The two parameterisations of the Andrade rheological model in planetary science: a comparative study

We discuss two parameterisations of the popular Andrade rheological model that appear in planetological literature and illustrate how different assumptions affect the estimates of tidal dissipation and Love numbers

Planetary core radii: from Plato towards PLATO

The boundary between rocky mantle and iron core constitutes the most significant discontinuity within the terrestrial planets, the core itself is one of the largest, if not the largest, structural features of these planets with consequences for the entire geodynamical evolution of the planet: It contains a significant amount of the planets iron inventory, and planetary magnetic fields are generated within the core. We take the occasion of the first seismic determination of the core size of Mars to look back into the development of theories about planetary interiors and cores, starting with early mythological narrations. The renaissance produced the first geologically and physically motivated inferences about the Earth's core, which were extended to the Moon, Mars and other planets in the 19th century. Theories based on telescopic observations soon found their limits, and spacecraft missions to the Moon and to Mars provided the necessary precision of radius, mass, and moment of inertia determinations, and finally seismic data, to determine the core radius precisely. Meanwhile, interest extended to beyond the solar system, and we discuss the observational foundations on which models for the core size of exoplanets are based

Tidal evolution of rocky (exo)planets

The long-term dynamics of close-in terrestrial exoplanets are strongly influenced by tidal interaction with the host star. Periodic tidal loading results in time-varying deformation, which is typically accompanied by energy dissipation. This phenomenon has two important consequences: First, the produced heat might enhance the interior dynamics of the planet and even trigger structural changes in its interior, such as partial melting. Second, the lost (or transferred) energy fuels orbital evolution, i.e., it leads to secular changes in the semi-major axis and eccentricity. Along with the orbital evolution, the spin rate of the planet evolves as well, such that the total angular momentum in the system is conserved. Here, we focus on coupling the effects introduced above. Combining semi-analytical modelling of secular spin-orbital evolution of multilayered planets [1,2,3] with parameterised 1d mantle convection [4,5], we illustrate the feedback between the thermal state of a planet, its spin rate, and the rate of orbit circularisation. As one of the results, we also show how a single planet orbiting a single star can retain nonzero orbital eccentricity by forming a subsurface magma ocean. In addition to the primary topic of this work, we further explore the dependence of stable spin states (spin-orbit resonances) on the planet's interior structure and orbital eccentricity, as well as the parameter dependence of tidal heating. [1] Kaula (1964), Rev. Geophys. and Space Phys., 2:661-685, doi:10.1029/RG002i004p00661. [2] Boué & Efroimsky (2019), CM&DA, 131(7):30, doi:10.1007/s10569-019-9908-2. [3] Sabadini & Vermeersen (2004), Kluwer Academic Publishers, Dodrecht, the Netherlands, ISBN: 9781402012686. [4] Grott and Breuer (2008), Icarus, 193(2):503-515, doi:10.1016/j.icarus.2007.08.015. [5] Tosi et al. (2017), A&A, 605:A71, doi:10.1051/0004-6361/201730728

Tables of Planetary Core Radii and Underlying Parameters (1.0.275) [Data set]

This document provides supplementary information concerning the history of planetary core radius research: ➢ Extended discussions of some more periphereal historical aspects ➢ Numerical values20 ➢ An overview of the current uncertainty of Newton's gravitational constant, G ➢ Mathematical relations used to convert some of the published values into the quantities tabulated in this document ➢ References for all numerical value

Coupled thermal and orbital evolution of tidally-loaded exoplanets

The long-term dynamics of close-in terrestrial exoplanets are strongly influenced by tidal interaction with the host star. Periodic tidal loading results in time-varying deformation, which is typically accompanied by energy dissipation. This phenomenon has two important consequences: First, the produced heat might enhance the interior dynamics of the planet and even trigger structural changes in its interior, such as partial melting. Second, the lost (or transferred) energy fuels orbital evolution, i.e., it leads to secular changes in the semi-major axis and eccentricity. Along with the orbital evolution, the spin rate of the planet evolves as well, such that the total angular momentum in the system is conserved. Here, we focus on coupling the effects introduced above. Combining semi-analytical modeling of the long-term spin-orbital evolution of anelastic multilayered planets with parameterised 1d approach to mantle convection, we illustrate the feedback between the thermal state of a planet, its spin rate, and the rate of orbit circularisation. In addition to the primary topic of this work, we explore the parameter dependence of stable spin states (spin-orbit resonances) for layered bodies, the parameter dependence of tidal heat rate, and the possible contribution of inter-planetary tides to the spin rate evolution in tightly-packed multi-planetary systems

Coupled thermal and orbital evolution of tidally-loaded exoplanets

The long-term dynamics of close-in terrestrial exoplanets are strongly influenced by tidal interaction with the host star. Periodic tidal loading results in time-varying deformation, which is typically accompanied by energy dissipation. This phenomenon has two important consequences: First, the produced heat might enhance the interior dynamics of the planet and even trigger structural changes in its interior, such as partial melting. Second, the lost (or transferred) energy fuels orbital evolution, i.e., it leads to secular changes in the semi-major axis and eccentricity. Along with the orbital evolution, the spin rate of the planet evolves as well, such that the total angular momentum in the system is conserved. Here, we focus on coupling the effects introduced above. Combining semi-analytical modeling of the long-term spin-orbital evolution of anelastic multilayered planets with parameterised 1d approach to mantle convection, we illustrate the feedback between the thermal state of a planet, its spin rate, and the rate of orbit circularisation. In addition to the primary topic of this work, we explore the parameter dependence of stable spin states (spin-orbit resonances) for layered bodies, the parameter dependence of tidal heat rate, and the possible contribution of inter-planetary tides to the spin rate evolution in tightly-packed multi-planetary systems

Core Radius: In Earth, in Mars, in History, and überhaupt

Der Vortrag faßt die wesentlichen Inhalte von Knapmeyer & Walterova (2022), "Planetary Core Radii: From Plato towards PLATO" (elib: https://elib.dlr.de/191002/) zusammen

Tidal response of the Moon: with and without a weak basal layer

Interpretation of the data obtained throughout the period of more than 40 years by Lunar Laser Ranging yields an interesting observation: the tidal quality factor of the Moon, which determines the magnitude of ongoing energy dissipation, follows a different frequency dependence than is measured for rocks in laboratory conditions. When the self-gravity of the lunar body is taken into account, the detected frequency dependence can be interpreted as a signal coming from strong dissipation at the lunar base, indicating a deep-seated layer with low viscosity and possibly containing partial melt. Such a layer would be consistent with the non-detection of deep farside moonquakes by nearside seismic stations and is often associated with the ilmenite-bearing cumulates, that are thought to have descended onto the core-mantle boundary during the lunar magma ocean solidification. Alternative models of a melt-free lunar mantle have also been proposed. These models fit the tidal quality factor Q at the monthly frequency but were unable to explain its observed frequency dependence. In this study, we propose a melt-free model, in which the frequency dependence of lunar Q emerges due to elastically accommodated grain-boundary sliding (GBS) in the lunar mantle. We discuss the implications of such a model and compare it with the traditional approach, which assumes a highly dissipative basal layer. For both alternatives, we perform a Bayesian inversion of the measured tidal parameters (tidal quality factor Q at the monthly and the annual frequency, degree-2 Love numbers h2, k2, and degree-3 Love number k3) and predict either the conditions at the base of the lunar mantle or the relaxation time of elastically accommodated GBS. Since the two alternative models prove to be indistinguishable from each other by tidal measurements, we conclude with an outlook on future observations