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Publication date: 15 September 2025

Source: Advances in Space Research, Volume 76, Issue 6

Author(s): Barun Raychaudhuri, Surajit Mandal, Ayanava Das

Publication date: 15 September 2025

Source: Advances in Space Research, Volume 76, Issue 6

Author(s): Haiyang Li, Jing Wang, Shuguang Wu, Yawei Wang, Yehemin Gao, Guigen Nie

Publication date: 15 September 2025

Source: Advances in Space Research, Volume 76, Issue 6

Author(s): Bikash Dutta, Sakir Laskar, Prionti Kundu, Sourajit Mal, Debasish Sing, Manas Das

Publication date: 15 September 2025

Source: Advances in Space Research, Volume 76, Issue 6

Author(s): Zhenqiang Tao, Zengke Li, Guoqing Wang, Zhaobing Chen, Wangqi Chen, Zhisheng Zhao

Publication date: 15 September 2025

Source: Advances in Space Research, Volume 76, Issue 6

Author(s): I. Wayan Gede Astawa Karang, Rinaldy Terra Pratama

Permafrost, ground frozen for at least two years underlying the cold Arctic and alpine regions of the Northern Hemisphere, covers about 17% of the global land surface and stores an estimated one-third of the world's soil organic carbon.

A research team led by Prof. Wu Qingbai from the Northwest Institute of Eco-Environment and Resources (NIEER) of the Chinese Academy of Sciences has identified important non-temperature environmental factors contributing to permafrost degradation on the Qinghai-Tibet Plateau.

The 2,175-mile system of interconnected, man-made canals crisscrossing Florida, from Orlando to the Keys, has a particularly important role when a hurricane happens to be pinwheeling toward the peninsula: Flood control.

One of the biggest obstacles on the road to a low-carbon energy future is caused by the rare-earth element lithium, a critical component for the batteries that can store the abundant and sustainable energy from renewable sources.

Throughout the planet, there are only a handful of known tektite strewn fields, which are large swaths of land where natural glass (tektite) was strewn about after forming from terrestrial material and being ejected from a meteorite impact. The tektite glass can be ejected extremely long distances, placing strewn fields far from their origins.

Scientists may be a step closer to solving the mystery of Siberia's giant exploding craters. First spotted in the Yamal and Gydan peninsulas of Western Siberia in 2012, these massive holes, known as giant gas emission craters (GECs) can be up to 164 feet deep. They seem to appear randomly in the permafrost and are formed when powerful explosions blast soil and ice hundreds of feet into the air.

Astronomers have recently found that roughly a third of planet-forming disks around young Sun-like stars are tilted relative to the direction that their star spins.

“All young stars start out with a disk. But the relative orientation between the disk and the star’s spin axis, little was known about that,” explained lead researcher Lauren Biddle, a planetary scientist at the University of Texas at Austin.

This discovery, published in Nature, could help answer the long-standing question of how planets come to orbit their stars at wonky angles: Maybe they were born that way.

Skewed from the Start

There’s a universal truth that when a new star collapses out of a cloud of gas, angular momentum must be conserved. That means that as the nebulous star shrinks in size, it also rotates faster, like when a spinning ice skater draws their arms in and speeds up. The surrounding leftover gas and dust flatten out into a disk that spins in the same direction as the star, and that disk may eventually form planets that spin and orbit in that same direction.

But the universe is rarely so neat and tidy.

Of the thousands of known exoplanets, dozens of them orbit at wonky angles relative to their star’s spin axis. In our own solar system, the plane in which the eight planets orbit is tilted by about 6º from the Sun’s spin axis. Astronomers have theorized that some of these misalignments, or obliquities, result from dynamical events that take place after a planetary system has already formed: A star passes by and disturbs the orbits, or a major collision knocks a planet off course.

