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SummaryNatural fractured reservoirs or artificially hydraulically fractured networks typically exhibit hierarchical microstructures characterized by porous backgrounds permeated by microcracks and intersected by macroscopic fractures. Prior theoretical frameworks predominantly decouple micro- and macro-scale heterogeneities, thereby overlooking the interplay between pore-scale squirt-flow dissipation and fracture-induced wave attenuation. By integrating microcracked porous wave-motion theory with fracture scattering theory, we present a unified model for characterizing wave propagation in fluid-saturated microcracked porous rocks with intersecting fractures. Five distinct attenuation mechanisms are concurrently incorporated: squirt flow at the microcrack scale, wave-induced fluid flow (WIFF) at both fracture-background and fracture-fracture mesoscales, elastic scattering, and Biot's global flow. The results show that microcrack density primarily affects matrix stiffness and shifts the attenuation of squirt flow to lower frequencies. In contrast, microcrack aspect ratios control the characteristic frequency and its coupling with fracture-related mechanisms. Fluid mobility governs the frequency range of WIFF and Biot flow, with high mobility potentially creating attenuation gaps where scattering-induced velocity drops disappear. The model also accommodates multiple-aspect-ratio microcrack systems and extends to planar fractures as linear-slip interfaces, enabling realistic characterization of anisotropic shale reservoirs. This unified approach provides a comprehensive basis for interpreting seismic dispersion and attenuation in complex fractured formations relevant to hydrocarbon exploration and reservoir monitoring. In parallel fractures and zero microcrack-limiting cases, our model predictions agree well with those of existing models.

SummaryRiver embankments are increasingly afflicted by intense and frequent flood events owing to climate change. The characterization and monitoring of river embankments are hence becoming crucial for climate change adaptation. Electrical resistivity tomography (ERT) is one of the most common geophysical techniques for the characterization of river embankments to identify local anomalies and potentially prevent damages during floods. ERT surveys are usually executed over the embankment crest and interpreted along a longitudinal section. However, 2D interpretation of ERT data can be strongly affected by the embankment morphology along the investigated portion (i.e., the shape of the longitudinal section and the presence of curves). To overcome this issue, we propose 3D inversion of ERT data acquired over embankments, and compare 2D and 3D inversions of both synthetic and field ERT data in order to understand the differences in results between the two approaches. We created a 3D synthetic model with several types of embedded anomalies to realistically represent the embankment geometry. We considered both a straight and a curved longitudinal profile of the embankment. Synthetic data were then generated with two tailored electrode-configuration arrays (i.e., dipole‒dipole and Wenner‒Schlumberger). 2D field data were acquired close to Turin (NW Italy) over an embankment that has often been damaged by floods. The results from 2D and 3D inversions were analyzed and compared. The main outcomes show that, with synthetic and field ERT data from the crest of the embankment, the subsurface was better characterized by means of 3D inversion, especially in presence of 3D eccentric buried features or complex/curved model domains. From the examples of synthetic data, the presence of the embankment slopes and curvatures negatively affected 2D inversion results, which presented more artefacts and higher misfit values than the 3D inversion results. From the field case study, the 3D resistivity volume presented good sensitivity in the transversal direction, thus allowing useful inspection of feature discontinuities or resistivity contrasts. Moreover, for the synthetic data the 3D results were more coherent than the 2D results with the true resistivity and position of the anomalies. For the field data, the 3D results were more coherent than the 2D results with known information from geological and geotechnical data. The more physically consistent 3D solutions may be further exploited for quantitative analysis on the petrophysical properties of the embankment material. In conclusion, 3D ERT inversion is recommended in presence of irregular domains (slopes, curves, strong discontinuities) even with 2D data.

SummaryImplicit full-waveform inversion (IFWI) has shown strong potential for seismic velocity reconstruction due to the implicit regularization of neural networks. However, conventional IFWI based on direct modeling represents multi-scale structures within a unified parameter space, where gradients associated with different wavenumber components may interfere, leading to slow convergence and limited recovery of deep structures. To address this issue, we propose a perturbation-based IFWI framework that decomposes the velocity model into a fixed background and a learnable perturbation. This parameterization reduces multi-scale gradient interference and improves optimization efficiency by restricting updates to the perturbation subspace. In addition, a coordinate normalization strategy is introduced to decouple spatial scale from the network frequency response, enabling stable optimization across different model sizes. Numerical experiments demonstrate that the proposed method achieves more stable convergence, improved structural resolution, and more reliable deep recovery compared to direct modeling IFWI. The approach also shows strong robustness under challenging conditions, including inaccurate initial models, varying spatial scales, and missing low-frequency data.

