October 2015
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doi: http://doi.org/10.2312/GFZ.LIS.2015.003 After the Chelyabinsk meteorite fall, many small fragments were found in the snow in the surrounding area. The fragments created funnels with walls of denser coarse-grained snow. Larger fragments penetrated through the 70-cm-thick snow layer and reached the frozen ground surface. Smaller fragments got stuck in the snow, showing a special characteristic: at the bottom, 15–25 cm in depth, the funnels narrow into a cone shape, forming so-called “snow car-rots” [1]. In our study, we describe the deceleration and the thermal evolution of those fragments during their traverse of the atmos-phere in order to constrain the initial conditions (velocity, tempera-ture) at impact onto the snow. We then model the penetration of the fragments into the highly prous snow using the iSALE 2D hydrocode [2,3,4] combined with a porosity compaction model [3]. We observe the creation of funnels in the snow with funnel walls that show an increased density. Densities reach up to 380 kg/m³. During the snow compaction due to the passing projectile, no temperature increase can be seen. Next, we also measure the decceleration and the final depth of the fragments in the snow. Our modelled terminal depth of the fragements is in good agreement with the observed Chelyabinsk funnels. By means of the Chelyabinsk snow funnels, we demonstrate the capability of the applied material models to describe the penetration of projectiles into highly porous materials (~70 % in this study). Such studies are of particular interest for the analysis of impact funnels in aerogel catchers of the Stardust experiments [5] and for impact cratering on highly porous targets as the recently visited comet Churyumov-Gerasimenko by the Rosetta mission. [1] Ivanova et al. (2013) MetSoc, Abstract #5366. [2] Amsden et al. (1980) LANL, LA-8095:101. [3] Wünnemann et al. (2006) Icarus, 180: 514-527. [4] Collins et al. (2004) MetPlanSci, 39: 217-231. [5] Greenberg and Ebel (2012) M&PS, 47, 634-648.