Some of those misalignments, however, are baked in from the start. Previous studies have attempted to observe young star systems and their planet-forming disks to see whether those disks start out tilted or aligned. But those studies were limited by the fact that not many protoplanetary disks had yet been discovered, and many of those that were known were part of binary star systems, Biddle explained. Although those studies found some tilted disks, the gravity from the binary star, rather than an intrinsic misalignment, may have been the culprit.

“If systems begin with primordially tilted orbits, then there is no need to invoke other mechanisms—many of which would destabilize neighboring planets—within those systems,” said Malena Rice, a planetary astrophysicist at Yale University in New Haven, Conn. “By understanding the range of primordial tilts and comparing that distribution with more evolved systems, we can piece together the evolutionary sequences of different classes of planetary systems.” Rice was not involved with this study.

“The one-third rate of misalignment stands independent of everything else.”

Biddle and her colleagues compiled a new sample of young star systems by combining observations of protoplanetary disks from the Atacama Large Millimeter/submillimeter Array (ALMA) and measurements of stars’ spin from the Transiting Exoplanet Survey Satellite (TESS) and retired K2 mission. Biddle explained that because ALMA, TESS, and K2 have released such large datasets, her team could curate their sample to look only at Sun-like stars that did not have any binary companions.

They found that 16 of the 49 stars in their sample (about a third) had protoplanetary disks with obliquities of at least 10°, the lower limit of what they could measure. The remaining two thirds of the systems showed no significant evidence of misalignment. This rate of high-obliquity disks is consistent with past studies but more than doubles the number of young, single, Sun-like stars for which astronomers know the degree of disk misalignment.

The 16 stars that host tilted disks did not share any obvious characteristics like mass, temperature, and size, and the disks themselves also had different sizes, masses, and structures.

“We didn’t find any correlation there,” Biddle said. “At this point, independent of other system parameters, the one-third rate of misalignment stands independent of everything else.”

Oblique Across Space and Time

Past studies have suggested that moderate disk obliquities might rise from imperfections in the nebulous cloud that formed the star system: An odd clump in the right spot might create turbulence that grows stronger as the cloud collapses, or the clump might fall onto the disk late and tip it off its axis.

“Moderate misalignments of a few tens of degrees can be produced naturally by either turbulence in the natal molecular cloud, late-stage disk accretion, or some combination of the two,” Rice said.

However, that doesn’t necessarily mean that every misaligned exoplanet, or even a third of them, started out that way.

“It would be great to take a crack at mapping stellar obliquities across space and time.”

“A misalignment between a planet’s orbital plane and its host star’s spin axis can originate in two broad phases: during the star and planet formation stage…[and] later, during the system’s main sequence lifetime,” explained Simon Albrecht, an astronomer at Aarhus University in Denmark who was not involved with this research. “If we can determine the fraction of systems that are already misaligned right after birth, that helps us distinguish between these two broad possibilities.”

Determining how much of a system’s tilt comes early or late and whether that tilt changes over a planetary system’s lifetime will require observing a lot more misaligned planetary systems at all stages of evolution, Biddle said. She added that the upcoming data release from the now-retired Gaia mission will be key to answering both of those questions.

“It would be great to take a crack at mapping stellar obliquities across space and time,” Biddle said. “Being able to fill in that time parameter space will help quantify how important dynamics is for generating that final [obliquity] distribution that we observe in planetary systems.”

—Kimberly M. S. Cartier (@astrokimcartier.bsky.social), Staff Writer

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Citation: Cartier, K. M. S. (2025), Tilted planet system? Maybe it was born that way, Eos, 106, https://doi.org/10.1029/2025EO250338. Published on 17 September 2025. Text © 2025. AGU. CC BY-NC-ND 3.0
Except where otherwise noted, images are subject to copyright. Any reuse without express permission from the copyright owner is prohibited.

With CO2 emissions continuing unabated, an increasing number of policymakers, scientists and environmentalists are considering geoengineering to avert a climate catastrophe. Such interventions could influence everything from rainfall to global food supplies, making the stakes enormous.

