Solar System Research最新文献

The influence of the solar radiation pressure and the Yarkovsky effect on the long-term orbital dynamics is estimated for a number of asteroids experiencing successive planetary encounters. The variation in the asteroid’s proper rotation period due to its approach to the planet and its effect on the asteroid’s further orbital dynamics through the Yarkovsky effect is considered. It is shown that close planetary encounters of small asteroids (tens of meters in diameter) with short rotation period (less than 10 h), which change the asteroid’s rotation period by several hours, significantly affect the magnitude of the Yarkovsky effect.

Asteroid surface boulders contain important information about the origin and geological evolution of asteroids. Previous insights into boulders on the surface of Toutatis are based on direct measurements from two-dimensional images, the accuracy of these measurements needs to be further improved. Therefore, this study uses radar shape models to correct the dimensions of those Toutatis boulders with well-defined contours. 22 boulders are corrected and their distributions before correction have similar statistics to those boulders (222 in total) in Jiang et al. (2015). We re-examine the size and shape distributions of these corrected boulders and results show that the power-law index of boulders larger than 40 m, –1.27 ± 0.05, is relatively flatter than that of other asteroids that have been observed by spacecrafts. If this index represents the distribution pattern of boulders larger than a few meters across on the Toutatis surface, it suggests that Toutatis may have undergone fewer and weaker fragmentation processes during its past than other spacecraft-detected NEAs, which further suggests that the boulders on the Toutatis surface are in a unique state of preservation. We also find that these boulders have an apparent axis ratio of 0.7, which predicts that most of the boulders on the Toutatis surface are in a gravitationally stable state. In addition, these larger boulders on the Toutatis surface are mainly distributed at the junction of the body and the head, it is possible that they were produced by sputtering during the low-velocity impact between the head and the body. High-resolution optical images and computer simulations in the future will be of great help in deeply understanding the origin and geological evolution of Toutatis.

Ground testing results are presented for the landing platform television system (TSPP) within the complex of scientific payloads onboard the ExoMars-2022 spacecraft. In the course of the ground testing, the different operation modes have been checked and the camera characteristics have been measured and calibrated. The Space Research Institute (IKI RAS) has obtained photographic material from each camera, with the cameras being installed on a stand that simulates in full scale the ExoMars-2022 landing platform. In addition, special measurements have been collected for the cameras’ most important characteristics: horizontal and vertical angular field of view, distortion, focal length, resolution, dynamic range, vignetting coefficient, and absolute sensitivity.

Modern ideas about objects approaching the Earth are discussed. This population includes near-Earth asteroids (NEAs), including potentially hazardous asteroids, short-period comets, meteoroid streams, and large sporadic meteoroids. An overview is given of the currently available information on the dynamic and physical properties of NEAs and comets. Almost 5% of the currently known NEAs are extinct cometary nuclei or their fragments. Being outwardly similar with true asteroids, they differ markedly in their dynamic and physical properties. In order to distinguish between these groups of objects, it is necessary to study both their dynamic and physical parameters. Some of the known meteoroid streams are shown to contain, along with the countless small meteoroids, also large extinct fragments of cometary nuclei, which are classified as NEAs. A meteoroid stream and such bodies belonging to it form together an asteroid–meteoroid complex. Observational and theoretical data are presented to confirm the modern understanding of near-Earth objects.

Temperature and pressure sensors, which are part of the ExoMars-2022 landing platform (LP) meteorological complex, are designed to measure the main parameters of the Martian atmosphere: temperature, pressure, and vertical component of wind speed. Temperature and pressure measurements begin during the descent, after the separation of the lower hemisphere, when the height above the surface will be from 2.1 to 8.5 km, depending on the descent trajectory. Above, before opening the parachute, the vertical profile of the atmosphere can be obtained using the accelerometer block, which is also part of the meteorological complex. After landing, a long-term monitoring of the near-surface layer of the atmosphere is carried out. Measurements are taken at different heights from the surface. Taking into account the measurement of the vertical component of the wind after landing, the local surface-to-atmosphere heat flux is calculated. The measurements make it possible to obtain the dynamics of the interaction between the atmosphere and the surface. In the paper we considered the scientific problems solved by the sensors, briefly described the measurement program and described in detail the sensors and their characteristics.

The stability of the secular orbital dynamics of a number of potentially existing satellites of exoplanets has been analyzed. The secular dynamics of possible satellites (“exomoons”) of the planets KOI-268.01, Kepler-1000b, and Kepler-1442b have been found to be stable. The possible values of the exomoon orbital parameters for these systems have been estimated. The dynamics of the satellites discovered around the planets Kepler-1625b and Kepler-1708b from the analysis of observations are considered. It has been found that the semimajor axis of the orbit of the moon of the planet Kepler-1625b can range from 5 to 25 planetary radii. It has been shown that the solution available for the satellites of the planet Kepler-1708b (Kipping et al., 2022) corresponds to a stable orbit of the satellites.