Scientists Propose a “Glass Ceiling” Inside Venus That Explains Why Coronae and Giant Volcanic Rises Coexist

A new study uses computer models and mineral physics to show that a layer about 600 km beneath Venus’s surface can trap warm mantle rock and spawn two families of upwellings, from small blobs that make coronae to huge plumes that build volcanic rises. The result argues Venus’s mantle is hundreds of kelvins hotter than Earth’s and rewrites how we think surface features map to deep planetary plumbing.

A planetary puzzle, and a surprising answer

Venus and Earth are often called planetary twins because they are similar in size and bulk density, yet their surfaces tell very different stories. Earth wears plates and mid-ocean ridges, while Venus is dominated by broad volcanic rises and more than 700 enigmatic, circular features called coronae, which are not found on Earth. How can a single planet produce both enormous, long-lived mantle plumes and a widespread population of much smaller, diverse features?

Madeleine C. Kerr and colleagues tackled that question with physics-rich convection models and new mineral data. Their conclusion is elegant and intuitive: a particular sequence of mineral phase changes in a warm Venusian mantle makes a “glass ceiling” at roughly 600 km depth that changes how hot and cold mantle material moves. That trapped layer seeds many small upwellings while allowing only the strongest deep plumes to punch through and build the biggest rises. The models reproduce key surface signals such as the length scales seen in topography and volcanic deformation.

Why coronae have been such a mystery

Coronae are quasi-circular, volcano-tectonic features that number in the hundreds on Venus. They come in many shapes and sizes, from central depressions to rimmed uplifts, and their mean diameter is about 200 km, though a subset exceed 500 km. Many researchers have tied coronae to localized thermal upwellings, lithosphere dripping, or magmatic intrusion, but a unified origin that explains their global abundance and variability has been lacking.

At the same time, Venus has roughly ten very large volcanic rises, broad topographic swells about 2,000 km across, that look like the surface expression of long-lived deep plumes. Explaining both populations in one convective picture is the central challenge the paper addresses.

How the researchers modeled Venus’s interior

Kerr et al. used two-dimensional mantle convection simulations that explicitly include the thermodynamics of realistic mantle minerals for an anhydrous pyrolite composition. The models span a range of interior potential temperatures (roughly 1,600 K to 2,000 K) and explore different viscosity contrasts across the mantle. They also add a modest amount of bottom heating to produce a few strong plumes from the core–mantle boundary, while letting the stagnant outer lid of Venus control surface heat loss.

Key to the approach is using mineral phase data generated with HeFESTo, a thermodynamic tool, so that phase changes like wadsleyite turning into majorite plus ferropericlase are represented with realistic thermodynamic effects. That allows the models to capture the way mineral reactions change density, heat capacity, and thermal expansivity with depth and temperature.

The “glass ceiling” idea, in plain language

Deep in the mantle, minerals change crystal structure as pressure and temperature increase. In a warmer Venusian mantle, the paper shows, a multiphase assemblage involving wadsleyite, majorite, and ferropericlase forms a broad transition zone. Across that zone the relationship between temperature and density can invert so that colder rock is effectively heavier and warmer rock is relatively lighter in non-intuitive ways. The lower edge of that zone, at about 600 km depth, acts like a glass ceiling, temporarily trapping warm, buoyant mantle material below it.

Analogy: imagine a layer of slightly sticky gelatin sloshing inside a pot. Big, strong bubbles can burst through and break the surface, but smaller ones get caught and accumulate beneath the sticky sheet. When enough disturbance builds up, the trapped layer can slosh and send out many smaller plumes. On Venus that trapped, warm layer is the source of many small-scale upwellings, while only the biggest plumes from the deep thermal boundary layer pierce the ceiling to form giant rises.