From the air, Wainwright, Alaska, looks like a perfectly stable band of homes and roads between the Chukchi Sea and a vast, flat tundra. But just below the surface, the frozen ground on which this town was built contains large bodies of ice. Along the eroding coastal bluffs, that hidden ice is becoming exposed and melting away.

While not quite a fatal attraction, the gravitational pull of the moon and sun creates tiny stresses on Earth that can trigger events known as slow earthquakes. These are movements along fault lines (fault slips) that release their energy gradually over much longer periods than ordinary quakes. Although they have been observed, exactly how these celestial bodies trigger them has been a relatively tough nut to crack.

Three much-loved glaciers in British Columbia are set to disappear completely within a few decades, according to a Simon Fraser University study.

body {background-color: #D2D1D5;} Research & Developments is a blog for brief updates that provide context for the flurry of news regarding law and policy changes that impact science and scientists today.

A recent investigative report found that spending for NASA’s research and analysis programs has remained relatively flat for 15 years, ignoring recommendations from community-led decadal surveys and directives by Congress. Given inflation, spending for these programs has actually decreased 30% in value from Fiscal Year (FY) 2011 to FY2025.

“The consequences are devastating,” wrote Mark Sykes in the blog that accompanied his investigation. “NASA is losing the intellectual content needed to identify and answer the breadth of significant scientific questions it is faced with today and it is losing the community of scientists (young and old) our nation needs to pursue these questions and maintain leadership in the world.”

Following the Money

Research and analysis (R&A) programs fund openly competed proposals that generate basic research and data analysis. This basic science underpins most of the agency’s mission and research portfolios, from high-profile, high-budget space telescopes to interplanetary spacecraft to lunar science.

In the two most recent decadal surveys for planetary science, published in 2011 and 2022, the scientific community recommended that NASA increase its budget for planetary science R&A to better support its expanded research portfolio, and that those increases should slightly outpace inflation.

What’s more, Congress also directed that NASA grow its R&A grant programs. As recently as the 2022 CHIPS and Science Act, it set a goal that R&A “reaches a level of not less than 10 percent of the total annual funding of relevant divisions of [NASA’s] Science Mission Directorate by fiscal year 2025.” That is, planetary R&A should strive to reach 10% of the Planetary Science Division (PSD) budget.

While neither decadal surveys nor goals set by Congress are legally binding, ignoring both is decidedly against the norm.

Sykes, a planetary scientist at the Planetary Science Institute in Tucson, Ariz., obtained data on NASA’s R&A funding through the Freedom of Information Act (FOIA) and publicly available documents. R&A is not listed as a single line item in NASA’s budget or the President’s Budget Request to Congress, but rather spread throughout individual programs and missions. Sykes’s investigation tallied separate R&A contributions across PSD programs for 15 years to reveal the total level of funding.

NASA systemically underspent on its planetary research and analysis for 15 years (blue) when compared with funding levels recommended by the 2011 Planetary Science Decadal Survey (green), the 2022 Planetary Science Decadal Survey (yellow), and the level recommended by Congress in the 2022 CHIPs and Science Act (arrow). Credit: Mark Sykes, CC BY 4.0

The data show that in the first year covered by the 2011 planetary science decadal survey recommendations (which was 2013), planetary R&A spending ($119 million) was already lower than the recommended funding level ($140 million). The discrepancy between recommended and actual spending only grew over the years covered by the 2011 survey.

The 2022 planetary science decadal survey, as well as Congress, then recommended that planetary R&A spending reach 10% of the total PSD budget. In 2023, planetary R&A spent only 2.5% the PSD budget, a discrepancy of about $185 million.

Shortchanging Basic Science

The only significant change in planetary R&A spending since 2011 was in 2025. NASA budgeted $144 million for planetary R&A in FY2025, still a relatively flat amount. But halfway through that fiscal year, it had spent just 47% of that ($68 million).

