Proposal Summary

In 1877, Asaph Hall, an astronomer at the United States Naval Observatory, discovered that Mars is accompanied by two satellites, Phobos and Deimos. The origin of the two has remained uncertain to the present day. A Martian origin has been difficult to model and to match to their spectra, but models for their capture also have major shortcomings. Spectral signatures and the overall low density suggest that Phobos (the larger of the two) has a composition similar to carbonaceous chondrites and therefore raises the possibility that Phobos contains a large fraction of volatiles. US, Russian, and other space mission planners have identified Phobos as a target, from where the recovery of extraterrestrial samples may be comparably straightforward. Mars Express, currently the only Mars spacecraft to carry out Phobos flybys, has returned new data on Phobos, including imagery, spectral data, and gravity field measurements. The next step of Phobos study is the Phobos sample return mission (Phobos Grunt) which is under development by the Russian space agency. There are other suggestions for missions to study Phobos and Deimos in USA and Europe. We propose workshops including astronomers, geophysicists, geologists, cartographers, and planetary explorers from East and West to review our present state of knowledge on this small Martian satellite, and to discuss measurements and observations that are required to further our understanding of Phobos.