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.
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.
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
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.
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.
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.
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 283-nm and 365-nm spectral channels of the Ultraviolet Imager on board the Akatsuki spacecraft of the Japan Aerospace Exploration Agency (JAXA) enabled observations of features at two altitude levels in the atmosphere of Venus and estimate wind speeds from the displacement of these features. The main absorber in the 283-nm channel is sulfur dioxide SO2, present in the upper haze. An unknown UV absorber located at the cloud top (70 ± 2 km) is responsible for the formation of contrasting features in the 365-nm channel. Analysis of wind speed fields observed in both channels allows us to estimate the relative vertical position of both observation levels. Based on a series of sequential UV images (283 and 365-nm) of the cloud cover of Venus, wind velocity fields were obtained for two periods, each covering a Venusian year (October 2019–April 2020 and April 2022–September 2022). The article provides a comparative analysis of the results. Zonal velocities demonstrate dependence on local time and phase angle of observations. In equatorial latitudes, minimum of the average zonal velocity is shifted toward the evening terminator. The average zonal velocities in the 283-nm channel are systematically larger than those in the 365-nm channel, indicating that the 283-nm channel provides information from a relatively higher altitude. A dependence of the dynamic parameters of the atmosphere and image brightness on the position of Y-feature was discovered. In the frontal part of the Y‑feature, the greatest correlation is observed between simultaneous images obtained in different spectral channels, which leads to a convergence of wind speeds in these channels.
On the basis of models of the trans-Neptunian disk, which take into account the gravitational interaction of planetesimals, we consider the origin of near-Neptunian objects with perihelion distances of 28 < q < 35.5 AU and semimajor axes 60 < a < 1000 AU, which are the source of observed comets of the Jupiter family. It is shown that the majority of objects come to the near-Neptunian region from the distant trans-Neptunian region, defined in this work by orbits with q > 60 AU, a < 1000 AU or 40 < q < 60 AU, 200 < a < 1000 AU. This result has a crucial difference from the previously considered models, which propose as a source of near-Neptunian objects and comets of the Jupiter family the so-called scattered disk, defined by orbits with q < 60 AU, 50 < a < 200 AU. Distant trans-Neptunian objects are a natural result of the dynamical evolution of the outer planetesimal disk taking into account its self-gravity, and the gravitational interaction of these objects creates a flux of bodies into the near-Neptunian region.
Protons (and heavier ions) with anisotropic velocity distributions and nonthermal deviations from the Maxwellian distribution are frequently observed in the solar wind in the magnetosphere and at different altitudes. The present paper investigates the influence of hyperthermal populations on the main characteristics of mirror and firehose instabilities in a rarefied gravitating plasma using the Chew–Goldberger–Low (CGL) equations modified to account for the effect of anisotropic thermal conductivity. The plasma distribution anisotropy, including hyperthermal populations, is modeled using bi-kappa functions, and new dispersion relations for the kappa distributions are derived using the modified plasma distribution function. An important feature of the proposed approach is that some terms introduced by higher-order moments have the same order as terms in the classical CGL equations. These terms lead to modified conditions for mirror and firehose instabilities. However, in the limit of vanishing zero heat flux, the firehose instability condition in a heat-conducting plasma remains unchanged. Deviations associated with superthermal tails from the standard cosmic Maxwellian plasma dispersion may ultimately be used to estimate the presence of superthermal populations during solar flares and in the magnetosphere.
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.
Observations show that situations sometimes arise when the solar wind, which is super-Alfvénic where the planets of the Solar System are located, becomes sub-Alfvénic in the orbit of Mercury and even at 1 AU. The work considers the event described in detail in the article (Bowers et al., 2025), which occurred on May 1, 2013, when a coronal mass ejection that reached Mercury simulated a sub-Alfvénic flow of magnetized solar wind plasma. At the same time, a strong interplanetary magnetic field (IMF) was directed towards the Sun and towards the dawn. In this case, we used a semiempirical modified paraboloid model to present the changes in Mercury’s magnetosphere. The results of the calculations were compared with the calculations in the MHD-model in the work (Bowers et al., 2025) for super-Alfvénic and sub-Alfvénic flow regimes. A good correspondence between the calculations in these two models was obtained and a new effect of the possible splitting of the Alfvén wings, caused by the presence of neutral points of the magnetic field in the cusps and in the tail in the paraboloid model of the magnetosphere, was revealed.
Mascon gravity models are widely used to represent the near-field gravity of small bodies, yet practical criteria to verify whether a given mascon resolution is sufficient for local dynamics are rarely quantified. We propose a reproducible convergence protocol centered on a dynamically meaningful feature that controls accessibility in the rotating frame: the four external saddle equilibria and the associated connectivity of equatorial zero-velocity curves (ZVCs). We build controlled mascon families for two contrasting bodies, the irregular asteroid (16) Psyche, represented by a convex triangular mesh, and the elongated dwarf planet (136108) Haumea, represented by a triaxial-ellipsoid model. For each resolution N = 500, 1000, 3000, 5000, 10 000, 15 000, 20 000, we detect the external saddles and track them against a fixed reference set at Nref = 20 000 via a one-to-one three-dimensional matching. A resolution reproduces the external equilibrium-point configuration if all four saddles are matched within an acceptance radius dmax = αRmean, where Rmean is the volume-equivalent radius and α is a dimensionless tolerance. Using the conservative tolerance α = 0.05, full recovery, defined as nmatch = 4, is not guaranteed at low and intermediate N and can be non-monotonic. For Psyche, nmatch(N) = 1, 1, 2, 1, 2, 3, 4; for Haumea, nmatch(N) = 0, 4, 2, 2, 4, 4, 4. The external equilibrium-point configuration thus provides a sensitive diagnostic of mascon-resolution adequacy. Reporting nmatch(N) together with reference-based displacement metrics provides a compact verification step prior to downstream dynamical surveys.
