New Computer Model of Phobos: Martian Moon’s Gravitational Field


Home / New Computer Model of Phobos: Martian Moon’s Gravitational Field

Phobos imaged by the Viking 1 Mission in 1978 Image Credit: NASA

Gravitational Field of Phobos

Shi Xian led a team of Chinese and German astronomers from the Shanghai Astronomical Observatory and the Technical University of Berlin in computing a new theoretical model of the gravitational field of Phobos. This moon, like most small bodies in the solar system, is irregularly shaped rather than spherical. This shape complicates calculations of the gravitational field. The team of astronomers used the many Phobos images collected since 2003 by the Mars Express mission to compute the detailed shape of Phobos.

From the shape information, they then computed the gravitational field and surface gravity of Phobos, using three different calculation methods. Results from the three different methods agree fairly well, giving astronomers more confidence in the calculated gravitational field.

A Closeup Image of Stickney Crater on Phobos imaged by the Mars Reconnaissance Orbiter in March 2008. Image Credit: NASA

Origins and Composition of Phobos

As science probes study Phobos in more detail, comparing the theoretically calculated gravitational field of Phobos with the measured gravitational field will help scientists deduce the internal structure of Phobos. For example, is Phobos entirely rocky material, or is it a mixture of rock and metal? Such studies will provide insights to help astronomers understand the origin and evolution of Phobos.


Xian Shi, Konrad Willner, Jürgen Oberst, JinSong Ping and ShuHua Ye. Working models for the gravitational field of Phobos. (2012). SCIENCE CHINA Physics, Mechanics & Astronomy, 2012, Vol 55(2). Accessed March 7, 2012.

Click to Return to Page One: New Study of Phobos’ Gravitational Field

Leave a Comment