3D representations of two corona structures on Venus. The black line is a data gap. (Photo Laurent Montési, University of Maryland)
The evidence is growing: our mysterious neighbor is still changing her face, according to a study. Researchers have identified 37 volcanic structures on Venus that appear to have been active recently. These so-called coronae seem to form a kind of fire belt on Venus, the cause of which they now want to research further.
She is so close to us and yet Venus has long eluded the explorer’s gaze. Because in contrast to its divine namesake, it is always veiled – the view of the surface of Venus is blocked by thick clouds of sulfuric acid. It was only possible to map the surface of Venus using X-rays. In particular, NASA’s Magellan mission provided information about the structures under the dense atmosphere. An important question when exploring Venus was to what extent it could still be geologically active. There are now several studies that have provided indications that some structures are relatively young and that there could be active volcanism on the planet.
The US and Swiss researchers are convinced that the current results are the most convincing evidence to date of the activity of Venus. As part of your study, you dealt with the so-called coronae, which are known from the high-resolution images of the Magellan mission. It was already assumed that these ring-shaped structures were created by volcanic activity, because there are similar structures on Earth. They come in different shapes and sizes on the surface of Venus. The question so far has been how old they are.
The coronae of Venus in sight
As the researchers clarify, these structures were created by so-called mantle plumes. These are structures made of molten rock that reach the crust through convection movements in the lower mantle and can break through it. There the uppermost part of the structure then spreads mushroom-shaped. The heat carried along melts the top crust in a circle. Further material from the depths then widens the head of the plume and expands the ring structure so that a corona is created. The hard crust that surrounds this structure then finally breaks and dips under the edge of the corona, which locally leads to tectonic processes, the researchers explain.
So far it has been assumed that the coronae on Venus are traces of long-past activity and that the planet could have cooled down so far that no hot material from the depths can penetrate the hardened crust. In addition, the details of how the plumes formed the coronae were unclear and the reasons for the structural differences between the various coronae were also the subject of debate. As part of their study, the researchers have therefore now examined the structures and their educational history using 3D modeling. They simulated the processes in the top hundred kilometers of the mantle plumes.
Activity signatures
The simulations showed that the structural features of a corona depend on how active the magma column below is. In other words, there is a recognizable signature of age or activity. Using this differentiation option, the researchers were then able to divide over a hundred large coronae into two groups: structures under which an active plume is currently rising and others under which the material has become cold and inactive. “Now we can point to certain structures and say: This is a volcanic structure that is still active today – maybe dormant, but not dead,” says co-author Laurent Montési of the University of Maryland in College Park. “This study changes the view of Venus from a largely inactive planet to a celestial body, the interior of which is still agitated and can feed many active structures”.
As the researchers further report, it became apparent that most of the structures that have active mantle plumes lie on a belt in the southern hemisphere of Venus. “We therefore called this volume, based on the ‘Pacific Ring of Fire of the Earth’, the ‘Ring of Fire of Venus’”, says the first author of the study, Anna Gülcher from the Swiss Federal Institute of Technology in Zurich. The researchers assume that this band coincides with a zone in which a particularly large amount of plume material can penetrate from the depths to the top.
Why the mantle plumes form such a belt on Venus and what this means in relation to the processes that take place deep inside the planet is now an open question. The scientists now want to continue pursuing this through computer simulations. According to them, these models could also provide insights into earthly processes. Because mantle plumes are considered to be the cause of hotspot volcanism, which, for example, characterizes the Hawaiian islands.
Source: University of Maryland, ETH Zurich, specialist article: Nature Geoscience, doi: 10.1038 / s41561-020-0606-1