The 2026 Launch to Phobos and Deimos
Scheduled to lift off on October 19 aboard a Japanese H3 rocket, the international Martian Moons Exploration mission—known as MMX—will target a return of 10 grams of samples to Earth by 2031, as reported by Les Numériques. The spacecraft carries a micro-ondas-sized rover named Idefix, a collaborative development by the French CNES space agency and the German DLR, built to land directly on the Martian moon Phobos.
Weighing Captured Asteroids Against Impact Debris
For decades, researchers have debated whether Phobos and Deimos are captured asteroids or the result of debris ejected from a massive impact on early Mars. The MMX mission carries a suite of twelve precision instruments to settle this question once and for all. These include the MIRS infrared spectrometer, built by CNES and the Observatoire de Paris, alongside the MEGANE gamma-ray and neutron spectrometer provided by NASA.
Conquering the Complex Gravitational Field of Mars
Stationary orbits around Phobos are physically impossible due to the tiny moon’s 24-kilometer diameter and proximity to Mars. The gravitational pull of Mars, located just 6,000 kilometers away, dominates the region and limits Phobos’s gravitational sphere to a few hundred meters. To maintain a prolonged presence, the main spacecraft will use quasi-satellite orbits. The MMX probe will orbit Mars while precisely matching its velocity to escort Phobos step by step.
Crawling Across an Ultra-Low Gravity Surface
Before the main spacecraft lands, MMX will release the 25-kilogram rover Idefix onto the surface of Phobos. Gravity on Phobos is roughly 2,000 times weaker than on Earth. A 75-kilogram adult would weigh 40 grams there, while Idefix will experience a downward pull equivalent to just 15 grams. Because any sudden jolt could launch the rover into space, Idefix will crawl across the surface at speeds between one and three centimeters per second. Four motorized legs allow the rover to right itself automatically if it lands upside down.
Applying Lessons from Rosetta to Drill and Return
The landing strategy draws lessons from the 2014 Rosetta mission, where the Philae lander bounced off comet 67P due to unexpected surface mechanics. Idefix will act as a structural test probe to evaluate regolith consistency before the main module attempts a touchdown. Ultimately, the mission will drill two centimeters into the surface to collect ten grams of dust. MMX will then transport these pristine samples back to Earth, with arrival projected for 2031.