“For years, money budgeted has been very close to money expensed,” Sykes told Eos via email. “I noticed that FY2025 budget numbers did not appear to [be] in the President’s Budget Requests for FY2026 and FY2027, which made me wonder what might be going on.”

NASA has 2 years to spend appropriated funds, but historically has spent those funds by the end of the fiscal year.

 
Related

•  An Investigative Report on the Funding of NASA Planetary Research and Analysis Programs, FY2011-FY2025
•  An Update for FY2025
•  Trump’s Attacks on Science: The State of the Science 1 Year On
•  Get Involved: AGU Science Policy Action Center
 

“It would be pretty notable for NASA to incur costs amounting to 50% of its R&A budgets in the last three months!” Sykes said. “I would say that the accrued costs for FY2025 reflects a de facto change in the budget by the Administration.”

He added that this may be one of the many examples of the second Trump administration choosing not to spend Congressionally allocated funds for programs that don’t align with their politics.

Despite anticipating the shortfall, Sykes said, “it was still a shock to actually see it.”

This investigation spans 15 years, 8 NASA administrators, and four presidential administrations with varying levels of support for NASA and for science. FY2025 spending aside, the systemic underfunding of research and analysis cannot be laid at the feet of any individual or group of appropriators.

However, “When coupled with huge cuts to science proposed by the Administration, the discouragement of foreign students from all nations and international collaborations, and the deep reductions in experienced NASA personnel that has already occurred over the past year and a half, the U.S. may not recover,” Sykes wrote.

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

These updates are made possible through information from the scientific community. Do you have a story about how changes in law or policy are affecting scientists or research? Send us a tip at eos@agu.org. Text © 2026. 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.

Climate patterns in the tropics help determine how much snow falls from year to year in Antarctica, one of the coldest, windiest and driest places on Earth. New research from the University of Utah shows that tropical conditions and the oceans also influence the continent's massive ice sheets.

The South Asian summer monsoon has long been known to shape the Mediterranean climate thousands of kilometers away as part of a phenomenon known as the "monsoon–desert" mechanism. Through this mechanism, intense monsoon convection during the summer releases large amounts of heat into the atmosphere, triggering large-scale circulation changes that promote sinking air over the Mediterranean. This process suppresses clouds and rainfall and contributes to the Mediterranean region's hot, dry climate.

Extending some 1,200 kilometers (750 miles) along the length of Italy, the Apennine Mountains present a challenging puzzle for geologists. In some places, the mountains are steadily being stretched apart, while in regions just tens of kilometers away, they are squeezing together.

More than 80% of plants on Earth partner with mycorrhizal fungi to extract nutrients from soil.

Underground, in a zone of soil known as the rhizosphere, these fungi grow into vast networks of tubular cells called mycelium (individual cells are called hyphae). These tiny hyphae—about one tenth to one hundredth the width of a human hair—can gather nutrients in the soil and send them into plants.

A network of hyphae is seen under a microscope, magnified 630 times.

Some researchers estimate that the amount of mycelium, such as the specimen seen here, in the top 10 centimeters of soil on Earth adds up to about 450 quadrillion kilometers of length—or about half the width of our galaxy. Credit: Christian Scheckhuber/Wikimedia Commons, CC BY-SA 4.0

If plants don’t get enough nutrients, neither do the animals that depend on them or the animals that depend on those animals. Furthermore, some research has suggested that mycorrhizal fungi absorb the equivalent of 13 billion tons of carbon dioxide annually.

All of this makes the rhizosphere essential to the health of our planet and its inhabitants.

“Basically everyone on Earth is dependent on this really, really tiny zone around roots, in a way.”

“Basically everyone on Earth is dependent on this really, really tiny zone around roots, in a way,” said Henri Braunmiller, a soil ecologist and graduate student at the Technical University of Munich.

Again, hyphae are tiny: One gram of soil can contain up to 90 meters of mycelium. Most of the time, imaging them requires removing them from soil, which means scientists don’t have a 3D view of what the interconnected networks of roots, hyphae, and fungal spores look like.

But in new research published in New Phytologist, Braunmiller and his colleagues report a way to study this network in its natural environment for the first time using a technique called synchrotron computed tomography (CT).

