According to Louis Friedman, Executive Director of The Planetary Society, a Mars sample return mission is often described by the planetary science community as one of the most important robotic space missions, due to its high expected scientific return on investment. Over time, several missions were planned but none of the proposed missions got beyond the planning phase. The three latest proposals for a MSR mission are a NASA-ESA proposal, a Russian proposal (Mars-Grunt), and a Chinese proposal.