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Experimental impact shock chemistry on planetary icy bodies

AutorNna Mvondo, Delphine ; Khare, Bishun; Ishihara, Tomoko; McKay, Christopher P.
Palabras claveIces
Impact processes
Prebiotic chemistry
[AGU] Planetary Sciences: Astrobiology
[AGU] Planetary Sciences: Solid Surface Planets
[AGU] Impact phenomena, cratering
[AGU] Ices
[AGU] Origin and evolution
Fecha de publicación6-nov-2007
CitaciónIcarus 194(2): 822-835 (2008)
ResumenSeveral icy satellites of the outer planets show impact cratering features and it is recognised that this process may have played a crucial role in the formation and evolution of icy bodies. The effect of impact by extraterrestrial objects into the surface is commonly related to physical changes. Most of the research applied to impacts on ices has been developed to study and understand the cratering formation process and their physical, geophysical characteristics. Chemical changes and synthesis occurring on icy planetary surfaces are generally explained by the influence of UV photons and high-energy charged particles on ices. Nonetheless, impact process onto ices could be a source of local or global endogenic process and could be especially advantageous as an efficient energy source for driving interesting chemistry. Impacts can ensure that icy surfaces are eventually exposed, for a limited period of time, to aqueous melt in impact craters and ejecta and one can imagine that impurities included in the ice may undergo hydrolysis and other reactions under such conditions. Upon impact, the kinetic energy of the bolide is transferred to the ground liberating a great deal of stress energy which could initiate in situ a diverse series of chemical reactions in the fracture zone beneath the crater (Borucki et al., 2002; Jones and Lewis, 1987). Here we present a new approach testing in laboratory the chemistry conducted by impacts into planetary ices and we report the first experimental results. We have irradiated with a powerful pulsed laser icy mixtures of pure water ices containing CO2, Na2CO3, CH3OH and CH3OH / (NH4)2SO4 at 77K. GC-MS and FTIR analyses show that hydrogen peroxide, carbon monoxide and methanol are formed in irradiated H2O / CO2 ices. Ice containing sodium carbonate generates under simulated impact CO and CO2 which are also produced in impacted H2O / CH3OH and H2O / CH3OH / (NH4)2SO4 ices. But, in both latter icy mixtures, methane and more complex molecules are also formed. We have detected acetone, methyl formate and dimethyl formal. Adding ammonium sulfate to ice containing methanol induces the production of N2O, HCN and CH3CN.
Descripción15 pages, 14 figures.-- AGU nrs.: 5200, 5400, 5420, 5422, 5455.-- Printed version published on April 2008.
The original publication is available at http://www.sciencedirect.com/science/journal/00191035
Versión del editorhttp://dx.doi.org/10.1016/j.icarus.2007.11.001
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