We consider the effect of tidal deformation, spin-orbit resonance, non-zero eccentricity, despinn... more We consider the effect of tidal deformation, spin-orbit resonance, non-zero eccentricity, despinning, and reorientation on the global-scale gravity, shape, and tectonic patterns of planetary bodies. Large variations of the gravity and shape coefficients from the synchronous rotation and zero eccentricity values, J2/C22=10/3 and (b-c)/(a-c)=1/4, arise due to non-synchronous rotation and non-zero eccentricity even in the absence of reorientation or despinning. Reorientation or despinning induce additional variations. As an illustration of this theory, we consider the specific example of Mercury. The large gravity coefficients estimated from the Mariner 10 flybys cannot be attributed to the Caloris basin alone since the required mass excess in this case would have caused Caloris to migrate to one of Mercury's hot poles. Similarly, a large remnant bulge due to a smaller semimajor axis and spin-orbit resonance can be dismissed since the required semimajor axis is unphysically small (< 0.1 AU). Reorientation of a large remnant bulge recording an epoch of faster rotation (without significant semimajor axis variations) can explain the large gravity coefficients. This requires initial rotation rates > 20 times the present value and a positive gravity anomaly associated with Caloris capable of driving 10-45° equatorward reorientation. The required gravity anomaly can be explained by infilling of the basin with material of thicknesses > 7 km, or an annulus of volcanic plains emplaced around the basin with annulus width ~ 1200 km and fill thicknesses > 2 km. The predicted tectonic pattern due to these despinning and reorientation scenarios and radial contraction is in good agreement with the observed lobate scarp pattern.
The figure of the Moon is triaxial, with three different principal moments of inertia, as expecte... more The figure of the Moon is triaxial, with three different principal moments of inertia, as expected. However, the moment differences are significantly larger than those predicted assuming hydrostatic equilibrium. This has been explained as due to a fossil bulge that retains a figure for prior rotational and tidal deformation, at a time when the Moon was closer to Earth (Jeffeys, 1915; Lambeck & Pullan, 1980; Garrick-Bethell et al.,2006). Garrick-Bethell et al. (2006) illustrated that a fossil figure can entirely account for the moment differences if it is established at a time when the orbital eccentricity was high. They approximate the Moon as a strengthless homogeneous body; however, a strengthless Moon cannot support a fossil figure over billions of years. We extend the analysis of Garrick-Bethell et al. (2006) by taking into the presence of an elastic lithosphere capable of supporting a fossil figure. The fossil figure is established when the elastic lithosphere forms. For a 50 km thick elastic lithosphere, the moment differences can be explained by a lunar orbit with an initial semimajor axis a=17.1 Earth radii and eccentricity e=0.49 if the Moon remains locked in synchronous rotation. If the fossil figure is established during a 3:2 spin-orbit resonance, a=18.1 Earth radii and e=0.16, or a=20.0 Earth radii and e=0.60. The initial semimajor axis decreases with decreasing elastic lithospheric thickness, as expected. The initial orbital eccentricity is not sensitive to the elastic lithospheric thickness. As Lambeck & Pullan (1980) noted, it is unlikely that the moment differences are due to a fossil figure alone. Therefore, we also consider the effect of including other contributions to the moment differences. This work is supported by the Miller Institute for Basic Research.
Mercury's slow rotation period of 59 days is presumably the result of solar tides driving its ini... more Mercury's slow rotation period of 59 days is presumably the result of solar tides driving its initial rotational state to the present 3:2 spin-orbit resonance. The observed large gravity coefficients can be explained as due to a remnant rotational bulge recording an initial rotation period of a few days (Matsuyama and Nimmo 2009). Despinning changes the shape of the rotational bulge, generating both compressional and extensional stresses (Melosh 1977). However, Mercury's surface is dominated by compressional tectonic features (Watters et al. 1998), and the inferred global contraction has been explained as due to thermal cooling (Solomon 1976). In addition to non-isotropic changes associated with the rotational flattening, despinning causes isotropic contraction of the entire planet. We consider the effect of the compressional stresses generated by this isotropic contraction on the predicted tectonic pattern. References Matsuyama and Nimmo. Gravity and tectonic patterns of Mercury: Effect of tidal deformation, spin-orbit resonance, nonzero eccentricity, despinning, and reorientation. J. Geophys. Res. (2009) vol. 114 pp. E01010 Melosh. Global tectonics of a despun planet. Icarus (1977) vol. 31 pp. 221-243 Solomon. Some aspects of core formation in Mercury. Icarus (1976) vol. 28 pp. 509-521 Watters et al. Topography of lobate scarps on Mercury: New constraints on the planet's contraction. Geology (1998) vol. 26 pp. 991-994
Photoevaporation may provide an explanation for the short lifetimes of disks around young stars. ... more Photoevaporation may provide an explanation for the short lifetimes of disks around young stars. With the exception of neutral oxygen lines, the observed low-velocity forbidden line emission from T Tauri stars can be reproduced by photoevaporating models. The natural formation of a gap in the disk at several AU due to photoevaporation and viscous spreading provides a possible halting mechanism for migrating planets and an explanation for the abundance of observed planets at these radii.
