The origins of Phobos and Deimos have remained uncertain to the present day. Models for their Martian origin or models for their capture have major shortcomings. Spectral signatures and the overall low density suggest that Phobos has a composition similar to carbonaceous chondrites. The satellite therefore may contain a large fraction of volatiles, a precious resource for future explorers. Mars Express, currently the only Mars spacecraft to carry out Phobos flybys, has returned new data on Phobos in the past year. This session will bring together planetary scientists and future explorers to review our present state of knowledge on the Martian companions and other small Solar System satellites.