Lithospheric Dripping explains Corona Formation on Venus

Introduction

The Venusian surface is profoundly shaped by complex endogenic phenomena, among which coronae represent critical insights into mantle-lithosphere interactions distinct from Earth’s plate tectonics. These volcanic-tectonic structures, circular to elliptical in geometry and spanning from tens to over a thousand kilometers, serve as windows into Venus's internal dynamics. Contrasting Earth's tectonic activity, Venus exhibits alternative geodynamic modes, including stagnant lid [1], episodic lid [2], and plutonic squishy lid regimes [3], dictated by its unique thermal state and lithospheric properties. Such conditions have led to extensive resurfacing events, resulting in a planetary surface younger than one billion years [4].

Various numerical and conceptual models have been proposed for coronae formation. Early models emphasized diapir-driven processes creating dome-shaped topography, followed by gravitational relaxation into annular configurations [5], the retrograde subduction as a potential mechanism for larger coronae, exhibiting trench-outer rise morphology [6]. Recent modeling has revealed complex plume-lithosphere interactions, including lithospheric instabilities at plume margins [4], plume-induced subduction [7], and intricate processes such as episodic subduction and plume underplating [8]. Peel-back delamination [4], plume-induced melt accumulation dynamics [9], and fracture-rim relationships [10]. These diverse mechanisms suggest corona formation may involve multiple processes rather than a singular mechanism.

Here, we present results from three-dimensional scaled analog experiments designed to investigate the influence of lithospheric drips—downward-moving dense lithospheric segments—and mantle dynamics on corona evolution. Employing precisely scaled laboratory simulations, complemented by detailed structural analyses, we demonstrate the significant role lithospheric instabilities play in governing deformation patterns and morphological characteristics of coronae. Our approach effectively reconciles modeled strain distributions with observed corona structures, highlighting the fundamental importance of mantle downwellings as drivers of tectonic complexity on Venus, thus expanding our understanding beyond conventional tectonic paradigms.

Results & Conclusion

The Venusian surface presents intricate tectonic patterns that have persistently challenged conventional geodynamic interpretations. Historically, mantle plume processes have dominated explanations of corona formation, potentially overshadowing the significant role lithospheric drips may play. In this work, we argue for a refined geodynamic model that explicitly incorporates lithospheric instabilities alongside mantle plumes to explain observed corona structures more comprehensively. Experimental outcomes clearly demonstrate spatial associations between areas of crustal thickening and shortening at corona troughs and corresponding subsurface downwelling zones, coupled simultaneously with tensile regimes inducing localized crustal stretching. These laboratory-derived models yield temporal deformation predictions that strongly align with structural observations at Atahensik Corona [11].

Terrestrial analogs underscore the critical role lithospheric instabilities—specifically drip processes—have in crustal deformation, producing characteristic central compression zones surrounded by peripheral extensional regions [12]. Our quantitative analysis of asymmetric corona topography reveals systematic correlations between corona rim elevation and central depression depth. Further structural analysis, examining cross-cutting fault relationships, elucidates a clear sequence of deformation marked by oblique faulting to radial and concentric patterns as the geodynamic regime evolves. During the evolution of the model, our results sequentially predict crustal thickening driven by surface stresses, initiating with subsidence, progressing through concentric trough, and this dynamic regime is consistent with observed fault developments. These structural criteria offer measurable parameters capable of distinguishing between coronae driven predominantly by mantle plume processes and those significantly influenced by lithospheric dripping. The coexistence of extensional and compressional tectonic features, such as rift zones adjacent to fold-and-thrust belts, emphasizes the value of integrating lithospheric drip processes into broader planetary tectonic frameworks.

References

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