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New laboratory research suggests that some organic molecules previously detected in plumes erupting from Saturn’s moon Enceladus may be products of natural radiation, rather than originating from the moon’s subsurface ocean. This discovery complicates the assessment of the astrobiological relevance of these compounds.

Enceladus hides a global ocean buried beneath its frozen crust. Material from this liquid reservoir is ejected into space from cracks in the ice near the south pole, forming plumes of dust-sized ice particles that extend for hundreds of kilometers. While most of this material falls back onto the surface, some remains in orbit, becoming part of Saturn’s E ring, the planet’s outermost and widest ring.

Between 2005 and 2015, NASA’s Cassini spacecraft flew repeatedly through these plumes and detected a variety of organic molecules. The detection was viewed as evidence of a chemically rich and potentially habitable environment under the ice, where molecules essential to life could be available. However, the new study offers an explanation in which radiation, not biology, is behind the presence of at least some of these organic molecules.

To test the role of space radiation, a team of researchers led by planetary scientist Grace Richards, a postdoc at the National Institute for Astrophysics in Rome, simulated conditions near Enceladus’s surface by creating a mixture of water, carbon dioxide, methane, and ammonia, the main expected components of surface ice on Enceladus. They cooled the concoction to −200°C inside a vacuum chamber and then bombarded it with water ions, which are an important component of the radiation environment that surrounds the moon.

The radiation induced a series of chemical reactions that produced a cocktail of molecules, including carbon monoxide, cyanate, ammonium, and various alcohols, as well as molecular precursors to amino acids such as formamide, acetylene, and acetaldehyde. The presence of these simple molecules indicates that radiation could induce similar reactions on Enceladus.

Richards presented these findings at the Europlanet Science Congress–Division for Planetary Sciences Joint Meeting (EPSC-DPS 2025) in Helsinki, Finland. She and her coauthors also published a detailed report in Planetary and Space Science.

Enceladus and Beyond

The new research raises the question of whether the organic molecules detected in Enceladus’s plumes truly come from the moon’s buried ocean, whether they are formed in space, or whether they form close to the surface after the plumes leave the Enceladean interior.

While the finding doesn’t exclude the possibility of a habitable ocean on Enceladus, Richards urges caution in assuming a direct link between the presence of these molecules in the plumes, their origin, and their possible role as precursors to biochemistry.

“I don’t necessarily think that my experiments discredit anything to do with Enceladus’s habitability.”

“I don’t necessarily think that my experiments discredit anything to do with Enceladus’s habitability,” Richards said.

However, she added, “when you’re trying to infer this ocean composition from what you’re seeing in space, it’s important to understand all the processes that go into modifying this material.” Apart from radiation, these processes include phase changes, interactions with the moon’s ice walls, and interactions with the space environment.

“We need a lot of experiments of that type,” said planetary scientist Alexis Bouquet, a French National Centre for Scientific Research (CNRS) researcher at L’Université d’Aix-Marseille who wasn’t involved in the study. “They demonstrated that you can produce a certain variety of species in conditions that are relevant to the south pole of Enceladus.”

Bouquet highlighted the importance of simulating these environments in a lab for planning future missions to Enceladus and for interpreting the much-anticipated data from current missions to Jupiter’s icy moons. These missions are NASA’s Europa Clipper, which will explore Europa, and the European Space Agency’s (ESA) JUICE (Jupiter Icy Moons Explorer), which will visit all three of the giant planet’s moons with subsurface oceans: Ganymede, Calisto, and also Europa.

The intense radiation around Jupiter makes these experiments especially relevant. “Radiation chemistry for Europa or the Jovian moons in general [is] a big deal, a bigger deal than in Enceladus,” Bouquet says.

Another Story Completely

As Richards’s work questions the origin of organic compounds around Enceladus, researchers keep adding more molecules to the puzzle.

After a new analysis of data gathered during one of Cassini’s close approaches to Enceladus in 2008, researchers led by planetary scientist Nozair Khawaja at the Freie Universität Berlin and the University of Stuttgart reported the discovery of new types of organic molecules, seemingly emanating from the icy vents. They include ester and ether groups and chains and cyclic species containing double bonds of oxygen and nitrogen.

On Earth, these molecules are essential links in a series of chemical reactions that ultimately produce complex compounds needed for life. And while these molecules could have an inorganic origin, “they increase the habitability potential of Enceladus,” Khawaja said. The findings appeared in Nature Astronomy.

Khawaja’s team’s analysis suggests that complex organic molecules are present in fresh ice grains just expelled from the vents. During its last flyby, Cassini got as close as 28 kilometers to the moon’s surface.