Editors’ Highlights are summaries of recent papers by AGU’s journal editors. Source: AGU Advances

To help project Earth’s future climate, it is critical to understand how the capacity of ecosystems to take up and store carbon is changing as atmospheric carbon dioxide levels rise and climate change intensifies.

Bilir et al. [2025] integrate satellite data with a model of terrestrial carbon cycling to parse regionally-specific influences of CO2 and climate on carbon storage in living and dead plant material, and the associated residence time of carbon in those pools.

For the specified regions, changes in total carbon storage (left Y axis, solid bars) and percent change in mean residence time of carbon (right Y axis, hatched bars) that can be attributed to atmospheric CO2 (top panel), climate trends (middle panel), and the combined, interacting effects of CO2 and climate (bottom panel). Credit: Bilir et al. [2025], Figure 6

Their work helps untangle the mechanisms driving what they and others have observed: that CO2 increases carbon storage more than climate effects decrease it. They find greater carbon storage in living plants globally and a shift in dead carbon storage from mid- and high latitudes to the tropics. They also demonstrate a reduction in mean carbon residence times across all latitudes. The shift in carbon storage from dead to live pools underscores the sensitivity of terrestrially-mediated carbon cycling and residence times to living plant carbon uptake and storage potentials.

These efforts help us understand, at a global scale, how rising atmospheric CO2 and climate change interact to prompt a latitudinally-specific reorganization of our planet’s terrestrial carbon cycling, and thus its climate.

Citation: Bilir, T. E., Bloom, A. A., Konings, A. G., Liu, J., Parazoo, N. C., Quetin, G. R., et al. (2025). Satellite-constrained reanalysis reveals CO2 versus climate process compensation across the global land carbon sink. AGU Advances, 6, e2025AV001689. https://doi.org/10.1029/2025AV001689

—Sharon Billings, Editor, AGU Advances

Text © 2025. The authors. CC BY-NC-ND 3.0
Except where otherwise noted, images are subject to copyright. Any reuse without express permission from the copyright owner is prohibited.

Climate change caused 16,469 deaths in European cities this summer, new research estimates.

This summer was the fourth hottest in European history, and its effects on the continent’s population have been widely reported. Spain experienced its most intense heat wave in history in August 2025. Türkiye saw its highest recorded temperature ever (50.5°C, or 122.9°F). Finland saw an “unprecedented” three straight weeks of 30°C heat.

A new, rapid-analysis study by researchers at Imperial College London (ICL) and the London School of Hygiene & Tropical Medicine estimated that 24,400 people across 854 European cities and urban centers died from heat-related causes between June and August 2025. Using climate models and a comparison of this figure with how many heat-related deaths would have occurred in a 1.3°C cooler world, the researchers estimated that climate change was responsible for 68% of these deaths.

“These numbers represent real people who have lost their lives in the last months due to extreme heat.”

“In other words, it could have tripled the death toll,” said Garyfallos Konstantinoudis, a biostatistician at ICL’s Grantham Institute – Climate Change and the Environment.

Though the planet has warmed about 1.3°C overall since preindustrial times, Europe is warming more quickly than the rest of the planet, meaning that temperatures on the continent this summer were about 1.5°C to 2.9°C warmer than they would have been without anthropogenic warming.

In a Tuesday press conference, the researchers explained that their estimate of 16,649 climate-related deaths is likely conservative, in part because climate models are known to underestimate warming in Europe. In addition, their estimate includes only deaths in urban centers with populations above 50,000 people—areas that represent only about 30% of Europe’s population. They focused on these urban areas because these locations had greater data availability, but that means the estimate is just a snapshot.

“These numbers represent real people who have lost their lives in the last months due to extreme heat,” said Friederike Otto, a climatologist at ICL’s Centre for Environmental Policy. “Many of these would not have died if it wasn’t for climate change. And if we continue on the path that we are on now, continue burning fossil fuels, these deaths will only increase.”

