Japan launches MMX mission to study Mars’s moons and return a Phobos sample

Japan’s space agency, JAXA, has launched its Martian Moons eXploration spacecraft from Tanegashima toward Mars to study the planet’s two moons and attempt to return material from Phobos to Earth. Science News dated the launch October 19, 2026, while the Times of India reported it as taking place Tuesday, October 20, in Japan. A returned sample could help scientists test competing explanations for how the moons formed.

What MMX will collect from Phobos

The mission aims to collect at least 10 grams of surface material from Phobos, the larger of Mars’s two moons, and will also study Deimos. The planned return to Earth is in 2031. Sampling and the journey home remain future stages of the mission.

Why scientists want a sample of Mars’s moon

The origins of Phobos and Deimos remain unsettled. One explanation holds that debris from a large impact on Mars formed the moons; another proposes that they are asteroids captured by Mars’s gravity. WIRED reported that aspects of the moons’ reflected light support the capture idea. Material brought to Earth would let scientists examine the question directly.

Planetary scientist Briony Horgan of Purdue University, who is not involved in MMX, told Science News that the mission offers ‘a totally different sample and view of Martian materials.’ Science News also reported that 15 percent of the sample will eventually go to NASA’s Johnson Space Center, where planetary scientist Michael Zolensky said even a few grams would be valuable to researchers.

Three earlier Russian probes sent toward Phobos failed, WIRED reported. Japan has returned material from two asteroids: its Hayabusa spacecraft brought back a sample from Itokawa in 2010, and Hayabusa2 delivered material from Ryugu in 2020. MMX would extend that sample-return experience to the Martian region.