Justin Stewart, an ecologist with the Society for the Protection of Underground Networks and Vrije Universiteit Amsterdam, told Eos in an email that the capacity to study fungal hyphae within intact soils at higher resolution represents a “major advance.”

“This makes it possible to examine the interface between living fungal networks and the mineral soil matrix, and opens new avenues for studying how fungal-derived carbon is transferred to soil minerals,” he said.

Shedding Some Light

Hyphae are seen stretching between soil particles in a petri dish. This light microscopy image, taken by paper coauthor Jan Jansa, measures less than 1 millimeter across.

Credit: Jan Jansa

Researchers can learn about mycorrhizal networks when they form in a petri dish like in the above photo or in soil chips, which are silicon wafers designed to mimic the structure of soil. But the information scientists gain from these methods is limited because the rhizosphere’s many facets are not replicated in these environments.

That’s where CT, the same technology used in medical scans, comes in. A typical laboratory CT, especially a high-resolution model, can take hours to image a sample, however. In those hours, fungi move and grow, blurring the image.

“A synchrotron produces a million times the energy that your lab CT produces.”

So the team turned to a synchrotron, a specialized particle accelerator that can create highly intense beams of light.

“A synchrotron produces a million times the energy that your lab CT produces,” Braunmiller said. “So you don’t want to stand in the way of the beam. But then you can do the same images in a couple of minutes.”

Braunmiller and his team set out to grow tomato plants in both loam and sandy soils containing fungi spores, hyphae, and colonized root fragments.

Then, they added small cylinders of soil, about 12 millimeters across and 60 millimeters tall, to the pots. The cylinders acted as baskets, covered in holes big enough—2 by 4 millimeters—for both the hyphae and plant roots to grow into. When removed after about 8 weeks of tomato growth, the cylinders contained a cross section of the rhizosphere’s various elements.

In this microscopy image, fungal structures, stained blue, are growing inside the root of a tomato plant.

Credit: Henri Braunmiller

The team drove the samples 9 hours from Munich to SOLEIL just outside of Paris, one of France’s very large scale research infrastructures and home to one of only a few dozen existing synchrotrons.

It was after midnight by the time researchers began to scan the samples. When the team looked through the images in succession, they saw tiny white points moving across the image.

This stack of images, shown one by one, shows how hyphae (the small white dots) move through soil in and around a root (the gray circle). The larger white blobs are grains of soil. Credit: Henri Braunmiller

They were hyphae.

“It was so exciting, because nobody was expecting that we could see them, because they’re so tiny,” Braunmiller said. “They’re right at resolution edge.”

Understanding a Tool

By stacking the images they’d gathered using CT, Braunmiller and his team could reconstruct 3D images of the full rhizosphere in its natural environment for the first time.

A 2D image (right) can be seen as the cross section of a 3D depiction (left).

In the left image, the large cylinder is a root, the thin filaments are hyphae, and the surrounding blobs are soil aggregates.

Credit: Henri Braunmiller

The researchers expanded their visualizations from there.

For instance, adding colors allowed them to conduct image analysis on the volume and surface area of the hyphal network.

Here a 3D reconstruction shows hyphae (pink) and fungal spores (red) growing in sandy soil.

This CT image shows hyphae (pink threads) connecting fungi spores (red spheres) in soil. On the left, grains of sand cover parts of the image. On the right, the sand grains have been removed from the image, and color has been added to represent different structures. Credit: Henri Braunmiller

Visualizing these networks is important because of the crucial role the rhizosphere plays in plant health, food systems, and the carbon cycle.

The team hopes their findings could be particularly useful for helping plants get enough water during drought, especially as drought increases in the face of climate change. Mycorrhizal fungi can help plants with nutrient uptake and pathogen resistance, so using these networks strategically could help improve crop yield stability and reduce dependence on herbicides and fungicides.

These networks “are a tool, but you also have to understand the tool,” Braunmiller said, explaining that these networks are more helpful in some settings than others, and researchers don’t fully understand why. “We’ll look also at how these networks work in different kinds of soils, so we can give recommendations on when to use them and when to maybe not.”

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

Correction: This article was updated on 1 October to correctly describe soil aggregates in a photograph.