After modeling the plumes and the icy grains’ residence times in space, they think that the ice grains sampled by Cassini did not spend a lot of time in space, likely just “a few minutes,” Khawaja said. “It is fresh.”

This short duration in space questions whether space radiation had enough time to produce the organic molecules Khawaja detected. Just a few minutes would not be long enough for such complex chemistry to take place, even in a high-radiation environment.

“Big grains coming from the surface full of organics? That is much harder to explain through radiation chemistry,” Bouquet said.

While the types of experiments performed by Richards “are valuable and take the science to the next level,” Khawaja said, “our results tell the other story completely.”

Back to Enceladus

Both studies reinforce the complexity of Enceladus’s chemistry, upholding it as a prime target in the search for extraterrestrial life, or at least life’s building blocks. Enceladus has all three prerequisites for life: liquid water, an energy source, and a rich cocktail of chemical elements and molecules. Even if the subsurface ocean is out of reach—it lies at least a few kilometers beneath the ice close to the poles—the plumes offer the only known opportunity to sample an extraterrestrial liquid ocean.

Studies for a potential ESA mission dedicated to Enceladus are already underway, with plans that include high-speed flybys through the plumes and, potentially, a lander on the south pole. The insights from both recent studies will help researchers design the instrumentation and guide the interpretation of future results.

“There is no better place to look for [life] than Enceladus,” Khawaja said.

—Javier Barbuzano (@javibar.bsky.social), Science Writer

Citation: Barbuzano, J. (2025), Space radiation can produce some organic molecules detected on icy moons, Eos, 106, https://doi.org/10.1029/2025EO250383. Published on 14 October 2025. 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.

Author(s): Min-Seok Kim, Jeong-Hyun Lee, Jung-Eun Choi, and Chin-Wook Chung

The effect of the Ramsauer-Townsend effect, a quantum mechanical phenomenon, is investigated by generating an ultralow electron temperature plasma (Te<1 eV) in a weakly magnetized inductively coupled argon plasma using a dc-biased grid. In the ultralow electron energy regime, the Ramsauer-Townsen…

[Phys. Rev. E 112, 045208] Published Tue Oct 14, 2025

About 140 mm triggered 143 landslides in an area of about 10 km2, killing two people.

Loyal readers will have noticed that I’m fascinated by dense clusters of landslides triggered by intense rainfall (or earthquakes). Over the years, I have written about these on multiple occasions, but increasing numbers are being described in the literature.

Another very interesting example has just been published in the journal Landslides (Xie et al. 2025). This example occurred on 12 July 2024 close to Puzi in Pengshui County, Chongqing, China. The centre of the cluster as at [29.56790, 108.28781] – this is the marker on the images that follow.

The Planet image below shows the area on 24 May 2024, before the rainfall:-

The site of the 12 July 2024 landslides in Pengshui County, Chongqing, China. Image copyright Planet, used with permission. Image dated 24 May 2024.

And this is the same site after the event on 12 July 2024:-

The aftermath of the 12 July 2024 landslides in Pengshui County, Chongqing, China. Image copyright Planet, used with permission. Image dated 1 August 2024.

And here is an image compare:-

Images copyright Planet, used with permission.

Xie et al. (2025) show that this cluster of landslides was triggered by a rainstorm that deposited about 140 mm of rainfall in a few hours. In total, 143 landslides were triggered in an area of about 10 km2. The failures were mostly disrupted avalanches, some of which formed channelised debris flows. However, Xie et al. (2025) also show that there are a number of interesting aspects of this cluster of landslides.

Note the geographical isolation of these landslides. The slopes to the east and west suffered far fewer failures. Perhaps surprisingly, this cluster of landslides did not occur in the area of highest rainfall – a short distance to the west, more than 200 mm was recorded, but few landslides occurred.

The analysis of Xie et al. (2025) shows that this cluster occurred because of a weak geological unit (sandstone) that was highly fractured, a geological structure that promoted instability and steep slope gradients (which may be associated with erosion by the river). Thus, it is the combination of the meteorological, geological and geomorphological factors that led to the cluster of landslides.

Fortunately, the area had been mostly evacuated ahead of the rainfall, so there were just two fatalities. There was extensive damage to properties though.

This event illustrates well the ways in which extreme rainfall events are combining with local factors to create clusters of landslides that have the potential to generate high levels of damage.

Many thanks to Xie et al. (2025) for such an interesting example.

References

Xie, X., Liu, S., Macciotta, R. et al. 2025. Spatial heterogeneity in landslide response to a short-duration intense rainfall event on 12 July 2024 in Pengshui County, Chongqing, China. Landslides. https://doi.org/10.1007/s10346-025-02624-6.

