Solar System Research最新文献

In the current formulation of the asteroid and comet hazard (ACH) problem, it is considered necessary to detect a sufficiently large number (more than 90% of the total amount) of hazardous bodies that can collide with our planet. A vast majority of these bodies are near-Earth asteroids (NEAs). Based on the analysis of statistical characteristics of the NEA population, it has been shown that, on a practically significant time scale (~1000 years), the main danger is posed by NEAs of size 10–50 m, since they collide with the Earth more often than larger bodies. Consequently, the main practically significant task of counteracting the ACH is to detect such decameter-sized NEAs. They can can only be detected in close proximity, at distances of less than 0.05 AU from the Earth. The detection timescale is short, measured in hours (up to one day). This problem is still far from being solved. Larger bodies can be detected with more success. They can be detected at greater distances and, accordingly, the detection timescale is much longer. A rational approach to detecting NEAs has been proposed, the essence of which is that it is necessary to accelerate the development of instruments and methods to detect NEAs in the near zone. This is the most immediate challenge. At the same time, it is also necessary to continue work on searching for larger bodies in the far zone. These detection strategies require different technical means.

On the basis of the photogeologic analysis of images acquired with the ShadowCam and the Narrow Angle Cameras of the Lunar Reconnaissance Orbiter (LROC NAC) as well as with the use of the Lunar Orbiter Laser Altimeter (LOLA) measurement data, we study the surface morphology of near-polar craters Schomberger A, Rozhdestvenskiy K, and Lovelace, the floors of which are only partially shadowed. The Schomberger A crater is located in the south polar region. This crater is the smallest of the three under consideration (its diameter is 31 km) and the youngest (it dates back to the Copernican period). There is almost no regolith on its floor and inner slopes. In the study areas on its floor, small craters exhibit no lobate rims, which is evidently caused by almost complete absence of regolith there. The Rozhdestvenskiy K crater is located in the north polar region. It is medium in size among the three considered (its diameter is 42 km) and medium in age (it dates back to the Eratosthenian period). On the floor of this crater, the regolith is rather thick; and there are small craters with lobate rims there, which is considered a sign of a rather high amount of water ice in the target material. However, the measurements with the Lunar Exploration Neutron Detector (LEND) did not detect any increased content of hydrogen associated with this crater. The Lovelace crater is also located in the north polar region. It is the largest of the three under consideration (its diameter is 54 km) and the oldest (it dates back to the Late Imbrian period). On the floor of this crater, the regolith is quite thick; and craters with lobate rims are observed there, which is considered an indication of a rather high amount of water ice in the target material. However, the LEND measurements did not detect any increased content of hydrogen in this region either.

In addition to craters, radar-bright and dark spots are observed on the surface of Venus. Their formation is presumed to be caused by the effects of shock waves generated by “meteor airbursts.” One reason for the formation of dark spots, which correspond to a smoother surface, could be the melting and evaporation of the surface layer due to radiation from the shock wave. Direct calculations of the fragmentation and deceleration of asteroids with sizes of 0.6–1 km conducted in this work, along with assessments of the resulting radiation and its effect on the surface, have shown that within an area with a characteristic size of several tens of kilometers, the thickness of the evaporated/melted layer is several centimeters. The flow of the melt and the deposition of condensed vapors can significantly smooth the surface and affect its reflective properties.

We constructed a scenario for the formation of the young Emilkowalski asteroid family based on numerical modeling of the probabilistic evolution of the orbits of the family members. Various variants of the orbital evolution of asteroids were considered depending on the drift rate of the semimajor axes of the orbits, caused by the influence of the diurnal the Yarkovsky effect. We estimated the time of possible formation of pairs of family members in accordance with the preliminary scenario of cascade fragmentation of the parent body of the asteroid (14627) Emilkowalski based on the analysis of the moments of reaching the minimum of the Kholshevnikov metric and the convergence of the nodes and pericenters of the orbits. The moments of pair formation were clarified, the order of disintegration of the parent body was adjusted. We confirmed the scenario of the formation of the Emilkowalski family as a result of the step-by-step destruction of the parent body of the asteroid (14627) Emilkowalski with elements of cascade disintegration of some fragments. It was concluded that the age of the family does not exceed 1.8 Myr.

