The Mississippi River Basin covers approximately 41% of the contiguous United States and encompasses roughly 65% of U.S. croplands. For generations, farmers in this area have utilized liming to manage soil pH, reduce acidity, and improve crop yields. The practice involves spreading crushed limestone over agricultural fields. While the primary goal has historically been agricultural productivity, the new study reveals that this activity also has significant implications for climate change mitigation by removing carbon dioxide from the atmosphere.

Tim Jesper Suhrhoff, a geochemist at Yale and the first author of the study, noted that the results align climate action with practices that are already beneficial for farmers. Suhrhoff, a postdoctoral associate at the Yale Center for Natural Carbon Capture, explained that the study provides a more complete picture of the liming process. The research team analyzed more than 120 years of historical records to trace the long-term effects of adding crushed carbonate rock to agricultural soil. This extensive dataset allowed the researchers to evaluate the net carbon impact of liming over a significant period.

The mechanism by which liming stores carbon is similar to a related practice known as enhanced weathering. In this process, adding crushed rock to soil reacts with carbon dioxide to form stable bicarbonate ions. These ions can be transported through soils, groundwater, and rivers, eventually reaching the ocean where the associated carbon can remain stored for long periods. While enhanced weathering has often focused on silicate rocks, the new study demonstrates that carbonate-based liming also contributes to net carbon removal when evaluated against a realistic baseline.

A key advance of the study is its accounting for what would have occurred without liming. The researchers noted that even in the absence of lime, acidity generated by fertilizer use and air pollution would cause chemical reactions in the soil and water that release carbon dioxide. By comparing the liming scenario to this more complex baseline, the study finds that liming results in long-term net carbon removal. This approach provides a more accurate assessment of the practice’s climate benefits than previous methods that did not account for these background emissions.

The findings challenge the way agricultural liming is currently treated in conventional greenhouse gas accounting. The default methodology of the Intergovernmental Panel on Climate Change treats the carbon contained in applied lime as emitted carbon dioxide. However, the study suggests that a more complete framework could recognize situations where liming benefits both farmers and the climate. Suhrhoff and his colleagues emphasized that they support the IPCC’s efforts to document emissions but argued that accounting for liming’s net carbon removal would better align climate and agricultural incentives.

Christopher Reinhard, a professor at the Georgia Institute of Technology and co-corresponding author of the study, stated that better soil pH management can improve yields and soil health while also benefiting the climate. He suggested that this provides another reason to expand access to liming where it is sensible. The study’s results indicate that carbonate-based enhanced weathering may deserve renewed attention as a strategy for scaling up climate change mitigation. The researchers highlighted the potential for this practice to contribute significantly to global carbon removal efforts if adopted more broadly.

Noah Planavsky, a professor of Earth and planetary science at Yale and a corresponding author, described the study as a unique opportunity to trace historical records that demonstrate the effectiveness of enhanced weathering. He noted that the process already provides benefits to farmers and is now shown to be beneficial for the climate by removing carbon dioxide from the atmosphere. Planavsky, who is also a faculty member of the Yale Center for Natural Carbon Capture, emphasized the importance of understanding the long-term impacts of agricultural practices on the global carbon cycle.

The study estimates that since 1900, liming in the Mississippi River Basin has removed between 300 and 400 million metric tons of carbon dioxide. This substantial amount of carbon removal suggests an opportunity to scale up enhanced weathering by helping more farmers conduct agricultural liming. However, the researchers noted that the climate impact of liming will vary depending on local factors such as existing soil acidity, soil buffering capacity, and hydrology. The magnitude and duration of any upfront carbon dioxide emissions, as well as the efficiency of carbon removal, depend on these specific conditions.

