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JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 107, NO. E11, 5114, doi:10.1029/2002JE001841, 2002

A new energy source for organic synthesis in Europa's surface ice

Jerome G. Borucki

">NASA Ames Research Center, Moffett Field, California, USA


Bishun Khare

SETI Institute, NASA Ames Research Center, Moffett Field, California, USA


Dale P. Cruikshank

">NASA Ames Research Center, Moffett Field, California, USA


Abstract

Colored regions on Jupiter's satellite Europa and other icy bodies in the outer solar system may be contaminated by organic macromolecular solid material that is produced when surface ices are exposed to electrical energy. Hypervelocity meteorite impacts and fracture may release tidal and tectonic stresses in icy crusts in the form of electrical discharges, which provide the energy for in situ synthesis of the organic solids. We report for the first time here on measurements of electrical discharge, light emission, and magnetic phenomena in hypervelocity impacts into ice with small iron projectiles having velocities ∼5 km s−1. In these experiments, part of the impacting projectile's kinetic energy is converted into electrical potential, while the mechanical disruption of the impact also causes the release of stress energy as light, heat, and electrical and magnetic fields as secondary emissions. These new energy sources described here suggest that the dark material in the area of impact craters may be solid phase, complex organic material called tholin, generated from the energy of the impacts. The morphology of Europa's impact craters is suggestive of fluidized colored material welling up from the fracture zone, probably during crater formation, but possibly later. Large pools of liquid water might persist under the meteorite crater for thousands of years [ Thomson and Sagan, 1992 ], with the potential for prebiotic chemistry to take place at an accelerated rate due to energy pumped in from the secondary emissions.

Published 23 November 2002.

Index Terms: 6020 Planetology: Comets and Small Bodies: Ice; 6022 Planetology: Comets and Small Bodies: Impact phenomena; 6218 Planetology: Solar System Objects: Jovian satellites.

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Citation: Borucki, J. G., B. Khare, and D. P. Cruikshank (2002), A new energy source for organic synthesis in Europa's surface ice, J. Geophys. Res., 107(E11), 5114, doi:10.1029/2002JE001841.