In an extraordinary breakthrough that delves deep into the cosmic past, an international consortium of scientists from Dresden, Sydney, and Canberra has uncovered rare signatures of radioactive isotopes embedded within a deep-sea manganese crust. This discovery provides unprecedented insights into the astrophysical phenomena responsible for forging the universe’s heaviest elements, particularly illuminating the timeline of the last significant r-process nucleosynthesis event in the solar system’s vicinity. Their findings, published in the esteemed journal Nature Astronomy, draw a cosmic map that stretches back over 100 million years, signaling the rarity and tremendous scale of cataclysmic events such as neutron star mergers or exceptionally energetic supernovae.

Ferromanganese crusts, mineral deposits found at profound ocean depths ranging from hundreds to thousands of meters, serve as unparalleled geological time capsules. These crusts accrete slowly—millimeters over millions of years—absorbing trace elements, including rare radioactive isotopes transported from distant cosmic events. By decoding these isotopic deposits, researchers can trace the history of cosmic explosions and paint a detailed portrait of stellar processes that shaped the chemical evolution of our galaxy.

Central to this research is the isotope plutonium-244, with its rare genesis through the rapid neutron-capture process, known simply as the r-process. During such events, atomic nuclei experience a rapid succession of neutron captures, instigating the synthesis of heavy elements beyond iron. Conditions conducive to this process are believed to arise predominantly during titanic neutron star collisions or hyper-energetic supernovae, events many orders of magnitude less frequent than typical supernova explosions. Detecting plutonium-244 within the Earth’s geological record offers direct evidence of these rare phenomena.

The team’s meticulous analyses utilized state-of-the-art detection methods to isolate and quantify iron-60, plutonium-244, and curium-247 isotopes in Pacific Ocean crust samples. Iron-60 serves as a definitive marker of conventional supernovae, and its isotope profile corresponded precisely to two well-documented near-Earth supernova events occurring within the past few million years. In stark contrast, plutonium-244 exhibited a distribution pattern dramatically different—one consistent with deposition over a much longer timespan, pointing to a rare cosmic event that transpired at least a hundred million years ago.

Intriguingly, plutonium-244’s widespread but time-extended presence suggests it did not originate from the same near-Earth supernovae that deposited iron-60. Instead, it implies an older, more distant event where the synthesized elements had ample time to diffuse through the interstellar medium, creating a diffuse veil of heavy atoms engulfing the solar neighborhood. This insight recalibrates our understanding of when and how the most massive elements were introduced into our galactic environment.

Adding further weight to this narrative is the absence of curium-247, another isotope forged by the r-process. Despite its pivotal role—curium-247 decays more rapidly than plutonium-244, with a half-life of approximately 15.6 million years—its conspicuous scarcity in the crust sample indicates no recent r-process activity within the last 100 million years. This “expiry date” phenomenon serves as a cosmic clock, reinforcing the conclusion that the solar system’s immediate neighborhood has been devoid of major r-process events for many millions of years.

The technical sophistication required for these measurements cannot be overstated. Detecting individual plutonium atoms amidst an ocean of roughly ten sextillion non-plutonium atoms illustrates the extraordinary sensitivity needed. Recent advancements at the VEGA facility in Sydney, led by Michael Hotchkis, have pushed the boundaries of accelerator mass spectrometry, enabling researchers to detect and map plutonium distribution layer by layer with unparalleled time resolution. This breakthrough is complemented by the pioneering use of the Heavy Ion Accelerator Facility in Canberra for iron-60 detection, underscoring the collaborative, multinational nature of this endeavor.

Furthermore, a comprehensive age model was constructed using beryllium-10 isotopes measured at the DREAMS facility in Dresden. These measurements were instrumental in refining the growth history of the ferromanganese crust, allowing the researchers to place each isotopic signature accurately within a cosmic timeline spanning more than ten million years. Coupled with advanced imaging techniques such as X-ray scanning and 3D reconstruction of smaller drill cores, the team assembled a remarkably precise chronicle of element deposition.

The implications of this research extend beyond the confines of our solar system. Prof. Anton Wallner, head of the Accelerator Mass Spectrometry and Isotope Research Department at HZDR, emphasized that the detected plutonium likely originated from extraordinarily rare cosmic explosions, such as neutron star mergers recently observed via gravitational waves—albeit occurring far outside our own galaxy. These discoveries not only challenge preexisting assumptions about local r-process events but also rule out alternative hypotheses, including the crossing of the solar system through dense interstellar clouds, as a source of these heavy elements.

This research heralds a new era in studying cosmic nucleosynthesis. Upcoming analyses involving lunar samples provided by NASA promise to enrich our understanding of recent r-process events further. Equally exciting is the anticipated operational commencement of the HAMSTER facility at HZDR, which aspires to replicate and surpass current detection capabilities. This facility aims to detect a broader spectrum of rare radionuclides, potentially unlocking fresh insights into the astrophysical origins of our universe’s elemental diversity.

