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  • 1
    Publication Date: 2023-02-24
    Description: We use the tidal deformations of the Moon induced by the Earth and the Sun as a tool for studying the inner structure of our satellite. Based on measurements of the degree-two tidal Love numbers $k_2$ and $h_2$ and dissipation coefficients from the GRAIL mission, Lunar Laser Ranging and Laser Altimetry on board of the LRO spacecraft, we perform Monte Carlo samplings for 120,000 possible combinations of thicknesses and viscosities for two classes of the lunar models. The first one includes a uniform core, a low viscosity zone (LVZ) at the core-mantle boundary, a mantle and a crust. The second one has an additional inner core. All models are consistent with the lunar t otal mass as well as its moment of inertia. By comparing predicted and observed parameters for the tidal deformations we find that the existence of an inner core cannot be ruled out. Furthermore, by deducing temperature profiles for the LVZ and an Earth-like mantle, we obtain stringent constraints on the radius (500 $\pm$ 1) km, viscosity, $(4.5 \pm 0.8) \times10^{16}$ Pa$\cdot$s and the density (3400 $\pm$ 10) kg/m$^3$ of the LVZ. We also infer the first estimation for the outer core viscosity, (2.07 ± 1.03) × 10$^{17}$ Pa·s, for tw o different possible structures: a Moon with a 70 km thick outer core and large inner core (290 km radius with a density of 6000 kg/m$^{3}$), and a Moon with a thicker outer core (169 km thick) but a denser and smaller inner core (219 km radius for 8000 kg/m$^{3}$).
    Description: Published
    Description: 115426
    Description: 5IT. Osservazioni satellitari
    Description: JCR Journal
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 2
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    Oxford University Press - The Royal Astronomical Society
    Publication Date: 2022-08-16
    Description: This article has been accepted for publication in Geophysical Journal International ©: The Authors 2022. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved. Uploaded in accordance with the publisher's self-archiving policy.
    Description: The computation of the Love numbers for a spherically symmetric self-gravitating viscoelastic Earth is a classical problem in global geodynamics. Here we revisit the problem of the numerical evaluation of loading and tidal Love numbers in the static limit for an incompressible planetary body, adopting a Laplace inversion scheme based upon the Post-Widder formula as an alternative to the traditional viscoelastic normal modes method. We also consider, whithin the same framework, complex-valued, frequency-dependent Love numbers that describe the response to a periodic forcing, which are paramount in the study of the tidal deformation of planets. Furthermore, we numerically obtain the time-derivatives of Love numbers, suitable for modeling geodetic signals in response to surface loads variations. A number of examples are shown, in which time and frequency-dependent Love numbers are evaluated for the Earth and planets adopting realistic rheological profiles. The numerical solution scheme is implemented in ALMA3 (the plAnetary Love nuMbers cAlculator, version 3), an upgraded open-source Fortran 90 program that computes the Love numbers for radially layered planetary bodies with a wide range of rheologies, including transient laws like Andrade or Burgers.
    Description: Published
    Description: 1502–1517
    Description: 1T. Struttura della Terra
    Description: JCR Journal
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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