Likelihood of Martian moons as dust sources in light with Juno observations

Abstract

ABSTRACT Juno observations show dust halo near Mars, contributing to Zodiacal light, the source of which is yet to be known. It is interesting for scientists to understand whether dust primarily comes from the Martian moons. Here, we investigate Phobos/Deimos as likely sources of interplanetary dust near Mars. Incoming dust at the Martian moons impact their surface and produce ejecta, a part of which can escape easily to space. Results of escaping mass rates are presented and compared with incoming mass rates through a parameter called mass escape ratio. The results show higher ratio for a wide range of particles, inferring a large amount of effective mass loss from the moons. From whatever is lost, smaller particles (<0.1 µm) can escape, while larger particles are influenced by the gravitational pull of Mars. Furthermore, from the larger particles, those with sizes greater than critical size (i.e. ∼10 µm) remain in a ring/torus for a specific lifetime and afterwards, they get released from the gravitational effect of Mars. Since, incoming dust creates the ejecta continuously from Phobos/Deimos, the process of the release of particles after the lifetime is also continuous. On the other side, flux of interplanetary dust is derived from Juno observations of dust impact rates between 1 and 5 au heliocentric distance. An increase in the flux observed by Juno around 1.5 au and the results of larger, continuous escaping mass from the moons indicate Phobos and Deimos to be the local sources of dust bands observed by Juno spacecraft.