The Martian moons may seem small and unremarkable compared to larger, more dynamic worlds. But they hold mysteries that could shed light on the history of the entire inner Solar System, including how Earth may have gotten its water. Many of these missions also observed Phobos and Deimos, including NASA's Mariner 9, Viking, and Mars Reconnaissance Orbiter missions, ESA's Mars Express, India's Mars Orbiter Mission, and others. There is evidence that could support each hypothesis, and both all implications for how the inner Solar System formed. This mystery is one of the motivations behind the Martian Moons eXploration (MMX) mission, which aims to launch as soon as November 2026.