Why explore Phobos and Deimos?
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.
Mars is the planet that humans have sent the most spacecraft to study. 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. Despite all this study, the origins of these moons remain unknown.
The main hypotheses are that Phobos and Deimos were asteroids from the outer Solar System that were captured by Mars’ gravity, that they both formed from the disruption of a single parent body, or that they accreted from debris left over from the formation of Mars. 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.