Solar System Research最新文献

Precise orbit determination of non-cooperative cislunar objects requires measurements that do not depend on onboard transponders or retroreflectors. This study evaluates whether optical astrometry and radar echo range can provide useful tracking performance in a two-station Earth–Moon geometry. Three configurations were tested with weighted batch least-squares estimation in the SPOT orbit-determination toolkit. Configuration A used Earth optical astrometry and Earth radar range. Configuration B added lunar optical astrometry, and Configuration C added lunar radar range. The targets were an Earth–Moon L4 case, a low circular lunar orbit, a highly elliptical lunar orbit, and an Apophis close-approach reference arc. The Earth-only baseline converged for all targets, but the benefit of a lunar station depended strongly on target distance and geometry. Lunar optical was most effective for the two lunar orbiters. Lunar radar range was most effective for distant geometries. The preferred lunar-station observable is therefore not universal. It depends on station–target distance, target dynamics, and parameter correlation.

The problem of selecting storage orbits for end-of-life GLONASS global navigation system satellites is considered. The storage orbit requirement is that the satellite located in this orbit should not enter the zone of operating navigation satellites over a 200-year interval. We performed numerical modeling of the orbital evolution of objects in the vicinity of the GLONASS system over a 200-year interval. The initial values of the orbital semimajor axis varied from 25 400 to 25 950 km, as well as the longitude of the ascending node. Objects with area-to-mass ratios of 0.001, 0.01, 0.1, 1, and 10 m² kg^–1 were considered. We recommend storage orbits with initial semimajor axes 200–500 km above the nominal GLONASS orbit for objects with an area-to-mass ratio corresponding to satellites. It is shown that when choosing the initial orientation of the orbit, it is necessary to consider the features of the long-period evolution of eccentricity under the influence of the luni–solar resonance determined by the orbital inclination, and the secondary secular apsidal–nodal resonance induced by the solar radiation pressure.

It has been shown quantitatively for the first time that the main source of hot oxygen atoms in the Earth’s polar atmosphere during strong geomagnetic storms are exothermic reactions of odd nitrogen chemistry activated by auroral electron precipitation, compared to direct dissociation of O₂ by an electron impact. At altitudes of 500–600 km and above, the concentration of hot oxygen is 10–20% of the thermal concentration, which must be taken into account when calculating the atmospheric drag of low-orbit satellites, since the error in estimating the density of the atmosphere can reach values of up to 20%. The calculations were performed using kinetic Monte Carlo models for the conditions of the geomagnetic storm of November 9, 2004.

The oxidized-reduced state of a planetary mantle affects its degassing and the trends of differentiation. Unlike on Earth, the redox evolution of lunar mantle remains unclear due to limited oxygen fugacity (fO₂) constraints from lunar samples. Here, we report oxygen fugacity (fO₂) in silicate minerals (olivines, pyroxenes) selected from a special types of basalts in the Earth’s upper mantle (such as kimberlites of Yakutia and subduction zone of Kamchatka) and lunar breccia basalts (meteorite NWA 7611). The intrinsic value of oxygen fugacity was determined by the method of a double electrochemical cell in the temperature range from 800 to 1100°C. In general, the dependence of fO₂ on temperature in minerals is described with good accuracy (R2 ~ 0.9) by the expression log fO₂ = A + B/T(K). The values of regression coefficients A and B for minerals from some terrestrial/lunar samples were obtained and compared with known Fe-buffers—wustite–magnetite (WM), iron–wustite (IW) and others. For minerals from terrestrial samples, the proportions of iron atoms in various valence states of Fe²⁺/Fe³⁺ were independently verified by Mössbauer spectroscopy. Minerals from the lunar meteorite NWA 7611 demonstrate the lowest oxygen fugacity which indicates significantly more reduced conditions of the lunar mantle.

In periods from December 2023 to March 2024 and from December 2024 to March 2025, we performed two series of UBVRI survey observations of 39 and 75 Main-belt asteroids, respectively, in order to find active objects among them. The surveys primarily included primitive-type asteroids moving near perihelion, which ensures the highest subsolar temperatures of the asteroids’ surface at that time. Based on short-term changes in the shape of the normalized approximated reflectance spectra of asteroids, as well as on differences from the spectra available in the SMASII database, we detected signs of dust activity in asteroids 210 Isabella, 271 Penthesilea, 372 Palma, 481 Emita, 569 Misa, and 1599 Giomus during the first survey and in asteroids 10 Hygiea, 11 Parthenope, 326 Tamara, 495 Eulalia, 973 Aralia, 1182 Ilona, and 1479 Inkeri during the second survey. The results of the second survey also suggest that asteroids 65 Cybele and 596 Scheila exhibit low activity. To explain the unusual features in the measured spectra, numerical simulations were performed for the reflectance spectra of a hypothetically active asteroid with a dust exosphere consisting of submicron- and micron-sized particles under various variants of their structure and chemical–mineral composition. It has been shown that the shape of the measured approximated reflectance spectra agrees well with the behavior of model spectra for asteroids surrounded by a dust exosphere. This paper is the first in a series devoted to various aspects of the study of asteroid activity. Here, we demonstrate the potential of the multiband photometric method for detecting active asteroids and discuss the results of the last observations and the signs of activity in the reflectance spectra of asteroids. In the subsequent papers of this series, we will examine the main mechanisms of dust activity in asteroids and the key factors that enable the detection of active asteroids and facilitate the analysis of this phenomenon.