In sum, the discovery of plutonium-244 traces scattered throughout ancient oceanic crust reframes our knowledge of cosmic history and nucleosynthesis. It reveals a universe punctuated by rare, monumental events that have imprinted an indelible trace on Earth’s geological archives. These findings not only illuminate the elemental assembly of the cosmos but also open up new frontiers for studying the universe’s most violent and transformative phenomena with unprecedented detail and temporal precision.

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Subject of Research: Not applicable

Article Title: The timing of the last r-process event near Earth from interstellar 60Fe, 244Pu and 247Cm deposition on Earth

News Publication Date: 15-Jun-2026

Web References: http://dx.doi.org/10.1038/s41550-026-02841-6

References: Published in Nature Astronomy

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Keywords

r-process nucleosynthesis, plutonium-244, curium-247, iron-60, deep-sea manganese crust, neutron star mergers, supernova, radioactive isotopes, accelerator mass spectrometry, interstellar medium, cosmic explosions, element formation

In the profound depths of rocky planets like Earth and Mars, the precise chemical states of mantle minerals play a foundational role in shaping planetary evolution. Among these chemical states, the oxidation state of iron profoundly influences mantle melting behaviors, volcanic gas compositions, and ultimately, the nature of a planet’s surface environment. While the elemental presence of iron in the mantle is well-known, the subtle balance between its ferrous (Fe²⁺) and ferric (Fe³⁺) forms remains a challenging frontier to unravel, particularly under the extreme pressures and temperatures encountered in planetary interiors.

The early stages of planetary formation are marked by the existence of a vast magma ocean—a molten silicate layer blanketing the young Earth and Mars. During this epoch, the oxidation state at which iron integrates into forming minerals dictates subsequent mantle properties and evolution. Accurately determining the Fe³⁺ content in minerals crystallized within this magma ocean stands as a critical step toward understanding the oxidation dynamics that influenced core-mantle differentiation and surface volatile release in nascent planets.

A mineral of prime relevance in this context is majorite, a high-pressure silicate phase stable at depths ranging roughly from 500 to 600 kilometers within Earth’s mantle and near the base of the Martian mantle. Its stability under simultaneously high-pressure and high-temperature conditions makes majorite a significant reservoir for iron deep within these planetary interiors. Therefore, quantifying the Fe³⁺ concentration hosted within majorite under early magma ocean conditions bears directly on models of mantle redox evolution and volatile mobility.

Researchers at Ehime University’s Geodynamics Research Center have pioneered the synthesis of Fe³⁺-rich majorite coexisting with molten silicate magma at pressures around 18 gigapascals and temperatures between 2150 and 2200 degrees Celsius. Utilizing a multi-anvil apparatus capable of reproducing these extreme conditions, the team closely simulated the environment of the early magma ocean. High-precision X-ray Absorption Near Edge Structure (XANES) spectroscopy was then employed at the renowned SPring-8 synchrotron facility to accurately assess the valence state of iron within the synthesized majorite crystals.

The findings reveal an unexpectedly high Fe³⁺ content in majorite crystallized from the magma ocean, second only to bridgmanite, Earth’s most abundant lower mantle mineral. This marked enrichment in ferric iron suggests that early mantle minerals could accommodate significant oxidation capacity, challenging earlier assumptions that high-pressure silicates predominantly contain iron in the ferrous state. The implication is that the early mantle harbored more oxidized iron species than previously anticipated, impacting mantle viscosity, melting relations, and the capacity to store volatile elements.

Importantly, as mantle solids ascend toward shallower depths, phase transitions or mineral decompositions can liberate excess Fe³⁺ that no longer fits within the crystal structures. This released ferric iron potentially contributes to the generation of oxidized magmas, influencing volcanic gas emissions and surface oxidation states. Such a mechanism presents a plausible link between deep mantle oxidation states and the chemical makeup of magmas erupted at the surface, offering fresh insights into the geological histories of both Earth and Mars.

The study’s revelations offer a new lens through which to interpret the evolution of mantle oxidation state gradients over geological time. Understanding how iron’s valence shifts across depth-dependent mineralogical boundaries and during mantle convection cycles will refine planetary differentiation models and volatile cycling frameworks. The presence of Fe³⁺-rich majorite highlights a previously underappreciated redox reservoir deep within planetary interiors.

These results not only enhance our appreciation of Earth’s early differentiated mantle but also extend to Mars, where recent seismic and geochemical data point to a similarly complex mantle composition. The redox state plays an outsize role in Martian volcanic outgassing and atmospheric evolution, making this research vital for reconstructing Mars’ geochemical past and assessing its potential habitability.

From a methodological standpoint, the study exemplifies the power of integrating high-pressure experimental petrology with cutting-edge synchrotron techniques. The ability to recreate extreme planetary interior conditions and directly probe valence states in situ offers a transformative approach to addressing longstanding questions about deep Earth and planetary chemistry.

Furthermore, the recognition that Fe³⁺ can be abundant in magma ocean-derived minerals necessitates revisiting thermodynamic and geochemical models of mantle melting and evolution. Oxidation state strongly influences melting temperatures and mantle rheology, thereby controlling convection patterns and surface tectonics. Such feedbacks are essential to comprehend in the broader context of planetary habitability and evolution.

