Years ago, planetary researchers discovered unusual circular structures on the surface of Venus when observing high-resolution images from NASA’s Magellan mission. Such structures are known as coronae (from the Latin meaning “crowns”; singular: corona). A few years ago, a team of ETH researchers led by Taras Gerya, Professor of Geophysics at the Department of Earth Sciences, used computer models to investigate how these structures may have formed (see ETH News article).
Most researchers assume that these odd circular surface features are formed by mantle plumes from deep within the planet.
A mantle plume is an upwelling of hot, molten rock that is transported by convection currents from the lower mantle to the crust in a column that widens in a mushroom-shape at the top. The heat it carries melts the surface of the crust in a circular form. Continuous material rising from greater depths widens the plume head and expands the ring structure on the surface to form a corona. The solid crust surrounding the mantle plume may crack and ultimately sink below the edge of the corona, triggering local tectonic processes.
Computer simulations of structural variations of coronae
However, the topography of coronae is by no means homogeneous or easy to describe. “These structures exist in a large variety of shapes and dimensions on the Venusian surface,” says Anna Gülcher, a doctoral student in Gerya’s research group.
Following up on this observation, Gülcher used a larger set of improved 3D simulations to re-examine the coronae as she sought to establish a link between the variation in surface topography and the processes at work beneath. Her study was recently published in the journal Nature Geoscience.
The new simulations show that a corona’s topography depends on the thickness and strength of the crust where the mantle plume strikes it and, above all, that their topographies are directly related to how active the column of magma beneath the surface is.