Japan Launches MMX Probe to Study Mars' Moons, Seeks Phobos Sample Return

Japan’s space agency said it has launched the Martian Moons eXploration spacecraft aboard H3 Launch Vehicle flight No. 10, with the rocket placing the probe into its planned post-launch orbit to begin a high-profile mission to study Mars’ two moons and attempt a sample return from Phobos. In a press release, the Japan Aerospace Exploration Agency said MMX lifted off from the Tanegashima Space Center at 04:41:03 JST on Oct. 20, 2026, or 19:41:03 UTC on Oct. 19.

The launch marks the opening step in a mission designed to answer a major question about the Martian system: how Phobos and Deimos formed. If the mission proceeds as planned, MMX also aims to become the first mission to return material from the Martian sphere — the region around Mars that includes its moons — back to Earth.

JAXA said, “Japan Aerospace Exploration Agency (JAXA) launched the Martian Moons eXploration (MMX) spacecraft aboard H3 Launch Vehicle flight No.10 at 04:41:03 JST on October 20, 2026 from the Tanegashima Space Center.” The agency added: “The H3 Launch Vehicle flew as planned, and approximately 71 minutes and 13 seconds after liftoff, the separation of the MMX spacecraft was confirmed. The MMX spacecraft was then injected into the predetermined orbit.”

That makes the immediate launch outcome clear: JAXA is reporting a successful ascent, spacecraft separation and orbit injection. It is not, however, a declaration that the multiyear mission itself has succeeded. MMX still faces a long interplanetary journey and a complex sequence of operations at Mars and its moons before any sample could be returned to Earth.

MMX is a JAXA-led mission focused on Phobos and Deimos, the two small moons of Mars. The spacecraft is intended to study both bodies to help scientists understand their origin, while carrying out operations at Phobos aimed at collecting material for return to Earth. JAXA materials describe the mission as lasting roughly five years, with partner timelines showing arrival at Mars around 2027 and sample return in 2031.

That science goal gives the launch broader significance beyond a routine departure from Earth. Researchers want to know whether Phobos and Deimos are captured asteroids or formed from debris produced by a giant impact involving Mars. Samples from Phobos could help settle that debate while also offering new evidence about the history of the Martian environment.

MMX is led by JAXA but includes international participation. NASA is contributing science hardware and support, while France and Germany are contributing the small Idefix rover for operations on Phobos.