On the model structure of the gravity field of Mars

A discussion is presented about the constraints used in constructing a model for the internal structure of Mars. The most important fact is that the Martian chemical model proposed by Wänke and Dreibus (WD) has stood the test of time. This means that the chondritic ratio Fe/Si = 1.71 can be used as a constraint in constructing an interior structure model of the planet. Consideration is given to the constructing of the reference surface of Mars. It is concluded that the effectively hydrostatic-equilibrium model of Mars is well suited for this purpose. The areoid heights and gravity anomalies in the model of Mars are calculated. The results are shown in the figures (maps) and comments made. The results are compared with the similar data for the Earth. Mars deviates much more strongly from the hydrostatic equilibrium than the Earth. It is suggested that the average thickness of the Martian elastic lithosphere should exceed that of the Earth’s continental lithosphere.     

On the scientific aims of the MISS seismic experiment

The paper deals with how the data on structure of the Martian near-surface layers and deep interiors can be obtained using the only broadband seismometer in the framework of the planned MISS (Mars Interior Structure by Seismology) experiment. For this purpose, both traditional and nontraditional seismic methods of interior sounding are used. These methods process meteorite impact data, seismic noise from meteorological effects, and the data from strong Martian lithoshere quakes.     

Physical Libration of the Moon: An Extended Problem

Astronomy Reports - The work is devoted to the study of the physical libration of the Moon. Interest in the traditional topic related to the rotation of the Moon is stirred up by the activity of...     

Nonhydrostatic Stress State in the Martian Interior for Different Rheological Models

Izvestiya, Physics of the Solid Earth - We analyze nonhydrostatic stress field in the Martian interior for two types of heterogeneous elastic models: the ones with a lithosphere and the ones with a...     

Spectrum of the free oscillations of the moon

The determination of the internal structure of the Moon using bulk waves is largely complicated due to inhomogeneities in its uppermost layer. We investigate the possibility of studying the Moon’s interior by a sensing method using the free oscillations of the Moon. The spectrum of the free oscillations is calculated for two current models of the internal structure of the Moon derived from the analysis of the Apollo seismic network data, based on new methods: the MG (Garsia, et al., 2011) and MW (Weber, et al., 2011) models. In contrast to the MG model, the MW model includes a solid inner core. In this latter model, we estimate how the shear modulus of the inner core affects the structure of the oscillations.     

On Estimating the Dissipative Factor of the Martian Interior

An attempt is made to construct a trial Q_μ(l) distribution in the silicate mantle of Mars. With the allowance for the fact that on the P–T plane the Earth’s geotherm is close to the distribution of areotherms, it was concluded that Q_μ(l) should be distributed in the Martian interior topologically close to the Q_μ(l) distribution in the Earth. The initial distribution was specified by the four-layer piecewise-constant distribution from the QML9 model. An important step was to select the power index in the frequency dependence of Q_μ. Based on the laboratory data and on the experience of studying this problem for the Earth, n was specified in the interval 0.1–0.3. It was found that with the conversion of the initial distribution to the orbital period of Phobos around Mars, which is the only constraint for the problem derived from the observations, this distribution agrees reasonably well with the observational data at n = 0.1.     

The Spectrum of Torsional Oscillations of the Moon

The diagnostic potentialities of the torsional oscillations for probing the structure of the interiors of the Moon are investigated. Models with no core, a liquid core, and a solid core are considered. The profiles of compressional and shear wave velocities V _P and V _S for the lunar interior estimated by Bills and Ferrari (1977), Goins et al. (1981), and Nakamura (1983) from the Apollo lunar seismic network are used. For all these models, the periods of torsional oscillations for n = 2–100 and four overtones have been calculated. The derivatives of the dimensionless eigenfrequency with respect to the dimensionless shear modulus and density are calculated and tabulated for use. These data can be used to determine corrections to the model density and shear modulus distributions due to their small change. The damping of torsional oscillations is studied. Several trial radial distributions of the dissipative function Q are considered.     

Analytical Modeling of the Magnetic Field of Mars from Satellite Data Using Modified S-Approximations

Doklady Earth Sciences - An analytical model of the magnetic field over the Martian surface in the southwestern part of the Elysium Planitia is constructed using satellite data and modified...     

On Zones of Potential High Seismic Activity on Mars

The joint analysis of current data on the topography and nonequilibrium part of the Martian gravity field allowed us to obtain a detailed pattern of the distribution of nonhydrostatic stresses in the Martian interior. The criteria for selection of possible sources of marsquakes were large values of shear stress against the background of significant tensional stresses. The rheological models considered were the elastic model, the one with the lithosphere, and the model with the lithosphere and possible melting zones in it. Independently from the rheological model chosen, zones of high shear and tensional stresses in the Martian crust and mantle were revealed beneath the Hellas and Argyre impact basins, Mare Acidalium, Arcadia Planitia, and Valles Marineris.