The spin and inertia of Venus

Spada, Giorgio; Sabadini, R.; Boschi, E.

doi:10.1029/96gl01765

Cited by 7 publications

(10 citation statements)

References 23 publications

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“…The non-monotonic profiles of the channels on a 1000-km wavelength suggest that the topography of Venus has changed since their emplacement, possibly because of timedependent convection. The ∼0.5 • offset between the spin and maximum inertia axes may be due to rising plumes within the mantle (Spada et al 1996). Therefore, though plate tectonics is not a significant process on Venus at the moment, the planet nonetheless seems likely to be geologically active.…”

Section: Mantle Processesmentioning

confidence: 99%

Volcanism and Tectonics on Venus

Nimmo

McKenzie

1998

Annu. Rev. Earth Planet. Sci.

196

126

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We review recent developments in the study of volcanism and tectonics on Venus. Venus's crust is basaltic, dry, and probably about 30 km thick. The mantle convects, giving rise to plumes, and has a similar composition and mean temperature (∼1300 • C), but a higher viscosity (∼10 20 Pa s), than that of the Earth. Inferred melt generation rates constrain the lithospheric thickness to between 80 and 200 km. The elastic thickness of the lithosphere is about 30 km on average. The present-day lack of plate tectonics may be due to strong faults and the high viscosity of the mantle. Most of the differences between Earth and Venus processes can be explained by the absence of water. Venus underwent a global resurfacing event 300-600 Ma ago, the cause and nature of which remains uncertain. The present-day surface heat flux on Venus is about half the likely radiogenic heat generation rate, which suggests that Venus has been heating up since the resurfacing event.

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Section: Mantle Processesmentioning

confidence: 99%

Volcanism and Tectonics on Venus

Nimmo

McKenzie

1998

Annu. Rev. Earth Planet. Sci.

196

126

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“…The influence of cold blob (or slab) sinking in the mantle (Ricard et al 1993a) or hot blob rising in the mantle (Spada et al 1996) with constant velocity has been investigated using a simple geometrical model. Here, we model a plume crossing the mantle from the D layer to the bottom of the lithosphere using the analytical approach proposed by (Bercovici & Mahoney 1994).…”

Section: Modelling Of the Plume Crossing The Mantlementioning

confidence: 99%

Upwelling plumes, superswells and true polar wander

Greff-Lefftz

2004

Geophysical Journal International

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S U M M A R YThe geological evolution of the rotational axis of the Earth is most likely controlled by internal mass redistribution within the mantle. Palaeomagnetic observations suggest that it is episodic in nature, with periods of quasi-standstill alternating with periods of faster wander. Here, we investigate two models for the influence of mantle plumes that vary at different spatial wavelengths on the time variations of the rotational axis (true polar wander; TPW). In the first model, we represent an upwelling plume as a sphere whose radius varies as a function of the flux of material in the conduit and that traverses the mantle at the Stokes velocity. Such a plume produces very little wander of the rotational axis. We then study the effects of two superswells that mimic the ones observed with seismic tomography and conclude that a doming regime within the mantle involves significant polar wander. Some of the features of this TPW that are directly linked to the periodicity of doming are reminiscent of observed phases of slow and fast TPW, with similar peak velocities.True polar wander (TPW) is the coherent motion of Earth with respect to its rotation axis. In view of the angular momentum theorem, it may be interpreted physically as the motion of the rotational axis with respect to the fixed terrestrial frame described by hotspots. On geological timescales, this motion is most likely controlled by internal mass redistribution within the mantle.Palaeomagnetic evidence from recent Earth history suggests that this motion has been small. Palaeomagnetic studies combine apparent polar wander based on palaeomagnetic data (the palaeomagnetic reference frame) with motions of hotspots with respect to lithospheric plates (the hotspot reference frame). Given the relative motions between the plates, the position of these plates with respect to the rotation axis (provided by palaeomagnetic results), and the relative motions between plates and a reference frame attached to the mantle, TPW can be defined as the motion of the mantle with respect to the rotation axis. A recent study (Besse & Courtillot 2002), hereafter referred to as BC02, confirms earlier findings that TPW appears to be episodic in nature, with periods of quasi-standstill alternating with periods of faster TPW (Fig. 1). Specifically, the path back to 200 Ma shows a standstill at 160-130 Ma, then a circular track from 130 to 70 Ma and finally a standstill at 50-10 Ma. As a result of the uncertainties in models of hotspot kinematics prior to 130 Ma, the behaviour of the TPW prior to that time is doubtful. The major event since 130 Ma is the end of the 130-60 Ma period of relatively fast polar wander (where the TPW rate averages 30 km Ma −1 ), with a standstill (i.e. no or little TPW) from 50 Ma (possibly as early as 80 Ma because of larger 95 per cent confidence circles) to 10 Ma. It seems that TPW may have been negligible for approximately 50 Ma, but accelerated a few millions years ago, with a velocity of the order of 100 km Ma −1 ; this recent acceleration ...

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“…To represent a slowly rotating body, I study the mega-wobble on Venus, similarly to Spada et al (1996b) and Hu et al (2017b). Model parameters are listed in Table 1.…”

Section: Tablementioning

confidence: 99%

“…To represent the first group, I employ the viscoelastic Earth model M3-L70-V01 (Spada et al, 2011), in which the viscosity profile is inferred from measurements of postglacial rebound. The second group is represented by the Venus model from Spada et al (1996b), used also in Hu et al (2017b). Before TPW is investigated, each model is rotated with a constant angular speed Ω 0 until hydrostatic equilibrium is reached, and only then the body is loaded.…”

Section: Model Setupmentioning

confidence: 99%

See 1 more Smart Citation

True Polar Wander on Dynamic Planets: Approximative Methods Versus Full Solution

Patočka

2021

JGR Planets

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Internal and external planetary processes such as mantle convection, deglaciation, or large meteorite impacts cause bodies to move as a whole relative to their rotation axis. The rotation poles of planets and moons thus wander on their surfaces, as shown by paleomagnetic, astrometric, and geodetic measurements (e.g., Mitrovica & Wahr, 2011). Such reorientation in space is commonly referred to as true polar wander (TPW).The TPW mechanism can be described as follows. Let us assume that a rotating planet in hydrostatic equilibrium is subject to a sudden loading with a positive geoid anomaly, shifting the principal directions of the planet's inertia tensor in effect (the principal direction that has the largest associated moment of inertia is hereafter referred to as the main inertia axis, MIA). When viewed by an observer on the surface of the planet, the rotation axis will start a circular motion, known as free oscillations, around the new MIA. As soon as free oscillations dampen out (Nakada & Karato, 2012), the resulting position of the rotation pole will be closer to the principal axis of the load than in the initial state. Such motion of the rotation axis misaligns it with the hydrostatic rotational bulge, which effectively prevents the rotation axis from moving further toward the load axis (see figure 1 in Matsuyama et al., 2014). Gold (1955) argued that the stabilization is only transient, because the rotational bulge will eventually adjust to the new direction of rotation. The planet is then free to reorient further, and the process gradually

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The spin and inertia of Venus

Cited by 7 publications

References 23 publications

Volcanism and Tectonics on Venus

Volcanism and Tectonics on Venus

Upwelling plumes, superswells and true polar wander

True Polar Wander on Dynamic Planets: Approximative Methods Versus Full Solution

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