Ultimately, these insights pave the way for multidisciplinary endeavors bridging mineral physics, planetary science, and geochemistry. They underscore the dynamic interplay between deep Earth processes and surface conditions, revealing how the smallest changes in iron’s electron configuration resonate across planetary systems.

This breakthrough in understanding iron’s complex behavior under extreme conditions promises to guide future explorations of terrestrial and extraterrestrial geology. It sets new constraints on the interior states of rocky planets and sharpens our vision of how early planetary environments were sculpted by subtle shifts deep within.

Subject of Research: High-pressure mineralogy and mantle oxidation states in terrestrial and Martian planets.

Article Title: (Not explicitly provided in the original content.)

News Publication Date: (Not indicated in the original content.)

Web References: http://dx.doi.org/10.1029/2025JB033231

References: Journal of Geophysical Research Solid Earth

Image Credits: Hideharu Kuwahara

Keywords:
– Fe³⁺ in mantle minerals
– Majorite synthesis under high pressure
– Magma ocean oxidation states
– Mantle redox evolution
– XANES spectroscopy at SPring-8
– High-pressure experimental petrology
– Earth and Mars mantle comparison
– Ferric iron incorporation in majorite
– Oxidized magma generation
– Planetary interior chemistry
– Lower mantle mineralogy
– Planetary differentiation processes

New claims challenge inconsistencies in one of the foundational principles of physics.

New research from a team of scientists led by Cornell is transforming how researchers understand one of the

Krotite is a cosmic relic, one of the oldest minerals in the Solar System.

A look at the quest to mine the bottom of the ocean for valuable minerals, the connection between light pollution and allergies and more climate news.

© The New York Times

Most people think of Mars as a big red dustball, but researchers recently found Martian mineral deposits suggesting it was once warm and humid. The team used the Compact Reconnaissance Imaging Spectrometer aboard NASA’s Mars Reconnaissance Orbiter to analyze specific wavelengths of visible and near-infrared light from minerals on Mars’s surface to determine their chemical composition from afar.

Past researchers identified layered silicate minerals, called clays, across the Martian surface. Clays form when water interacts with rock, and record the amounts and chemical compositions of the waters that formed them. As water interacted with Martian surface rocks, it picked up more mobile elements like magnesium and iron and carried them to lower depths in the Martian soils, while less mobile elements like aluminum stayed in place. This process, called leaching, created 2 distinct layers of clays in the Martian rocks. 

Scientists have proposed 2 main hypotheses for how these layered clays formed on Mars. The first is that they formed through underwater leaching in pools or lakes sometime in Mars’ past. The second is that they formed across the Martian surface, where a widespread humid environment provided the moisture needed to leach them. 

To evaluate these hypotheses, a team led by researchers at Purdue University recently estimated the “true” thicknesses of Martian clay layers with a method scientists had previously only used on Earth. Rock layers containing clays can become tilted, making them appear thicker or thinner than they actually are. To address this discrepancy, the team used the High Resolution Imaging Science Experiment (HiRISE) tool on the Mars Reconnaissance Orbiter to create high-resolution elevation maps of the Martian surface. Then they combined these maps with surface composition data from the Compact Reconnaissance Imaging Spectrometer to create 3D composition maps. 

Using the 3D composition maps, the researchers found where each clay layer was exposed at the surface and traced it underground to estimate an angle of tilt. They then used trigonometry to calculate the true thicknesses of each clay layer. They analysed 46 regions across the Martian surface, and found that the combined thickness of both clay layers was around 20 to 680 feet (6 to 200 meters), with an average of about 190 feet (60 meters). That’s a maximum thickness as high as a 60-story building! 

Next, the researchers tested the extent of the clay deposits in a large ancient Martian valley known as the Mawrth Vallis Region. They focused on this region because it had large elevation changes, and scientists in the past had already collected high-resolution chemical composition and elevation data there. 

They explained that if the clay layers were restricted to the lowest parts of the valley where water once existed, and had changing thicknesses and boundaries between layers, this would provide strong evidence in favor of the “underwater leaching” hypothesis. In contrast, if the clay layers were more widespread, with consistent layer boundaries and thicknesses, this would provide strong evidence of a humid surface environment, in favor of the “surface leaching” hypothesis. 

The researchers found that the clay layers extended beyond the lowest parts of the valley and had consistent layer boundaries across more than half a mile (about a kilometer) of elevation change. Thus, they concluded that the clay layers formed by surface leaching in a humid environment. 

These findings conflict with climate models of early Mars, which generally suggest that the Martian surface rarely got above freezing temperatures. To address this discrepancy, the team proposed that these deposits could have formed over a long period of time rather than in a consistently warm and wet environment. If the surface was frozen most of the time, but got above freezing in short bursts, these clay deposits could still have formed, just over a much longer time period. In this case, the Mars climate models and the researchers’ findings would agree.

The researchers acknowledged that their study has some limitations, particularly regarding the sparse sample locations. Though they found strong evidence for a widespread humid environment on early Mars, more in-depth studies of locations like Mawrth Vallis could better constrain the specific surface environmental conditions under which these clays formed and potentially reconcile their data with Martian climate models.

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