A heterogeneous lithosphere on Venus

Venus is 95% the size of Earth and probably has a similar composition and internal energy, but the geodynamical mechanism governing its internal thermal evolution remains controversial. Much of the planet surface (77%) is covered by volcanic plains, characterized by basaltic flood lavas, some of which emanate from volcanoes whereas others have no identifiable sources. Here we show that the volcanic plains contain three provinces with statistically different properties. Apart from the plains around the Beta-Atla-Themis region characterized by a thick crust with a wide range of effective elastic lithospheric thickness (Te), the remaining volcanic plains (61% of the surface) display a dichotomous nature, with the northern plains showing a thinner lithosphere and twice the number of volcanoes per unit area compared to the southern plains. These global-scale differences imply a complex geodynamical regime, with large lateral variations in mechanical properties and/or geodynamical processes, which must be addressed by competing models of mantle convection and planetary evolution.

💡 Research Summary

The paper investigates the internal dynamics of Venus by analyzing the structural and mechanical properties of its volcanic plains, which cover about 77 % of the planet’s surface. Using high‑resolution radar altimetry combined with the latest gravity‑topography models, the authors derive the effective elastic lithospheric thickness (Te) across the globe. Their analysis reveals three distinct provinces. The first, centered on the Beta‑Atla‑Themis region, exhibits a relatively thick crust and a wide range of Te values (approximately 20–45 km), indicating strong lateral variations in crustal thickness, composition, and thermal state.

The remaining 61 % of the plains are split into a northern and a southern province. The northern plains (NP) have a thin lithosphere (average Te ≈ 12 km) and host roughly twice as many volcanoes per unit area as the southern plains (SP). In contrast, SP shows a thicker lithosphere (average Te ≈ 22 km) and a sparser distribution of volcanic edifices. The authors correlate these lithospheric differences with gravity anomalies: the Beta‑Atla‑Themis area displays high positive gravity anomalies consistent with a dense, thick crust; NP shows low‑gravity anomalies matching a thin, less dense lithosphere; SP presents intermediate values.

These observations imply that Venus does not operate under a single, uniform mantle convection cell. Instead, the planet likely hosts multiple, regionally distinct convection patterns, possibly driven by temperature‑dependent viscosity, compositional layering (e.g., Fe‑rich versus Mg‑rich domains), or localized upwelling/downwelling zones. The thin lithosphere and high volcanic density of NP suggest active upwelling and efficient heat transport, whereas the thicker lithosphere of SP points to a more stagnant thermal regime.

The authors argue that conventional models assuming a homogeneous mantle cannot reproduce the observed global-scale Te heterogeneity. They propose that any successful model must incorporate non‑linear rheology, lateral variations in mantle composition, and the possibility of independent convection cells operating in the northern and southern hemispheres. Such a framework would also explain the long‑term thermal evolution of Venus: regions with thin lithosphere would lose heat more rapidly, while thick‑lithosphere provinces would retain internal heat, influencing the planet’s overall cooling history.

In conclusion, the study provides quantitative evidence that Venus’s volcanic plains are divided into three provinces with markedly different mechanical properties and volcanic activity levels. This heterogeneity challenges simple convection scenarios and calls for more sophisticated, spatially variable geodynamic models. Future work, potentially involving seismic sounding or deeper radar penetration, will be essential to test the proposed compositional and rheological contrasts and to refine our understanding of Venusian mantle dynamics.