Sub-Neptune-sized planets, the most prevalent class of exoplanets discovered to date, exhibit mass and size characteristics that position them intriguingly between Earth and Neptune, typically hosting thick hydrogen-rich atmospheres with rocky interiors. These planets serve as natural laboratories to investigate early planetary processes, including the origin of internal water reservoirs, which are fundamental to understanding how life-essential environments could arise across the cosmos. Until now, the production of water during planet formation remained largely modeled through computational means, without experimental verification under representative conditions.

The researchers employed diamond anvil cells to replicate pressures approaching 60 gigapascals and temperatures exceeding 4,000 degrees Celsius—parameters that realistically mimic the conditions within a magma ocean overlain by a dense H₂ atmosphere during the nascent stages of planet building. By squeezing and heating iron-bearing silicate melts in the presence of molecular hydrogen, the team observed a remarkable chemical transformation: hydrogen molecules actively interacted with iron oxides in the melt, inducing reduction reactions that liberate water molecules within the molten silicates. Concurrently, significant quantities of hydrogen dissolved into the magma, potentially altering the planet’s compositional and physical traits.

This experimental demonstration bands together planetary geophysics, mineral physics, and atmospheric chemistry, revealing that early planetary interiors are not merely passive reservoirs but dynamic actors in water generation. The dissolution of hydrogen in the magma could influence melting behavior, core formation dynamics, and long-term volatile cycling between the atmosphere and interior. Moreover, the accumulation of water dissolved in the magma ocean could provide a substantial and stable supply of this vital liquid, persisting long before the planet’s magma solidifies and the atmosphere evolves operationally.

From an astronomical perspective, this mechanism elegantly solves the quandary of how rocky planets like Earth could harbor abundant water without relying entirely on late-stage delivery from comets or asteroids. Instead, water emerges as a natural product of formative chemical processes during the molten planet phase, mediated by the ubiquitous presence of hydrogen-dominated primordial atmospheres. Such atmospheres commonly blanket young planets due to residual gas in protoplanetary disks, sustaining high temperatures that maintain global magma oceans over geological durations.

The AEThER collaborative framework, spearheaded by Shahar and funded by the Alfred P. Sloan Foundation, furnished the interdisciplinary environment necessary for such a complex undertaking. This consortium melded expertise from astronomy, cosmochemistry, petrology, and planetary dynamics, generating a unified approach to deciphering the early evolution of exoplanetary systems. By integrating experimental data with theoretical models and observational constraints, AEThER advances predictions about planetary interiors’ chemical composition and the viability of habitable conditions in diverse planetary environments.

The implications of this study extend beyond the laboratory, reaching into the realm of observational astronomy and the search for life beyond Earth. If large quantities of water can form intrinsically during planet formation, planets within the habitable zones of distant stars may be more likely to host liquid water on or beneath their surfaces than previously believed. This enhances the prospects of identifying potentially habitable exoplanets simply by characterizing their bulk properties and atmospheric compositions rather than relying solely on indirect evidence of water delivery through impacts.

Furthermore, these findings challenge traditional interpretations of exoplanet atmospheres by illustrating that water signatures detected might not exclusively indicate surface oceans or cometary delivery but could derive from a rich interplay between interior processes and atmospheric chemistry during early evolution. This paradigm shift alters the way scientists prioritize targets for next-generation telescopes and space missions aimed at detecting biosignatures and assessing planetary habitability.

From a geochemical standpoint, understanding how hydrogen is incorporated and stored within silicate melts under extreme conditions informs models of core differentiation and mantle evolution. Hydrogen’s solubility in magma and concurrent water formation can affect melting points, viscosity, and electrical conductivity, consequently influencing magnetic field generation and tectonic activity—key factors that modulate a planet’s capacity to sustain life over billions of years.

The new experimental evidence is part of a broader scientific endeavor to unravel the complex narrative of planet formation, atmospheric evolution, and volatile cycling. By establishing hydrogen-rich atmospheres as not merely protective blankets but active chemical agents in creating water, this research bridges gaps between astrophysics, planetary science, and geochemistry. It heralds a new chapter in astrobiology, illuminating natural paths through which life-enabling conditions might arise across diverse planetary systems.

