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Compact and amorphous ice spray

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In space, the ice at the heart comets or one that coats the interstellar dust grains is predominantly observed in amorphous and compact form. Researchers from the Iramis show that irradiation by heavy ions of very high energy, even a very small minority in the cosmic radiation is very effective to transform the fresh ice crystalline and amorphous and dense ice.

On Earth, the new snow layers slowly turn into compact ice under the influence of wind, changes in temperature or humidity. But in interplanetary space, frozen water on planetary satellites and comets she remains eternally fresh snow or ice ?

To know the influence of the impact of heavy ions, a thin layer of ice cooled to a few degrees Kelvin was subjected to various flows, produced by the GANIL. The effects of irradiation - the structural evolution of the ice as well as the number of water molecules released by spray - were studied by infrared spectrometry. Whatever its original state, ice evolves into an amorphous and compact state. Nearly ten thousand molecules are "ejected" each ion impact.

The work of the CIMAP / Iramis were conducted in collaboration with the Ganil (Caen), the Astrophysics Institute spatiale (Orsay), the Institute of Nuclear Physics of Orsay and the Catholic University of Rio de Janeiro.

Contact : Hermann Rothard, Philippe Boduch

Ref. : Heavy ion irradiation of crystalline water ice - Cosmic ray amorphization cross-section and sputtering yield Dartois E., B. Augé, P. Boduch, R. Brunetto, Mr Chabot, A. Domaracka, JJ Ding, O. Kamalou, XY Lv, H. Rothard, EF da Silveira and JC