Planet Team 2025. Planet Application Program Interface: In Space for Life on Earth. San Francisco, CA. https://www.planet.com/.

Return to The Landslide Blog homepage Text © 2023. 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.

SummarySubduction zones are tectonic plate boundaries where one tectonic plate is being forced beneath another and known for producing some of the most powerful earthquakes in history. Understanding the regional-scale structural heterogeneity in the subduction zone is crucial for deciphering the genesis of megathrust earthquakes and the factors that control rupture dynamics. The rupture dynamics of the earthquakes in Andaman-Sumatra region are primarily hindered due to the lack of velocity and anisotropy information at the lithospheric level. Compression wave (Pn) waves propagate in the uppermost mantle and can provide velocity and anisotropy constraints for this portion of the mantle along their ray-path. We generated the first comprehensive high-resolution Pn-wave tomography, restricting the turning of diving ray paths less than 50 km deep in the collision zones, to map lithospheric velocity and anisotropy by inverting 65 297 Pn arrivals extracted from 6958 regional events recorded at 384 stations. The results show a strong variation in Pn-wave velocity and fast polarization directions (FPDs) in the entire study region that may be an essential factor for earthquake nucleation. We observed an abrupt change in the Pn-FPDs from Andaman to Sumatra and Sumatra to Java regions. We suggest that well defined plate boundaries between Indian and Capricorn plates, that was earlier reported to be diffused one. Such observation is also supported by the lower spreading rate and higher crustal age of the old Indian oceanic plate in the Andaman region, compared to the faster spreading rate and lower crustal age of the Capricorn oceanic plate in the north Sumatra region. We suggest that the Sunda plate strongly coupled with subducting oceanic slab causes the mega events of 2004 and 2005 supported by trench-normal Pn-FPDs along with rigid-slab nature, and both the rupture propagation terminate near Simeulue Island region due to abrupt material changes beneath it. Our study also reveals the presence of low Pn velocity anomalies in the west of the Andaman Sea, suggesting the existence of a magma reservoir pouring out lava through the steeply torn Indian oceanic slab.

SummaryThe converted wave technique, namely Receiver function (RF), has been routinely employed for estimating one-dimensional velocity models of the Earth’s crust and mantle structures. Physics-driven methods such as inversions are employed to receiver function data to estimate velocity models. Despite their wide utility, the presence of dipping and anisotropic geological structures often complicates this process. To address these complexities, here we introduce a Physics-Guided unsupervised deep learning approach for the inversion of receiver function data. An unsupervised deep learning approach together with implicit neural representations is developed here, for prediction of subsurface model parameters such as the layer thickness, S-wave velocity, anisotropy, trend, plunge, strike and dip without requiring any labelled data. In addition, we incorporate a dynamic layer setting criterion to automatically pick the optimal number of layers required to fit the data, which is found to be particularly effective for identifying pronounced discontinuities like the crust-mantle boundary. For determining the optimal model parameters, neural network output parameters (the model parameters) are used in forward modelling of the receiver functions. Inversion results from both synthetic and real field data from the Indian shield and Hi-CLIMB network suggest that the physics-guided unsupervised deep learning approach is effective in inversion tasks, particularly when dealing with dipping and anisotropic media.

SummaryWe explore the potential of utilizing Distributed Acoustic Sensing (DAS) for Back-projection (BP) to image earthquake rupture processes. Synthetic tests indicate that sensor geometry, azimuthal coverage, and velocity model are key factors controlling the quality of DAS-based BP images. We show that mitigation strategies and data processing modifications effectively stabilize the BP image in less optimal scenarios, such as asymmetric geometry, narrow azimuthal coverage, and poorly constrained velocity structures. We apply our method to the Mw7.6 2022 Michoacán earthquake recorded by a DAS array in Mexico City. We also conduct a BP analysis with teleseismic data for a reference. We identify three subevents from the DAS-based BP image, which exhibit a consistent rupture direction with the teleseismic results despite minor differences caused by uncertainties of BP with DAS data. We analyze the sources of the associated uncertainties and propose a transferrable analysis scheme to understand the feasibility of BP with known source-receiver geometries preliminarily. Our findings demonstrate that integrating DAS recordings into BP can help with earthquake rupture process imaging for a broad magnitude range at regional distances. It can enhance seismic hazard assessment, especially in regions with limited conventional seismic coverage.