In conclusion, the discovery that significant quantities of water can be synthesized naturally and efficiently during planetary formation via interactions between hydrogen atmospheres and magma oceans reshapes fundamental concepts of planetary habitability. It invites scientists to rethink how water is measured, detected, and interpreted in relation to planetary history and to deepen interdisciplinary collaborations aimed at exploring the origins and distribution of life-giving volatiles throughout the Milky Way. This breakthrough provides a powerful lens to view newly discovered planets not just as passive recipients of water but as chemically dynamic worlds capable of self-generating the essential ingredient for life.

Subject of Research: Experimental study on planetary formation and water genesis under extreme conditions

Article Title: Experiments reveal extreme water generation during planet formation

News Publication Date: 30-Oct-2025

Web References: DOI: 10.1038/s41586-025-09816-z

Image Credits: Image courtesy of Navid Marvi/Carnegie Science.

Keywords: Planet formation, water generation, magma ocean, hydrogen atmosphere, Sub-Neptune, exoplanets, planetary habitability, high-pressure experiments, diamond anvil cell, volatile cycling, astrobiology, early planetary evolution

The preparation of starting materials was a critical first step in this investigation. Researchers synthesized glasses representing diverse compositions, carefully controlling the ratios of calcium, magnesium, iron, aluminum, silicon, and oxygen. Melting powders of MgO, SiO₂, CaO, and Fe₂O₃ at temperatures exceeding 1900 K in a high-temperature furnace, they rapidly quenched the melts in cold water, producing homogenous glassy substances. These glasses were rigorously characterized using energy-dispersive X-ray spectroscopy integrated within scanning electron microscopy, ensuring precise compositional verification and uniformity essential for subsequent high-pressure experiments.

Following synthesis, the materials were subjected to ultrahigh-pressure multi-anvil press experiments to simulate the forbidding conditions of the lower mantle, where pressures reach up to 50 gigapascals and temperatures soar beyond 2700 kelvin. These experiments utilized state-of-the-art assemblies and heating systems tailored to maintain precise control over pressure and temperature profiles. Intricate sample assemblies involved platinum or rhenium capsules encased within aluminum oxide sleeves and LaCrO₃ heaters, demonstrating a sophisticated approach to balancing thermal insulation and mechanical stability. Remarkably, strategies such as embedding trace amounts of magnesium hydroxide promoted grain growth through the release of water vapor, optimizing the quality of mineral grains for chemical analysis.

Temperature monitoring employed type-D thermocouples strategically positioned between rhenium capsules, enabling highly accurate real-time measurement during the ramp-up and annealing stages. Annealing at target conditions for extended durations, typically 24 hours, ensured equilibrium attainment within samples. This rigorous control of temperature, pressure, and time allowed for the faithful reproduction of the natural processes governing mineral formation and transformation in Earth’s deep mantle, ultimately facilitating the detection of subtle phase equilibria essential for understanding mineral stability fields.

Post-experiment analyses leveraged advanced microscopy and spectroscopy to unravel the mineralogical evolution of the samples. The polished cross-sections underwent scanning electron microscopy to assess grain size distributions and morphologies. Ultrathin lamellae prepared via focused ion beam techniques allowed for high-resolution chemical mapping using scanning transmission electron microscopy combined with energy-dispersive X-ray spectroscopy. Such detailed compositional mappings revealed the distribution of constituent elements at nanometric spatial scales, with corrections applied to account for complex effects such as atomic number (Z) and X-ray absorption for more accurate quantification.

Beyond elemental analysis, electron energy-loss spectroscopy provided discerning insight into the iron oxidation states within the synthesized minerals. By analyzing the Fe-L₂,₃ edges, researchers quantified Fe³⁺/ΣFe ratios, shedding light on redox conditions that influence mineral stability and phase relations. Such measurements are essential because the valence state of iron profoundly affects the structural properties and seismic signatures of mantle phases, thereby linking laboratory experiments directly to geophysical observations.

Complementary microprobe analyses validated the compositions of recovered phases, employing standards precise for magnesium, silicon, calcium, and iron to ensure analytical fidelity. Meanwhile, phase identification utilized micro-focused X-ray diffraction with Co–Kα radiation and cutting-edge two-dimensional detectors, offering definitive confirmation of crystallographic structures formed under extreme conditions. Extended exposure times and focused beam sizes optimized diffraction patterns, facilitating the detection of even minor phases critical to the mineralogical assemblage.