How small upwellings become coronae

In the models, cold dense drips peeling away from the base of the stagnant lithosphere collect above the glass ceiling. When those drips reach a critical volume they trigger flushing events, called mantle avalanches, that displace and mobilize trapped warm material. That return flow spawns many secondary upwellings that rise through the ceiling and impinge on the lithosphere at scales from tens to about a thousand kilometers. Those small, transient plumes provide exactly the kind of thermal diapirs that regional studies typically assume as initial conditions when modeling corona formation. The variety in timing, size, and interaction with lithospheric structure can produce the wide range of corona morphologies observed on Venus.

The models suggest secondary upwellings can be adjacent yet different in size because they do not follow classical boundary layer scaling once they are advected along the base of the glass ceiling and then locally regain their normal buoyancy to rise. This explains why neighboring coronae can look dissimilar even if they formed from the same deep disturbance.

Why the result argues for a much hotter mantle

A central prediction of the study is that the glass-ceiling regime is active only in a narrow range of mantle potential temperatures, roughly 1,850 to 2,000 K. That corresponds to a mantle at least 250 to 400 K hotter than Earth’s present-day mantle, depending on assumptions. Within that window, the phase sequence that produces the effective negative thermal expansivity and the trapping layer exists, enabling the two-scale convective behavior. If Venus’s mantle were much cooler or much hotter outside that range, the glass-ceiling behavior would be weaker or absent.

That warmer interior also helps explain Venus’s observed dynamic topography and apparent low mantle viscosities inferred in previous studies, because hotter mantles are less viscous and therefore produce stronger, shorter-wavelength flow features near the surface.

Model results meet observations: the Baltis Vallis signal

A persuasive part of the paper is how the modeled dynamic topography compares to measured surface signals. The scientists compare the power spectra of modeled surface deformation to the long Baltis Vallis canali and the Beta-Atla-Themis region, which is dense in coronae. In models with mantle temperatures near 1,895 K and 1,984 K and a roughly 100-fold viscosity increase with depth, the dynamic topography shows a clear spectral bump at wavelengths near 500 to 700 km. That lines up with an unexplained observational peak at about 640 km reported for Baltis Vallis. The match suggests the secondary convection driven by the glass ceiling could leave a measurable imprint on Venus’s surface.

Broader implications

If correct, the glass-ceiling mechanism unifies several long-standing puzzles about Venus. It provides a plausible physical source for the abundant population of coronae, links corona diversity to mantle and lithosphere interactions, and explains why Venus can host both small transient upwellings and a dozen or so long-lived plume-driven highs. The theory also implies Venus’s interior has remained relatively hot and perhaps less processed by melting and recycling than Earth’s, which has implications for volatile budgets and the planet’s thermal history.

The prediction is timely because upcoming and recent missions such as VERITAS will measure Venus’s gravity and deformation more precisely, allowing independent tests of mantle viscosity, core size, and dynamic topography signatures that could corroborate or falsify the glass-ceiling picture.

Caveats and what comes next

Kerr et al. are clear about limitations. The models assume an anhydrous pyrolite mantle composition and do not explicitly include melting, intrusive magmatism, or a full treatment of multiple rock chemistries such as basalt and harzburgite. The simulations are two dimensional, and 3D behavior could strengthen or alter layering and plume dynamics. Reaction kinetics, water content, and long term compositional evolution could shift the phase transition depths and strengths, changing whether the glass ceiling forms and how long it persists. The scientists call for future 3D models, melting-aware simulations, and exploration of mixed mantle compositions to test the robustness of their results.

All model inputs and sample outputs are available in a Zenodo repository linked by the paper, so other groups can reproduce and extend the work. That openness will accelerate follow-up tests and comparisons with upcoming observational data.

Bottom line

Kerr and colleagues offer a physically grounded, testable mechanism that explains how Venus can produce both a global forest of coronae and a handful of enormous volcanic rises from the same deep convective engine. The key is a mineral-driven glass ceiling near 600 km that traps warm mantle rock and seeds a secondary scale of instability. If subsequent 3D, melting-inclusive models and new data from missions like VERITAS support this picture, the glass-ceiling regime will become a major pillar in our understanding of Venusian geodynamics, and a vivid example of how mineral physics can shape planetary surfaces.

The study was published in the journal PNAS on September 16, 2025.