The paper presents the results of photometric observations of the near-Earth asteroid (65803) Didymos, conducted on the 70-cm AZT-8 telescope of the Hisar Astronomical Observatory of the Institute of Astrophysics of the National Academy of Sciences of Tajikistan over seven nights from August 29 to September 6, 2022. Using the Lomb–Scargle method, the asteroid’s rotation period was determined to be P = 2.3562 ± 0.0040 h. The uncertainty ΔP was estimated using three independent methods: Bootstrap (Monte Carlo), FWHM, and Q-factor. Analysis of the phase curve using a two-harmonic Fourier series confirms the double-humped shape of the light curve, characteristic of rotating irregularly shaped objects. The results are consistent with period estimates obtained before the DART space experiment and can be used for further modeling.
In our work, we show that the surface material at the landing sites of the Venera-8, -9, -10, -13, -14 and Vega-1 and -2 spacecraft may represent ejecta from impact craters located elsewhere, deposited from the atmosphere at the landing sites in the form of radar-dark parabolas. This raises the question of whether the lithified surface material observed at each of these sites originates from the geological and morphological units of these sites, or whether it partially or completely consists of solidified deposits of impact ejecta settled from the atmosphere. In any case, it would be prudent in future missions aimed at measuring the composition of local bedrock to drill to depths of several meters to ensure reliable sampling and analysis, and to avoid the possible influence of mapped radar-dark parabolas by selecting landing sites outside them.
The isotopic content of water is a key indicator of its quality and suitability for the human use. The full IR interval, from far- to near-IR, is considered to define spectral features of the various isotopic forms of water (–OH/–OD and H2O/HDO/D2O) contained in anorthite. Herewith, water can be included in the crystal structure and/or adsorbed on the surface. Anorthite is important as the main rock-forming mineral of lunar polar crust which covers more than 70
By calculating the Lyapunov characteristic exponents in the hierarchical three-body problem (star–planet–planet’s satellite), an analysis of the applicability of a number of criteria for estimating the maximum possible value of the semimajor axis acrit of a satellite’s orbit was carried out, corresponding to its long-term stable orbital dynamics. It has been shown that the empirical criterion from the work (Domingos et al., 2006), which is often used to determine potential orbits of exomoons (satellites of exoplanets), significantly overestimates the value of acrit. In a planar problem for a prograde orbit (the directions of orbital motion of the planet and satellite coincide) of an exomoon, when estimating acrit the criterion proposed by Rosario-Franco et al. (2020) works better, for the retrograde orbit of the exomoon, the criterion from the work (Quarles et al., 2021) works better. If the angle between the orbital planes of the planet and the satellite can be significant (>30°), a reliable estimate for acrit can be obtained by numerical modeling of the long-term orbital dynamics of the exomoon and using rigorous methods of motion stability analysis (calculation of Lyapunov characteristic exponents, the MEGNO parameter, etc.).
Kappa distributions, which make it possible to effectively model the observed distributions of particles in cosmic and astrophysical plasma media throughout the heliosphere, are now widely used. In this paper we discuss the physical foundations and theoretical justification of kappa distributions naturally appearing within the Tsallis nonextensive statistical mechanics. These distributions provide an adequate description of rarefied plasma configurations in stationary states that are out of thermal equilibrium. The main formulas for theoretical kappa distributions are presented, and their application to studies of decaying fine-scale turbulence in cosmic plasma is briefly overviewed. It has been shown that these distributions, which follow from the Tsallis entropy functional in nonextensive statistical mechanics, provide the missing link between the empirical Vasyliunas kappa distributions and theoretical power-law models of the suprathermal characteristics of astrophysical plasma media.
The results of numerical calculations of cylindrical explosions in the atmosphere are presented, simulating the energy release during the vertical fall of meteoroids with radii of 1–10 m. It is shown that the dependence of the shock wave amplitude on the direction of its propagation differs significantly from the same dependence for spherical explosions of the same energy. This difference becomes more pronounced as the meteoroid size decreases. Calculations of excess pressure on the Earth’s surface have shown that the maximum of this pressure during a vertical fall of meteoroids is observed not at the point of intersection of the trajectory with the surface (i.e., under the region of energy release), but at some distance from it, which is determined by the height of destruction and deceleration of the meteoroid.
The mass distributions of unevaporated fragments of meteoroids and asteroids disrupted in the atmosphere, as well as the mass distributions of fragments of bodies disrupted in impact experiments modeling the fragmentation of asteroids at collisions in outer space, are considered. Analytical description of these distributions is carried out using the method (Brykina and Egorova, 2021), which expresses the cumulative number of fragments depending on the fragment mass, the total mass of fragments, the mass and number of maximum fragments and a free parameter—the power index. We described the results of impact experiments on the disruption of the Allende, Mbale, NWA 620, MOR 001 meteorite samples and Mauna Loa basalt samples available in the literature. We constructed and described the distributions of the Bruderheim, Villalbeto de la Peña, St-Robert, and Motopi Pan meteorites, recovered after observed passages of cosmic bodies through the atmosphere, as well as the distributions of meteorites whose falls occurred thousands of years ago: the Gold Basin, Jiddat al Harasis 073, Whitecourt, Campo del Cielo, and Canyon Diablo. The results of the description of experimental distributions confirm the previously proposed analytical dependence of the power index on the specific impact energy. Based on the description of fragment mass distributions for 22 meteorite falls, the dependence of the power index on the number of fragments in a meteorite collection is analyzed. The features of various distributions are pointed out.
