Japan launches MMX mission to collect samples from Mars moon Phobos

Japan launched an uncrewed spacecraft toward Mars's moon Phobos before dawn on Tuesday, aiming to become the first country to retrieve surface samples from the Martian system and return them to Earth.

The Japan Aerospace Exploration Agency (JAXA) launched its Martian Moons eXploration (MMX) spacecraft aboard an H3 rocket from the Tanegashima Space Center in Kagoshima prefecture at 4:41 a.m. local time (1941 GMT Monday). JAXA confirmed an hour later that the probe had separated cleanly from the launcher's upper stage and begun its cruise toward Mars, with signals indicating all onboard systems were operating as expected.

The journey to the Martian system

The 4.5-tonne spacecraft is scheduled to reach Martian orbit in August 2027. It will sync with the orbit of Phobos, a potato-shaped body measuring roughly 27 kilometres by 22 kilometres by 18 kilometres that circles Mars three times a day at an altitude of approximately 6,000 kilometres.

Operating near Phobos poses distinct navigation hurdles due to the moon's minimal gravitational pull. To prepare the ground, the mission carries Idefix, a 25-kilogram rover developed jointly by France's CNES and Germany's DLR. Roughly the size of a microwave oven, the four-wheeled rover will drop onto the surface in late 2028 or early 2029. Moving at just one millimetre per second across a planned 100-day expedition, Idefix will assess surface stability and radiation to ensure the main craft can touch down safely.

Once scouting is complete, the four-legged stationary lander will touch down for approximately two hours. It will drill and vacuum up at least 10 grams of dust, soil, and rock fragments before lifting off back into Martian orbit.

Resolving planetary origins

Planetary scientists want Phobos samples to settle a long-standing question: whether the Martian moons are captured asteroids or debris hurled into space after a collision struck early Mars. Because material blasted off the Martian surface over billions of years has likely settled on Phobos, researchers expect the collected material will also yield insight into the Red Planet's early geological history.

Before leaving the area in 2030, the spacecraft will carry out flybys of Mars's smaller outer moon, Deimos. The sample-return capsule is scheduled to land in the Australian desert in 2031.

International backing and budget

The five-year mission represents a combined investment of $578 million across several partner space agencies.

For Japan, the launch also marks a key milestone for its flagship H3 launch system, which overcame an early 2023 flight failure to secure its first interplanetary deployment. With the probe on course, Japan enters a direct timeline with China, which plans its own Martian sample return attempt for 2028, with both countries targeting 2031 for arrival on Earth.