MMX Lifts Off on Mission to Explore Moons of Mars
Japan’s MMX, or Martian Moons eXploration, lifted off Monday from the Tanegashima Space Center in southern Japan. The launch marked the beginning of a five-year mission to return samples from Mars’ moon Phobos, which will answer long-standing questions about the moon’s origin.
MMX was propelled towards Mars by Mitsubishi’s new H3 rocket, making its tenth flight. The H3 is the successor to the venerable H-IIA and H-IIB launchers, that had a storied history launching the HTV resupply vehicle to the International Space Station, as well as scores of commercial and scientific payloads to destinations throughout the solar system. H3 has had a rocky start to service, experiencing catastrophic failures on its first flight in 2023 and its seventh flight last December. Despite that, H3 performed admirably on MMX’s late-night launch, with JAXA confirming the following morning that the spacecraft had been placed into the proper orbit and separated from the launch vehicle as planned.
Prime Minister Sanae Takaichi expressed her gratitude to the mission teams in a post on X, where she also described her enthusiasm for the H3 vehicle’s performance across three consecutive successes. Yoshihiro Seki, the Minister of Education, Culture, Sports, Science, and Technology, echoed the Prime Minister’s words in a statement, focusing again on the launch as a step in building out H3’s track record of reliability.
The MMX spacecraft itself is composed of three modules: the Exploration Module, the Return Module, and the Propulsion Module. Upon arrival at Mars in 2027, MMX will use its Propulsion Module to capture into Mars orbit. After jettisoning the Propulsion Module, it will enter a Quasi-Satellite Orbit, or QSO, near Phobos. Phobos’ weak gravity is too insubstantial to hold the spacecraft in a regular orbit, so the QSO allows the spacecraft to stay near Phobos for an extended period without requiring a capture into a full orbit.
After an extended observation campaign of Phobos to identify a suitable landing site, the MMX spacecraft will deploy the joint German/French rover Idefix onto the surface. Idefix is a micro-rover co-developed by France’s CNES and Germany’s DLR. The Idefix rover will scout the landing site to identify hazards and help determine the scientific value across the site prior to MMX’s own landing.
Once MMX lands, it will gather about 10 grams of Phobos’ regolith for return to Earth. The spacecraft will then lift back off, and depart Phobos for a flyby campaign of Mars’ other moon, Deimos. The origin of both moons is not known: a major scientific objective of the MMX mission is to determine whether the tiny moons coalesced from debris caused by an object impacting Mars, or whether the two are asteroids captured by Mars’ gravity.
After the conclusion of the Deimos observation campaign, the Return Module will separate and power itself back to Earth, delivering its precious sample to the deserts of Australia sometime in 2031. If successful, the mission will mark the first time samples have ever been returned to Earth from the Mars system.
MMX, however, is not the first attempt at returning samples of Phobos. Russia’s Roscosmos attempted a similar feat with the Fobos-Grunt spacecraft, which was also intended to deliver China’s first Mars orbiter to the Red Planet. After its launch in 2011, the spacecraft’s Fregat-derived Main Propulsion Unit was intended to ignite to propel the spacecraft towards Mars. However, the orbit-raising burns failed, leaving the spacecraft stranded in low orbit around the Earth until it reentered over the Pacific Ocean in January of 2012. While China made a spectacular return to Mars missions in 2020 with Tianwen-1, a combination orbiter/lander/rover, Russia has had markedly less success in their deep space endeavors. The Luna 25 mission to the Moon crashed into the surface due to a faulty orbital insertion in 2023, while a proposed Fobos-Grunt do-over has remained in limbo since the original’s failure.
Japan, for their part, have significant experience in sample returns from low-gravity bodies like Phobos. Japan pioneered asteroid sample return with the Hayabusa mission, which launched in 2003, and, after a series of close-calls, returned a microscopic sample of the asteroid Itokawa to Earth in 2010. A successor, Hayabusa2, launched in 2014, and returned about 5 grams of the asteroid Ryugu to Earth in 2020. The Hayabusa2 spacecraft remains operational as part of the Hayabusa2♯ mission, which is set to make a landing on the tiny asteroid 1998 KY26 in 2031.
MMX represents a continuation of Japan’s legacy of complex sample-return missions. Yesterday’s launch was an exciting first step in MMX’s mission, but, as with any planetary mission, the real work has only just begun.
