Solar System Research最新文献

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.

The realization that primordial black holes (PBHs) might be some fraction of the dark matter begged the question, how often do PBHs enter the solar system? For a Neptune radius solar system the answer is, rarely. For an Oort cloud sized system the answer is different. Simulations of bombardment of the Oort cloud by dark matter suggest that dislodgement of protocomets and their entry into the inner solar system can match the observed frequency of comets, if that PBH fraction is high enough. Comets were traditionally considered as messengers, usually omens. After 50 years of puzzlement regarding dark matter, we need a hint from the dark universe about the size and nature of dark matter particles.

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.

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.

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.

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 N_ref = 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 d_max = αR_mean, where R_mean is the volume-equivalent radius and α is a dimensionless tolerance. Using the conservative tolerance α = 0.05, full recovery, defined as n_match = 4, is not guaranteed at low and intermediate N and can be non-monotonic. For Psyche, n_match(N) = {1, 1, 2, 1, 2, 3, 4}; for Haumea, n_match(N) = {0, 4, 2, 2, 4, 4, 4}. The external equilibrium-point configuration thus provides a sensitive diagnostic of mascon-resolution adequacy. Reporting n_match(N) together with reference-based displacement metrics provides a compact verification step prior to downstream dynamical surveys.

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% of the lunar surface. The results of numerical modeling with ALT/CUSTEP module (Biovia Materials Studio) and experimental studies by IR Fourier spectrometer with plug-ins for transmission/diffuse reflection as well as Raman InVia Renishaw Reflex spectrometer are presented. Numerical calculations demonstrated that the crystal lattice of anorthite remains stable when hydroxyl groups and molecular water are included in it. Raman spectra indicated complex network of water clusters on the anorthite surface after wetting. The calculated IR spectra of anorthite containing water isotopologues were compared with the observations of SOFIA IR observatory (NASA/DLR). The presence of ‒OH/–OD and HDO isotopic forms of water is well confirmed, but additional probing is needed to detect pure D₂O water more precisely. Suggestions on the most efficient orbital measurements for water mapping on the lunar highland by IR spectroscopy are provided.

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.

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.