Martian Moons eXploration

JAXA's Martian Moons eXploration (MMX) mission, first announced in June 2015, is a robotic probe slated for an October 2026 launch. Its primary goal is to retrieve the first-ever samples from Phobos, the larger of Mars's two moons. The spacecraft will land on Phobos once or twice to collect at least 10 grams of surface material using a pneumatic system, then perform several flybys of the smaller moon Deimos before releasing a return capsule that is expected to land in Australia in 2031. Along the way, MMX will also monitor Mars's climate.

The mission aims to settle a long-standing debate: whether the Martian moons are captured asteroids or debris from a giant impact on Mars. JAXA and Japanese officials gave the project formal development approval in February 2020. The probe arrived at Tanegashima Space Center on March 31, 2026, and is set to launch during that year's window.

Weighing about 4,000 kilograms at launch—including roughly 1,900 kg of propellant—the spacecraft is built from three main sections: a 1,800 kg propulsion module, a 150 kg exploration module, and a 1,050 kg return module. Because Phobos and Deimos are too small for stable satellite orbits, MMX will use quasi-satellite orbits (QSOs) to stay close to the moons for extended periods. The mission is led by Yasuhiro Kawakatsu.

International partners include NASA, France's CNES, Germany's DLR, and the European Space Agency. NASA is supplying MEGANE (Mars-moon Exploration with GAmma rays and NEutrons), a gamma-ray and neutron spectrometer whose name also means "eyeglasses" in Japanese. CNES is providing the Near IR Spectrometer (NIRS4/MacrOmega) and expertise in flight dynamics for orbital and landing maneuvers. ESA is contributing deep-space communication gear—a transponder and power amplifier—plus ground station support from its Estrack network. Development and testing of key components, including the sampler, continue as of December 2023.

The spacecraft carries seven scientific instruments: TENGOO (a narrow-field camera for terrain study), OROCHI (a wide-field visible-light camera), LIDAR (for surface altitude and albedo), MIRS (a near-infrared spectrometer for mineral analysis, developed with CNES), MEGANE, CMDM (a dust monitor), and MSA (a mass spectrum analyzer for the ion environment). JAXA is also working with NHK to develop a "Super Hi-Vision Camera" that combines 4K and 8K resolution—the first time Mars will be imaged in 8K. Original image data will be stored in the return capsule and brought to Earth along with the samples. Additional instruments like the Gravity GradioMeter, Laser-Induced Breakdown Spectroscope, and Mission Survival Module were proposed but not confirmed.

A small rover named IDEFIX—after the French name for Dogmatix, Obelix's dog in the Asterix comics—will be delivered to Phobos by the spacecraft. Built by CNES and DLR, the rover weighs under 30 kg and is equipped with two navigation cameras, two wheel cameras to study wheel-regolith interaction, a Raman spectrometer (RAX), and a miniaturized radiometer (miniRad). Its objectives are to touch the surface, test how the regolith behaves under mechanical action, demonstrate wheeled locomotion in low gravity, and take in-situ measurements at 100-micrometer resolution.

For sampling, MMX uses two methods: a Coring Sampler (C-SMP) to collect material from depth, and a pneumatic system to gather surface regolith.