A Radar Determination of the Rotation of the Planet Mercury

Pettengill, G. H.; Dyce, R. B.

doi:10.1038/2061240a0

Cited by 167 publications

(83 citation statements)

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“…1), the effects of which would surely modify greatly the planetary surface. If the surface of Mercy is as old as has been inferred from photogeology (Aurray et al, 1974a(Aurray et al, , b, 1975 Mercury's rotation is clearly a product of tidal evolution (Pettengill and Dyce, 1965;Peale and Gold, 1965;Colombo, 1965;Goldreich and Peale, 1966). The tidal heating is dependent on the original rotation period of the planet, on the time scale for deceleration, and on the distribution of inelasticity with depth and time, none of which are known well enough to estimate whether tidal heating could have prevented core solidification, though this possibility is pro:ably doubtful.…”

Section: Is There a Core?mentioning

confidence: 99%

Some aspects of core formation in Mercury

Solomon

1976

Icarus

107

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Section: Is There a Core?mentioning

confidence: 99%

Some aspects of core formation in Mercury

Solomon

1976

Icarus

107

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“…The tidal bulges moving across the planet at different frequencies result in a gradual loss of kinetic energy through friction and heating. The energy dissipation rate is normally so slow that most of the major planets in the solar system still rotate faster than they revolve around the Sun, with the exception of Venus with its slow retrograde rotation and Mercury, which is in a 3:2 spin-orbit resonance (Pettengill & Dyce 1965). Presumably, the planet traversed a number of higher-order resonances before it reached this state.…”

Section: Introductionmentioning

confidence: 99%

Conditions of Passage and Entrapment of Terrestrial Planets in Spin-Orbit Resonances

Макаров

2012

ApJ

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The dynamical evolution of terrestrial planets resembling Mercury in the vicinity of spin-orbit resonances is investigated using comprehensive harmonic expansions of the tidal torque taking into account the frequencydependent quality factors and Love numbers. The torque equations are integrated numerically with a small step in time, including the oscillating triaxial torque components but neglecting the layered structure of the planet and assuming a zero obliquity. We find that a Mercury-like planet with a current value of orbital eccentricity (0.2056) is always captured in 3:2 resonance. The probability of capture in the higher 2:1 resonance is approximately 0.23. These results are confirmed by a semi-analytical estimation of capture probabilities as functions of eccentricity for both prograde and retrograde evolutions of spin rate. As follows from analysis of equilibrium torques, entrapment in 3:2 resonance is inevitable at eccentricities between 0.2 and 0.41. Considering the phase space parameters at the times of periastron, the range of spin rates and phase angles for which an immediate resonance passage is triggered is very narrow, and yet a planet like Mercury rarely fails to align itself into this state of unstable equilibrium before it traverses 2:1 resonance.

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“…Mercury is in a stable spin-orbit resonance in which the rotational angular velocity is precisely 1.5 times the mean orbital motion (Pettengill and Dyce 1965;Colombo and Shapiro 1966). This rotation state is a natural outcome of tidal evolution (Goldreich and Peale 1966) or other dissipative effects, although the details of the resonance capture mechanism are still debated Laskar 2004, 2009;Wieczorek et al 2012;Correia and Laskar 2012;Noyelles et al 2014).…”

Section: Introductionmentioning

confidence: 99%

Consequences of a solid inner core on Mercury’s spin configuration

Peale

Margot

Hauck

et al. 2016

Icarus

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The pressure torque by a liquid core that drove Mercury to the nominal Cassini state of rotation is dominated by the torque from the solid inner core. The gravitational torque exerted on Mercury's mantle from an asymmetric solid inner core increases the equilibrium obliquity of the mantle spin axis. Since the observed obliquity of the mantle must be compatible with a solid inner core of any size, the moment of inertia inferred from the occupancy of the Cassini state must be reduced to compensate the torque from the inner core and bring Mercury's spin axis to the observed position. The unknown size and shape of the inner core means that the moment of inertia is more uncertain than previously inferred.

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A Radar Determination of the Rotation of the Planet Mercury

Cited by 167 publications

References 0 publications

Some aspects of core formation in Mercury

Some aspects of core formation in Mercury

Conditions of Passage and Entrapment of Terrestrial Planets in Spin-Orbit Resonances

Consequences of a solid inner core on Mercury’s spin configuration

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