The ethereal dust envelopes of the Martian moons

We consider the impact ejecta from Phobos and Deimos to study the statistics, spatial distributions and volume densities of the dust debris in the vicinities of the moons. Apart from the gravitational forces, we take into account solar radiation pressure, which makes our model valid for micrometer-sized particles. The radiation pressure modifies the shapes of the circumsatellite dust clouds, displacing them in the anti-solar direction; the effect is much larger for the Deimos ejecta. Another radiation pressure effect is the decrease of the mean escape velocity of the Deimos ejects from 5.5 m s(-1) for 10-100 mu m-sized grains to 4.5 m s(-1) for 1 mu m-sized ones. We also explore the time variations in the dust clouds caused by individual impacts or larger meteorites. These events have little effect on the amount of the micrometer-sized dust but may change considerably the number of scanty, centimeter-sized debris. (C) 1999 Elsevier Science Ltd. All rights reserved.