention owing to its excellent physical properties, which are highly valued by the industrial community. However, determining the electron temperature in nonequilibrium plasmas proves challenging unless the energy distribution function is approximate…

[Phys. Rev. E 112, 015201] Published Mon Jul 07, 2025

Author(s): B. Disson, N. Bonifaci, O. Lesaint, C. Poulain, R. Dussart, and S. Iseni

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[Phys. Rev. E 112, 015202] Published Mon Jul 07, 2025

SummarySeasonal variations in Nepalese seismicity have been reported with varying degrees of confidence. We re-investigate these claims by analysing 20 years of Nepalese seismicity before the 2015 Gorkha earthquake, as detected by the Nepalese national network, and focusing on earthquakes located along the eastern and central sections of the Nepalese Main Himalayan Thrust. Using several declustering techniques, we find no statistically robust evidence of seasonal seismicity in the studied record, regardless of magnitude threshold above completeness. This suggests that previously reported seasonality may be restricted to the western section of the Nepalese orogeny, may be an artefact, or may indicate that nucleation times of earthquakes are longer than the year. We also investigate potential annual variations in the Gutenberg-Richter b-value, given its recent observed modulation by transient stressing. Additionally, we use large-scale mass redistribution estimated from the monthly gravity field retrieved from the Gravity Recovery And Climate Experiment and Follow-On (GRACE/-FO) missions, to resolve stress variations at depth induced by transient surface loads. We find that the mean annual b-value peaks when seasonal Coulomb stress rates reach their minimum value at the height of the summer rainy season. When considering the combined effect of tectonic and seasonal loading, this corresponds to a recurring period of stress reversal, when Coulomb stress momentarily decreases. This suggests that periodic clamping of the Main Himalayan Thrust reduces the likelihood of earthquakes growing to larger magnitudes in accordance with hierarchical rupture models. The susceptibility of b-value to stress variations of roughly 0.1 points.kPa−1 is consistent with recent estimates of b-value sensitivity to transient loading, although it remains high when compared to the stress-dependency associated with both static differential stress, and with long-term evolution during the seismic cycle. This discrepancy points to the large impact of stress transients on the dynamics of seismic rupture.