JAXA to launch MMX probe to study Mars moons Phobos and Deimos

Japan's space agency JAXA plans to launch the Martian Moons eXploration (MMX) spacecraft in late 2026. The probe will fly to Mars and capture detailed images of its two small, irregular moons, Phobos and Deimos, whose origins have long puzzled scientists.

Three main hypotheses compete to explain the moons' formation: a giant impact that ejected material from Mars, capture of asteroids from the nearby belt, and the remnants of a larger, earlier moon. By sampling and imaging the moons, MMX aims to test these theories and determine whether the bodies are collision debris, captured asteroids, or fragments of an older satellite.

The mission is expected to provide the first direct measurements of the moons' composition and surface properties, potentially resolving a decades‑long debate about the evolution of the Martian system.