Vol 57, No 1 (2023)

Observations of vibrationally excited hydroxyl (OH*) emissions are widely used to obtain information about the dynamics and composition of the atmosphere. We present some analytical approximations for the characteristics of the hydroxyl layer in the Martian atmosphere such as OH* concentration at the maximum and height of the maximum, as well as relations for estimating the influence of various factors on the OH* layer in night conditions. These characteristics depend on the temperature of the environment, concentration of atomic oxygen, and their vertical gradients. The relations are applied to the results of numerical modeling using the global atmospheric circulation model for prediction of seasonal behavior of the hydroxyl layer on Mars. Annual and intra-annual variations in the concentration of excited hydroxyl and layer height from the modeling data have both some similarities with those of the Earth and significant differences. The concentration and height maximum in the equatorial, northern and southern midlatitudes vary depending on the season; the maximum concentration and the minimum height fall on the first half of the year. Model calculations confirmed the presence of the peak OH* concentration at polar latitudes in winter at an altitude of approximately 50 km with the volume emission densities of 2.1, 1.4, and 0.6 × 104 photons cm–3 s–1 for vibrational level transitions 1–0, 2–1, and 2–0, respectively. The relations obtained may be used for the analysis of measurements and interpretation of their variations.

The lunar regolith delivered to Earth in the 1970s by the Soviet automatic stations Luna-16, -20, and -24, despite the small amount of material, is of great value for science and requires careful study. How ever, since soil samples have gone quite a long way from the moment of extraction to direct examination, there is a danger of possible contamination of the samples with foreign material, both man-made and terrestrial natural minerals. The probability of contamination of the finest fraction of regolith, the particle size of which is less than 100 microns, is especially high, since their detection is possible only by electron microscopy. Using the methods of analytical scanning electron microscopy in regolith samples, contaminant phases that con taminated the original preparations were found, and the sources of these artifacts were shown. The examples of contamination of regolith samples given in this paper and the methods for their identification will make it possible in the future to more accurately diagnose the phases of lunar origin.

In the absence of a dense atmosphere and a general magnetic field around the Moon, solar wind particles reach the lunar surface and are almost completely absorbed. When the Moon passes through the plasma medium of the solar wind magnetic ropes, the electric currents of the rope can strongly change the electric potential of the lunar surface on the day and night surfaces, and in the case when the current density vectors of the rope and the direction to the Sun are close to colinear, there is the possibility of sufficiently strong ring currents, the magnetic field of which tends to displace the magnetic field of the rope and lead to the formation of a plasma layer with a height of the order of the electron Larmor radius.

The brief review summarizes data on the chemical and mineral composition, as well as on the phys ical properties, of the first extrasolar comet 2I/Borisov, obtained from observations that were carried out from September 2019 to the end of March 2020. It is noted that the qualitative chemical composition of the volatile and mineral components comet 2I/Borisov is similar to the composition of comets in the Solar System, but there are differences that indicate the specific conditions for the formation of its nucleus in a circumstellar gas and dust disk. Different release rates of CO and H2O molecules in the vicinity of perihelion indicate the pos sible heterogeneity of the comet’s nucleus, which was formed from more homogeneous ice blocks, but differ ing in composition. These constituent blocks could have formed over a wide range of radial distances: from the snow line of H2O to the CO snow line. Their accumulation in the comet’s nucleus indicates large-scale mixing of protocometary bodies in the circumstellar disk. No spectra of finely crystalline magnesium silicates were found in cometary coma of 2I/Borisov, which can be interpreted as the absence of a significant amount of gas and dust transfer from the inner hot regions of the disk to the outside, into the zone of formation of protocometary bodies.