Solar System Research最新文献

Predicting the motion of near-Earth asteroids (NEAs) is a complex task that requires the use of sophisticated technology, various techniques, and significant computational resources. In recent decades, significant progress has been achieved in this area, but many problems still await their solution. In this paper, we consider the main methods used for predicting the motion of NEAs at various stages, starting from observations and ending with the study of motion specifics such as close encounters and planetary collisions, orbital and secular resonances, as well as chaoticity and predictability of motion. The article is based on a report presented at the scientific-practical conference with international participation “Near-Earth Astronomy-2022” (April 18–21, 2022, Moscow).

The problem of self-gravitational instability of an astrophysical rotating plasma in a strong magnetic field with an anisotropic pressure tensor is studied on the basis of the Chew–Goldberger–Low (CGL) quasi-hydrodynamic equations modified by generalized polytropic laws. Using the general form of a dispersion relation obtained by the normal-mode perturbation method, a discussion is provided of the propagation of small-amplitude perturbation waves in an infinite homogeneous plasma medium for transverse, longitudinal, and oblique directions with respect to the magnetic field vector. It is shown that different polytropic indices and anisotropic pressures not only change the classical Jeans instability condition but also cause the appearance of new unstable regions. Modified Jeans instability criteria are obtained for isotropic MHD equations and anisotropic CGL equations owing to the influence of the polytropic indices on gravitational and firehose instabilities for astrophysical plasma. It is shown that in the case of a longitudinal mode of perturbation wave propagation, the Jeans instability criterion does not depend on uniform rotation. In the case of the transverse propagation regime, the presence of rotation reduces the critical wave number and exerts a stabilizing effect on the growth rate of the unstable regime.

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.

Cometary nuclei located in the Oort cloud accumulate high concentration of radicals in surface layers under cosmic ray irradiation at low temperatures. Recombination of radicals induced by an increase in the surface temperature of a comet by a close passing star, O/B stars, or nearby supernovae leads to the heating of the ice layer with the releasing of volatiles from the amorphous ice. When high gas pressure builds up beneath the cometary surface, dust and gas are ejected. The resulting jet of gas and dust can change the comet’s orbit in the Oort cloud. The studied non-gravitational mechanism can effectively expel comets with a radius of ≤1 km from the Oort cloud into the inner part of the Solar system. The total effect of cometary outbursts on the stability of cometary orbits during the evolution of Solar system can result in a decrease in the number of long-period small-radius comets.

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).

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.