ИСТИНА

Spectral signs of a strong simultaneous sublimation activity of the main-belt primitive asteroids 779 Nina, 704 Interamnia, and 145 Adeona were discovered in 2012 near their passage of perihelion. We consider light scattering by evaporated micron-sized water ice particles as a main token of the process. According to Mie theory and subsequent numeric modeling [4, 5], intensity of light scattering by particles with refractive index of water ice (n = 1.33) is maximal for the dimensionless parameter х = (2π·ρ /) ≈ 6 or ρ / ≈ 1, where ρ is the average radius of the particles and  is the wavelength of light. In other words, ρ and the spectral position of maximum of scattered light are matching in this case. This is probably the main reason of registered unusual maximum near 0.50 μm in asteroid reflectance spectra of mentioned asteroids. A simple suggestion is made that due to eccentricity of the orbits, the asteroids with some content of ice in the matter undergo changes of subsolar temperatures with revolution around the Sun (~222÷257 K on Adeona, ~206÷240 K on Interamnia, and ~208÷262 K on Nina). As a consequence, a sublimation process starts to develop or intensify on each of the body with approaching to perihelion. We discuss previous and new observational data and consider possible reasons of the phenomenon.