Despite the promising findings, the researchers cautioned that the results from the Mississippi River Basin will not always transfer directly to every agricultural setting. Planavhoff noted that many farmers currently cannot afford optimal soil pH management and suggested that funding mechanisms could be developed to support this process by taking into account the carbon removals. The study was supported by funding from the Yale Center for Natural Carbon Capture, the Swiss National Science Foundation, the Environmental Defense Fund, the Foundation for Science and Technology, and the U.S. Department of Energy. Co-authors of the study include researchers from Yale, the Georgia Institute of Technology, Newcastle University, and Texas A&M University.

Subject of Research: Climate Change

Article Title: Adding limestone to Mississippi River Basin farmlands acts as a major carbon sink, study finds

Article References: Adding limestone to Mississippi River Basin farmlands acts as a major carbon sink, study finds. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: carbon sink, agricultural liming, Mississippi River Basin, enhanced weathering, soil management, climate mitigation, Yale University, Nature journal, Adding, limestone, Mississippi, River

The achievement, led by Yu Guo and Yubo Wang in Hong X. Tang’s laboratory in Yale’s Department of Electrical Engineering, rests on an architectural insight borrowed from high-power laser engineering: the master-oscillator-power-amplifier, or MOPA, design. In a MOPA system, a small, exquisitely stable seed laser generates the optical signal, and separate amplifier stages then boost that signal to useful power levels without degrading its spectral purity or noise characteristics. This division of labour is what allows industrial Nd:YAG systems to be simultaneously precise and powerful. Reproducing that architecture on a chip, however, demanded that the researchers solve two problems that have long stymied integrated solid-state photonics: how to make a chip-scale Nd:YAG oscillator that can actually start lasing with modest pump power, and how to build waveguide amplifiers with enough gain to be useful.

The seed oscillator is the quieter triumph of the work. The team fabricated a microring resonator — a tiny circular waveguide that traps light as it circulates — directly in neodymium-doped YAG. The device operates in a double-resonant configuration, meaning that both the pump light and the lasing light are simultaneously resonant with the ring, dramatically enhancing the light-matter interaction at both wavelengths. The result is a laser threshold of just 2.9 microwatts of absorbed pump power, an extraordinarily low figure for a solid-state laser. For comparison, conventional diode-pumped Nd:YAG lasers typically require orders of magnitude more pump power before they begin to oscillate. This low threshold matters because it means the seed can be driven gently, preserving the narrow linewidth and low noise that make solid-state lasers so valuable, while leaving the task of power generation to the amplifiers downstream.

Those amplifiers form the second half of the system. When optimized as standalone devices, the single-pass neodymium-doped waveguide amplifiers demonstrated up to 46.6 decibels of small-signal gain — a factor of nearly 46,000 in optical power. Achieving such gain in a rare-earth-doped waveguide is notoriously difficult: the ions must be pumped efficiently, the waveguide must confine both pump and signal over a sufficient interaction length, and parasitic losses and unwanted lasing must be suppressed. The Yale team’s amplifiers also achieved a photon conversion efficiency of up to 53.2 percent under large-signal conditions, meaning that more than half of the pump photons arriving at the chip were converted into signal photons — a figure that approaches the performance of much larger bulk solid-state amplifiers and reflects careful engineering of the pump geometry and waveguide design.

When the low-threshold microring seed was combined with cascaded waveguide amplifiers on the microchip platform, the complete integrated MOPA system delivered more than 12 dBm of amplified continuous-wave output. That power level, while modest compared with industrial Nd:YAG lasers that produce tens of watts, is significant in the context of integrated photonics, where on-chip laser sources frequently struggle to produce even a few milliwatts of usable light. More importantly, the architecture is inherently scalable: additional amplifier stages can be cascaded, and the design principles established here — efficient pump utilization, low-threshold oscillation, and high-gain single-pass amplification — provide a roadmap for pushing chip-scale solid-state lasers toward watt-class output in future iterations.

