Venus: Interpreting the spatial distribution of volcanically modified craters

O’Rourke, J. G.; Wolf, Aaron S.; Ehlmann, B. L.

doi:10.1002/2014gl062121

Cited by 36 publications

(35 citation statements)

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“…Using an automated matching routine, Herrick et al () derived a new digital elevation model with a horizontal resolution of ∼1 km—more than an order‐of‐magnitude improvement—from the overlapping coverage of Cycles 1 and 3. Gaps in stereo topography are filled with GTDR data to produce rectangular swaths composing this new, publicly accessible data set, which has already motivated a reinterpretation of the impact cratering record (e.g., Herrick & Rumpf, ; O'Rourke et al, ).…”

Section: Methodsmentioning

confidence: 99%

Signatures of Lithospheric Flexure and Elevated Heat Flow in Stereo Topography at Coronae on Venus

O’Rourke

Smrekar

2018

JGR Planets

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Signatures of lithospheric flexure were previously identified at a dozen or more large coronae on Venus. Thin plate models fit to topographic profiles return elastic parameters, allowing derivation of mechanical thickness and surface heat flows given an assumed yield strength envelope. However, the low resolution of altimetry data from the NASA Magellan mission has hindered studying the vast majority of coronae, particularly those less than a few hundred kilometers in diameter. Here we search for flexural signatures around 99 coronae over ∼20% of the surface in Magellan altimetry data and stereo‐derived topography that was recently assembled from synthetic aperture radar images. We derive elastic thicknesses of ∼2 to 30 km (mostly ∼5 to 15 km) with Cartesian and axisymmetric models at 19 coronae. We discuss the implications of low values that were also noted in earlier gravity studies. Most mechanical thicknesses are estimated as <19 km, corresponding to thermal gradients >24 K km−1. Implied surface heat flows >95 mW m−2—twice the global average in many thermal evolution models—imply that coronae are major contributors to the total heat budget or Venus is cooling faster than expected. Binomial statistics show that “Type 2” coronae with incomplete fracture annuli are significantly less likely to host flexural signatures than “Type 1” coronae with largely complete annuli. Stress calculations predict extensional faulting where nearly all profiles intersect concentric fractures. We failed to identify systematic variations in flexural parameters based on type, geologic setting, or morphologic class. Obtaining quality, high‐resolution topography from a planetwide survey is vital to verifying our conclusions.

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Section: Methodsmentioning

confidence: 99%

Signatures of Lithospheric Flexure and Elevated Heat Flow in Stereo Topography at Coronae on Venus

O’Rourke

Smrekar

2018

JGR Planets

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“…A mobile lid, equivalent to plate tectonics in numerical models, implies active subduction, a process characterized by the descent of oceanic lithosphere as a coherent slab into the mantle due to its negative buoyancy (e.g., Bédard, ). Venus, in turn, has been proposed to be in an “episodic lid” regime, characterized by bursts of surface mobility due to episodic overturns of an unstable stagnant lid (Armann & Tackley, ; Moresi & Solomatov, ; Noack et al, ; Rozel, ; Turcotte, ) or internal mantle instabilities (Bédard, ; Davies, ), although continuous, random resurfacing may also match cratering statistics (O'Rourke et al, ). In this work, we define an overturn or a resurfacing event as the process where all or almost all of the lithosphere of a planet descends into the mantle in a short period of time.…”

Section: Introductionmentioning

confidence: 99%

Plutonic‐Squishy Lid: A New Global Tectonic Regime Generated by Intrusive Magmatism on Earth‐Like Planets

Lourenço

Rozel

Ballmer

et al. 2020

Geochem Geophys Geosyst

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The thermal and chemical evolution of rocky planets is controlled by their surface tectonics and magmatic processes. On Earth, magmatism is dominated by plutonism/intrusion versus volcanism/extrusion. However, the role of plutonism on planetary tectonics and long-term evolution of rocky planets has not been systematically studied. We use numerical simulations to systematically investigate the effect of plutonism combined with eruptive volcanism. At low-to-intermediate intrusion efficiencies, results reproduce the three common tectonic/convective regimes as are usually obtained in simulations using a viscoplastic rheology: stagnant-lid (a one-plate planet), episodic (where the lithosphere is usually stagnant and sometimes overturns into the mantle), and mobile-lid (similar to plate tectonics). At high intrusion efficiencies, we observe a new additional regime called "plutonic-squishy lid." This regime is characterized by a set of small, strong plates separated by warm and weak regions generated by plutonism. Eclogitic drippings and lithospheric delaminations often occur close to these weak regions, which leads to significant surface velocities toward the focus of delamination, even if subduction is not active. The location of the plate boundaries is strongly time dependent and mainly occurs in regions of magma intrusion, leading to small, ephemeral plates. The plutonic-squishy-lid regime is also distinctive from other regimes because it generates a thin lithosphere, which results in high conductive heat fluxes and lower internal mantle temperatures when compared to a stagnant lid. This regime has the potential to be applicable to the Early Archean Earth and present-day Venus, as it combines elements of both protoplate tectonic and vertical tectonic models. Plain Language SummaryThe evolution of Earth-like planets is controlled by the dynamics of their rigid outer part, called the lithosphere, and magmatic processes. Studies of terrestrial magmatic processes show that most melt is intruded into the crust. However, the effect of intrusive magmatism on the long-term evolution of rocky planets has not been systematically studied. Here we use numerical models to simulate global mantle convection in a rocky planet. When eruptions dominate, our results reproduce the three tectonic regimes found in previous studies: mobile lid, similar to plate tectonics operating on modern-day Earth; stagnant lid or a planet covered by a single plate; and episodic lid where the planet is covered by one plate that resurfaces into the mantle more or less frequently. For high intrusion efficiencies, we describe the new "plutonic-squishy-lid" regime. Hot intrusions make the lithosphere squishy and lead to drippings and delaminations of the crust. In turn, these processes lead to significant surface velocities (even if subduction is not active), and small, short-lived plates. The lithosphere is kept thin, and therefore, the loss of heat from the interior is efficient. The new regime has the potential to be applicable to the Archean Earth and ...

