Japan launched MMX mission to bring Mars moon samples

Japan launched a spacecraft on an outbound trip exceeding 500 million kilometers on October 20, 2026, targeting the Martian moon Phobos in an attempt to bring physical samples back to Earth. Propelled by the country’s flagship H3 rocket from Tanegashima Space Center, the Martian Moons Exploration mission aims to settle long-running scientific debates over the origin of Mars’s two moons and search for potential traces of early solar system history.

Reaching the Martian System and Landing on Phobos

The five-tonne probe is scheduled to arrive at Mars in 2027, where it will sync with Phobos’s orbit. The spacecraft will eject a small French-German rover named Idefix, which will bounce across the surface of Phobos to survey landing sites before the main stationary lander touches down to drill and vacuum up material.

Navigating Low Gravity and Technical Hurdles

Landing on Phobos presents a major engineering hurdle because the moon’s gravity is only about one-2,000th that of Earth’s, creating a risk that the probe could bounce off the surface due to the impact and tip over. To mitigate this risk, engineers equipped the spacecraft with four landing legs designed to absorb impact and integrated image-based navigation technology that was previously tested during the Smart Lander for Investigating Moon mission in 2024. Seiichiro Watanabe, a professor at Nagoya University, noted that high-precision course control makes this mission extremely difficult, even compared to the Hayabusa2 asteroid sample return.

Testing Competing Hypotheses on Lunar Origins

Scientists have long debated whether Phobos and its smaller companion Deimos formed as captured asteroids or accumulated from debris following a giant impact between Mars and another celestial body. Kiyoshi Kuramoto, an expert on planetary science, stated that analyzing the chemical and mineral compositions of the returned samples will definitively settle the question, as the two hypotheses imply completely different compositions. If the material is rich in water-bearing minerals and organic matter like past asteroid samples, the capture hypothesis gains ground.

Delivering Samples and Future Expedition Planning

International space agencies are collaborating on the project, with NASA contributing navigation support through the Deep Space Network, funding participating US scientists, and providing a pneumatic P-Sampler mechanism to collect surface material alongside JAXA’s core-extracting C-Sampler. NASA will receive about 15% of the returned sample to curate at the Johnson Space Center Astromaterials Lab. Following sample collection and planned flybys of Deimos, the MMX spacecraft is scheduled to leave Mars’s orbit in November 2030 and deliver the samples to Earth in 2031.

International Collaboration and Strategic Significance

Kazuto Suzuki, a University of Tokyo professor, said Japan was “consciously taking decisions to do sample returns as something the US cannot or has not done”. “Material returned from Phobos could serve as a time capsule of ancient Mars,” said Yasuhiro Kawakatsu, the MMX expedition’s project manager. “We are part of the first sample return mission from the Martian system,” said the Germany Space Agency’s rover chief Markus Grebenstein. “The more we can do some of these ‘firsts’ before we send people, the fewer we need to do later – and therefore the lower the risk.”

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