There are many unsolved problems in the physics of planet formation and the evolution of their pa... more There are many unsolved problems in the physics of planet formation and the evolution of their parent disk is expected to play an important role in resolving them. In part I of this thesis, I discuss the evolution of protoplanetary disks under the influence of viscous evolution, photoevaporation from the central source, and photo evaporation by external stars; and explore the consequences for planet formation. The discovery of hot jupiters orbiting at a few AU from their stars compliments earlier detections of massive planets on very small orbits. The short period orbits strongly suggest that planet migration has occurred, with the likely mechanism being tidal interactions between the planets and the gas disks out of which they formed. The newly discovered long period planets, together with the gas giant planets in our solar system, show that migration is either absent or rapidly halted in at least some systems. I propose a mechanism for halting type-II migration at several AU in a gas disk: the formation of a photoevaporation gap prevents planets outside the gap from migrating down to the star. The final planet location relative to the habitable zone is often used to discuss the planet habitability. But a planet in the habitable zone may experience large amplitude motion of its rotation axis, which may cause severe climate variations and have major consequences for the development of life. In part II of this thesis, I investigate the true polar wander (TPW) rotational stability of planets. I revisit the classic problem of the long-term rotational stability of planets in response to loading using a new, generalized theoretical development based on the fluid limit of viscoelastic Love number theory. Finally, I explore the time dependent (rather than the equilibrium fluid limit) rotational stability of planets by considering the example of an ice age Earth. I present a new treatment of the linearized Euler equations that govern rotation perturbations on a viscoelastic planet driven by surface loading.
We model the evolution of protoplanetary disks under the influence of viscous accretion and photo... more We model the evolution of protoplanetary disks under the influence of viscous accretion and photoevaporation by the central star. Previous studies are extended by considering the evolution of disks around different types of parent stars in which extrasolar planets have been discovered. We consider stellar masses in the range 1 to 4.7 solar masses, and extreme ultraviolet (EUV) fluxes in the range 1040 to 1043 photons/second. The disk evolves on the viscous diffusion time scale at the gravitational radius, the disk location inside which ionized hydrogen is gravitationally bound to the central star. Photoevaporation is initially powered by the diffuse EUV flux arising from recombinations in the gravitationally bound region. Following the analysis of Alexander et al. (2006), we include the direct contribution from the direct EUV flux as the gravitationally bound region is removed by the combination of viscous diffusion and photoevaporation. The disk is removed in ≈ 70 Myr for a 4.7 M⊙ central star and a EUV flux ≈ 1040. Increasing the EUV flux results in shorter disk life times, as expected. Reducing the stellar mass results in shorter disk lifetimes for two reasons. First, photoevaporation is more easily accomplished since material is less tightly bound to the central star (the gravitational radius moves inward). Second, the viscous diffusion time scale at the smaller gravitational radius decreases, speeding up the overall disk evolution. This work is supported by an NSF grant.
