An Erratum to this paper has been published: https://doi.org/10.1134/S0038094623330018
An Erratum to this paper has been published: https://doi.org/10.1134/S0038094623330018
The topography of the Moon’s surface and the possible distribution of density anomalies in its interior have been determined for the early stage of the Moon’s evolution. The distribution of gravitational anomalies and gravitational potential in various layers of the upper mantle has been found, which is due to the gravitational influence of anomalous structures of the crust and mantle. The analysis of the results leads to the conclusion about the possibility of convective motions in the molten electrically conductive layers of the crust and mantle, which could create an ancient magnetic field. For the current state of the lunar density structure, gravitational anomalies in various layers, which may lead to solid-state convection in some solidified regions of the Moon, have also been identified.
A discussion is presented of the effects generated by the imbalance between the insolation energy of polar-day zones and the radiation energy of polar-night zones on multicentennial changes in the Earth’s climate. The dependence of this imbalance on the Earth’s orbital parameters is determined. The energy imbalance curves are compared with the known temperature curves for the polar regions, which have been estimated from the results of an analysis of ice cores taken in Antarctica and Greenland. The curves clearly reveal a difference between the contributions of cosmic and terrestrial factors to the temperature profiles for the regions in question and demonstrate a synchronicity of these factors. Algorithms are obtained for calculating the magnitude of fluctuations in the size of the Earth’s polar caps relative to their averages. The results obtained within the assumptions taken in this work enable predictions to be made about the development of the current global warming and about changes in the size of the Arctic and Antarctic polar caps. It is predicted that over the next three millennia, changes in the Earth’s orbital parameters will contribute to the slow melting of the northern polar cap. Then, the trend for a new growth of the northern polar cap will again manifest itself. In the Southern Hemisphere, a trend towards increased glaciation has already formed. Influenced by the cosmic factor, it will intensify over the next 20 000 years.
The motion of planetesimals initially located in the feeding zone of the planet Proxima Centauri c, at distances of 500 AU from the star to the star’s Hill sphere radius of 1200 AU was considered. In the analyzed non-gaseous model, the primary ejection of planetesimals from most of the feeding zone of an almost formed planet c to distances greater than 500 AU from the star occurred during the first 10 million years. Only for planetesimals originally located at the edges of the planet’s feeding zone, the fraction of planetesimals that first reached 500 AU over the time greater than 10 million years was more than half. Some planetesimals could reach the outer part of the star’s Hill sphere over hundreds of millions of years. Approximately 90% of the planetesimals that first reached 500 AU from Proxima Centauri first reached 1200 AU from the star in less than 1 million years, given the current mass of the planet c. No more than 2% of planetesimals with aphelion orbital distances between 500 and 1200 AU followed such orbits for more than 10 million years (but less than a few tens of millions of years). With a planet mass equal to half the mass of the planet c, approximately 70–80% of planetesimals increased their maximum distances from the star from 500 to 1200 AU in less than 1 million years. For planetesimals that first reached 500 AU from the star under the current mass of the planet c, the fraction of planetesimals with orbital eccentricities greater than 1 was 0.05 and 0.1 for the initial eccentricities of their orbits eo = 0.02 and eo = 0.15, respectively. Among the planetesimals that first reached 1200 AU from the star, this fraction was approximately 0.3 for both eo values. The minimum eccentricity values for planetesimals that have reached 500 and 1200 AU from the star were 0.992 and 0.995, respectively. In the considered model, the disk of planetesimals in the outer part of the star’s Hill sphere was rather flat. Inclinations i of the orbits for more than 80% of the planetesimals that first reached 500 or 1200 AU from the star did not exceed 10°. With the current mass of the planet c, the percentage of such planetesimals with i > 20° did not exceed 1% in all calculation variants. The results may be of interest for understanding the motion of bodies in other exoplanetary systems, especially those with a single dominant planet. They can be used to provide the initial data for models of the evolution of the disk of bodies in the outer part of Proxima Centauri’s Hill sphere, which take into account gravitational interactions and collisions between bodies, as well as the influence of other stars. The strongly inclined orbits of bodies in the outer part of Proxima Centauri’s Hill sphere can primarily result from bodies that entered the Hill sphere from outside. The radius of Proxima
The degassing of Murchison carbonaceous chondrite (CM2 type) was studied using a setup specially designed for this purpose. The experiments involved stepwise heating (without gas accumulation) and isothermal annealing of meteorite samples with the composition of released gases determined through gas chromatography methods in the temperature range from 200 to 800°C. To account for sorbed water, degassing at 50 and 110°C was additionally analyzed. The IR spectra of the Murchison meteorite were obtained after annealing at different temperatures and used to trace the thermal degradation. The comparison with the degassing of the ordinary chondrite Chelyabinsk (type LL5) revealed a significant increase in the release of carbonaceous gases for the Murchison meteorite.
This paper presents a method for solving the inverse problem of thermal sounding using calibrated data from the ACS TIRVIM experiment on board the ExoMars Trace Gas Orbiter. The 1.7–17 µm range TIRVIM Fourier spectrometer as part of the ACS instrument complex aboard the ExoMars TGO operates in the nadir and solar occultation modes in orbit around Mars. The main scientific goal of TIRVIM in the nadir observation mode is the long-term constant monitoring of the thermal structure of the Martian atmosphere and the general content of aerosols and water vapor from measurements in the range of 5–16.7 µm (600–2000 cm–1). To process the TIRVIM nadir measurements, an algorithm was developed, allowing the retrieval of the vertical temperature profile from the surface to 60 km, the surface temperature, and the general content of dust and water ice in the atmosphere from the TIRVIM spectrum in the range of 600–1250 cm–1, as well as the water vapor column abundance according to measurements in the range of 1250–1830 cm–1. The processing method widely uses the achievements of previous similar experiments, taking into account the features of the TIRVIM spectra. Using the developed method 2.28 × 106 spectra obtained by TIRVIM in nadir by regular measurements, were processed with retrieval of the thermal structure up to 60 km altitude and the aerosol content in the atmosphere as well as additional 2.3 × 105 specially averaged TIRVIM spectra, were processed with retrieval of the water vapor column abundancein the Martian atmosphere.