The Hidden Costs of Heat

The study also notes that northern Europe experienced a higher proportion of heat-related deaths than southern Europe, despite southern Europe enduring higher heat (some cities in the region have warmed by up to 3.6°C) and more excess mortality overall. The reason is that prior to climate change, heat in northern Europe rarely reached levels that affected human health at all. Now, explained Konstantinoudis, “almost all of the heat-related deaths in northern Europe…are due to climate change.”

“Reducing fossil fuel use is one of the most important public health interventions of our time.”

Courtney Howard, vice-chair of the Global Climate and Health Alliance and an emergency physician in Canada’s Yellowknives Dene Territory, who was not involved in the study, noted that extreme heat can raise the risk of deadly heart attacks and strokes because high heat causes the heart to work harder. It can also fatally worsen respiratory conditions such as asthma because ozone pollution tends to increase during extreme heat events. Thus, many of the deaths that occur during heat waves are not necessarily recorded as heat deaths.

“The result is that heat numbers capture only a small fraction of the real story at the bedside,” she said. “Experts do not believe that we can adapt health systems adequately to cope with the temperatures that we are currently facing. That’s why reducing fossil fuel use is one of the most important public health interventions of our time.”

To estimate heat deaths, researchers turned to an existing dataset that showed relationships between temperature and mortality across the 854 urban areas used in the study. They then estimated the number of daily deaths during the heat wave using historical Eurostat data and information on which days exceeded minimum mortality temperature.

It’s Not Just Europe Click image for larger version. Credit: Imperial Grantham Institute

Among the countries included in the study, the Baltic nations of Estonia, Latvia, and Lithuania were the only three that did not experience hotter-than-usual summers.

Rome, Athens, and Bucharest saw the highest heat-related death rates per capita among European capital cities, the study found. In general, cities are hotter than surrounding areas because of the urban heat island effect, in which concrete surfaces trap heat and raise city temperatures.

Chris Callahan, a climate scientist at Indiana University Bloomington who was not involved in the study, said that though the study is not peer reviewed, its methods appear to be “standard and based on extensive peer-reviewed research.”

The researchers noted several factors their study did not consider, including cities’ efforts to adapt to climate change and all adverse health effects of heat. It also did not capture changes to baseline populations that occurred post-COVID-19, which might have led to higher numbers for some cities.

“The findings in this study are stark and concerning, as they illustrate that climate change is already the dominant influence on heat-related mortality in Europe,” Callahan told Eos in an email.

“We are warming the world through our fossil fuel emissions and other activities and that…is causing people to die.”

Europe faces particularly high risks related to climate change, he added, both because temperatures are rising more quickly in western Europe than in other parts of the world and because Europe’s aging population is highly vulnerable to heat. In fact, this study found that people over 64 made up 85% of the climate-related deaths in European cities this summer.

However, the study authors noted that the growing toll warming is taking on human health is not unique to Europe.

“The specifics will vary wherever you’re looking in the world, but the basic point of these studies will always be the same: that we are warming the world through our fossil fuel emissions and other activities and that this is causing people to die,” said Clair Barnes, a statistician at ICL’s Centre for Environmental Policy.

—Emily Gardner (@emfurd.bsky.social), Associate Editor

Citation: Gardner, E. (2025), Climate change may have killed 16,469 people in Europe this summer, Eos, 106, https://doi.org/10.1029/2025EO250348. Published on 17 September 2025. Text © 2025. AGU. CC BY-NC-ND 3.0
Except where otherwise noted, images are subject to copyright. Any reuse without express permission from the copyright owner is prohibited.