SummaryShort-duration instrumental earthquake catalogues, sparsity in seismic stations, and paucity of near-source earthquake data impose strong limitations on data-driven seismic hazard assessment. In contrast, regional-scale multi-cycle earthquake simulations that generate realistic rupture scenarios provide physics-based earthquake rupture forecasts for seismic hazard assessment. In this study, we use the physics-based multi-cycle earthquake simulation engine MCQsim to compute long-term synthetic seismic catalogues that include multi-segment ruptures on a complex-geometry fault system. We expand on previous research by conducting systematic statistical analyses of synthetic earthquake catalogues for the Gulf of Aqaba (GoA, Saudi Arabia) that forms the southern extension of the Dead Sea Fault (DSF). The GoA is characterized by predominantly left-lateral strike-slip faulting and its seismic activity is revealed by past seismic swarms and large-magnitude events, including the 1995 M 7.2 Nuweiba earthquake. To address epistemic uncertainties in the seismic source characterization (SSC) of this region, we explore several modelling realisations by altering the fault system’s geometric configuration and frictional properties. Our simulations reveal that multi-segment ruptures reaching M 7.6 are possible in the GoA. The simulated catalogues reveal source-scaling properties of rupture area and stress drop consistent with global observations and empirical scaling laws. Additionally, the statistical properties of the synthetic catalogues, including the earthquake magnitude-frequency distribution, align with the short-term recorded seismicity in the study region. In summary, our simulation-based study provides insights into the GoA’s seismic behaviour through comprehensive parameter-space exploration and sensitivity analyses that document the possibility for geometrically complex, large multi-segment magnitude earthquakes.

SummaryFull waveform inversion (FWI) is a high-precision subsurface imaging technique that inverts subsurface parameter models by minimizing the discrepancy between observed and synthetic seismic data. However, complicated wave propagation mechanisms, non-convexity of the loss function, and limited seismic acquisition system necessitate the incorporation of sufficient prior and physical constraints to alleviate the ill-posedness and cycle-skipping. Although the implicit FWI (IFWI) can encode implicit spectral bias (i.e., inverting model parameters from low frequencies to high frequencies) to reduce the dependency on an accurate initial model, its limited high-frequency inversion capability results in thousands of iterations for the final results. In this paper, we indicate that the frequency hyperparameters of the sine activation function in IFWI modulate the spectral bias, making a trade-off between inversion accuracy and stability, i.e., lower frequencies yield robust FWI but lower accuracy, while higher frequencies achieve higher accuracy on the premise of an accurate initial model. To improve both the stability and accuracy of IFWI, we propose a novel implicit FWI method with an adaptive Fourier reparameterization strategy (termed FR-IFWI), which explicitly encodes multi-frequency information by reparameterizing the network weights using a learnable coefficient matrix and fixed Fourier frequency bases. The role of learnable matrices in neural networks can evolve from determining frequencies in IFWI to actively selecting frequencies from fixed frequency bases through FR-IFWI, which alleviates the dependence on activation function frequency and obtains more robust and accurate inversion results. Extensive numerical experiments on the modified Marmousi, 2D SEG/EAGE Salt and Overthrust models confirm that FR-IFWI successfully achieves superior inversion efficiency and accuracy compared with conventional FWI and IFWI methods.

For billions of years, Earth's continents have remained remarkably stable, forming the foundation for mountains, ecosystems and civilizations. But the secret to their stability has mystified scientists for more than a century. Now, a new study by researchers at Penn State and Columbia University provides the clearest evidence yet for how the landforms became and remained so stable—and the key ingredient is heat.

Deep inside caves, water dripping from the ceiling creates one of nature's most iconic formations: stalagmites. These pillars of calcite, ranging from centimeters to many meters in height, rise from the cave floor as drip after drip of mineral-rich water deposits a tiny layer of stone.

Accurately modeling gross primary productivity (GPP) and evapotranspiration (ET) in terrestrial ecosystems is essential for understanding and predicting the global carbon and water cycles. However, current models face considerable uncertainties and limitations when estimating these two core components.

An international research team led by the University of Bremen has investigated what influenced the expansion of the Patagonian ice sheet during the last ice age. The scientists found evidence that the advances and retreats of glaciers in South America over the past 120,000 years were primarily influenced by changes in summer solar radiation and the duration of the summers.

A new study has challenged the long-standing assumption that global warming will inevitably turn humid subtropical forests into carbon sources, revealing these ecosystems may instead continue accumulating soil carbon under moderate temperature rises. The study was published in One Earth on Oct. 6.

Magnetotelluric (MT) data, which contain measurements of electric and magnetic field variations at Earth's surface, provide insights into the electrical resistivity of Earth's crust and upper mantle. Changes in resistivity, or the ability to conduct an electrical current, can indicate the presence of geologic features such as igneous intrusions or sedimentary basins, meaning MT surveys can complement other kinds of geophysical surveys to help reveal Earth's subsurface. In addition, such surveys can play an important role in improving understanding of the risks space weather poses to human infrastructure.