Citation: Gardner, E. (2026), Fungi are holding the food web together. New research images this underground network., Eos, 107, https://doi.org/10.1029/2026EO260307. Published on 29 September 2026. Text © 2026. 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.

Lakes may cover only a small fraction of Earth's surface, but new research suggests they play a bigger role in regulating the planet's climate than previously recognized. By reflecting sunlight back into space when covered in snow and ice, lakes in the Northern Hemisphere have a stronger cooling effect than the surrounding land.

Author(s): E. A. Smith, J. J. Ruby, D. A. Chin, D. T. Bishel, M. E. Signor, T. E. Evans, K. N. Lofton, N. V. Kabadi, J. R. Rygg, and G. W. Collins

Laser-driven spherical implosion experiments create some of the most extreme states of matter accessible in the laboratory. However, experimental observables in implosion experiments are highly integrated, meaning that measurements cannot be straightforwardly inverted to characterize the thermodynam…

[Phys. Rev. E 114, 035216] Published Tue Sep 29, 2026

Videos show a large landslide on the Kaligandaki River at Lete in Mustang.

On 27 September 2026, a large landslide occurred on the Kaligandaki River in Nepal. The landslide, which was triggered by heavy rainfall over the last few days, has been widely shared on social media. The Straits Times has posted a version to Youtube, although there are many more versions on social media platforms. I note also that all of these reports are somewhat vague:-

The location is reported to be Lete, although this is difficult to pin down. It appears to be in the area of [28.63113, 83.61219], although this is peculation. The image below is the Google Earth representation of the terrain in the area of Lete:-

Google Earth image of the site of the 27 September 2026 landslide on the Kaligandaki River in Nepal.

The landslide appears to have been valley-blocking, but news reports suggest that the breach event occurred within a short period, minimising the hazard.

There is some uncertainty as to whether this landslide caused loss of life. At present, it does not appear on the Bipad portal as a mass fatality event.

Return to The Landslide Blog homepage Text © 2026. 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.

SummaryWe introduce a new 1D model of shear attenuation in the mantle (QM1D) constructed from measurements of differential attenuation of S and ScS body waves. We build a dataset of over 90,000 measurements of $\delta t^*_{\text{ScS-S}}$ from seismograms with high-quality S and ScS waveforms from deep earthquakes between 20–75° epicentral distance from 1990–2024. To ensure that measurements are robust, we require that values of differential attenuation are similar between the instantaneous frequency matching and waveform matching methods. Using this dataset, we perform a Bayesian inversion to construct 1D profiles of mantle shear quality factor Qμ and its uncertainties. Our dataset has a high sensitivity to the mid-mantle (660–2000 km) corresponding to the turning depths of the S phases, which maps into lower uncertainty in the ensemble distribution at these depths. QM1D suggests that the mantle is more attenuating than PREM on average; but, notably, that there is a strongly attenuating layer around 750 km depth and that there are weakly attenuating layers around 900 km and 2000 km depth. Due to the source-receiver distribution for the phases, our dataset has a sampling bias in the mantle around the edge of the Pacific which may not be representative of the whole mantle. The weakly attenuating zones in the mantle may correspond to a viscosity jump around 900 km depth and a further viscosity jump in the deep mantle around 2000 km depth, whilst the thin strongly attenuating layer may correspond to regions of slab stagnation caused by a potential thin layer of low viscosity beneath the mantle transition zone in the circum-Pacific region.

SummaryWe report the first explicit derivation of the Rikitake dynamo as a direct approximation of mean-field magnetohydrodynamics (MHD), establishing a systematic connection between a classical conceptual reversal model and the governing large-scale field equations. Starting from the mean-field induction and momentum equations, we show that a strongly truncated Galerkin expansion already retains the nonlinear couplings among magnetic induction, diffusion, convective driving, and Lorentz-force feedback required for reversal dynamics. Within this framework, a family of low-dimensional models arise as a limiting approximation of the reduced mean-field system. Placing further constraints on the Galerkin basis functions results in what we call the canonical Rikitake model. We provide an explicit harmonic realization that fulfills these constraints and preserves the minimal nonlinear structure capable of producing irregular oscillations and spontaneous polarity reversals. The reduced parameters acquire clear physical meaning in terms of inductive regeneration, effective magnetic diffusivity, forcing, and magnetic backreaction. Using representative outer-core scalings, we obtain characteristic amplitudes and timescales consistent with geophysical estimates, including observed chron durations. Numerical integrations reproduce several features of geomagnetic variability, including polarity reversals, irregular oscillations, and extended intervals of persistent polarity. The canonical model supports both short and long chrons, including superchrons, whereas the harmonic realization yields only short chrons, indicating that richer basis functions may be needed to recover broader reversal statistics. These results place Rikitake-type models on firm physical grounds and provide a route toward systematically constructed low-dimensional dynamos derived from MHD.