SummaryMineral exploration is frequently centred around delineating discrete geological units with, typically, sharp boundaries that could represent economic targets. In the case of complex resistivity (CR) inversions, the choice of regularisation and model parameterisation significantly impacts the inversion’s ability to delineate targets. Initially, however, a prudent researcher may not wish to bias their inversion towards sharp distinct units without prior justification. Here we explore how a suite of regularisation approaches to the CR inverse problem allows to encompass different classes of prior beliefs. We present these as a progression as more information becomes available regarding the likelihood of distinct geological units. The most weakly informed approach with respect to the delineation of geological units we consider is the classic ℓ2-type regularisation, tend to produce smeared-out fuzzy images. However this is typically not what is expected for distinct geological units, and we compare this with schemes that increasingly resolve sharp boundaries. We test a range of ℓ1-type regularisations, which have been frequently touted in the geophysics and optimisation literature as being well-suited for such tasks. We experiment with using a so-called overcomplete parameterisation of the CR field, which aims to separate smooth background and sharp foreground features. These ℓ1 schemes are shown to produce generally sharper images than ℓ2. In the most informed case, where strong assumptions can be made about the local geology, we represent the CR field as a foreground ellipse in a homogenous background. This approach significantly reduces the size of the parameter space, and tends to have a simple geometric interpretation. While the anomaly parameterisation has some unique challenges, we show it clearly resolves distinct units compared to both the ℓ2 and ℓ1 regularisations. Applications first to synthetic data and then to field data from Century Zinc Deposit in northern Australia, demonstrate the progression from weakly informed to strongly informed regularisation and parameterisation and the sharpness of the recovered geological units.

SummaryFollowing reanalysis of data from 8 seismic networks that operated in the region surrounding the Pampean flat slab during the past several decades, we generated 3D images of Vp, Vs, and Vp/Vs from a combination of arrival times of P and S waves from local earthquakes, and Rayleigh wave dispersion curves from both ambient noise and existing shear wave models. Among the robust features in these images is a low velocity, root-like structure that extends beneath the high Andes to a deflection in the flat slab, which suggests the presence of an overthickened Andean crust rather than a hypothesized continental lithospheric root. Most of the larger scale features observed in both the subducted Nazca plate and the overriding continental lithosphere are related to the intense seismic activity in and around the Juan Fernandez Ridge Seismic Zone (JFRSZ). Vp/Vs ratios beneath, within, and above the JFRSZ are generally lower (∼1.65–1.68) than those in the surrounding Nazca and continental lithosphere (∼1.74–1.80). While the higher continental lithosphere ratios are due to reduced Vs and likely a result of hydration, the lower JFRSZ related ratios are due to reduced Vp and can be explained by increased silica and CO2 originating from beneath the slab, perhaps in concert with supercritical fluid located within the fracture and fault networks associated with the JFR. These and related features such as a region of high Vp and Vs observed at the leading edge of the JFRSZ are consistent with a basal displacement model previously proposed for the Laramide flat-slab event, in which the eroded base of the continental lithosphere accumulates as a keel at the front end of the flat slab while compressional horizontal stresses cause it to buckle. An initial concave up bend in the slab facilitates the infiltration of silica and CO2-rich melts from beneath the slab in a manner analogous to petit spot volcanism, while a second, concave down bend, releases CO2 and supercritical fluid into the overlying continental lithosphere.