Lunar swirls are one of the most enigmatic features on the Moon, the spectral characteristics of which have been extensively studied. However, the quantitative statistical validation of the difference between the swirl interiors and the surrounding areas remains limited. In the present work, reflectance data from Moon Mineralogy Mapper on Chandrayaan-1 were used to examine four swirl areas, viz. one mare and three highland swirls. The Principal Component Analysis (PCA) was applied to hyperspectral reflectance data to isolate the albedo variation and optical maturity. We combined three PCA axes corresponding to the albedo, high Optical Maturity (OMAT) and low OMAT to generate RGB composite images that allow identification of swirl patterns. Several hundreds to thousands of pixels were selected from each ON-swirl and OFF-swirl region to characterize their spectral features. Pixel-wise reflectance and continuum-removed spectra were extracted for all four lunar swirl regions examined in this study, and absorption band depths at 1 and 2 µm were quantified. Following the continuum removal, a stability-based Monte-Carlo resampling approach was used to assess the statistical significance of ON and OFF-swirl changes. Welch’s two-sample t-test was used to evaluate statistical significance, and Cohen’s d affected size was computed to measure the magnitude of ON-OFF swirl difference in the absorption band depth. In addition to explicitly accounting for spatial heterogeneity and swirl-to-swirl variations, our combined spectral–statistical approach offers a reliable and repeatable framework for evaluating spectral variability across several lunar swirl regions.

We propose a method for predicting future collisions of asteroids with the Earth. To determine the true positions of the nodes in a heliocentric coordinate system for elliptical orbits, we developed a special algorithm. The evolution of orbits of the asteroid Apophis and the Earth was studied over a time interval of September 2023 to June 2029. The intersection zones for the orbits of Apophis and the Earth were plotted for the time interval considered. The number of intersection zones was determined at 135. We show that the simultaneous entry of Apophis and the Earth into one of these zones will lead to their inevitable collision. The relative positions of Apophis and the Earth with respect to these zones were analyzed. The most dangerous zones of intersection of the orbits of Apophis and the Earth were identified. We demonstrate how a close approach of Apophis to the Earth on April 13, 2029, can influence the formation of intersection zones.

The paper presents the results of modeling the atmospheres of planets that are part of morphologically similar planetary systems—the ultra-hot Jupiters WASP-121b and WASP-76b. For the first time, the absorption in the Fe(II) 501.8-nm line was calculated using a complete kinetic modeling of the population of excited iron levels. Together with the absorption calculations in the 1083-nm metastable helium line, comparison with observations allowed us to estimate two important parameters: the flux of ionizing radiation from the star and the metallicity of the planets’ atmospheres. The modeling results showed that at supersolar abundances of heavy elements, strong compression of the atmosphere occurs, while subsolar abundances are consistent with the observed absorptions.

The results of the calculation of the period of the Chandler wobble of Mars for the set of test models of the internal structure are presented. The crust is represented by a homogeneous layer of a given thickness with a constant density. For the silicate mantle model, the distribution of density and elastic parameters was obtained using the Perple_X program. The thickness of the silicate molten layer in the mantle at the boundary with the core is taken to be 200 km. The core is believed to be composed of a mixture of iron–nickel and light elements. During the modeling, the following were varied: the density and thickness of the crust, the mineral composition and temperature of the mantle (seven mineralogical models of the mantle along three areotherms were used). The Andrade model is adopted as a working rheological model. The viscosity is given by a piecewise constant profile that varies. The internal structure models are controlled by mass, average radius, moment of inertia, Love number k₂ and the radius of the core. With fixed rheology and viscosity parameters the spread in the value of the Chandler period is about 1 day for different mineral compositions and temperatures of the mantle.

In this paper, we present the results of numerical calculations of the motion of the Orion’s Sword Complex (open star clusters NGC 1977, NGC 1980, NGC 1981, the Orion Nebula Cluster (ONC)—M 42) and the planetary system TOI-2796 with a single star around the galactic center. It is shown that Orion’s Sword objects approached TOI-2796 to a distance of up to ≈7 pc about two million years ago. An assessment of the possible change in the spatial velocity of a small body on the periphery of the Oort cloud TOI-2796 has been carried out. The result of the approach could have been the loss of the small body into interstellar space. The applicability of the apex method for searching for approaching objects has been estimated.