High crystalline quality of large single crystals of subglacial ice above Lake Vostok (Antarctica) revealed by hard X-ray diffraction

X-ray diffraction experiments were carried out on large ice crystals from a ccreted ice above Lake Vostok, a subglacial lake lying beneath the East Ant arctic ice sheet. Results indicate a surprisingly very low lattice distorti on. This crystalline quality does not seem to be affected by impurities. Ab normal grain growth should occur and could explain both the large grain siz e and the low lattice distortion. Accreted ice is therefore supposed to be non-plastically deforming. These results should be taken into account for f urther studies of the permeability of accreted ice to drilling fluid presen t in the borehole. (C) 2001 Academie des sciences / Editions scientifiques et medicales Elsevier SAS.