Japan's space agency JAXA is set to launch its Martian Moons eXploration (MMX) mission, a high-stakes attempt to return the first samples ever collected from a moon other than Earth's. The mission, launching from Tanegashima Space Center, follows three failed Russian probes to Phobos since the 1980s, underscoring the difficulty of the endeavor. For the scientists involved, the challenge is offset by the prospect of answering a long-standing question: whether Mars' moons are captured asteroids or debris from an ancient collision.
MMX will spend nearly a year traveling to Mars, then survey Phobos and Deimos with a suite of instruments. The MEGANE instrument will measure the elemental composition of Phobos, looking for volatiles like hydrogen or potassium that could indicate a captured asteroid, or a lack thereof that would support an impact origin. After a rover scouts the surface, the spacecraft will land and collect at least 10 grams of material using two sampling methods as a safeguard, with samples due back on Earth by 2031.
The mission is a feat of international collaboration, drawing on expertise from NASA, the European Space Agency, and German and French space agencies. JAXA brings a proven record in sample-return missions, having previously retrieved material from asteroids Itokawa and Ryugu. While Phobos presents new challenges—its orbit and gravity differ from those asteroids—the team is confident that the combined expertise makes the objectives achievable. The returned samples could also contain Martian soil, offering a window into how the planet evolved over billions of years.