SummaryTomographic inversion of traveltime picks from both P-wave and S-wave wide-angle seismic data acquired along and across the Louisville Ridge Seamount Chain (LRSC) provides key insights into its magmatic construction and subsequent subduction-related deformation. Our P-wave velocity-depth models reveal that each seamount along the LRSC comprises an intrusive mafic-ultramafic core that rises within the crust to within 1–2 km of the seabed summit (P-wave velocity, Vp = 5.5–6.5 km s−1; S-wave velocity, Vs < 3.6 km s−1), with each underlain by a crustal root ∼4–5 km thick. Notably, Canopus seamount comprises two adjacent eruptive centres, and our modelling shows that the more northern is currently being internally deformed as it rides up (ascends) the Tonga-Kermadec Trench (TKT)-related plate bending outer rise. Lateral variation in Vs within models along and across the LRSC also primarily reflects subduction-related deformation, with low-velocity regions corresponding to large-scale faulting constrained within the crust. Comparison of pre- and post-LRSC-TKT collision forearc crustal structure indicates that bulk Vp properties recover within ∼50 kyr, whereas Vs structure retains it fault-related fabric for at least ∼740 kyr. Vp/Vs ratios (1.75–1.85) confirm a magmatic origin for all LRSC seamounts, with evidence of localized water-filled cracks due to seawater infiltration along faults, particularly beneath the TKT-ward side of the Osbourn seamount. Estimated water content within the upper crust ranges from 12–15 per cent by weight, decreasing to < 10 per cent in the mid-lower crust, with no evidence of > 12 per cent water content within the Pacific crust being subducted. In comparison with post-collision subduction further north, where the observed upper mantle velocity suggests up to 30 per cent water content, our models suggest that, although deformed and faulted as part of subduction, the LRSC appears more resistant to this deformation than the background Pacific crust adjacent. Our findings provide new constraints on the mechanical and compositional evolution of the LRSC, both prior to and during its collision with the overriding Indo-Australian plate.

SummaryThis research had an initial goal to quantitatively fit and then separate an induced polarization (IP) contribution to extensive ground electromagnetic (EM) data from the Girrilambone area, NSW. A secondary goal identified during the study was to explain why inversion of data from two different EM systems covering the same area each consistently predicted different IP time-constants and chargeabilities. The mineral exploration area was originally surveyed by a 6.25 Hz central loop SIROTEM survey measuring dB/dt. The area was later resurveyed with 1 Hz base-frequency Slingram survey using a Landtem B field sensor. The targets were economic sulphides at depth, with expected signatures being slowly decaying EM responses of small amplitude. Most of the data was affected by inductive IP effects of negative sign, with potential late-delay time EM responses of positive sign obscured. The Girrilambone area surveyed includes the Tritton Mine, discovered in 1995 as a result of the 6.25 Hz SIROTEM survey. To enable the subtraction of IP effects from the EM data, our primary goal, we used the EM data to predict Cole-Cole IP parameters that are consistent with documented values associated with extensive in-situ regolith clay resulting from weathering. The data sets were inverted using a polarisable thin-sheet model that estimated regolith conductivity-thickness or conductance S, chargeability m, IP frequency dependence c and conductivity IP time constant τσ. The thin sheet model was generally able to fit the observed responses, with the fitted IP contribution subtracted from the observed data to produce an ‘IP corrected’ data set of EM data more suitable for the detection of slow decays indicative of sulphide targets. The 6.25 Hz dB/dt data was however modelled with quite different parameters to the1 Hz B field data. The 6.25 Hz IP conductivity time constant was smaller by a factor of 10 while the chargeability was smaller by a factor of more than 2. This initial goal of the research was achieved in that subtraction of the fitted IP contributions in either case improved the capability to identify deeper conductive targets. We are confident that the systematic differences in fitted IP conductivity time constant and chargeability are not due to data or system description error, or to inversion constraints. We conclude that TEM systems will not accurately estimate intrinsic IP conductivity time-constants as rigorously defined from wideband laboratory physical property measurements but rather estimate an IP time-constant whose characteristic frequency (inverse of IP time constant) lies within the bandwidth of the TEM system used. Further, the chargeability estimate will reflect only that fraction of polarizable material whose response is within the bandwidth of the system.

SummaryThe magnitudes of earthquakes are generally described by an empirical relation called the Gutenberg-Richter law. This relation corresponds to a well-known statistical distribution, i.e. the exponential distribution. In this work, we verify the validity of the Gutenberg-Richter law using a 44-year-long worldwide seismic catalog of strong (Mw ≥ 6.5) events, by testing the exponentiality and the independence of the magnitudes. Moreover, we suggest a new way to visualize the distribution of the magnitudes, which complements the classical magnitude frequency distribution plot.