Phobos in the Spotlight: Deriving Regolith Properties from the Opposition Surge

The opposition surge is the strong increase of brightness displayed by planetary surfaces when observed at phase angles close to zero, i.e. when the Sun is behind the observer.

The surge parameters are determined by the physical properties of the surface, like particle size distribution and porosity. We propose a project to study the opposition surge of Phobos, the largest moon of planet Mars.

Our approach is threefold: (1) Analysis of opposition images acquired by the Mars Express mission, (2) experimental observation of the opposition surge for a Phobos regolith simulant, and (3) modelling the Phobos observations and the experimental data.

The results will be useful in several ways: they will improve our understanding of the physical properties of the Phobos regolith, improve our understanding of the opposition surge as a physical phenomenon, and support JAXA’s upcoming MMX space mission to Phobos, in which the applicants are involved.

Our project will benefit science planning for both MMX elements, a Japanese orbiter/lander and a European rover, leading to a deeper involvement of LTU and Sweden in the mission.