Scientists Uncover Heat Dynamics Behind Venus’ Mysterious Coronae
The enigmatic crown-shaped geological features on Venus, known as coronae, may finally have an explanation, according to a new study led by Madeleine Kerr, a doctoral candidate at the University of San Diego’s Scripps Institution of Oceanography. Researchers propose that a “glass ceiling” in Venus’ mantle is trapping heat and driving slow, shifting currents, which contribute to the formation of these unique surface features.
Kerr stated, “On Venus, there is a pattern that is telling us something. We think what we found is the key to unlocking the mystery of the origin of these coronae.”
Venus and Earth are often referred to as “twin” planets due to their similar size, density, and distance from the sun. Despite these similarities, their surfaces reveal drastically different evolutionary paths. The coronae are one of the most striking differences between the two planets, with over 700 identified across Venus’ surface, varying widely in size and characteristics.
Currently, the origin of these coronae remains unclear. Unlike Earth, which has shifting tectonic plates, Venus is covered in a single, continuous crust. Some hypotheses have attributed the formation of larger coronae—those exceeding 310 miles (500 kilometers) in diameter—to mantle plumes and tectonic processes such as subduction. In contrast, the smaller coronae, averaging around 124 miles (200 kilometers) in diameter, may arise from smaller hot upwellings in the mantle.
Despite these theories, substantial evidence has been lacking. David Stegman, a professor of geosciences at the same institution, likened the current understanding of Venus to the pre-plate tectonic era of the 1960s, noting the absence of a unifying theory that connects heat transfer from the planet’s interior to its observable tectonic and magmatic features.
The researchers propose that cold material sinking from the surface and hot material rising from the deeper mantle encounter a barrier approximately 370 miles (600 kilometers) below the surface, termed the “glass ceiling.” Most rising hot plumes are insufficiently strong to breach this barrier and are instead deflected, spreading laterally beneath it. Only the most substantial plumes manage to reach the surface, forming large volcanic rises.
The material trapped beneath this ceiling remains warm but does not melt, acting as a hidden reservoir of heat in the mantle. The study indicates, “This layer of warm fluid trapped between 600 to 740 kilometers depth provides a global source of smaller-scale thermal instabilities.”
Using computational models, the research team demonstrated how these small-scale plumes beneath Venus’ crust could form through natural processes. A cold “drip” of rock from the base of Venus’ stagnant crust cools and becomes denser, eventually sinking into the hotter mantle below. This action triggers a chain reaction, leading to the upward movement of pockets of hot rock.
Previous research relied on the assumption that these hot blobs existed below the lithosphere—Venus’ rigid outer layer—before modeling how coronae and volcanoes form. The current study advances the understanding by providing a plausible natural origin for these initial conditions.
As these secondary plumes rise and interact with Venus’ mantle, they could account for the diverse crown-shaped coronae observed across the planet’s surface. The models suggest that this mechanism is effective when the mantle is 250 to 400 kelvins hotter than that of Earth, although the duration of such a state remains uncertain.
The scientists emphasize that further research is essential. They recommend future studies to model plume dynamics in three dimensions, incorporate melting processes both within the mantle and on the surface, consider varying mantle compositions, and analyze changes across Venus’ entire geological history. These investigations will enhance the understanding of how Venus’ internal heat and movements shape its coronae, volcanoes, and overall surface characteristics.
This research, published on September 16, 2023, in the journal PNAS, marks a significant step toward unraveling the geological mysteries of one of Earth’s closest planetary neighbors.