The significance of this work becomes clearer when viewed against the broader landscape of integrated photonics. Most chip-scale lasers today rely on semiconductor gain media, such as indium phosphide or III-V compounds bonded to silicon, or on nonlinear conversion processes in materials like lithium niobate. These approaches excel in certain regimes but struggle to reach the exceptional spectral purity, efficiency, and wavelength coverage that diode-pumped solid-state lasers offer. Rare-earth-doped crystals such as Nd:YAG occupy a special niche: their narrow emission lines produce highly coherent light, their four-level energy structure enables efficient operation, and their emission wavelengths — including 1064 nanometres and harmonics at 532, 355, and 266 nanometres — are inaccessible to ordinary semiconductor diodes. Bringing this gain medium onto a wafer-scale, lithographically defined platform means the precision of solid-state lasers can finally be married with the manufacturability of chips.

The potential applications span an impressive range of fields. In quantum information science, trapped-ion quantum computers require multiple precisely controlled laser beams at specific wavelengths to cool and manipulate individual qubits; integrated Nd:YAG sources could replace the laboratory-scale laser systems that currently make such machines enormous and fragile. In coherent optical communications, stable narrow-linewidth lasers at 1064 nanometres and nearby bands serve as local oscillators and carriers. In precision metrology, optical clocks and interferometric sensors demand exactly the combination of low noise and high power that the MOPA architecture provides. Even nonlinear photonics stands to benefit, since efficient frequency conversion and frequency-comb generation in on-chip resonators require pump lasers with both adequate power and exceptional coherence — precisely what this integrated system is designed to deliver.

The path to this result also reflects a broader trend in the Tang group’s research programme, which has previously demonstrated photonic-integrated titanium:sapphire lasers by diffusing dopants into sapphire substrates and building low-loss waveguides on top. The same philosophy — take a proven bulk gain medium, engineer a low-loss photonic platform around it, and apply system-level architectures from laser engineering — has now been extended to neodymium-doped garnets. The fabrication relies on wafer-scale processing techniques, and the authors note that the underlying substrate platform, a heterogeneous sapphire-supported low-loss photonic system, was developed in their earlier work. This lineage suggests that the Nd:YAG MOPA is not an isolated demonstration but part of a maturing toolkit for building solid-state photonic integrated circuits, with data and code from the study made publicly available through Zenodo to support reproducibility.

Challenges remain before chip-scale Nd:YAG lasers can displace their benchtop ancestors. Output power must climb by another two to three orders of magnitude to compete in industrial materials processing, thermal management on chip becomes increasingly demanding at higher pump powers, and the pump lasers themselves — currently off-chip diode sources — would ideally be integrated or fibre-coupled with minimal loss. Nevertheless, the demonstration of a complete master-oscillator-power-amplifier system in which every functional element, from the 2.9-microwatt-threshold seed to the 46.6-decibel-gain amplifiers, operates on a single microchip platform marks a genuine milestone. It transforms Nd:YAG from a symbol of photonics’ macroscopic past into a building block for its integrated future, and it signals that the most trusted laser crystal in science may soon be etched, by the millions, onto silicon wafers.

Subject of Research: An integrated photonic Nd:YAG laser-amplifier system using a microchip master-oscillator-power-amplifier architecture

Article Title: Microchip Nd:YAG laser with master-oscillator–power-amplifier architecture

Article References: Guo, Y., Wang, Y., Zhao, H., Yang, F., Yang, G., Xie, H., & Tang, H. X. (2026). Microchip Nd:YAG laser with master-oscillator–power-amplifier architecture. Nature Photonics. https://doi.org/10.1038/s41566-026-01984-2

Image Credits: AI Generated

DOI: 10.1038/s41566-026-01984-2

Keywords: Nd:YAG laser, integrated photonics, master-oscillator power-amplifier, microring resonator, waveguide amplifier, solid-state lasers, rare-earth doping, photonic integrated circuits, laser threshold, coherent light sources, Yale University, Nature Photonics