We find analytic solutions for the stresses associated with distortions of biaxial or triaxial pl... more We find analytic solutions for the stresses associated with distortions of biaxial or triaxial planetary figures. Distortions of biaxial figures may be driven by variations in rotation rate, rotation axis orientation, or the combination of both. Distortions of triaxial figures may be driven by the same mechanisms and/or variations in tidal axis orientation for tidally deformed satellites. While the magnitude of the resulting stresses depends on the adopted elastic and physical parameters, the expected tectonic pattern is independent of these parameters for these mechanisms. We consider the tectonic pattern on Saturn's moon Enceladus. The global scale tectonic pattern on this satellite has been interpreted as due to a rotation rate increase (Porco et al. 2006), perhaps due to a suitably oriented impact. In this scenario, the flattening increases, forcing the tidal bulge to expand and the polar regions to contract. We show that the observed tectonic pattern is more easily explained by a large reorientation (~90°) of the rotation axis roughly around the tidal axis, than by spin-up. In the spin-up scenario, extension occurs centred on the sub- and anti-Saturnian points and strike-slip faulting centered on the leading and trailing hemispheres. In the reorientation scenario, these patterns are reversed, and are more consistent with the available geological observations (Kargel and Pozio 1996, Porco et al. 2006, Helfenstein et al. 2007). Furthermore, the latitude of the predicted polewards transition to compressional stresses is comparable to that of the observed south polar terrain margin. Reorientation of ~90° may be driven by mass redistribution associated with an internal load (Nimmo & Pappalardo 2006), ice shell thickness variations (Ojakangas and Stevenson 1989), or an equatorial large impact (Melosh 1975). Given Enceladus' orbital evolution constraints, the effect of despinning due to tidal disspation on the predicted tectonic pattern is negligible.
Abstract. We present a model for the dispersal of protoplanetary disks by winds from either the c... more Abstract. We present a model for the dispersal of protoplanetary disks by winds from either the central star or the inner disk. These winds obliquely strike the flaring disk surface and strip away disk material by entraining it in an outward radial-moving flow at the disk-wind inter-face. ...
A number of geologic and topographic features within the northern plains of Mars have been interp... more A number of geologic and topographic features within the northern plains of Mars have been interpreted as shorelines formed by ancient oceans. Several recent studies have challenged this interpretation, arguing that the present topographic profiles do not appear to originate from surfaces of equal gravitational potential. Elevations along the ``shorelines'' are especially variable at long wavelengths (thousands of km), with amplitudes of hundreds of meters to kilometers. To test the hypothesis that the features in the northern plains are deformed shorelines, we compare the long-wavelength topography (solid surface position relative to the areoid) of the two most prominent shorelines (the Arabia and Deuteronilus contacts of Clifford and Parker, Icarus, 2001) with the deformation expected for: (1) flexural response of the lithosphere to surface loading from the growth of Tharsis and ocean (i.e., sea level) redistribution, (2) true polar wander (TPW), and (3) dynamic topography linked to internal convective flow. We find that TPW and dynamic topography are both capable of reconciling the longest-wavelength variation in topography (the former is a purely degree two signal). The predicted TPW path that best fits the shoreline record is a function of the effective elastic thickness of the Martian lithosphere and it is consistent with recent inferences based on paleomagnetic evidence. The inference is also compatible with our recent re-analysis of the rotational stability of Mars subject to Tharsis and internal loading, which we briefly summarize.
ABSTRACT Mercury&#39;s slow rotation period of 59 days is presumably the result of solar tide... more ABSTRACT Mercury&#39;s slow rotation period of 59 days is presumably the result of solar tides driving its initial rotational state to the present 3:2 spin-orbit resonance. The observed large gravity coefficients can be explained as due to a remnant rotational bulge recording an initial rotation period of a few days (Matsuyama and Nimmo 2009). Despinning changes the shape of the rotational bulge, generating both compressional and extensional stresses (Melosh 1977). However, Mercury&#39;s surface is dominated by compressional tectonic features (Watters et al. 1998), and the inferred global contraction has been explained as due to thermal cooling (Solomon 1976). In addition to non-isotropic changes associated with the rotational flattening, despinning causes isotropic contraction of the entire planet. We consider the effect of the compressional stresses generated by this isotropic contraction on the predicted tectonic pattern. References Matsuyama and Nimmo. Gravity and tectonic patterns of Mercury: Effect of tidal deformation, spin-orbit resonance, nonzero eccentricity, despinning, and reorientation. J. Geophys. Res. (2009) vol. 114 pp. E01010 Melosh. Global tectonics of a despun planet. Icarus (1977) vol. 31 pp. 221-243 Solomon. Some aspects of core formation in Mercury. Icarus (1976) vol. 28 pp. 509-521 Watters et al. Topography of lobate scarps on Mercury: New constraints on the planet&#39;s contraction. Geology (1998) vol. 26 pp. 991-994
ABSTRACT We make predictions for Pluto&#39;s global tectonic pattern due to despinning, orbit... more ABSTRACT We make predictions for Pluto&#39;s global tectonic pattern due to despinning, orbital migration, contraction, and expansion.
