Localized Lithospheric Deformation in Vinmara Planitia, Venus: Insights from Morphological and Geophysical Observations

The tectonic and volcanic evolution of Venus remains a fundamental open question in planetary science. The absence of a globally recognized system of mobile lithospheric plates, as seen on Earth, suggests that alternative geodynamic regimes must be considered to explain the planet’s surface features [1, 2, 3, 4, 5]. In this context, localized deformation and regional-scale tectonic activity offer useful frameworks for investigating how Venus may accommodate internal heat and lithospheric stresses.In this study, we present a geological and geomorphological analysis of two adjacent regions in Vinmara Planitia, based on Magellan radar and altimetric datasets [6]. These areas exhibit contrasting structural and topographic patterns, including arcuate ridge belts, extensional fault systems, organized and diffuse volcanism, and broad elevation gradients. Detailed mapping and morphometric analyses reveal features suggestive of significant lithospheric deformation, including broad elevation variations and fault systems that suggest lithospheric deformation, which are reminiscent of processes typically associated with convergent and extensional tectonic settings on Earth.Additionally, we integrate gravity and radio thermal emissivity data from the Magellan mission to investigate subsurface structure and potential thermal variations. The gravity anomalies suggest density heterogeneities beneath key tectonic structures, while emissivity trends may indicate compositional differences or varying degrees of surface alteration. These observations, although limited by spatial resolution, provide supportive context for the tectonic interpretations derived from surface morphology.The spatial configuration and inferred relative motion between these regions suggest a dynamic interaction among these areas, potentially driven by a combination of surface deformation and deeper lithospheric or mantle contributions. Rather than invoking a globally coherent tectonic framework, our findings support the idea that Venus may experience localized, possibly transient, episodes of lithospheric mobility. This is consistent with recent models proposing a fragmented or partially mobile lithosphere, where short-lived deformation zones can emerge in response to regional stresses or mantle-driven processes [5, 7].While further data are necessary to fully characterize the nature and evolution of these structures, our analysis highlights the potential for active or recent deformation in the Venusian lowlands. Future orbital missions with higher resolution topography, gravity, and spectral imaging will be critical for testing the hypothesis of spatially confined lithospheric activity and for refining our understanding of how planets like Venus manage internal heat in the absence of a global pattern of plate tectonics [8, 9]. Acknowledgements:D.S and G.M. acknowledge support from the Italian Space Agency (Grant No. 2022-15-HH.0).Bibliography[1] Solomatov, V. S. & Moresi, L. N. Stagnant lid convection on Venus. Geophys. Res. Planets 101, 4737-4753 (1996).[2] Lenardic, A. The diversity of tectonic modes and thoughts about transitions between them. Trans. R. Soc. A 376, 20170416 (2018).[3] Solomatov, V. S. & Moresi, L. N. Three regimes of mantle convection with non-Newtonian viscosity and stagnant lid convection on the terrestrial planets. Res. Lett. 24, 1907-1910 (1997).[4] Moresi, L. & Solomatov, V. Mantle convection with a brittle lithosphere: Thoughts on the global tectonic styles of the Earth and Venus. J. Int. 133, 669-682 (1998).[5] Lourenço, D. L., Rozel, A. B., Ballmer, M. D. & Tackley, P. J. Plutonic-squishy lid: A new global tectonic regime generated by intrusive magmatism on Earth-like planets. Geophys. Geosyst. 21, e2019GC008756 (2020).[6] Ford, J. P. Guide to Magellan Image Interpretation (NASA, 1993).[7] Byrne, P. K. et al. A globally fragmented and mobile lithosphere on Venus. Natl Acad. Sci. USA 118, e2025919118 (2021).[8] Smrekar, S. et al. VERITAS (Venus emissivity, radio science, InSAR, topography, and spectroscopy): A discovery mission. IEEE Aerosp. Conf. 1-20 (2022).[9] EnVision Definition Study Report (2023) ESASCI-DIR-RP-003