Previous research had already hinted that something like this preferential sorting was taking place, but only in objects that formed between two and four million years after the solar system’s origin. Among carbonaceous chondrites, the primitive stony meteorites that contain organic compounds and water within their silicate minerals, those that formed earlier consistently contained a higher percentage of chondrules and a lower percentage of matrix. This pattern suggested that in the regions where the first planetesimals were coalescing, the icy, volatile-rich dust was already being squeezed out in favor of the heat-forged rocky beads. What was missing was direct evidence from the very earliest epoch, the first million years, when the first generation of solid bodies came together. No undifferentiated bodies from that period survive intact today, leaving a critical gap in the record of how the solar system’s construction began.

Damanveer Grewal, an assistant professor of Earth and planetary sciences in Yale’s Faculty of Arts and Sciences and first author of the study, set out to close that gap with an unconventional approach. Rather than searching for preserved early bodies, which do not exist, he turned to iron meteorites whose parent bodies formed in the outer solar system during that missing first million years. These parent bodies had accumulated so much of the radioactive isotope aluminum-26 that they melted completely, destroying every physical trace of their original chondrule-to-matrix composition. On the surface, that total melting would seem to erase all useful information. But Grewal and his colleagues realized that the chemical fingerprints of the original ingredients would survive the melting, locked into the metallic cores of these differentiated bodies.

The team identified two independent chemical tracers, both tied specifically to the matrix component. The first is sulfur, which exists in concentrated form within matrix material. The amount of sulfur preserved in the iron meteorites therefore reveals how much fine-grained, volatile-rich dust the original parent body had incorporated before it melted. The second tracer is the oxidation state of iron, which reflects how much water ice and oxidized dust the original body contained. Because matrix is the component that carries water ice and oxidized material, a low oxidation state in the surviving metal indicates that very little icy dust was present when the body assembled. By measuring both tracers in the same set of meteorites, the researchers could reconstruct the original composition of bodies that had otherwise lost all physical memory of their building blocks.

The results were striking. Using the paired tracers, the researchers calculated that matrix made up only 8 to 17 percent of the original bodies sampled by these iron meteorites. That range is lower than the matrix fraction found in any known chondrite, meaning the earliest planetesimals of the outer solar system were more chondrule-dominated than any primitive meteorite ever recovered on Earth. In other words, the first solid bodies ever built in the solar system were constructed from 83 to 92 percent chondrules, with only a small admixture of the icy, volatile-rich dust that dominates objects that formed later. The two tracers, measured independently, converged on the same answer, giving the team confidence that the reconstruction was robust rather than an artifact of any single measurement.

Both tracers independently tell the same story: these early planetesimals were remarkably matrix-poor, Grewal explained. That convergence is what makes the result robust. The finding demonstrates that the assembly process was remarkably selective from the very beginning, sorting heat-forged chondrules into the first generation of solid bodies while excluding most of the cold, volatile-bearing dust. This selectivity implies that physical processes in the young protoplanetary disk, such as aerodynamic sorting of particles by size and density, were already operating efficiently within the first million years, concentrating the millimeter-sized chondrules and winnowing away the finer matrix grains before the first planetesimals accreted.

The discovery also resolves a long-standing puzzle about the meteorite record itself. Chondrules from the earliest epoch are scarce among the meteorites collected on Earth, and the new study explains why. The bodies that incorporated those oldest chondrules were the same bodies that accumulated enough radioactive aluminum-26 to melt completely, and that melting erased the physical evidence of their chondrule-rich composition. The oldest chondrules were not absent from the early solar system; they were simply swallowed by bodies that later transformed beyond recognition, leaving only their chemical ghosts in the iron meteorites that survive today. The scarcity of ancient chondrules in chondrites is thus a consequence of planetary differentiation, not of their original rarity.