We consider the effect of tidal deformation, spin-orbit resonance, non-zero eccentricity, despinn... more We consider the effect of tidal deformation, spin-orbit resonance, non-zero eccentricity, despinning, and reorientation on the global-scale gravity, shape, and tectonic patterns of planetary bodies. Large variations of the gravity and shape coefficients from the synchronous rotation and zero eccentricity values, J2/C22=10/3 and (b-c)/(a-c)=1/4, arise due to non-synchronous rotation and non-zero eccentricity even in the absence of reorientation or despinning. Reorientation or despinning induce additional variations. As an illustration of this theory, we consider the specific example of Mercury. The large gravity coefficients estimated from the Mariner 10 flybys cannot be attributed to the Caloris basin alone since the required mass excess in this case would have caused Caloris to migrate to one of Mercury's hot poles. Similarly, a large remnant bulge due to a smaller semimajor axis and spin-orbit resonance can be dismissed since the required semimajor axis is unphysically small (< 0.1 AU). Reorientation of a large remnant bulge recording an epoch of faster rotation (without significant semimajor axis variations) can explain the large gravity coefficients. This requires initial rotation rates > 20 times the present value and a positive gravity anomaly associated with Caloris capable of driving 10-45° equatorward reorientation. The required gravity anomaly can be explained by infilling of the basin with material of thicknesses > 7 km, or an annulus of volcanic plains emplaced around the basin with annulus width ~ 1200 km and fill thicknesses > 2 km. The predicted tectonic pattern due to these despinning and reorientation scenarios and radial contraction is in good agreement with the observed lobate scarp pattern.
The figure of the Moon is triaxial, with three different principal moments of inertia, as expecte... more The figure of the Moon is triaxial, with three different principal moments of inertia, as expected. However, the moment differences are significantly larger than those predicted assuming hydrostatic equilibrium. This has been explained as due to a fossil bulge that retains a figure for prior rotational and tidal deformation, at a time when the Moon was closer to Earth (Jeffeys, 1915; Lambeck & Pullan, 1980; Garrick-Bethell et al.,2006). Garrick-Bethell et al. (2006) illustrated that a fossil figure can entirely account for the moment differences if it is established at a time when the orbital eccentricity was high. They approximate the Moon as a strengthless homogeneous body; however, a strengthless Moon cannot support a fossil figure over billions of years. We extend the analysis of Garrick-Bethell et al. (2006) by taking into the presence of an elastic lithosphere capable of supporting a fossil figure. The fossil figure is established when the elastic lithosphere forms. For a 50 km thick elastic lithosphere, the moment differences can be explained by a lunar orbit with an initial semimajor axis a=17.1 Earth radii and eccentricity e=0.49 if the Moon remains locked in synchronous rotation. If the fossil figure is established during a 3:2 spin-orbit resonance, a=18.1 Earth radii and e=0.16, or a=20.0 Earth radii and e=0.60. The initial semimajor axis decreases with decreasing elastic lithospheric thickness, as expected. The initial orbital eccentricity is not sensitive to the elastic lithospheric thickness. As Lambeck & Pullan (1980) noted, it is unlikely that the moment differences are due to a fossil figure alone. Therefore, we also consider the effect of including other contributions to the moment differences. This work is supported by the Miller Institute for Basic Research.
Mercury's slow rotation period of 59 days is presumably the result of solar tides driving its ini... more Mercury's slow rotation period of 59 days is presumably the result of solar tides driving its initial rotational state to the present 3:2 spin-orbit resonance. The observed large gravity coefficients can be explained as due to a remnant rotational bulge recording an initial rotation period of a few days (Matsuyama and Nimmo 2009). Despinning changes the shape of the rotational bulge, generating both compressional and extensional stresses (Melosh 1977). However, Mercury's surface is dominated by compressional tectonic features (Watters et al. 1998), and the inferred global contraction has been explained as due to thermal cooling (Solomon 1976). In addition to non-isotropic changes associated with the rotational flattening, despinning causes isotropic contraction of the entire planet. We consider the effect of the compressional stresses generated by this isotropic contraction on the predicted tectonic pattern. References Matsuyama and Nimmo. Gravity and tectonic patterns of Mercury: Effect of tidal deformation, spin-orbit resonance, nonzero eccentricity, despinning, and reorientation. J. Geophys. Res. (2009) vol. 114 pp. E01010 Melosh. Global tectonics of a despun planet. Icarus (1977) vol. 31 pp. 221-243 Solomon. Some aspects of core formation in Mercury. Icarus (1976) vol. 28 pp. 509-521 Watters et al. Topography of lobate scarps on Mercury: New constraints on the planet's contraction. Geology (1998) vol. 26 pp. 991-994
Photoevaporation may provide an explanation for the short lifetimes of disks around young stars. ... more Photoevaporation may provide an explanation for the short lifetimes of disks around young stars. With the exception of neutral oxygen lines, the observed low-velocity forbidden line emission from T Tauri stars can be reproduced by photoevaporating models. The natural formation of a gap in the disk at several AU due to photoevaporation and viscous spreading provides a possible halting mechanism for migrating planets and an explanation for the abundance of observed planets at these radii.