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“…These observations led to models in which the regional plains of Venus, which cover ~80% of the planet, were emplaced in a catastrophic outpouring of lava in a short period of time sometime between 300 Ma and 1 Ga, with a much reduced level of planetary volcanism after that time (e.g., McKinnon et al, ; Romeo , ). However, it has long been recognized that equilibrium resurfacing models can also explain the cratering observations (Bjonnes et al, ; Hauck et al, ; O'Rourke et al, ; Phillips et al, ). Moreover, detailed analysis of stereo topography data demonstrates that many Venus craters have several hundred meters of post‐impact volcanic fill on their floors (Herrick & Rumpf, ; Herrick & Sharpton, ).…”

Section: Introductionmentioning

confidence: 99%

The Physics of Changing Tectonic Regimes: Implications for the Temporal Evolution of Mantle Convection and the Thermal History of Venus

Weller

Kiefer

2020

JGR Planets

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Given similar sizes and compositions, Venus invites comparisons with Earth. While Earth convects in the plate tectonic regime, Venus' current and past tectonic states remain uncertain. Venus' impact crater distribution has led to competing models for its tectonic state, steady (e.g., stagnant lid) or catastrophic (e.g., episodic lid). Terrestrial geochemical evidence and geodynamic models suggest that planets may transition between tectonic states over time. Transitions can be triggered by increasing yield stress due to loss of water or by increasing surface temperature. Here, we revisit the classic endmember models of Venusian tectonics by modeling the transition from stable mobile lid convection into a stable stagnant lid in 3D spherical geometry. Transitions between states are governed by both regional and global scale instabilities, resulting in oscillations in heat flux, velocity, and magma production over Gyr time scales. The thermal and tectonic evolution of a convectively transitioning planet is neither catastrophic nor steady. Volcanism and tectonic yielding may be non-global in nature. At any given time, portions of the planetary surface may reflect apparently different styles of convection, with some regions being highly active and other regions being sluggish and inactive. For Venus, the implications are that global melt production and resurfacing are a natural consequence of lid-state evolution, without needing ad hoc resurfacing mechanisms which rely on a single governing lid-state. Geologic evidence suggests that the transition from mobile lid to stagnant lid is still on-going. Venus may have lost liquid surface water in the last third of its history. Plain Language Summary Given broad similarities, Venus naturally invites comparisons withthe Earth, yet Venus' surface reveals a world strikingly different. Mantle convection on Earth is linked to plate tectonics, but the current tectonic state of Venus is hotly debated. The distribution of impact craters on Venus' vast volcanic plans have been used to generate two endmember tectonic models: a steady single plate with waning melt production over time, or a catastrophic overturn model with strong, short-lived melting events. Here, we explore a change in tectonic regimes for Venus triggered by either loss of water or increasing surface temperature. Transitions in regimes are highly disruptive with significant changes in surface motions, mantle temperatures, melt production, and heat flow. These disruptive events can be restricted to hemispheric or sub-hemispheric regions, indicating that different portions of the planet may record apparently contrasting tectonic regimes. Such a transition between tectonic regimes is neither steady nor catastrophic, and it naturally results in punctuated resurfacing and melting events. This can explain many puzzling aspects of Venus' geologic evolution within the framework of a single evolutionary model.

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Venus: Interpreting the spatial distribution of volcanically modified craters

Cited by 36 publications

References 48 publications

Signatures of Lithospheric Flexure and Elevated Heat Flow in Stereo Topography at Coronae on Venus

Signatures of Lithospheric Flexure and Elevated Heat Flow in Stereo Topography at Coronae on Venus

Plutonic‐Squishy Lid: A New Global Tectonic Regime Generated by Intrusive Magmatism on Earth‐Like Planets

The Physics of Changing Tectonic Regimes: Implications for the Temporal Evolution of Mantle Convection and the Thermal History of Venus

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