Beyond solving that puzzle, the findings carry broader implications for understanding how the planets themselves came to be. Chondrules are the ubiquitous little beads of rock that served as the basic building blocks from which the planets were eventually assembled, and the new work shows that they were already being sorted and incorporated into the first generation of solid bodies from the very start. If the earliest planetesimals were so strongly enriched in chondrules and so depleted in volatile-rich matrix, then the seeds of the planets began their lives chemically dry and rocky, with the water and organic material arriving later or in different proportions than many models had assumed. This has consequences for theories of how Earth acquired its water and for understanding the volatile budgets of the outer solar system’s icy bodies.

The study was co-authored by Zhongtian Zhang of Princeton University and Joanna Drążkowska of the Max Planck Institute for Solar System Research in Germany, and the research was funded by Yale University. For Grewal, the work also carries a sense of deep connection to the deep past. Chondrules are found inside chondrites, the most primitive meteorites in geological collections, and holding one in your hand means holding a fragment of a process that started billions of years ago, a timescale that is hard to wrap your head around. By reading the chemical memory preserved in melted iron cores, the team has recovered a chapter of solar system history that physical evidence alone could never provide, revealing that when the solar system first began to build, it chose fire over ice.

Subject of Research: Geochemical reconstruction of the chondrule-to-matrix composition of the solar system's first planetesimals

Article Title: From the start, the solar system chose fire over ice to build its first bodies

Article References: From the start, the solar system chose fire over ice to build its first bodies. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: chondrules, matrix, planetesimals, iron meteorites, carbonaceous chondrites, solar system formation, aluminum-26, protoplanetary disk, Yale University, Nature Astronomy, oxidation state, volatile-rich dust

Carbonaceous chondrites, the primitive meteorites that fall to Earth from the outer Solar System, are textural hybrids. They consist of a fine-grained, volatile-rich matrix—essentially preserved interstellar and nebular dust—interspersed with chondrules, millimeter-sized spherical beads that were thermally sintered in brief, high-temperature events before being assembled into rock. The relative proportions of these two ingredients are not random. Among carbonaceous chondrite parent bodies that accreted roughly two to four million years after the formation of the first solids, the calcium–aluminium-rich inclusions or CAIs, the fraction of matrix increases steadily with accretion time. That correlation had previously been interpreted as the fingerprint of aerodynamic sorting in the protoplanetary disk, where gas currents physically separate particles by size and density.

What remained unknown was whether this sorting machinery was already operating during the very first wave of planetesimal formation, within the first one to two million years of Solar System history. Answering that question requires a probe of bodies older than any surviving chondrite parent body—and the study found one in an unexpected place: iron meteorites. These are fragments of the metallic cores of differentiated planetesimals, bodies that grew large and hot enough, thanks to heat from the decay of aluminium-26, to melt, separate into metal and silicate layers, and then shatter in later collisions, scattering core fragments across space. The parent bodies of the carbonaceous-type iron meteorites are the earliest known planetesimals of the outer Solar System.

The challenge was to reconstruct how much matrix such bodies originally contained, given that only their metal cores survive as samples. Grewal and colleagues solved this with two independent chemical proxies. The first is bulk sulfur content. Sulfur in primordial outer Solar System material was carried overwhelmingly in the fine-grained matrix, so a planetesimal’s sulfur inventory scales directly with how much dusty matrix it accreted. By reconstructing the sulfur content of the parent cores from the chemistry of iron meteorites—using decades of experimental work on how elements partition between solid metal and sulfur-bearing liquid metal during core crystallization—the team could back-calculate the sulfur, and hence the matrix fraction, of the original bulk planetesimals.

The second proxy is the valence state of iron, the balance between oxidized and metallic iron in the body. In carbonaceous chondrites, the oxidized iron budget reflects the combined abundance of water ice and pre-accretionary oxidized silicate precursors, both of which likewise reside preferentially in the matrix. By performing a careful core–mantle mass balance for each parent body, corrected for sulfur dissolved in the core, and comparing the results against published Mössbauer and X-ray absorption measurements of chondrites, the researchers obtained a second, fully independent estimate of matrix mass fraction. Both proxies delivered the same answer, and they agreed with each other.