Based on photogeological and spectral analysis of the Martian region in the upper reaches of the Nirgal Vallis between 24°−52° W and 20°−29° N, within Her Desher Vallis and in the craters of this region, outcrops of rock enriched with clay minerals were identified, and the geological and stratigraphic positions of these outcrops were determined. Based on the results obtained, it is concluded that a clay-bearing unit, representing a mixture of saponite and nontronite, was formed in the study area. At the same time, aluminum-rich clay minerals were not identified. The process of clay mineral formation occurred in the Late Noachian period. It is assumed that the clay-bearing unit was formed by the surface/subsurface weathering of basalts. The liquid water necessary for the formation of the clays could have been present on the surface due to episodic warming caused by impact activity at that time. In the Early Hesperian period, the clay-bearing unit was overlain by a lava plain and was exposed during the formation of Her Desher and Nirgal Valles and during the formation of impact craters.

The paper describes the Sun-Terahertz space experiment planned for 2025–2027 onboard the Russian segment of the International Space Station (ISS). The main goals of the experiment are to obtain information on the terahertz radiation of the Sun, as well as to study active regions and solar flares. The scientific instrumentation of the Sun-Terahertz experiment contains eight channels (detectors) sensitive to radiation in a frequency range of 0.4–12.0 THz. The purpose of this study is to estimate the voltage at the output of scientific instrumentation detectors during the ISS onboard experiment from the ground-based measurement data and to determine minimal increases in the radiation flux reliably registered by the scientific instrumentation against the background of inherent noises.

This study employs high-precision numerical integration methods to analyze the phenomenon of coexistence of weak chaos and strong stability in the Sun–Earth–Moon system, taking into account factors such as tidal perturbations, planetary rotation, and relativistic corrections. Key chaos indicators were calculated, including Lyapunov exponents, Poincaré sections, and fractal dimensions, to quantify the system’s dynamic behavior. For the Sun–Earth system, the estimated Lyapunov exponent is on the order of 10^–6 per year, while the Earth–Moon system exhibits stronger chaotic characteristics with a Lyapunov exponent of approximately 10^–4 per year, corresponding to an orbital divergence time scale shorter than million years. Poincaré section analysis and the box-counting method reveal that the fractal dimension of the Earth–Moon subsystem is 1.768, indicating the existence of a mixed phase space where KAM tori and chaotic resonance layers coexist. Comparison with an idealized two-body model validates the numerical accuracy and highlights the destabilizing effect of solar perturbations. Furthermore, the influence of other planets is quantitatively proven to be negligible. Long-term stability analysis (over 10⁴ years) shows that variations in eccentricity and the Earth–Moon distance remain within limited ranges, with tidal dissipation acting as a stabilizing mechanism. The drift in energy and angular momentum is minimal, verifying the reliability of the numerical results. Multi-scale entropy analysis further supports the conclusion of weak chaos, showing low overall complexity but dynamic structures that vary over time.

Finite difference time domain (FDTD) simulations are applied to study the amplification and decay of nonlinear whistler waves in solar wind plasma in the vicinity of Earth’s foreshock. The considered plasma system comprises of streaming, hot protons and electrons. The main emphasis is on the feedback process between particle streaming and triggered nonlinear waves. It is determined that accelerated and parallel streaming electrons and protons significantly amplify whistler waves and lead to highest pitch angle scattering rates for electrons. The protons mostly show wave like smooth pitch angle scattering rates. However, electrons pitch angle scattering rates are characterized by random and sudden peaks. The counter streaming electrons and protons damp the whistler waves and exhibit negligible effects on the pitch angle scattering rates. Whistler waves at smaller propagation angles increases electron pitch angle scattering rates. Contrarily the whistler waves at high propagation angles resulted in the reduction of pitch angle scattering rates for electrons. The highest pitch angle scattering rates are noticed for protons in plasma system dominated by electrons streaming speeds. Our results may be important for comprehensive understanding of nonlinear turbulence (because whistler waves have a band of frequencies and some of the frequencies will be in resonance with particles cyclotron motion) in the neighborhood of Earth’s foreshock.

The review examines the main aspects of the current state of observational meteor astronomy. Information is provided on the goals and objectives of observations, the modern equipment used, the methods of observations and data processing, the available international databases of accumulated network observational data and their contribution to the development of meteor astronomy and, in particular, to the establishment of new meteor showers. The current state of meteor observations in the post-Soviet space is considered. The meteor video observations launched as part of a joint Russian–Tajik project in 2024 could mark the beginning of the creation of a global meteor observation network in the territories of the Russian Federation and the Republic of Tajikistan. The progressive factors of modern observational meteor astronomy, as well as existing problems and prospects for further development are formulated.