Surface thermoelastic erosion of atmosphereless solar system bodies under bombardment by multicharge cosmic ray ions

The mechanism of ion-stimulated erosion of atmosphereless solar system bodies is suggested and investigated. A theoretical model for the brittle surface erosion resulting under the effect of multicharge ion cosmic rays is analyzed. It is shown that the thermoelastic waves originated in the energetic track of a very heavy ion can result in the near-surface stresses exceeding the dynamic tensile strength of the surface material for any atmosphereless solar system body. The thermoelastic wave surface arrival yields brittle erosion of the material and ejection of this latter fragments (the track-breaking process). Thus ejected dust grains have plano-oblong shape, average mass on the order of 10^–17 g and velocity up to 400 m/sec providing the surface erosion rate of 10^–1 ÷ 3 · 10² »/year (near the Earth orbit) which depends upon the surface material (rock or ice). Possible track-breaking consequences, in particular, presence of the dust fraction of ultramicron grains and their aggregates on the lunar surface are discussed. Near the bodies with the radii from 10 to 300 km predicted is the existence of extended dust cocoons consisting of ultramicron and submicron grains. Smaller objects (asteroids, comets, smallest satellites of planets, meteoroids, etc.) can serve sources of permanent dust wind of ultramicron and submicron sized grains escaping from their surfaces. The interplanetary dust yield owing to the ion-stimulated erosion of these bodies is not less than 10¹² g/year. Possible interpreting in the frames of track-breaking process some observational data and effects, including existence of dust grains with the mass of 10^–18 ÷ 10^–17 g near the Halley's comet and the nature of 2060 Chiron dust coma is discussed. To prove the theory, observational identification and investigation of dust phenomena complex related to the ion-stimulated erosion of atmosphereless bodies, suggested is employing extreme ultraviolet and far infrared/submillimeter wavelengths, as well as polarimetric methods.     

A review of possible optical absorption features of oxygen molecules in the icy surfaces of outer solar system bodies

In this review we provide the data needed to interpret remote spectroscopic studies of O₂ molecules embedded in the icy surfaces of outer solar system bodies. O₂ produced by radiolysis has been seen in the gas phase and as the so-called ‘solid O₂’ trapped in the icy surfaces of Ganymede, Europa and Callisto. It may also have been indirectly observed on a number of objects by its radiolysis product, O₃. These observations indicate the importance of O₂ for understanding the chemical processes occurring on icy outer solar system surfaces. Therefore, the published absorption spectra of gaseous, liquid and solid O₂ and of O₂ embedded in H₂O ice are reviewed in some detail. Particular emphasis has been placed on the presentation of transition probabilities for the various O₂ spectral series so that their relative importances can be assessed when they are used for modelling the radiation chemistry occurring in such environments.     

On the “strength” of the small bodies of the solar system: A review of strength theories and their implementation for analyses of impact disruptions

Composed of rocks, dirt, ices and metals, the small bodies of the Solar System generally show features of strength; and that property undoubtedly played a major role in their collisional evolution. But the quantification of strength is difficult because there are many different measures of strength, and those measures depend significantly on a body's composition, previous history and size. Although it is at the foundations of our scaling theories for the disruption of small bodies, and an essential part of code calculations, we have only recently begun to understand and come to grips with that strength property and in appropriate ways to model it in our theories and calculations.This is a general overview of strength theories for geological-type materials as needed for impact analyses. Dominant features of strength models are discussed, and comparisons of various models in the literature against that feature template is given. A summary of the use of strength theories in impact calculations is presented.