Complex volcano-tectonic structures, referred to as coronae, had not been described until the exploration of the surface of Venus. These large, generally circular structures are characterized by an elevated surface, concentric and radial fracture systems, and extensive volcanism. Thought to be unique to Venus, rare circular features on Mars bear a close resemblance to coronae. The most prominent corona-like feature on Mars is Alba Patera, a broad, low-relief, plateau-shaped volcano-tectonic center surrounded by an annulus of concentric fractures ∼600 km in diameter. A geophysical model for the formation of Venusian coronae involving uplift due to an ascending mantle diapir followed by gravitationally driven relaxation is applied to Mars. The results indicate that Alba Patera could have formed by such a mechanism. The formation of coronae and corona-like features on Venus and Mars from mantle diapirs suggests that similar structures may have formed in Earth's lithosphere.

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