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Seminar Minor bodies of the Solar system (21.10.2020, 15:00)

Опубликовано: 17/10/2020

1. Report by Ms Scherbina A.M. and Prof. V.V. Busarev (SAI MSU, INASAN)

“The research of spectral characteristics and assessment of the composition of matter of asteroids, including those approaching the Earth”

Asteroids are among the least modified objects in the Solar system since its formation. Now only in the Main Asteroid Belt located at 2.2 – 3.6 AU more than 894,000 asteroids are known from the Sun. However, for most of these bodies, only the elements of their orbits and approximate sizes are known. Knowledge of the physical, chemical, and mineralogical properties of these bodies is necessary for several both scientific-theoretical and applied problems. Considering that asteroids, as a rule, are atmosphereless bodies, this facilitates their study by ground based remote sensing methods, the most important of which is spectrophotometry.

Using the data obtained at the observatories “Terskol Peak” (branch of INASAN), Crimean laboratory of SAI MSU, “Sanglok” (Tajikistan) and TUBITAK (Turkey), the spectral type (and, accordingly, the chemical and mineralogical composition at a qualitative level) was determined according to Tolen’sand Bus-Binzel’sclassificationsfor 12 Main belt asteroids and 9 Near-Earth asteroids and Mars-crossers, among which there are 4 potentially dangerous objects. The spectral type of 8 asteroids was determined for the first time. Some objects have a mixed composition of the surface substance. The asteroid’s belonging to a spectral type was established on the basis of the features of the reflection spectra (general gradient, absorption bands characteristic of minerals), the physical characteristics of the body (albedo, rotation period), as well as by comparing with the reflection spectra from the SMASS-Iand SMASS-II databases (if available) and with reflection spectra of meteorites from the open database HOSERLab (Canada).

Spectrophotometric and (U)BVRI-photometric studies of asteroids of similar primitive types (with low-temperature mineralogy of matter) made it possible to confirm the sublimation activity of the Main belt asteroids 145 Adeona, 704 Interamnia, and 779 Nina near perihelion, discovered in 2012, and also to detect spectral signs of such activity at 51 Nemausa and 65 Cybele. To explain the lower activity of the first three asteroids during repeated observations, an assumption was made about the influence of solar activity on them in 2012.

The discovering in 2012 of simultaneous sublimation activity of four fairly large main-belt asteroids — 145 Adeona (D=128 km), 704 Interamnia (D=306 km), 779 Nina (D=81 km), and 1474 Beira (D≈14 km) — near perihelion (at high orbital eccentricities) is a sign of its mass character. Judging by the significant size of these bodies, they are not the cores of extinct comets that accidentally fell into the Main asteroid belt. The registered repeatability of ice sublimation (primarily water ice) let us to suggest that their stocks are quite large in the interiors of primitive asteroids. Comparing reflectance spectra of three of them (145, 704, and 779) obtainedin Sep. 2012 with model ones of a solid body enveloped by a dust exosphere (Busarev et al., 2020), we led to a conclusion about predominance of water ice submicron aggregates in the sublimation exosphere around these asteroids. It is natural to assume the formation of such asteroids (or their parent bodies) in the early Solar system beyond the boundary of water ice condensation, possibly in the growth zones of pro-Jupiter and other giant planets.

2. Message by corresponding member of the Russian Academy of Sciences Shustov B.M. (INASAN)

“Information about the IWC (International Asteroid Warning Network) meeting, the announced international campaign for Apophis asteroid observations, and the Planetary Defense Conference 2020 – 2021”.