In order to study the processes related to the origin and retention of water on the surface of the Moon, an experimental setup has been created at the Vernadsky Institute of Geochemistry and Analytical Chemistry, Russian Academy of Sciences (GEOKHI RAS), for the analysis of (re)sublimation processes of water ice in a vacuum at low temperatures. The temperature range for (re)sublimation varies from –100 to 0°C. The setup is connected to an Isotope Ratio Mass Spectrometer (IRMS), which allows for measuring the isotopic composition of the vapor of the evaporating substance and providing an estimation of the (re)sublimation rate under specific physicochemical conditions. The direct introduction of gases into the mass spectrometer in real-time mode sets the developed setup apart from foreign counterparts. The setup is equipped with a transparent quartz window through which the surface of the studied substance can be heated using a halogen lamp, simulating the movement of solar rays on the surface of mineral grain compositions under conditions similar to those on the lunar surface. In addition to studying gas (de)sorption on the surfaces of mineral grains of various compositions, the setup can also be used for researching the (re)sublimation of gas hydrates and CO2.
The degassing of Allende carbonaceous chondrite (CV3 type) was studied using a setup specially designed for this purpose. The experiments involved stepwise heating (without gas accumulation) and isothermal annealing of meteorite samples with the composition of released gases determined through gas chromatography methods in the temperature range from 200 to 800°C. To account for sorbed water, degassing at 50 and 110°C was additionally analyzed. The Raman and IR spectra of both the primary Allende substance and the substance after its annealing at three temperatures (200, 500, and 800°C) were obtained. These spectra were used to trace the thermal transformation of the substance of the meteorite’s parent body and estimate the maximum temperature of metamorphism. The results were compared with the degassing of the Murchison carbonaceous chondrite of another type (CM2).
In contrast to several classical studies, in which gravitational instability criteria for astrophysical disks are derived within traditional hydrodynamics or kinetics, it is proposed to consider the set of loose gas–dust clusters of an accretion protoplanetary disk as a special type of continuous medium, i.e., a fractal medium whose phase velocity space contains points and areas not filled by its components. Within the Tsallis formalism of nonadditive statistics (thermodynamics), intended to describe the behavior of anomalous systems, i.e., systems with a strong gravitational interaction of its individual parts and the fractal nature of the phase space, linearized equations are obtained for oscillations of a solid-state rotating disk on the basis of modified Navier–Stokes hydrodynamic equations (the so-called q-hydrodynamics equations) and in view of dissipative effects, and a derivation is given of the dispersion equation in the WKB approximation. An analysis is conducted of axisymmetric oscillations of a differentially rotating astrophysical gas–dust space object to obtain modified Jeans and Toomre gravitational instability criteria for disks with a fractal structure.
There are serious contradictions between the geophysical and geochemical classes of models of the chemical composition and internal structure of the Moon, associated with the assessment of the abundance of the main oxides. The search for a potential consensus between the models was carried out on the basis of a set of geophysical and geochemical data using the Monte-Carlo method using the Markov chain scheme in combination with a method of minimization of the Gibbs free energy. The influence of the chemical composition and mineralogy of several conceptual models on the internal structure of the Moon has been studied. Two classes of chemical composition models are considered—the E models with terrestrial values of Al2O3 and CaO and M models with their higher content, as well as two classes of the most popular geochemical models, the Taylor Whole Moon (TWM) and Lunar Primitive Upper Mantle (LPUM) models, with ~45 wt % SiO2, but with different concentrations of refractory oxides and FeO. In both classes of E and M models, the lunar mantle is enriched in silica (~50 wt % SiO2) and FeO (11–13 wt %, Mg# 79–81) relative to the bulk composition of the silicate Earth (BSE, ~45 wt % SiO2, ~8 wt % FeO, Mg# 89). Such high concentrations of SiO2 and FeO become the determining factors for understanding the features of the mineral, velocity, and density structure of the lunar mantle. For the E and M models and geochemical models TWM and LPUM, the speed of sound and the density of stable phase associations are calculated. For E and M models, good agreement was obtained between the velocities of P- and S-waves and seismic sounding data from the Apollo program, which supports the idea of a silica-rich (olivine-pyroxenite) upper mantle. Unlike the Earth’s upper mantle, the dominant mineral in the Moon’s upper mantle is low-calcium orthopyroxene, not olivine. In contrast, the sound velocities of silica-unsaturated compositions, both FeO and Al2O3 enriched (TWM) and depleted (LPUM) models, do not match the seismic signatures. Thermodynamically justified restrictions on the chemical composition, mineralogy, and physical characteristics of the mantle based on the E and M models make it possible to eliminate some contradictions between the geochemical and geophysical classes of models of the internal structure of the Moon. Simultaneous enrichment in ferrous iron and silica is difficult to reconcile with the hypothesis of the formation of the Moon as a result of a giant impact from the substance of the Earth’s primitive mantle or from the substance of a shock body (bodies) of chondrite composition. Limitations on lunar concentrations of FeO and SiO2 probably correspond to the parent bodies of some achondrites.
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