How do volcanoes work? What happens beneath their surface? What causes the vibrations—known as tremor—that occur when magma or gases move upward through a volcano's conduits? Professor Dr. Miriam Christina Reiss, a volcano seismologist at Johannes Gutenberg University Mainz (JGU), and her team have located such tremor signals at the Oldoinyo Lengai volcano in Tanzania.

According to a study by the Department of Physics and the Institute of Environmental Science and Technology of the Universitat Autònoma de Barcelona (ICTA-UAB), the Mar Menor saltwater lagoon in Murcia, Spain, the largest in Europe, contains sediments with levels of lead, arsenic, zinc, mercury, copper, and silver that exceed toxicity thresholds and values reported for similar coastal ecosystems worldwide. The findings are published in the journal Marine Pollution Bulletin.

Heat waves in the UK have led to unseasonable drying of vegetation bypassing natural ecological processes that limit the spread of wildfires, a new study has found.

Greenland is melting, the Alps are melting and the Himalayas are melting—yet in one vast mountain region, huge glaciers have remained stable, or even gained mass, in recent decades. Can it last?

A new fossil fuel site approved for development off Western Australia's coast is estimated to contribute 876 million tons of carbon dioxide (CO2) emissions over the course of its lifetime, according to new research led by The Australian National University (ANU) in collaboration with the ARC Center of Excellence for the Weather of the 21st century.

Reconstruction of landslides on the banks of Lake Rupanco in Chile, triggered by the 22 May 1960 Mw-9.5 earthquake, suggests that a slope failure with a volume of 161 million cubic metres triggered a tsunami with a maximum amplitude of 33.3 metres. About 120 people were killed.

A very interesting paper (Quiroga et al. 2025) has just been published in the journal Landslides that examines combined landslide – tsunami threats at Lake Rupanco [40.82, -72.50] in Chile. The context is a series of landslides, and a resultant tsunami, that was triggered by the 22 May 1960 Mw=9.5 Great Chilean earthquake. The paper reconstructs that landslides and models the tsunami that they generated.

This event is particularly interesting as the loss of life was significant. Quiroga et al. (2025) document about 120 fatalities:-

“The most severely impacted area was Las Gaviotas, a settlement situated on the southeast shore…, where tsunami run-up heights reportedly exceeded 10 m, according to eyewitness accounts… One of the most significant losses was the destruction of the popular Termas de Rupanco hotel located near geothermal springs …, which was swept away by the landslides, resulting in 11 confirmed fatalities … At that time, a road was also under construction along the southern shoreline to connect Osorno with Las Gaviotas; both the road and several worker camps were destroyed…”

The Chilean Enterreno site has a photograph of the Termas de Rupanco hotel prior to the tsunami:-

Hotel Termas de Rupanco, which was destroyed by the landslide-induced tsunami 1960. Image from Enterreno. Posted by Francisco Vidal Guzmán under a by-nc licence.

Quiroga et al. (2025) have tracked the source of the tsunami to a series of landslides that occurred on the north side of Lake Rupanco. The scars of these failures are still very visible on Google Earth:-

Google Earth image of the site of the landslides on the banks of Lake Rupanco triggered by the 22 May 1960 earthquake in Chile.

Quiroga et al. (2025) have identified eight landslide scars in this area, of which the most significant is the bowl-shaped scar in the centre of the image above. This is the most likely source of the tsunami. It is a rotational failure with lower runout zone, with a volume of 161 million m3. Of this volume, 12.1 million m3 became submerged to generate the wave.

Reconstruction of the wave suggests that it has a maximum amplitude of 33.3 metres close to the landslide itself. At Las Gaviotas, where the hotel was located, the wave had a maximum amplitude of 8.6 metres, arriving 261 seconds after initiation.

This elegant and useful paper illustrates well the threat posed by large landslides into lakes. For those located in the hotel, the events would have been terrifying, starting with a major earthquake for which the shaking would have been intense and long-lasting, followed by the noise and dust generated by the collapsing slopes, and finally the impact of this enormous tsunami. Keeping people safe in such circumstances is a very major challenge.

Reference

Quiroga, J.P., Aránguiz, R., Hernández-Madrigal, V.M. et al. 2025. Reconstruction and numerical modeling of historical and paleo-tsunamigenic landslides in Lake Rupanco, Chile. Landslides. https://doi.org/10.1007/s10346-025-02629-1.

Return to The Landslide Blog homepage Text © 2023. 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.