SummaryThis paper has analyzed the spatial and temporal distribution of the local seismic shear-wave splitting parameters at the source region of the Nepal Gorkha MW7.8 earthquake in 2015. There are significant spatial variations of valid results within the aftershock zone. The fast directions change abruptly from west to east, revealing heterogeneity in the physical property or geometry of the upper crustal medium along the strike of the seismogenic fault. Combined with seismic tomography and magnetotelluric sounding, it is inferred that the variation of the upper crust from west to east in this region may represent a response to the tearing of the Indian lithospheric plate. The aftershock area shows large time delays, with their average results decreasing southward, indicating that a large amount of stress accumulated in the upper crust along the seismogenic area during the seismogenic process of the Gorkha earthquake, with the stress gradually weakening from north to south. Furthermore, time delays in the dense aftershock zone remained highly unstable for nearly one year after the Gorkha earthquake, reflecting that the stress accumulated during the seismogenic process of this earthquake failed to fully release with the mainshock and strong aftershocks, and the stress still adjusted violently.

Tiny asteroid Chariklo, floating through the void between Saturn and Uranus, boasts two rings. It’s the first asteroid found to have them, and their existence took astronomers by surprise when they were spotted in 2013. Now, Chariklo’s rings are showing some unexpected and unexplained behavior.

“The opacity of the outer ring is now lower than in the previous observations, but also the opacity of the inner ring was stronger,” said Pablo Santos-Sanz, an astrophysicist at Instituto de Astrofísica de Andalucía in Granada, Spain, and lead researcher on the discovery.

When Santos-Sanz saw the results, he asked himself, “Oh, what has happened here?”

Dynamic Rings

Chariklo is a Centaur asteroid, meaning it orbits the Sun in the space between the giant planets. It’s 302 kilometers (108 miles) across, is not very spherical, and orbits about 2.3 billion kilometers (1.5 billion miles) from the Sun.

In 2013, Chariklo passed between earthbound observers and a distant star, an alignment called stellar occultation. Astronomers saw that the star’s light dimmed twice before Chariklo obscured the star and twice again after Chariklo passed by, revealing the presence of two thin rings orbiting the asteroid. That made Chariklo only the fifth solar system object, the first besides the four giant planets, discovered to have rings.

Later observations revealed that the rings are thin, sharply defined, and separated by a mere 14 kilometers (8.7 miles). Other measurements suggest they may contain water ice.

The James Webb Space Telescope observed Chariklo (moving dot) crossing in front of a background star (stationary dot). This occultation revealed that Chariklo’s rings (too faint to see) have changed since they were last observed. Credit: NASA, ESA, CSA, Nicolás Morales (IAA/CSIC)

But occultations are rare, and the rings themselves are too faint to observe directly. Santos-Sanz and his colleagues decided to see whether a space-based occultation might be possible. They turned to the James Webb Space Telescope (JWST), which is orbiting Earth’s L2 Lagrange point 1.5 million kilometers (nearly a million miles) away. With meticulous precision, the researchers calculated the future positions of JWST and Chariklo and searched the Gaia mission’s database to find stars along the lines connecting them.

But the positions and trajectories of JWST, Chariklo, and every background star each have some degree of uncertainty. JWST’s orbit is the trickiest aspect, as it is nearly impossible to predict the telescope’s position more than a few months ahead of time.

“At the beginning I felt like a crazy guy proposing this.”

“If you put these three things together, it’s really very challenging to predict an occultation from James Webb…At the beginning I felt like a crazy guy proposing this,” Santos-Sanz said.

