Gravity, equilibrium, and height system of Phobos and Deimos: an updated geodetic analysis

Abstract

We evaluate the gravity equilibrium forms of the irregular-shaped Martian moons, Phobos and Deimos. We derive their normal ellipsoids and propose the el- lipsoidal height system to characterize the surface to- pography. We study the height distributions on Pho- bos and Deimos and compare their statistics with those of nearly spherical terrestrial planets. We identify a new criterion for determining surface equilibrium of the Martian moons and discuss its generality to other small bodies.