Venus is one of the four terrestrial planets in our solar system. Geologists suggest that the geological activity on Venus today mirrors that of Earth around 4.5 billion years ago, shortly after Earth’s formation. The Ishtartera Highlands of Venus is a vast region comparable in size to Australia, marked by a rich crust and encircled by a long mountain range that reaches approximately 10 km (or 6 miles) in height, rising about 4 km (or 2.5 miles) above Venus’ surface. These highlands bear a resemblance to the Tibetan Plateau, the planet’s largest plateau, standing roughly 4.5 km (or 3 miles) high and spanning about 2.5 million square kilometers (or 1 million square miles).
While the Tibetan Plateau and the Ishtar Terra Highlands exhibit similar topographical features, researchers suspect that their formation processes differ significantly. Evidence suggests that the Tibetan Plateau emerged from the collision of tectonic plates on Earth, whereas Venus lacks a structured plate system. An examination of the geophysical aspects of the Ishtar Highlands revealed that it is underpinned by buoyant rocks. Scientists theorize that this buoyant rock could be remnants from the magmatic processes that formed the thick crust, though this remains uncertain. Understanding how Venus’ highlands formed is crucial for gaining insights into the evolution and transformation of rocky planets like Earth.
Previous research has primarily concentrated on Venus’ magmatism or structural dynamics to elucidate the development of the highlands, yet no models have effectively integrated these processes. Fabio Capitanio and his colleagues sought to create such a model. Geodynamic model.
To evaluate the large-scale processes responsible for the formation of the Ishtar Highlands, the team employed a geodynamic model that had previously simulated the formation of Earth’s thick crust. This model, known as a 3D Cartesian Model, was modified to cover an area of 3,650 x 3,650 km (or 2,268 x 2,268 miles) and extend 730 km (or 453 miles) deep, approximating the characteristics of the Ishtar Highlands.
The parameters for each model, including density and viscosity, were based on Earth’s conditions but adjusted for Venus’ higher surface temperature, which is around 450°C or 840°F. They executed 34 simulations of the Ishtar Highlands over a billion years, tracking changes in elevation, gravity characteristics, and temperature over time. This modeling successfully replicated the altitude and gravitational features observed in the Ishtar Highlands.
Subsequently, the team analyzed various model outcomes to identify how these features evolved over time. They determined that the most accurate simulations of Venus’ highlands corresponded to the outermost layer of the planet’s structure, known as the lithosphere, which is estimated to be 10 to 50 times thicker than that of Earth. In this model, extremely hot rocks from within the planet rise, resulting in a gradually thinner lithosphere.
The team clarified that as the strong lithosphere of Earth stretches, it can create slight openings, leading to the formation of volcanoes that release small amounts of lava on the surface. In contrast, as Venus’ weaker lithosphere stretches, it can fracture over much larger areas. When the lithosphere breaks apart, the rock that has accumulated pressure melts and rises to the surface, converting into magma.
The researchers proposed that this stretching and melting scenario could account for the formation of the Ishtar Highlands on Venus. Once the magma in this region solidifies, it forms a new, very thick crust. Unlike the current lithosphere, this new crust behaves like putty, making it challenging to move.
The team suggested that this scenario may clarify the presence of buoyant rocks beneath the Ishtar Highlands. The newly formed crust supports deeper rocks within the thickened Venus, resulting in a higher elevation for the crust. Meanwhile, the older lithosphere, having fractured, compresses the surface of Venus and its surrounding rocks. They postulated that the uplift associated with this process could be responsible for the long mountain range found at the periphery of the Ishtar Highlands.
In conclusion, the researchers indicated that the disintegration of the weak lithosphere and the melting of subsurface rock contributed to the formation of Venus’ highlands. Other highlands on Venus might have developed through similar processes. While the modern plateau on Earth formed differently from the Ishtar Highlands, it supports the idea that early Earth, with its hotter and weaker lithospheres, shares similarities with Venus.
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Source: sciworthy.com
