DEIMOS - AN OBSTACLE TO THE SOLAR-WIND

Two isolated solar wind disturbances about 5 minutes in duration were detected aboard the Russian spacecraft Phobos-2 upon its crossing the wake of the martian moon Deimos about 15,000 kilometers downstream fro m the moon on 1 February 1989. These plasma and magnetic events are in terpreted as the inbound and outbound crossings of a Mach cone that is formed as a result of an effective interaction of the solar wind with Deimos. Possible mechanisms such as remanent magnetization, cometary type interaction caused by heavy ion or charged dust production, and u nipolar induction resulting from the finite conductivity of the body a re discussed. Although none of the present models is fully satisfactor y, neutral gas emission through water loss by Deimos at a rate of abou t 10(23) molecules per second, combined with a charged dust coma, is f avored.