Japan launched historic round-trip mission to Mars Moon back to Earth
The MMX spacecraft is headed toward Phobos on a five-year journey that could reveal how Mars acquired its mysterious moons.
Japan has launched a spacecraft toward a small moon with an enormous scientific question: Where did it come from?
The Japan Aerospace Exploration Agency’s Martian Moons eXploration mission, or MMX, lifted off aboard an H3 rocket from Tanegashima Space Center at 4:41 a.m. Japan Standard Time on October 20, corresponding to October 19 in the United States. JAXA confirmed that the rocket flew as planned and successfully separated the spacecraft approximately 71 minutes after launch. Its destination is Phobos, the larger of Mars’s two moons. H3ロケット10号機による火星衛星探査機（MMX）の打上げ結果
If successful, MMX will accomplish something no mission has done: collect material from a Martian moon and carry it home. Its planned return in 2031 would bring a piece of Phobos into laboratories on Earth, where scientists could investigate the history of the moon—and the planetary system it inhabits. ISAS
A moon with an unresolved origin
Phobos and its smaller companion, Deimos, have been photographed by spacecraft, but their origins remain unsettled. One possibility is that they began as asteroids captured by Mars’s gravity. Another is that they formed from debris blasted into orbit by a giant impact.
Samples could help distinguish between those explanations. Their chemistry and mineral composition would give researchers evidence that distant observations alone cannot provide, helping establish whether Phobos contains material associated with Mars or a different population of Solar System objects. esa.int
For JAXA, the investigation reaches beyond the moons themselves. MMX’s scientific objectives include reconstructing the evolution of the Mars system and exploring how environments capable of supporting life developed on rocky planets. ISAS
A tiny rover before the main landing
MMX is expected to reach Mars in August 2027, then begin close observations of Phobos. Before the main spacecraft attempts sample collection, it will deploy Idefix, a small rover developed by the French and German space agencies.
The rover will examine the surface and help prepare for the spacecraft’s landing. Operating there presents an unusual challenge: Phobos’s gravity is so weak that even gentle movements require careful control. The main spacecraft carries two different sampling devices for collecting material during its planned surface operations. esa.int
MMX will operate near Phobos in what engineers call a quasi-satellite orbit, moving around Mars while maintaining a trajectory that keeps it close to the moon. The mission will also observe Deimos, allowing scientists to compare the two bodies. ISAS
The hardest part includes coming home
The current plan calls for sample collection in 2030, followed by a return to Earth in 2031. A capsule carrying at least 10 grams of Phobos material is intended to land in Australia before the samples are transferred to Japan for processing and scientific study. esa.int
The spacecraft has already passed its first post-launch checkpoint. On October 21, JAXA announced that MMX had completed its initial critical operations phase and that its health had been established. Instrument checks and preparations for the cruise toward Mars come next. 火星衛星探査機（MMX）の初期クリティカル運用フェーズ終了
Years of navigation, surface reconnaissance and precision operations still separate this launch from a successful return. But Japan has now begun a journey that could turn one of Mars’s most familiar silhouettes into something scientists can finally hold, measure and understand.
Sources
Japan Aerospace Exploration Agency. (2026, October 20). Launch results of MMX aboard H3 Launch Vehicle No. 10 [In Japanese].
Japan Aerospace Exploration Agency. (2026, October 21). Completion of MMX’s initial critical operations phase [In Japanese].
European Space Agency. (2026, October 13). Mars moon lander set to launch on 19 October.
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