Horizontal transport of the regolith,modification of features,and erosion rates on the lunar surface

New lunar soils, freshly deposited as impact ejecta, evolve into more mature soils by a complex set of processes involving both near-surface effects and mixing. Poor vertical mixing statistics and interregional exchange by impact ejection complicate the interpretation of soil maturization. Impact ejecta systematics are developed for the smaller cratering events which, with cumulative crater populations observed in young mare regions and on Copernicus ejecta fields, yield rates and a range distribution for the horizontal transport of material by impact processes. The deposition rate for material originating more than 1 m away is found to be about 8 mm m.y.^?1 Material from 10 km away accumulates at a rate of about 0.08 mm m.y.^?1, providing a steady influx of foreign material. From the degradation of boulder tracks, a rate of 5±3 cm m.y.^?1 is computed for the filling of shallow lunar depressions on slopes. Mass wastage and downslope movement of bedrock outcroppings on Hadley Rille seems to be proceeding at a rate of about 8 mm m.y.^?1 The Camelot profile is suggestive of a secondary impact feature.     

Strontium-90 in surface and groundwater of the reclamation systems at the Chernobyl exclusion zone

The left bank of the Pripiat' river, opposite of the Chernobyl Nuclear Power Plant (ChNPP) is covered with a developed network of drainage canals, built for the reclamation of the swampy floodplain. This area is highly contaminated after the disaster in 1986. Concentrations of the most mobile radionuclide, ⁹⁰Sr, are comparable with ¹³⁷Cs, and reach many MBq m^-2. Their ratio in the upper 10 cm of soil is about 1. The high surface contamination as well as precipitation and flooding have been responsible for the water pollution in this area. Some specifics of ⁹⁰Sr behaviour in surface and groundwater, controlled by the hydrological regime, are described.     

Analysis of a mixed discontinuous Galerkin method for instationary Darcy flow

We present an a priori stability and convergence analysis of a new mixed discontinuous Galerkin scheme applied to the instationary Darcy problem. The analysis accounts for a spatially and temporally varying permeability tensor in all estimates. The proposed method is stabilized using penalty terms in the primary and the flux unknowns.     

Cosmic-ray exposure history at the Apollo 16 and other lunar sites: lunar surface dynamics

Concordant ⁸¹K-Kr exposure ages for four station 11 breccias indicate an age of 50.3 ± 0.8m.y. for North Ray Crater. Ray structures visible from orbital photography suggest that stations 8 and 9 should contain a substantial amount of South Ray ejecta. Concordant ⁸¹Kr-Kr exposure ages at these sites indicate an age for South Ray Crater of 2.04 ± 0.08m.y. Surface effects (tracks, surface angularities, and micro-crater populations) show good general agreement with this young an age, but discrepancies on a sample-by-sample basis seem to indicate that extensive pre-surface irradiations must have occurred. A detailed pre-surface exposure history is derived for the parent boulder of samples 69935 and 69955. It is suggested that secondary impacts play a major role in near-surface regolithic stirring. Widespread pre-surface irradiation would in fact be expected if most of the newly excavated material had been transported to the surface by secondary impacts rather than by the South Ray event itself.