Nevertheless, after several months of searching, the researchers found one potential alignment in October 2022 in which JWST would likely pass through Chariklo’s tiny occultation “shadow.” They predicted it just a month ahead of time, secured time on the telescope, and kept refining their calculations. When the time came, the team triggered the telescope, and JWST successfully observed its first stellar occultation.

The telescope clearly detected both of Chariklo’s rings but revealed that the inner ring’s opacity increased 42% from previous observations. In contrast, the outer ring was so translucent it was barely visible.

The team published these results in Science Advances on 9 September.

Rings Might Not Be Forever

Right now, the team has no definitive answer to explain the rings’ opposing evolutions. It’s possible the inner ring particles are colliding and changing how much light they reflect while the outer ring particles are drifting away. Or Chariklo might have an unseen satellite driving the rings’ evolution, both keeping the rings in their orbits and providing extra material to the inner ring. Future stellar occultations, observed either from the ground or space, will be needed to reveal whether and why the rings are still changing.

“The existing observations of such miniature ring systems are still very sparse, compared to the vast amount of data collected of their giant-planet analogues,” said Heikki Salo, an astronomer at the University of Oulu in Finland. “Nevertheless, the dynamical processes in such ring systems around irregular small bodies are at least as challenging to understand as those governing the rings of the giant planets!”

Salo, however, thinks the evolution of Chariklo’s rings might not be so inexplicable after all.

“It’s a piece in the big puzzle that is solar system science.”

“The perturbations induced by the highly nonspherical shape of Chariklo make most orbits in its vicinity highly unstable,” said Salo, who was not involved with the new research. Chariklo’s rings orbit in a particular gravitational resonance—the ring particles orbit three times for every one rotation of Chariklo—that is known to make rings evolve. “In this sense, the Chariklo rings can be expected to resemble Saturn’s F ring, with highly time-variable structure.”

Salo added that an unseen moon around Chariklo might yet play some role, perhaps in replenishing material in the inner ring and keeping it stable over longer periods.

But for now, with the next occultation maybe 5 years away, Chariklo and the mystery of its changing rings will remain unsolved.

“It’s a piece in the big puzzle that is solar system science,” Santos-Sanz said. “In a few years we will have more pieces, and we will understand more what is really happening in Chariklo and probably in other ringed objects like Haumea, Chiron, and Quaoar.”

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

Citation: Cartier, K. M. S. (2026), Chariklo’s rings are evolving, Eos, 107, https://doi.org/10.1029/2026EO260308. Published on 28 September 2026. Text © 2026. 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.

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

Groundwater models are fundamental for tackling a wide range of water resources problems but are inherently challenging to parameterize due to the sparsity of subsurface data. Geophysical data can help address this by providing proxy measures of hydraulic properties, potentially offering a spatially rich dataset. There is growing interest in using airborne geophysical surveys for this purpose as they can provide insight into the spatial heterogeneity of an entire aquifer system.

Scantlebury and Harter [2026] offer a novel approach for deriving hydraulic structure models over large spatial scales from the integration of airborne geophysics models of subsurface electrical resistivity and borehole data, recognizing the uncertainty in resistivity-lithology relationships. The derived structures can then be incorporated into a groundwater model, as demonstrated by the authors in an application to the Scott Valley aquifer system. Such a workflow could improve significantly the utilization of large-scale geophysical data for reducing groundwater model predictive uncertainty.

Citation: Scantlebury, L., & Harter, T. (2026). From resistivity to hydraulic properties: Calibrating a groundwater flow model by integrating airborne electromagnetic and borehole data into a probabilistic multi-texture framework. Water Resources Research, 62, e2025WR042695. https://doi.org/10.1029/2025WR042695

—Andrew Binley, Associate Editor, Water Resources Research 

Text © 2026. 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.

Weather forecasts in the Southern Hemisphere (SH) are generally less accurate than those in the Northern Hemisphere because Antarctica and the surrounding Southern Ocean have relatively few weather observations. With limited information about atmospheric conditions in one of the world's most remote regions, forecasting models often struggle to predict the movement of weather systems. This is especially true for atmospheric rivers that can trigger heavy rain, snowfall, flooding and strong winds across Australia, New Zealand, South America and Antarctica. Improving forecasts of these weather systems is essential for protecting lives and property, supporting aviation and shipping, and helping communities prepare for hazardous weather.