Central to interpreting these experimental results was the development of an empirical model linking the mole fraction of calcium silicate (χ_Ca) in bridgmanite (Bdm) to pressure and temperature. This relationship was expressed as an exponential function incorporating fitted parameters to capture the thermal and baric dependencies observed. Drawing from thermodynamic principles, these parameters corresponded directly to changes in enthalpy, entropy, and volume associated with the equilibration reaction between calcium silicate in davemaoite (Dvm) and bridgmanite. Such an approach enabled researchers to extrapolate mineral stability fields beyond accessible experimental ranges reliably.

The fitted model predicted that davemaoite coexists with bridgmanite across a broad spectrum of lower-mantle conditions, persisting even at pyrolitic solidus temperatures. Calculations revealed mole fractions of CaSiO₃ in bridgmanite remain below pyrolitic levels across pressures extending to 120 GPa, signifying the continuous presence of davemaoite within the mantle’s complex mineralogy. This challenges earlier conceptions that davemaoite would break down or be significantly depleted under such extreme conditions, emphasizing its role as a stable and integral phase within Earth’s deep interior.

Seismic modeling further underscored the implications of these mineralogical findings. Using the BurnMan software, researchers simulated shear-wave velocities for regions enriched in davemaoite relative to those dominated by bridgmanite alone. They incorporated compositional variations involving magnesium, iron, and aluminum contents within bridgmanite to reflect realistic mantle compositions. By varying temperature and phase proportions, the models elucidated how the presence of davemaoite-enriched domains could contribute to observed seismic anomalies, thereby connecting mineral physics directly to geophysical phenomena.

The study’s meticulous experimental design, combined with comprehensive analytical precision, represents a transformative step in understanding Earth’s deep mantle. By establishing the persistence of davemaoite under lower-mantle conditions, it enriches our comprehension of the mineralogical diversity influencing mantle dynamics, chemical heterogeneity, and seismic wave propagation. These insights open new avenues for interpreting data from seismology, mineral physics, and geochemistry, fostering integrated models that reconcile observations from laboratory to planetary scales.

Moreover, the implications of persistent davemaoite affect geochemical cycling and mantle evolution. As a calcium-bearing phase stable in deep mantle assemblages, it influences element partitioning, melt generation, and the overall mineralogical framework governing mantle convection. Understanding its stability enhances predictive models of mantle composition and behavior, thereby refining interpretations of geodynamic processes shaping Earth’s interior through deep time.

The experimental approach, employing cutting-edge multi-anvil presses capable of replicating the ultrahigh pressures of the deep mantle, exemplifies the forefront of high-pressure mineralogy. The integration of multiple analytical methodologies, including synchrotron-based diffraction, transmission electron microscopy, and electron energy-loss spectroscopy, provides a holistic view of mineral structures, compositions, and valence states. Such technological synergy is essential for unraveling the profound complexities of Earth’s inaccessible depths.

Equally significant is the temperature control strategy, wherein samples were annealed for prolonged periods under tightly regulated thermal regimes, ensuring that equilibrium was established. This detail is crucial because kinetic barriers often hinder phase transformations at lower temperatures or shorter timescales, and the careful annealing protocols adopted here allow a more accurate reflection of natural mantle conditions.

The study also illuminates subtle effects such as selective magnesium diffusion caused by electron beam irradiation during transmission electron microscopy analysis, a factor that researchers accounted for in compositional quantifications. Recognizing and correcting for such intricacies enhances confidence in the precision of mineral composition data, fostering robust interpretations of the physicochemical behavior of deep mantle phases.

In sum, this comprehensive research not only confirms the persistence of davemaoite as a stable calcium silicate phase in Earth’s lower mantle but also bridges the realms of experimental petrology, mineral physics, and geophysics. It reinforces the complex mineralogical landscape within which mantle processes operate and underscores the indispensable role of interdisciplinary approaches in Earth sciences. As seismic and geochemical probing of our planet’s interior advances, such fundamental knowledge forms the backbone of our understanding of the dynamic Earth beneath our feet.

Subject of Research: Persistence and stability of davemaoite (CaSiO₃) under lower mantle pressure and temperature conditions.

Article Title: Persistence of davemaoite at lower-mantle conditions.

Article References:
Wang, L., Miyajima, N., Wang, F. et al. Persistence of davemaoite at lower-mantle conditions. Nat. Geosci. 18, 365–369 (2025). https://doi.org/10.1038/s41561-025-01657-9

Image Credits: AI Generated

DOI: https://doi.org/10.1038/s41561-025-01657-9