There are many unsolved problems in the physics of planet formation and the evolution of their pa... more There are many unsolved problems in the physics of planet formation and the evolution of their parent disk is expected to play an important role in resolving them. In part I of this thesis, I discuss the evolution of protoplanetary disks under the influence of viscous evolution, photoevaporation from the central source, and photo evaporation by external stars; and explore the consequences for planet formation. The discovery of hot jupiters orbiting at a few AU from their stars compliments earlier detections of massive planets on very small orbits. The short period orbits strongly suggest that planet migration has occurred, with the likely mechanism being tidal interactions between the planets and the gas disks out of which they formed. The newly discovered long period planets, together with the gas giant planets in our solar system, show that migration is either absent or rapidly halted in at least some systems. I propose a mechanism for halting type-II migration at several AU in a gas disk: the formation of a photoevaporation gap prevents planets outside the gap from migrating down to the star. The final planet location relative to the habitable zone is often used to discuss the planet habitability. But a planet in the habitable zone may experience large amplitude motion of its rotation axis, which may cause severe climate variations and have major consequences for the development of life. In part II of this thesis, I investigate the true polar wander (TPW) rotational stability of planets. I revisit the classic problem of the long-term rotational stability of planets in response to loading using a new, generalized theoretical development based on the fluid limit of viscoelastic Love number theory. Finally, I explore the time dependent (rather than the equilibrium fluid limit) rotational stability of planets by considering the example of an ice age Earth. I present a new treatment of the linearized Euler equations that govern rotation perturbations on a viscoelastic planet driven by surface loading.
We model the evolution of protoplanetary disks under the influence of viscous accretion and photo... more We model the evolution of protoplanetary disks under the influence of viscous accretion and photoevaporation by the central star. Previous studies are extended by considering the evolution of disks around different types of parent stars in which extrasolar planets have been discovered. We consider stellar masses in the range 1 to 4.7 solar masses, and extreme ultraviolet (EUV) fluxes in the range 1040 to 1043 photons/second. The disk evolves on the viscous diffusion time scale at the gravitational radius, the disk location inside which ionized hydrogen is gravitationally bound to the central star. Photoevaporation is initially powered by the diffuse EUV flux arising from recombinations in the gravitationally bound region. Following the analysis of Alexander et al. (2006), we include the direct contribution from the direct EUV flux as the gravitationally bound region is removed by the combination of viscous diffusion and photoevaporation. The disk is removed in ≈ 70 Myr for a 4.7 M⊙ central star and a EUV flux ≈ 1040. Increasing the EUV flux results in shorter disk life times, as expected. Reducing the stellar mass results in shorter disk lifetimes for two reasons. First, photoevaporation is more easily accomplished since material is less tightly bound to the central star (the gravitational radius moves inward). Second, the viscous diffusion time scale at the smaller gravitational radius decreases, speeding up the overall disk evolution. This work is supported by an NSF grant.