That answer is emphatic. The parent bodies of carbonaceous-type iron meteorites accreted systematically less matrix than any carbonaceous chondrite parent body, with reconstructed matrix mass fractions of only about 0.08 to 0.17—roughly a tenth or so of the original rock—compared with substantially higher matrix fractions in the later-forming chondrite parents. In other words, the earliest planetesimals in the outer Solar System were built predominantly from chondrule-rich, matrix-poor material, while bodies that assembled millions of years later became progressively richer in fine dust. The trend that had been observed among chondrites accreting between two and four million years after CAIs extends unbroken all the way back to the Solar System’s opening act.

The physical explanation lies in how gas and solids interact in a protoplanetary disk. Small dust grains are tightly coupled to the gas and drift slowly, while millimeter-sized chondrules experience stronger headwinds and migrate inward at different rates, and larger aggregates behave differently still. Turbulence, pressure bumps, and the streaming instability—the leading mechanism proposed for concentrating solids into gravitationally collapsing clumps—each sort particles by their aerodynamic properties. Under these conditions, the mixture of material available for planetesimal formation changes with time and location in the disk. The new results indicate that this sorting was not a late refinement but a fundamental, first-order control on planetesimal compositions from the onset of planet formation itself.

Perhaps the most consequential implication concerns chondrules. If the earliest planetesimals were chondrule-rich, then chondrule formation—brief episodes of melting that remain one of the great unsolved problems of meteoritics—must have been widespread from the very beginning of the Solar System, not a phenomenon that ramped up gradually. This conclusion dovetails with isotopic chronology: chondrule ages spanning the first several million years have been documented by lead–lead dating and aluminium–magnesium systematics, and tungsten isotope studies have long argued for early chondrule production. The new work adds a compositional argument that chondrules were abundant in the feeding zones of the first planetesimals, constraining models of disk thermal processing and challenging scenarios in which chondrule formation is tied to specific late-stage events such as planetesimal collisions alone.

Because iron meteorite parent bodies were among the first large objects to differentiate, their volatile and oxidized inventories also bear on the broader question of how Earth acquired its water and other volatiles. Matrix-rich carbonaceous material delivered to the inner Solar System is a leading candidate source of terrestrial volatiles, and quantifying how much matrix the earliest bodies carried helps trace how volatile-bearing dust was distributed and redistributed as the disk evolved. The study, funded by start-up funds from Yale University, thus connects the smallest scales of dust dynamics to the largest questions of planetary habitability.

What the results ultimately sketch is a Solar System whose architecture was set almost immediately. Within the first two million years, gas drag in the nebula had already segregated dust from beads, sorting the raw materials of worlds into distinct reservoirs whose chemical signatures meteorites preserve to this day. The iron cores that fell to Earth as metal-bearing relics now read as a chemical archive of that primordial wind, confirming that the disk was a sorting machine from day one—and that the humble chondrule, forged in transient furnace events before most planets existed, was already everywhere.

Subject of Research: Aerodynamic sorting of matrix and chondrules in the protoplanetary disk and its control on the compositions of the earliest outer Solar System planetesimals

Article Title: Planetesimal compositions governed by aerodynamic sorting from the onset of Solar System formation

Article References: Grewal, D. S., Zhang, Z., & Drążkowska, J. (2026). Planetesimal compositions governed by aerodynamic sorting from the onset of Solar System formation. Nature Astronomy. https://doi.org/10.1038/s41550-026-02976-6

Image Credits: AI Generated

DOI: 10.1038/s41550-026-02976-6

Keywords: planetesimals, aerodynamic sorting, carbonaceous chondrites, iron meteorites, chondrules, matrix, protoplanetary disk, early Solar System, meteoritics, sulfur content, iron valence state, Yale University