An international research team has made a groundbreaking discovery regarding the tectonic evolution of terrestrial planets. By employing advanced numerical models, the scientists classified six distinct planetary tectonic regimes for the first time, including a newly identified type called the “episodic-squishy lid.” This study sheds light on the contrasting geological features of Earth and Venus and was published in the journal Nature Communications.
Understanding Tectonic Regimes
Tectonic regimes refer to the large-scale deformation processes that shape a planet’s surface layers. These regimes play a crucial role in determining a planet’s geological activity, internal evolution, magnetic field, and even its potential to support life. A longstanding enigma in planetary science is why Earth exhibits active plate tectonics, while its neighboring planet Venus displays a vastly different geological profile.
The research team from the Department of Earth and Planetary Sciences at The University of Hong Kong included prominent figures such as postdoctoral fellow Dr. Tianyang Lyu and Professor Man Hoi Lee. They highlighted that the surface deformation of a planet is pivotal to its evolutionary trajectory. For instance, Mars is characterized by a “stagnant lid” regime, resulting in a largely immobile surface that preserves ancient impact craters. In contrast, Earth operates under a “mobile lid” regime, supporting a network of mid-ocean ridges, transform faults, and subduction zones.
While these plate boundaries can lead to geological hazards like earthquakes and volcanism, they have also helped stabilize Earth’s atmospheric conditions over millions of years, thereby fostering the development of life. The study revealed that climate-active compounds, such as carbon dioxide and water, can be recycled between the planet’s interior and atmosphere, maintaining a delicate balance of surface conditions.
New Insights into Planetary Evolution
Past studies have proposed various tectonic regimes, including the “sluggish lid” and “plutonic-squishy lid.” However, their interrelations and connections to terrestrial planets remained ambiguous. Dr. Lyu stated, “Through statistical analysis of vast amounts of model data, we were able to identify six tectonic regimes quantitatively for the first time.” These include the mobile lid, stagnant lid, and the newly identified episodic-squishy lid, which features alternating modes of tectonic activity.
A significant challenge researchers faced was the “memory effect,” where a planet’s tectonic state is influenced not only by current conditions but also by its geological history. Professor Man Hoi Lee elaborated, “Our models reveal that this ‘memory effect’ is not insurmountable. The transition between tectonic regimes can be surprisingly predictable, especially on an evolutionary path where the lithosphere weakens over time.”
The team created a comprehensive diagram mapping all six tectonic regimes, revealing potential transition pathways as a planet cools. Professor Guochun Zhao, an Academician of the Chinese Academy of Sciences, noted that geological records from early Earth align with characteristics of the newly identified regime. As Earth cooled, its lithosphere became increasingly susceptible to fracturing, paving the way for the active plate tectonics observed today.
The study also provides insights into the geological features of Venus. The research suggests that some of Venus’s surface formations, such as the >1,000 km wide circular “coronae,” align with the “plutonic-squishy lid” or “episodic-squishy lid” regimes. In these scenarios, magmatic intrusions weaken the lithosphere, resulting in intermittent tectonic activity governed by mantle plumes rather than global plate-boundary-driven deformation.
Professor Zhong-Hai Li from the University of Chinese Academy of Sciences, a co-author of the study, expressed enthusiasm about comparing model results with geological observations of Venus, emphasizing the importance of these findings for future missions to the planet.
This research establishes a new framework for understanding the diversity of planetary tectonics, providing tools for further exploration. Dr. Maxim D Ballmer from University College London concluded, “Our models link mantle convection with magmatic activity, allowing us to view the geological histories of Earth and the current state of Venus within a unified framework. This offers critical theoretical guidance for identifying potentially habitable Earth analogs and super-Earths beyond our solar system.”
The full details of this research can be found in the article by Tianyang Lyu et al, titled “Dissecting the puzzle of tectonic lid regimes in terrestrial planets” published in Nature Communications.