We find analytic solutions for the stresses associated with distortions of biaxial or triaxial pl... more We find analytic solutions for the stresses associated with distortions of biaxial or triaxial planetary figures. Distortions of biaxial figures may be driven by variations in rotation rate, rotation axis orientation, or the combination of both. Distortions of triaxial figures may be driven by the same mechanisms and/or variations in tidal axis orientation for tidally deformed satellites. While the magnitude of the resulting stresses depends on the adopted elastic and physical parameters, the expected tectonic pattern is independent of these parameters for these mechanisms. We consider the tectonic pattern on Saturn's moon Enceladus. The global scale tectonic pattern on this satellite has been interpreted as due to a rotation rate increase (Porco et al. 2006), perhaps due to a suitably oriented impact. In this scenario, the flattening increases, forcing the tidal bulge to expand and the polar regions to contract. We show that the observed tectonic pattern is more easily explained by a large reorientation (~90°) of the rotation axis roughly around the tidal axis, than by spin-up. In the spin-up scenario, extension occurs centred on the sub- and anti-Saturnian points and strike-slip faulting centered on the leading and trailing hemispheres. In the reorientation scenario, these patterns are reversed, and are more consistent with the available geological observations (Kargel and Pozio 1996, Porco et al. 2006, Helfenstein et al. 2007). Furthermore, the latitude of the predicted polewards transition to compressional stresses is comparable to that of the observed south polar terrain margin. Reorientation of ~90° may be driven by mass redistribution associated with an internal load (Nimmo & Pappalardo 2006), ice shell thickness variations (Ojakangas and Stevenson 1989), or an equatorial large impact (Melosh 1975). Given Enceladus' orbital evolution constraints, the effect of despinning due to tidal disspation on the predicted tectonic pattern is negligible.
Abstract. We present a model for the dispersal of protoplanetary disks by winds from either the c... more Abstract. We present a model for the dispersal of protoplanetary disks by winds from either the central star or the inner disk. These winds obliquely strike the flaring disk surface and strip away disk material by entraining it in an outward radial-moving flow at the disk-wind inter-face. ...
A number of geologic and topographic features within the northern plains of Mars have been interp... more A number of geologic and topographic features within the northern plains of Mars have been interpreted as shorelines formed by ancient oceans. Several recent studies have challenged this interpretation, arguing that the present topographic profiles do not appear to originate from surfaces of equal gravitational potential. Elevations along the ``shorelines'' are especially variable at long wavelengths (thousands of km), with amplitudes of hundreds of meters to kilometers. To test the hypothesis that the features in the northern plains are deformed shorelines, we compare the long-wavelength topography (solid surface position relative to the areoid) of the two most prominent shorelines (the Arabia and Deuteronilus contacts of Clifford and Parker, Icarus, 2001) with the deformation expected for: (1) flexural response of the lithosphere to surface loading from the growth of Tharsis and ocean (i.e., sea level) redistribution, (2) true polar wander (TPW), and (3) dynamic topography linked to internal convective flow. We find that TPW and dynamic topography are both capable of reconciling the longest-wavelength variation in topography (the former is a purely degree two signal). The predicted TPW path that best fits the shoreline record is a function of the effective elastic thickness of the Martian lithosphere and it is consistent with recent inferences based on paleomagnetic evidence. The inference is also compatible with our recent re-analysis of the rotational stability of Mars subject to Tharsis and internal loading, which we briefly summarize.
ABSTRACT Mercury&#39;s slow rotation period of 59 days is presumably the result of solar tide... more ABSTRACT Mercury&#39;s slow rotation period of 59 days is presumably the result of solar tides driving its initial rotational state to the present 3:2 spin-orbit resonance. The observed large gravity coefficients can be explained as due to a remnant rotational bulge recording an initial rotation period of a few days (Matsuyama and Nimmo 2009). Despinning changes the shape of the rotational bulge, generating both compressional and extensional stresses (Melosh 1977). However, Mercury&#39;s surface is dominated by compressional tectonic features (Watters et al. 1998), and the inferred global contraction has been explained as due to thermal cooling (Solomon 1976). In addition to non-isotropic changes associated with the rotational flattening, despinning causes isotropic contraction of the entire planet. We consider the effect of the compressional stresses generated by this isotropic contraction on the predicted tectonic pattern. References Matsuyama and Nimmo. Gravity and tectonic patterns of Mercury: Effect of tidal deformation, spin-orbit resonance, nonzero eccentricity, despinning, and reorientation. J. Geophys. Res. (2009) vol. 114 pp. E01010 Melosh. Global tectonics of a despun planet. Icarus (1977) vol. 31 pp. 221-243 Solomon. Some aspects of core formation in Mercury. Icarus (1976) vol. 28 pp. 509-521 Watters et al. Topography of lobate scarps on Mercury: New constraints on the planet&#39;s contraction. Geology (1998) vol. 26 pp. 991-994
ABSTRACT We make predictions for Pluto&#39;s global tectonic pattern due to despinning, orbit... more ABSTRACT We make predictions for Pluto&#39;s global tectonic pattern due to despinning, orbital migration, contraction, and expansion.
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